TAG HIV Basic Science, Vaccines, and Cure Project Blog

Latency-Reversing and Immunomodulatory Activities of HDAC Inhibitors

Results from the second clinical trial to test the HDAC inhibitor vorinostat as a latency-reversing agent, first presented at CROI 2013, have now been published in the open access journal PLoS Pathogens. The study design differed from the first trial, involving a longer 14-day dosing period. The results are broadly consistent, with a significant increase in cell-associated HIV RNA documented, but no change in multiple measures of the HIV reservoir or HIV RNA as assessed by the standard viral load test. Side effects experienced by participants were grade 1 or 2 (mild or moderate in severity) with lethargy, diarrhea and thrombocytopenia being most common; all resolved after the drug was stopped. The researchers noted long-term changes in expression of multiple cellular genes and caution that this could present a safety concern, stating: “the prolonged changes in host gene expression require careful long term follow up.”

The paper adds to the evidence that HDAC inhibitors can activate at least some latent HIV, but do not shrink the HIV reservoir in most cases, suggesting additional interventions are needed to kill latently infected cells that are induced to produce virus. In terms of the latency-reversing potency of HDAC inhibitors, the results presented to date are consistent with in vitro studies indicating a hierarchy of vorinostat > panobinostat > romidepsin, with the latter mediating the greatest effect based on the detection of HIV RNA by standard viral load testing (these data were presented at the AIDS 2014 conference by Dr. Ole Schmeltz Søgaard and the presentation is available on YouTube). The safety concerns raised by the persistent alterations in host gene expression will require ongoing assessment in all the clinical trials that are being conducted.   

HDAC inhibitors also have effects on the immune system, and this aspect is evaluated in study published recently in Blood. The research did not involve HIV-positive people but rather individuals undergoing hematopoietic cell transplantation who were receiving vorinostat to prevent graft-versus-host disease. The authors found increases in the numbers of immunosuppressive regulatory CD4 T cells (Tregs) and greater suppression by these cells on a per-cell basis, along with reduced inflammatory responses by peripheral blood mononuclear cells.

Similar anti-inflammatory effects were reported in an analysis of HIV-positive participants in a clinical trial of panobinostat that was presented at AIDS 2014; the presentation was covered by Jules Levin of NATAP and the abstract and slides are posted to the NATAP website. There are reasons to believe that the anti-inflammatory activity of HDAC inhibitors could be of some benefit in HIV, but Tregs have also been linked to lower HIV-specific immunity, which could potentially be a negative (particularly if HIV-specific immunity needs to be boosted to eliminate latently infected cells). There is already some evidence that HDAC inhibitors can suppress the killing of HIV-infected cells by virus-specific CD8 T cells in laboratory assays (this paper was published in PLoS Pathogens in August).

Complicating matters further, at the recent Strategies for an HIV Cure conference Jonathan Karn gave a presentation suggesting HDAC inhibitors may enhance natural killer (NK) cell responses by causing downregulation of MHC class I on target cells and upregulating NK cell receptors, possibly consistent with some preliminary evidence presented at the same conference indicating NK cell responses were associated with declines in HIV DNA levels in a few participants in the panobinostat trial.

Additional research will be needed to investigate how the various possible consequences of HDAC inhibition balance out in HIV-positive people, and to assess the extent to which these effects persist after dosing is stopped.

PLoS Pathog. 2014 Nov 13;10(10):e1004473. doi: 10.1371/journal.ppat.1004473. eCollection 2014.

Activation of HIV Transcription with Short-Course Vorinostat in HIV-Infected Patients on Suppressive Antiretroviral Therapy.

Elliott JH, Wightman F, Solomon A, Ghneim K, Ahlers J, Cameron MJ, Smith MZ, Spelman T, McMahon J, Velayudham P, Brown G, Roney J, Watson J, Prince MH, Hoy JF, Chomont N, Fromentin R, Procopio FA, Zeidan J, Palmer S, Odevall L, Johnstone RW, Martin BP, Sinclair E, Deeks SG, Hazuda DJ, Cameron PU, Sékaly RP, Lewin SR.

Abstract

Human immunodeficiency virus (HIV) persistence in latently infected resting memory CD4+ T-cells is the major barrier to HIV cure. Cellular histone deacetylases (HDACs) are important in maintaining HIV latency and histone deacetylase inhibitors (HDACi) may reverse latency by activating HIV transcription from latently infected CD4+ T-cells. We performed a single arm, open label, proof-of-concept study in which vorinostat, a pan-HDACi, was administered 400 mg orally once daily for 14 days to 20 HIV-infected individuals on suppressive antiretroviral therapy (ART). The primary endpoint was change in cell associated unspliced (CA-US) HIV RNA in total CD4+ T-cells from blood at day 14. The study is registered at ClinicalTrials.gov (NCT01365065). Vorinostat was safe and well tolerated and there were no dose modifications or study drug discontinuations. CA-US HIV RNA in blood increased significantly in 18/20 patients (90%) with a median fold change from baseline to peak value of 7.4 (IQR 3.4, 9.1). CA-US RNA was significantly elevated 8 hours post drug and remained elevated 70 days after last dose. Significant early changes in expression of genes associated with chromatin remodeling and activation of HIV transcription correlated with the magnitude of increased CA-US HIV RNA. There were no statistically significant changes in plasma HIV RNA, concentration of HIV DNA, integrated DNA, inducible virus in CD4+ T-cells or markers of T-cell activation. Vorinostat induced a significant and sustained increase in HIV transcription from latency in the majority of HIV-infected patients. However, additional interventions will be needed to efficiently induce virus production and ultimately eliminate latently infected cells.

Blood DOI: http://dx.doi.org/10.1182/blood-2014-10-605238

Histone deacetylase inhibition regulates inflammation and enhances Tregs after allogeneic hematopoietic cell transplantation in humans

Sung Won Choi, Erin Gatza, Guoqing Hou, Yaping Sun, Joel Whitfield, Yeohan Song, Katherine Oravecz-Wilson, Isao Tawara, Charles A. Dinarello, and Pavan Reddy

Key Points

• HDAC inhibition reduced pro-inflammatory cytokines and increased regulatory T cell number and function after allo-HCT.
• HDAC inhibition enhanced STAT-3 acetylation and induced IDO after allo-HCT.

Abstract

We examined immunological responses in patients receiving histone deacetylase (HDAC) inhibition (vorinostat) for graft-versus-host disease (GVHD) prophylaxis following allogeneic hematopoietic cell transplant (allo-HCT). Vorinostat treatment increased histone acetylation in peripheral blood mononuclear cells (PBMC) from treated patients, confirming target HDAC inhibition. HDAC inhibition reduced pro-inflammatory cytokine levels in plasma and from PBMC, decreased ex vivo responses of PBMC to pro-inflammatory TLR-4 stimuli, but did not alter the number or response of conventional T cells (Tconv) to non-specific stimuli. However, the numbers of regulatory T cells (Tregs) were increased, which revealed greater demethylation of the Foxp3 T regulatory-specific demethylation region. Vorinostat-treated patients showed increased expression of CD45RA and CD31 on Tregs, and these Tregs demonstrated greater suppression on a per-cell basis. Consistent with preclinical findings, HDAC inhibition also increased STAT-3 acetylation and induced indoleamine-2,3-dioxygenase (IDO). Our data demonstrate that HDAC inhibition reduces inflammatory responses of PBMC but enhances Tregs after allo-HCT.

Catching Up with Pathogenesis and Cure Research from CROI 2014

In addition to studies covered in prior posts (a possible second pediatric cure case, Sangamo’s gene therapy and limitations of latency-reversing agents), CROI 2014 featured a smorgasbord of presentations related to pathogenesis and cure research. Webcasts of all conference sessions are online, and many posters are now available in PDF format. Brief summaries of some notable studies are appended below, with links to webcasts and posters included where possible. Abstracts for posters that are unavailable as PDFs can be found in the final program and abstract book. 

HIV Rebound in the Boston Patients

Timothy Henrich provided details on the two individuals in Boston who experienced a delayed return of HIV replication after a period during which it had been hoped they might be cured (this sobering news was covered on the blog last December). Henrich’s presentation is available via webcast. Although they were monitored frequently after interrupting antiretroviral therapy (ART), viral load reached very high levels in both cases, and this was accompanied by symptoms of acute infection. The likely explanation is that their immune systems, having been newly generated by the stem cell transplants they had received to treat cancer, had not previously encountered HIV. Consistent with this possibility, HIV-specific cellular immune responses were undetectable prior to the viral load rebound but appeared afterward. At a community workshop on cure research immediately prior to CROI, Henrich noted that the size of the HIV reservoir had been reduced at least 3 logs in these individuals and was estimated to be very small at the time of the ART interruption; 290-2900 cells in one case, 40-730 cells in the other. The results suggest the bar is set very high for approaches that aim to cure HIV infection by shrinking the latent reservoir.

Treatment of Hyperacute HIV Infection 

A large crowd congregated at a poster presentation (397LB) by Hiroyu Hatano from UCSF describing extremely early ART treatment in an individual who acquired HIV infection just prior to enrolling in a pre-exposure prophylaxis (PrEP) demonstration project. The infection occurred during a short 13-day window between a final screening visit and the day Truvada PrEP was first administered. When viral load results from the sample taken at Truvada initiation became available after seven days and showed a reading of 220 copies, the individual was switched to a conventional ART regimen. The viral load seven days later was 120 copies and there was a single measurement of cell-associated HIV RNA at a level of 4.7 copies per million CD4 T cells ~32 days after infection, but all subsequent tests for HIV RNA, DNA and replication-competent virus have been negative. The results raise the possibility that ART given at such an early stage of infection may have led to an adult equivalent of the Mississippi baby case. However, the experience of the Boston patients offers a cautionary tale about the interpretation of negative virological assay results. A treatment interruption will be considered after 12 months of ART.

Three Cured Mice

Qingsheng Li displayed an interesting poster immediately adjacent to Hatano’s, but it didn't receive quite as much attention. Li’s work attempted to recapitulate the Mississippi baby outcome in the humanized mouse model, by administering ART six hours after the animals were infected with HIV. ART was maintained for two weeks and then interrupted. HIV RNA and DNA remained undetectable after interruption, even when CD8 T cells were depleted, leading the researchers to conclude that a cure had been achieved. The initial experiment (reported in the conference abstract book) involved three ART-treated mice and three controls, but the poster included data on additional groups that received ART at later timepoints after infection (12 hours and 18 hours). In these animals, HIV rebounded after ART interruption. Unfortunately the poster is not yet available on the CROI website (there is a link, but it goes to the abstract book).

HIV Integration, Latency, and CD4 T Cell Survival

At least two published studies (Josefsson et al and Imamich et al) have documented that the homeostatic proliferation of memory CD4 T cells containing integrated HIV provirus can increase the amount of HIV DNA in the body. These studies tracked copies of grossly defective virus genomes that could only multiply as a result of the proliferation of the host CD4 T cell. Homeostatic proliferation is a normal immunological mechanism that sustains memory T cells, and causes them to expand in the setting of T cell deficiency. The role of this process in maintaining the latent HIV reservoir was first described many years ago, based in part on the finding that lower CD4 T cell counts are associated with an increased rate of CD4 T cell proliferation and higher levels of HIV proviral DNA (although these levels remain extremely low compared to the overall size of the memory CD4 T cell pool). Several presentations at CROI documented the phenomenon in a different way, by demonstrating the proliferation of HIV proviruses integrated at precisely the same location in the CD4 T cell genome. Additionally, it was reported by Thor Wagner that HIV proviruses frequently integrate at very similar sites in certain CD4 T cell genes associated with the cell cycle and differentiation, leading to the suggestion that HIV integration into these genes may somehow be promoting the growth and longevity of latently infected CD4 T cells. Wagner highlighted the fact that some of the genes into which HIV appears to preferentially integrate have been identified as having roles in cancers, and this point was echoed in a poster from Stephen Hughes laboratory at the National Cancer Institute. However, some cited examples such as Bach2 are also involved in CD4 T cell differentiation (this is not mentioned in either CROI presentation), so it would be logical that genes such as this would be active in the CD4 T cells HIV infects, and the virus is already known to preferentially integrate into active genes. Additional research is needed to clarify whether there is anything sinister about these integration sites, or if they just reflect the locations HIV is most likely to have access to in the cells it is infecting. Based on the current evidence, it seems possible that these genes could simply be those that are active and available to HIV in CD4 T cells that are differentiating into a long-lived phenotype.

In an article about the research by Jon Cohen in Science, Wagner’s colleague Lisa Frenkel goes so far as to suggest that there may be a link with cancers that occur in HIV-positive people, but to me this is a wildly speculative stretch given that most of these cancers have been shown to be associated with immunodeficiency (in both HIV-positive and HIV-negative people) and inflammation. The article also could be misread as suggesting that long-term HIV treatment causes higher cancer rates, when what the literature reports is that some HIV-positive people on ART still have an elevated risk of some non-AIDS defining cancers (NADCs) compared to HIV-negative people (age is the strongest, most consistent risk factor). A review on the subject from 2012 states: “the higher risk of NADCs is primarily among males, with HIV-infected women having no higher rates of NADCs compared with the overall population.” A sex-biased cancer-promoting effect of HIV integration and latency does not appear very plausible, and T cell cancers remain rare in HIV-positive people. In sum, pending further data, I would advocate extreme skepticism about Frenkel's suggestion that there may be a connection between HIV latency and the development of cancer. Links to CROI presentations on the topic are below.

Thor Wagner, Proliferation of Cells With HIV Integrated Into Regulatory Genes Is a Mechanism of Persistence

Mary Kearney, Massive Expansion of HIV Infected Cells With Identical Proviruses in Patients On Suppressive ART 

Stephen Hughes, The Role of HIV Integration Sites in Extensive Clonal Expansion of Infected Cells in Patients 

Eli Boritz, Central Memory and Effector Memory CD4 T Cells From HIV Controllers Harbor Distinct HIV Strains 

Slim Success with Gut-Targeting Anti-Activation Strategies

Among the posters at CROI were results from four different clinical trials of therapies that aimed to ameliorate immune activation by targeting the microbial translocation pathway (the leakage of bacterial products from the gut into the systemic circulation). Sevelamer (a treatment for high blood levels of phosphorus that can bind bacterial lipopolysaccharide) and meselamine (a therapy that reduces mucosal inflammation in inflammatory bowel disease) had no effect on markers of microbial translocation or inflammation. The antibiotic rifaximin was associated with very small reductions in some markers of immune activation and inflammation. The probiotic supplement Biola was reported to significantly reduce the levels of the D-dimer by about one third over eight weeks in a small study (12 probiotic recipients, seven placebo recipients and six controls) and there were trends toward reduced CRP and IL-6. Markers of microbial translocation did not change. These results await confirmation in a larger trial with a longer duration of follow up. 

HIV-Specific CD4 T Cell Responses in the VISCONTI Cohort 

The VISCONTI cohort comprises individuals treated very early after acquiring HIV infection (for an average of around three years) who have maintained undetectable or extremely low HIV viral loads after interrupting ART. At the last published accounting, there were 14 members, although anecdotally it has been mentioned that there may now be as many as 20. The cohort appears to lack the robust HIV-specific CD8 T cell responses observed in most elite controllers, but until CROI no data had been presented on their HIV-specific CD4 T cell responses. Assia Samri reported in a poster that HIV p24-specific CD4 T cells are detectable at “relatively high frequencies” in the cohort and have a more polyfunctional profile—but are not more abundant—compared to individuals on ART. However, the data are cross-sectional and cannot answer the question of whether the presence of these responses is a cause or effect of the persistently low viral load in the absence of ART. 

Hospitalization Among Elite Controllers

Elite controllers are sometimes cited as a model of a “functional cure” of HIV infection, because they naturally maintain extremely low viral loads in the absence of ART. However, in recent years it has become apparent that most elite controllers have elevated levels of immune activation and inflammation compared to comparable HIV-negative people, and are not entirely free from the risk of disease progression. Trevor Crowell presented a poster looking at hospitalization rates among 149 elite controllers compared to 4,704 HIV-positive individuals with suppressed viral loads on ART. Elite control was associated with a significantly higher rate of hospitalization (approximately two-thirds greater), primarily for cardiovascular and pulmonary disease, compared to the cohort on ART. The data are consistent with research indicating that ART may be beneficial for at least some elite controllers, and also has implications for HIV cure research because it argues that the achievement of virological control in the absence of ART does not necessarily equate to ideal health.    

Anti-PD-L1 Antibody in Macaques

Targeting the PD-1 receptor pathway has been proposed as a method for both reversing HIV latency and reinvigorating exhausted HIV-specific T cell responses. The AIDS Clinical Trials Group is on the verge of launching a clinical trial of an antibody against the PD1 ligand, PD-L1. At CROI, Stephen Mason described results of a preclinical study of the anti-PD-L1 antibody in ART-treated SIV-infected macaques. Administration was found to be safe and associated with a significant but short-term reduction in viral rebound after an ART interruption.

EraMune 02 Results

Two of the first clinical trials launched to specifically attempt therapeutic reduction of HIV reservoirs were EraMune 01 and 02, sponsored by the French Objectif Recherche Vaccins SIDA collaboration. Both investigated intensified ART, combined with IL-7 (EraMune 01) or a DNA/Ad5 prime-boost therapeutic HIV vaccine (EraMune 02). Results from study 01 were presented at a prior CROI, showing no significant HIV reservoir reduction and some evidence of an IL-7-mediated increase in HIV DNA resulting from the proliferation of latently infected cells. Results from study 02 debuted as a poster this year, also showing no significant reduction in levels of HIV DNA. However, the vaccine did successfully induce significant T cell responses against HIV Gag, Pol and Env antigens in individuals on ART. 

Evidence Prednisolone Can Increase CD4 T Cell Counts and Slow Progression in the Absence of ART

In the early 1990s, there was some excitement about results from an uncontrolled, open-label study of the immune suppressant drug prednisolone in people with HIV infection. The investigators reported that administration of the drug led to sizable increases in CD4 T cell counts that had not been seen with the antiretroviral drugs that were being given as monotherapy or dual therapies at the time. The advent of three-drug ART consigned this prednisolone study to the haze of history, but at CROI there was a flashback in the form of results from a randomized clinical trial, which suggest that the prior data were not a fluke. The trial was conducted in Tanzania during a period when ART was only indicated for people with low CD4 T cell counts. Treating individuals for whom ART was not yet indicated with prednisolone was associated with a significant increase in CD4 T cell counts and a reduced risk of clinical progression. The results underscore the causative role of immune activation in the progression of HIV infection, since prednisolone acts via this pathway without directly inhibiting the virus. The researchers suggest the drug may be able to inhibit immune activation and improve immune reconstitution in immunological non-responders on ART, and perhaps could have a role as an early therapy for asymptomatic HIV infection in resource-limited settings (the latter suggestion is likely to be controversial given the understandable emphasis on trying to improve global access to ART, the efficacy of which is proven). 

Evidence of HIV-Induced Pyroptosis in Gut CD4 T Cells

Having recently criticized a widely publicized paper on HIV-induced pyroptosis for not providing much information relating to CCR5-tropic HIV infection, I’m duty bound to highlight a new study that includes some data addressing this topic. Pyroptosis is an inflammatory form of cellular suicide that has been shown by Gilad Doitsh from Warner Greene’s laboratory to result from abortive HIV infection of resting “bystander” CD4 T cells in lymphoid tissue, leading to a massive depletion of these cells. The effect is dramatic with CXCR4-tropic HIV isolates, because the majority of resting CD4 T cells express the CXCR4 receptor. In a paper published in Science earlier this year, Doitsh’s research group identified the human IFI16 protein as the sensor that detects HIV genetic material in these cells, leading to pyroptosis. Doitsh has also demonstrated that the phenomenon can be induced by CCR5-tropic HIV isolates in CCR5-expressing CD4 T cells, but because CCR5 is most commonly expressed on activated cells and is very rarely present on resting CD4 T cells, the number of bystander cells that might die as a result of pyroptosis in the setting of CCR5-tropic HIV infection is as yet unclear. The new study, published in Retrovirology by Amanda Steele and colleagues, reports evidence that pyroptosis occurs in gut CD4 T cells after exposure to CCR5-tropic HIV, despite the fact that most of these cells appear to be activated (and therefore potentially susceptible to productive, rather than just abortive, infection).

Unlike the work of Doitsh et al, which primarily used a lymphoid tissue culture system derived from tonsillar material (human lymphocyte aggregate culture or HLAC), Steele created a culture model from gut cells, naming it the Lamina Propria Aggregate Culture (LPAC). Infection of these cultures with a CCR5-tropic HIV isolate led to a statistically significant depletion of CD4 T cells after six days. Further analyses showed that the extent of the depletion correlated with the magnitude of productive HIV infection (as measured by p24 antigen expression), but that the majority of dying CD4 T cells were uninfected and undergoing necrosis associated with expression of caspase 1, an indication of pyroptosis (as opposed to apoptosis, the less inflammatory type of cellular suicide seen with productive infection). Approximately 63% of the dying CD4 T cells were negative for p24 and displayed a necrotic phenotype, while 13% were positive for p24 and apoptotic. Inhibition of caspase 1 did not affect productively infected cells but was able to reduce the extent of CD4 T cell depletion in the cultures from 36% to 18%, providing evidence that pyroptosis was contributing substantially to CD4 T cell death.

To try and model how HIV infection might interact with microbial translocation (the leakage of gut bacteria into the tissues and systemic circulation), the researchers conducted similar experiments with the addition of a commensal gut bacterial species, Escherichia coli. The presence of E. coli significantly enhanced CD4 T cell depletion, but also, surprisingly, seemed to cause a profound shift in the type of cell death, from pyroptosis (associated with expression of caspase 1) to apoptosis (associated with expression of caspase 3). This was established by testing the effects of caspase inhibitors on the extent of CD4 T cell death in the cultures; in the presence of E. coli, a caspase 1 inhibitor no longer had an effect, while a caspase 3 inhibitor significantly reduced CD4 T cell depletion. The authors suggest that perhaps the threshold for apoptosis is reduced in the presence of microbial products, and they propose a biphasic model of gut HIV pathogenesis in which pyroptosis dominates early on, contributing to the breakdown of gut wall integrity, followed by the onset of microbial translocation and increased HIV replication and CD4 T cell apoptosis. 

One possible question pertaining to the interpretation of these studies is whether the involvement of caspase 1 is always synonymous with pyroptosis caused by abortive HIV infection. In one study cited by Steele and collagues, which measured caspase 1 expression in CD4 and CD8 T cells from HIV-positive individuals, a significant sixfold upregulation was documented in CD8 T cells, and a non-significant increase of threefold in CD4 T cells. Not having any expertise in caspase 1 biology (to say the least), I’m not clear how these differences might be explained or how they relate to the use of caspase 1 as a marker of pyroptosis (it seems unlikely that the caspase 1 upregulation documented in CD8 T cells was due to abortive HIV infection). Additional research is likely to clarify current uncertainties, as this has clearly become an important and expanding area of investigation.

In another development linked to the work of the Greene laboratory on pyroptosis, a separate paper published in Clinical & Experimental Immunology by Sara Nissen and colleagues reports that the expression of IFI16, the DNA-sensing protein, is significantly elevated in untreated HIV-positive people. Levels of IFI16 expression were found to correlate positively with viral load and the activation of central memory and effector memory CD4 T cells (measured by the CD38 marker). There was also an inverse correlation between IFI16 and CD4 T cell count. The researchers note these findings are consistent with the proposed role of IFI16 in HIV-induced CD4 T cell death, and indicate a relationship between IFI16 and immune activation (although further work is needed to discern if elevated IFI16 expression is a cause or consequence of immune activation—or both).

Retrovirology. 2014 Feb 4;11(1):14. doi: 10.1186/1742-4690-11-14.

Microbial exposure alters HIV-1-induced mucosal CD4+ T cell death pathways Ex vivo.

Steele AK, Lee EJ, Manuzak JA, Dillon SM, Beckham JD, McCarter MD, Santia ML, Wilson CC.

Abstract

BACKGROUND: Early HIV-1 infection causes massive CD4+ T cell death in the gut and translocation of bacteria into the circulation. However, the programmed cell death (PCD) pathways used by HIV-1 to kill CD4+ T cells in the gut, and the impact of microbial exposure on T cell loss, remain unclear. Understanding mucosal HIV-1 triggered PCD could be advanced by an ex vivo system involving lamina propria mononuclear cells (LPMCs). We therefore modeled the interactions of gut LPMCs, CCR5-tropic HIV-1 and a commensal gut bacterial species, Escherichia coli. In this Lamina Propria Aggregate Culture (LPAC) model, LPMCs were infected with HIV-1BaL by spinoculation and cultured in the presence or absence of heat killed E.coli. CD4+ T cell numbers derived from flow cytometry and viable cell counts were reported relative to mock infection. Viable cells were identified by viability dye exclusion (AqVi), and intracellular HIV-1 Gag p24 protein was used to identify infected cells. Annexin V and AqVi were used to identify apoptotic versus necrotic cells. Caspase-1 and Caspase-3 activities were blocked using specific inhibitors YVAD and DEVD, respectively.

RESULTS: CD4+ T cell depletion following HIV-1 infection was reproducibly observed by 6 days post infection (dpi). Depletion at 6 dpi strongly correlated with infection frequency at 4 dpi, was significantly blocked by Efavirenz treatment, and was primarily driven by p24-negative cells that were predominantly necrotic. HIV-1 infection significantly induced CD4+ T-cell intrinsic Caspase-1 activity, whereas Caspase-1 inhibition, but not Caspase-3 inhibition, significantly blocked CD4+ T cell depletion. Exposure to E.coli enhanced HIV-1 infection and CD4+ T depletion, and significantly increased the number of apoptotic p24+ cells. Notably, CD4+ T cell depletion in the presence of E.coli was partially blocked by Caspase-3, but not by Caspase-1 inhibition.

CONCLUSIONS: In the LPAC model, HIV-1 induced Caspase-1 mediated pyroptosis in bystander CD4+ T cells, but microbial exposure shifted the PCD mechanism toward apoptosis of productively infected T cells. These results suggest that mucosal CD4+ T cell death pathways may be altered in HIV-infected individuals after gut barrier function is compromised, with potential consequences for mucosal inflammation, viral dissemination and systemic immune activation.

Clin Exp Immunol. 2014 Mar 5. doi: 10.1111/cei.12317. [Epub ahead of print]

Innate DNA sensing is impaired in HIV patients and IFI16 expression correlates to chronic immune activation.

Nissen SK1, Højen JF, Andersen KL, Kofod-Olsen E, Berg RK, Paludan SR, Ostergaard L, Jakobsen MR, Tolstrup M, Mogensen TH.

Abstract

The innate immune system has been recognized to play a role in the pathogenesis of HIV infection, both by stimulating protective activities, and through contribution to chronic immune activation, the development of immunodeficiency, and progression to AIDS. A role for DNA sensors in HIV recognition has recently been suggested, and the aim of the present study was to describe the influence of HIV infection on expression and function of intracellular DNA sensing. Here we demonstrate impaired expression of interferon-stimulated genes in responses to DNA in PBMCs from HIV positive individuals, irrespective of whether patients receive antiretroviral treatment. Furthermore, we show that expression levels of the DNA sensors IFI16 and cGAS were increased in treatment-naïve patients, and for IFI16 expression was correlated with high viral load and low CD4 cell count. Finally, our data demonstrate a correlation between IFI16 and CD38 expression, a marker of immune activation, in CD4+ central and effector memory T cells, which may indicate that IFI16-mediated DNA sensing and signaling contributes to chronic immune activation. Altogether, the present study demonstrates abnormal expression and function of cytosolic DNA sensors in HIV patients, which may have implications for control of opportunistic infections, chronic immune activation, and T cell death.

Confronting HIV with Immunological Calm

One of the less-discussed factors that influences susceptibility to HIV infection is immune activation, which is interlinked with the availability of potential target cells for the virus. Several recent papers and a poster presentation at CROI 2014 shed additional light on this topic. In an open access review published in Retrovirology last November, Catherine Card and colleagues provide an overview of the science, focusing particularly on data generated by their studies of HIV risk factors among female sex workers in the Pumwani district of Nairobi, Kenya. This work has identified lower levels of immune activation—described as immune quiescence—as protective against HIV acquisition, and implicated specific polymorphisms in the interferon regulatory factor 1 (IRF-1) gene as contributing to the phenomenon. The same research group also published a study in the Journal of Infectious Diseases in January reporting that long-term (>1 year) involvement in sex work is associated with reduced mucosal immune activation, perhaps as a result of chronic exposure to diverse foreign antigens inducing regulatory, tolerance-like immune mechanisms. Based on these observations, a trial is about to be launched in Nairobi that will evaluate if daily administration of aspirin or hydroxychloroquine can reduce systemic and mucosal immune activation in HIV-negative women.

At CROI 2014, investigators involved in two large HIV prevention studies (the Partners in Prevention HSV/HIV Transmission Study and the Couples Observational Cohort Study) presented a case-control analysis that assessed the influence of a panel of different cytokines on transmission risk. Two cytokines linked with immune activation, IL-10 and IP-10, emerged as significantly associated, both in the partner acquiring HIV infection and the HIV-positive transmitting partner. The authors note that the results “suggest a potential parallel function of immune activation risk for HIV-1 susceptibility and infectiousness.”

Lastly, a paper from the research group of Julie Overbaugh published online in the Journal of Virology on March 12th looks at whether cellular immune activation markers and the number of CCR5-expressing HIV target cells affect the risk of superinfection with a second strain of HIV in a cohort of HIV-positive women. In this case, several markers of T cell activation were not associated with superinfection, but levels of CCR5-expressing HIV target cells were (although CCR5 is upregulated on T cells after activation, and so to some extent may also be considered an activation marker). The authors argue that target cell availability may be more important in governing HIV acquisition risk than immune activation per se (at least as measured by T cell activation markers), but it's unclear to what extent these results involving superinfection translate to HIV-negative individuals. 

Taken together, these studies support the evaluation of strategies that promote immunological calm at sites of HIV exposure as potential prevention interventions (as has previously been suggested by Ashley Haase’s research in macaques). Catherine Card and colleagues caution that immune suppression should not be so profound as to blunt antiviral immune responses in the mucosa, and argue that enhancing HIV-specific immunity with vaccines while dampening generalized immune activation are potentially complementary approaches to reducing HIV acquisition risk. 

Update 3/19/14: Thanks to Nicolas Vabret on twitter for pointing out that a 2012 macaque study conducted by the laboratory of Jean-Marie Andrieu reported an unprecedented degree of protection against an SIV challenge using a novel vaccine strategy that induced virus-specific regulatory CD8 T cell responses. The paper is available open access in the journal Cell Reports. This finding suggests that HIV-specific immune regulation, and not only generalized anti-activation approaches, could play a role in protection against HIV infection. My understanding is that there are plans to try and repeat the macaque experiment prior to considering advancing the approach into humans. 

Retrovirology. 2013 Nov 20;10(1):141. [Epub ahead of print]

Immune Quiescence: a model of protection against HIV infection.

Card CM, Ball TB, Fowke KR.

Abstract

Aberrant immune activation is a strong correlate of HIV disease progression, but little is known about how immune activation alters susceptibility to HIV infection. Susceptibility to HIV infection varies between individuals, but the immunological determinants of HIV transmission are not well understood. Here, we present evidence from studies of HIV transmission in the context of clinical trials and HIV-exposed seronegative (HESN) cohorts that implicates elevated immune activation as a risk factor for acquiring HIV. We propose a model of protection from infection based on a phenotype of low baseline immune activation referred to as immune quiescence. Immune quiescence is evidenced by reduced expression of T cell activation markers, low levels of generalized gene transcription and low levels of proinflammatory cytokine and chemokine production in the periphery and genital mucosa of HESN. Since HIV preferentially replicates in activated CD4+ T cells, immune quiescence may protect against infection by limiting HIV target cell availability. Although the determinants of immune quiescence are unclear, several potential factors have been identified that may be involved in driving this phenotype. HESN were shown to have elevated proportions of regulatory T cells (Tregs), which are known to suppress T cell activation. Likewise, proteins involved in controlling inflammation in the genital tract have been found to be elevated in HESN. Furthermore, expression of interferon regulatory factor 1 (IRF-1) is reduced in HESN as a consequence of genetic polymorphisms and differential epigenetic regulation. Since IRF-1 is an important regulator of immune responses, it may play a role in maintaining immune quiescence. Based on this model, we propose a novel avenue for HIV prevention targeted based on reducing host mucosal immune activation.

J Infect Dis. 2014 Jan 12. [Epub ahead of print]

Association of sex work with reduced activation of the mucosal immune system.

Lajoie J, Kimani M, Plummer FA, Nyamiobo F, Kaul R, Kimani J, Fowke KR.

Abstract

Background. Unprotected intercourse and seminal discharge are powerful activators of the mucosal immune system and are an important risk factors for HIV transmission. This study was designed to determine if female sex work is associated with changes in the mucosal immunity.

Methods. Cervico vaginal lavage and plasma from 122 HIV uninfected FSW women (FSW) and 44 HIV uninfected low-risk non-FSW from the same socioeconomic district of Nairobi were analyzed for evidence of immune activation (IA). The cervico-mononuclear cells (CMC) were analyzed for cellular activation by flow cytometry.

Results. Lower IA was observed in the FSW compared to the low-risk as demonstrated by the lower level of MIP-3α (p<0.001), ITAC (p<0.001), MIG (p.0001), IL-1α (p<0.001), IL-1β (p<0.001), IL-1Rα (p=0.0002), IL-6 (p<0.001), IL-8 (p<0.001), IL-10 (p=0.01), IP-10 (p=0.0001), MDC (p<0.001), MIP-1α, (p<0.001), MIP-1β (p=0.005), MCP-1 (p=0.03) and TNF-α (p=0.006). Significant differences were noted as early as 1 year following initiation of sex work and increased with duration of sex work.

Conclusion. This study showed that sex work is associated with important changes in the mucosal immune system. By analyzing chemokine/cytokine levels and CMC activation, we observed a lower mucosal IA in HIV uninfected FSW compared to low-risk women.

Journal of Virology

Published ahead of print 12 March 2014, doi: 10.1128/JVI.00187-14

Association between Cellular Immune Activation, Target Cell Frequency, and Risk of Human Immunodeficiency Virus Type-1 Superinfection

Catherine A. Blish1,2#, Ozge C. Dogan1, Walter Jaoko3, R. Scott McClelland2,3,4,5, Kishorchandra Mandaliya6, Katherine Odem-Davis1, Barbra A. Richardson5,7,8 and Julie Overbaugh1

ABSTRACT 

We performed a case-control study of women at risk of HIV-1 superinfection to understand the relationship between immune activation and HIV-1 acquisition. An increase in the frequency of HIV-1 target cells, but not in other markers of T cell activation, was associated with a 1.7-fold increase in the odds of superinfection. This suggests that HIV-1 acquisition risk is influenced more by the frequency of target cells than by the generalized level of immune activation.

Updates on SB728-T, a CCR5-Targeting Gene Therapy

Recently there have been two widely publicized updates relating to SB728-T, a gene therapy for HIV infection developed by Sangamo BioSciences. On Wednesday March 5th the New England Journal of Medicine (NEJM) published results from a phase I study conducted by Pablo Tebas and colleagues at the University of Pennsylvania, and on the following day at CROI 2014 Gary Blick* presented new data derived from subsequent trials. The therapy is technologically complex: it involves extracting CD4 T cells from HIV-positive individuals and then modifying them with a method that aims to disable the gene that encodes the CCR5 receptor (which most HIV variants use as a foothold to gain entry into cells). The CD4 T cells are then expanded in number and ultimately infused back into the individual, typically with around 10% successfully modified so that they no longer express CCR5. The method for disabling the CCR5 gene involves an enzyme called a zinc finger nuclease (ZFN), which targets and breaks the DNA containing the gene; cellular repair enzymes then stitch the DNA back together in a way that prevents the gene from making a functional CCR5 receptor. The ZFN is delivered into the CD4 T cells by an adenovirus vector during the laboratory modification procedure. The goal of the therapy is to create a population of CD4 T cells that are resistant to infection by HIV.

The results described in NEJM relate to a clinical trial begun in 2009. There were 12 participants, all receiving antiretroviral therapy (ART): six classified as immunological responders with CD4 T cell counts above 450 and a nadir of no lower than 300, and six immunological non-responders with relatively low CD4 T cell counts despite HIV suppression (between 200 and 500 after a minimum of two years of ART). The primary purpose of the study was to evaluate the safety of a single infusion of gene-modified CD4 T cells, with secondary analyses including CD4 T cell count changes, persistence (and trafficking to gut mucosa) of modified cells, and viral load measurements.

CD4 T cell counts increased in all participants, although the paper notes there was variation between individuals, with seven experiencing large increases and the remainder more modest changes. After 36 weeks of follow up, the median increase was 615 cells. CD4/CD8 ratios, which are typically slow to improve on ART alone, rose significantly from a median of 0.99 at baseline to 2.62 after one week, before declining to 1.14 at week 36. Tracking the gene-modified CD4 T cells is complex, because only approximately 25% show a consistent, quantifiable genetic signature associated with the CCR5 gene disruption; the number measured by this technique is therefore multiplied by four to estimate the total. The median number of gene-modified CD4 T cells in blood was 250 cells per cubic millimeter one week after infusion, representing 13.9% of CD4 T cells, but declined thereafter with an average half-life of 48 weeks. Modified CD4 T cells remain detectable in the blood of all participants, and in the individual followed for the longest period (3.5 years), the level is now 13 cells per cubic millimeter, representing 1.7% of circulating CD4 T cells. Among 11 participants who agreed to repeat rectal biopsies, the median frequency of gene-modified cells was 0.8% of rectal mononuclear cells at day 21 after infusion with subsequent measurements ranging from 0.2-0.4%.

To assess effects on viral load, ART was interrupted in the six immune responder participants four weeks after the CD4 T cell infusion. The duration of the interruption was set at 12 weeks, but in two cases ART was restarted early (due to concern about rapidly rising viral load and three consecutive viral loads over 100,000 copies, respectively). In three of the four remaining individuals, viral load rebounded but subsequently declined to levels similar to their historical pre-ART setpoints at the end of the interruption. In the final participant, a surprising result was observed: viral load rebounded but declined to undetectable levels just before ART was resumed (the viral load graph in the paper appears to indicate there may have been a slight, temporary blip after treatment was begun again, but this is not clarified in the text). Subsequent analyses revealed that this individual is heterozygous for the CCR5-Δ32 mutation, meaning that in his CD4 T cells one copy of the CCR5 gene is already disabled (each cell contains two CCR5 genes, one on each set of chromosomes). As a result, in CCR5-Δ32 heterozygotes there is less work for the gene therapy to do: it only has to disable one CCR5 gene in each CD4 T cell in order to completely abrogate expression of the CCR5 receptor.

The need to disable two CCR5 genes per cell in most recipients adds an additional wrinkle to attempts to measure the number of CD4 T cells modified by the approach. Because laboratory studies indicate that approximately 33% of modified CD4 T cells have both CCR5 genes disabled, the estimated number of modified cells has to be multiplied by 1/3 to reach an approximate number of CD4 T cells that completely lack CCR5 receptor expression. In CCR5-Δ32 heterozygotes, the multiplier is 2/3. Using these formulas, the researchers were able to demonstrate a statistically significant inverse correlation (rho = -0.90, P=0.037) between the estimated numbers of CD4 T cells lacking CCR5 and the viral load decline during the ART interruption, although this is not reported in the paper itself but rather in figure S7 of the supplementary appendix.

Side effects from the administration of the CD4 T cells were generally mild to moderate infusion reactions comprising transient fever, chills, myalgia, arthralgia, and headache. In one case these symptoms were severe enough to lead to a visit to the emergency room within 24 hours after the infusion. A temporary garlic-like body odor was common after infusion due to the metabolism of the substance DMSO, which is used as a cryopreservative during the storage of the extracted CD4 T cells.

The media coverage of the NEJM paper has generally failed to note that the data are not new; Carl June first presented the trial at CROI in 2011. The results have informed the design of several subsequent studies being conducted by Sangamo BioSciences, including those covered in the presentation by Gary Blick at CROI 2014. Specifically, the apparent correlation between numbers of gene-modified cells and viral load reductions spurred an evaluation of whether the immunosuppressive drug cyclophosphamide (Cytoxan) could be used to deplete CD4 T cells prior to the infusion and thereby enhance the uptake of the modified CD4 T cells (essentially create immunological “space” for the new cells to expand into).

Blick reported results involving three different Cytoxan doses: 200mg, 500mg and 1000mg per meter squared. There were three, six and three participants in each dose group respectively. Two individuals receiving 500mg withdrew consent due to nausea and vomiting, and the protocol was subsequently amended to allow prophylactic antiemetic treatment prior to Cytoxan administration. Six weeks after receiving the CD4 T cell infusions (ranging from around 8-35 billion cells), participants underwent a 16-week ART interruption, with the exception of an individual in the 200mg group whose viral tropism (CCR5 vs. CXCR4) could not successfully be evaluated. Blick reported that the highest numbers of gene-modified CD4 T cells were seen in recipients of the 1000mg Cytoxan dose. Initial CD4 T cell count increases also appeared to be somewhat greater in this group. However both of these measures seemed to decline to levels that overlapped with the other groups by the end of the ART interruption. In terms of viral load, one individual in the 1000mg Cytoxan dose group experienced a decline of close to 2 logs from the peak during ART interruption, while another saw a drop to around 1 log below their pre-ART baseline; in other cases the drops were in the 0.3-1 log range. Two participants in the highest dose group remain off ART, based on protocol criteria that allowed the interruption to be continued if viral load stayed beneath 10,000 copies and CD4 T cell counts were maintained above 500 (the wisdom of this is could be questionable given recent evidence that cumulative exposure to detectable viral load is associated with an increased risk of mortality; levels of inflammatory biomarkers in these individuals were not reported). No statistical comparisons of the viral load outcomes between the different dose groups were provided in the presentation.

Based on these very limited numbers, Blick speculated that perhaps the highest Cytoxan dose is allowing the number of gene-modified CD4 T cells to get close to a level where a functional cure might be achieved. An additional arm administering 1,500mg of Cytoxan (preceded by prophylactic antiemetics) has now been added to the study. Blick also mentioned an individual under his care who is a participant in another Sangamo BioSciences clinical trial, which enrolled only CCR5-Δ32 heterozygotes (a design based on the promising data described in the NEJM paper). This person has now been off ART for over 31 weeks and continues to maintain viral load at or below the limit of detection (Sangamo BioSciences has previously provided updates on this individual via press releases at 7, 14 and 20 weeks of follow up). The complete data from this trial has not yet been presented or published.

Overall the results are encouraging, but preliminary. Many media stories have emphasized the exciting possibility of achieving ART-free containment of HIV, but it’s important to note that, as of now, there is only one CCR5-Δ32 heterozygous study participant who has maintained viral load levels beneath detection for an extended period. Because the CCR5-Δ32 heterozygote described in the NEJM paper restarted ART, it is not known if viral load would have remained controlled in that case. For the two individuals in the Cytoxan study who remain off ART, further follow up and additional studies are needed to assess if the relatively low but detectable viral load is leading to elevated inflammation, as is typical in untreated HIV infection, or if the gene therapy is ameliorating those effects.

The mechanism of viral load control also needs to be better understood; Dale Ando from Sangamo BioSciences has presented evidence that improved HIV-specific CD8 T cell responses may be playing a role, possibly suggesting that, in some cases, gene-modified HIV-specific CD4 T cells have been created that are protected from HIV infection and therefore able to provide appropriate help to CD8 T cells. As yet however, no data on HIV-specific CD4 T cell responses has been reported (at least to my knowledge). Because the play of chance would influence how many HIV-specific CD4 T cells are extracted and successfully modified by SB728-T for a given individual, this could be a potential contributor to the heterogeneous outcomes seen in the trials, along with other immunological factors such as variation in HLA genes that affect the quality and targeting of virus-specific CD4 and CD8 T cells responses. A better understanding of these issues might help further refine the approach in order to improve success (e.g. perhaps combining with therapeutic vaccination to try and boost HIV-specific T cell immunity prior to ART interruption). Although it’s only given for a short period, Gary Blick’s report indicates Cytoxan may have some drawbacks as an adjunctive modality.

Researchers are also pursuing the possibility of introducing CCR5 modification at the level of stem cells (based on the cure achieved in Timothy Brown, who received a stem cell transplant from a CCR5-Δ32 homozygote), although there are significant barriers to making this type of delivery possible in people who do not have cancer diagnoses requiring stem cell transplantation.

* Some community members with long memories were surprised to see Blick presenting these data. In the past Blick has been involved in studies of a controversial purported therapy called extracorporeal hyperthemia (a procedure for heating the blood outside the body that was associated with some recipient deaths), which briefly drew publicity, and harsh criticism, in the early 1990s. Blick is still listed as holding patents on hyperthermia, both as a treatment for HIV and hepatitis C.

N Engl J Med. 2014 Mar 6;370(10):901-10. doi: 10.1056/NEJMoa1300662.

Gene editing of CCR5 in autologous CD4 T cells of persons infected with HIV.

Tebas P1, Stein D, Tang WW, Frank I, Wang SQ, Lee G, Spratt SK, Surosky RT, Giedlin MA, Nichol G, Holmes MC, Gregory PD, Ando DG, Kalos M, Collman RG, Binder-Scholl G, Plesa G, Hwang WT, Levine BL, June CH.

Abstract

BACKGROUND: CCR5 is the major coreceptor for human immunodeficiency virus (HIV). We investigated whether site-specific modification of the gene ("gene editing")--in this case, the infusion of autologous CD4 T cells in which the CCR5 gene was rendered permanently dysfunctional by a zinc-finger nuclease (ZFN)--is safe.

METHODS: We enrolled 12 patients in an open-label, nonrandomized, uncontrolled study of a single dose of ZFN-modified autologous CD4 T cells. The patients had chronic aviremic HIV infection while they were receiving highly active antiretroviral therapy. Six of them underwent an interruption in antiretroviral treatment 4 weeks after the infusion of 10 billion autologous CD4 T cells, 11 to 28% of which were genetically modified with the ZFN. The primary outcome was safety as assessed by treatment-related adverse events. Secondary outcomes included measures of immune reconstitution and HIV resistance.

RESULTS: One serious adverse event was associated with infusion of the ZFN-modified autologous CD4 T cells and was attributed to a transfusion reaction. The median CD4 T-cell count was 1517 per cubic millimeter at week 1, a significant increase from the preinfusion count of 448 per cubic millimeter (P<0.001). The median concentration of CCR5-modified CD4 T cells at 1 week was 250 cells per cubic millimeter. This constituted 8.8% of circulating peripheral-blood mononuclear cells and 13.9% of circulating CD4 T cells. Modified cells had an estimated mean half-life of 48 weeks. During treatment interruption and the resultant viremia, the decline in circulating CCR5-modified cells (-1.81 cells per day) was significantly less than the decline in unmodified cells (-7.25 cells per day) (P=0.02). HIV RNA became undetectable in one of four patients who could be evaluated. The blood level of HIV DNA decreased in most patients.

CONCLUSIONS: CCR5-modified autologous CD4 T-cell infusions are safe within the limits of this study. (Funded by the National Institute of Allergy and Infectious Diseases and others; ClinicalTrials.gov number, NCT00842634.).

N Engl J Med. 2014 Mar 6;370(10):968-9. doi: 10.1056/NEJMe1400593.

Engineering cellular resistance to HIV.

Kay MA1, Walker BD.

The Relevance of the CD4/CD8 Ratio in the Antiretroviral Therapy Era

An inversion of the normal ratio between CD4 and CD8 T cells was noted in the very first case reports of individuals with AIDS, before HIV was even identified. Although a number of studies subsequently reported an association between the CD4/CD8 ratio and risk of disease progression, CD4 T cell counts were more extensively researched and became the most commonly used surrogate marker of immune system health in HIV-positive people. In recent years, data has emerged from cohort studies of very elderly HIV-negative people indicating that, in this population, the CD4/CD8 ratio is a strong predictor of the risk of aging-associated diseases and mortality. This new information prompted the research group of Sergio Serrano-Villar at the University Hospital Ramón y Cajal in Madrid to evaluate whether measurement of the CD4/CD8 ratio may provide information about the risk of morbidity and mortality in HIV-positive people in the current era of antiretroviral therapy (ART).

Last year, Serrano-Villar and colleagues published preliminary studies showing associations between the CD4/CD8 ratio and levels of immune activation and markers of immune system aging (immunosenescence) in HIV infection. In two new papers published in HIV Medicine and PLoS One, they now extend these findings and report statistically significant associations between the CD4/CD8 ratio and markers of age-associated disease and the clinical outcomes of non-AIDS-related morbidity and mortality in HIV-positive people. The PLoS One study assesses the link between the CD4/CD8 ratio and several dissimilar non-AIDS diseases in people on ART, and reports a significant association in each case. Separate analyses of participants with low CD4 nadirs (<200 cells) and those with good CD4 recovery on ART (to >350 cells) find that CD4/CD8 ratios remain independently associated with non-AIDS events in each subgroup.

In discussing the implications of their findings, the researchers write: “patients with failure to increase the CD4/CD8 ratio despite achieving full immunovirological response to ART might benefit from screening programs and aggressive management of concomitant risk factors for age-associated disease.” They also note that, since there appears to be a relationship between immune activation and the CD4/CD8 ratio, such individuals may be prime candidates for inclusion in clinical trials of interventions that aim to reduce immune activation and associated adverse clinical outcomes. However, several limitations to the study are acknowledged, and the authors stress that: “before using the CD4/CD8 ratio as a surrogate of serious non-AIDS-related illnesses, these results should be reproduced in larger and prospective studies.”

As it currently stands, there are very few reports of therapies capable of improving low CD4/CD8 ratios in HIV-positive people on ART. IL-7 increases both CD4 and CD8 T cell numbers, and according to a new study published in PLoS Pathogens, may reduce markers of inflammation, but the clinical impact of this cytokine has yet to be evaluated. A further complication is that the company behind IL-7, Cytheris, recently went bankrupt, leaving the rights to its development for HIV in the hands of the French Agence Nationale de Recherche sur le SIDA (ANRS) and a small biotech named Cognate Biosciences. SB-728-T, a gene therapy under development by Sangamo Biosciences, has been reported to significantly improve CD4/CD8 ratios in people on ART, but the duration of the effect is unclear and the company appears uninterested in developing the approach for people with suboptimal immune reconstitution (their focus is on attempting to achieve control of HIV replication after ART interruption). The therapy is also complex to administer because it involves the extraction, expansion and genetic modification of CD4 T cells, followed by reinfusion. A letter from TAG and many other community activists and organizations asking the company to continue to study the potential of SB-728-T to promote immune reconstitution fell on deaf ears.

Although not directly connected to the work of Sergio Serrano-Villar and colleagues, another study on the topic of the CD4/CD8 ratio in HIV infection was published online by the Journal of Immunology this past Monday. Marcus Buggert and a Swedish research team used a bioinformatics approach to explore the connections between several of the laboratory measures used to monitor HIV disease progression (including CD4 count and CD4/CD8 ratio) and a large suite of T cell markers that are perturbed by HIV infection (including activation, exhaustion and immunosenescence markers). Focusing primarily on untreated HIV infection, the researchers find that the CD4/CD8 ratio is the best predictor of the combined pathological changes to the T cell immune system that occur in HIV-positive people compared to uninfected controls. The paper concludes: “these findings are of particular interest to future therapy or cure studies, in which simple measurements are required to monitor ongoing pathological events of the T cell repertoire in HIV-infected subjects.”

HIV Med. 2014 Jan;15(1):40-9. doi: 10.1111/hiv.12081. Epub 2013 Sep 6.

The CD4:CD8 ratio is associated with markers of age-associated disease in virally suppressed HIV-infected patients with immunological recovery.

Serrano-Villar S, Moreno S, Fuentes-Ferrer M, Sánchez-Marcos C, Avila M, Sainz T, de Villar NG, Fernández-Cruz A, Estrada V. 

Abstract

OBJECTIVES: Inversion of the CD4:CD8 ratio (< 1) has been identified as a hallmark of inmmunosenescence and an independent predictor of mortality in the general population. We aimed to assess the association between the CD4:CD8 ratio and markers of age-associated disease in treated HIV-infected patients with good immunovirological response.

METHODS: A cross-sectional analysis was conducted in 132 HIV-infected adults on antiretroviral therapy (ART), with plasma HIV RNA < 50 HIV-1 RNA copies/mL for at least 1 year, CD4 count > 350 cells/μL and age < 65 years. We analysed the associations between the CD4:CD8 ratio and subclinical atherosclerosis [assessed using carotid intima-media thickness (IMT)], arterial stiffness [assessed using the augmentation index (AIx)], the estimated glomerular filtration rate (eGFR), muscle wasting and sarcopenia [assessed using appendicular lean mass/height(2) (ALM) measured by dual-energy X-ray absorptiometry (DEXA)].

RESULTS: CD4:CD8 ratio inversion was associated with higher IMT, lower eGFR and lower ALM (all values P < 0.05), but not with AIx. In multivariate analyses adjusted for age, sex, hypertriglyceridaemia, tobacco use and cumulative ART exposure, inversion of the CD4:CD8 ratio was independently associated with higher IMT [odds ratio (OR) 2.9; 95% confidence interval (CI) 1.2-7.1], arterial stiffness (OR 4.8; 95% CI 1.0-23.5) and lower eGFR (OR 5.2; 95% CI 1.0-64.4), but not sarcopenia (OR 0.7; 95% CI 0.2-2.7). These associations persisted when models were applied to subjects with nadir CD4 counts > 200 cells/μL and those with CD4 counts > 500 cells/μL.

CONCLUSIONS: The CD4:CD8 ratio in treated HIV-infected subjects with good immunovirological response is independently associated with markers of age-associated disease. Hence, it might be a clinically useful predictor of non-AIDS-defining conditions.

PLoS ONE 9(1): e85798. doi:10.1371/journal.pone.0085798 

Increased Risk of Serious Non-AIDS-Related Events in HIV-Infected Subjects on Antiretroviral Therapy Associated with a Low CD4/CD8 Ratio

Sergio Serrano-Villar, María Jesús Pérez-Elías, Fernando Dronda, José Luis Casado, Ana Moreno, Ana Royuela, José Antonio Pérez-Molina, Talia Sainz, Enrique Navas, José Manuel Hermida, Carmen Quereda, Santiago Moreno

Published: January 30, 2014DOI: 10.1371/journal.pone.0085798 

Abstract

Background

A low CD4/CD8 ratio has been identified in the general population as a hallmark of inmmunosenescence and a surrogate of all-cause mortality. We aimed to investigate in treated HIV-infected individuals the relationship between the CD4/CD8 ratio and serious non-AIDS events.

Methods

Case-control study within a prospective hospital-based cohort of HIV-infected subjects during at least one year of ART-mediated viral suppression. Cases were patients with serious non-AIDS events (non-AIDS malignancies, cardiovascular disease, and end-stage kidney disease), and controls individuals who did not developed non-AIDS events during follow-up. Data were analyzed using ROC analysis and multivariate logistic regression. Conditional logistic regression was performed in 200 cases/controls matched by age, sex, nadir CD4 and proximal CD4 counts.

Results

We analyzed 407 subjects (109 cases, 298 controls). The CD4/CD8 ratio was lower in cases (0.44 vs. 0.70, P<0.0001), with higher discriminatory ability for the detection of non-AIDS events than the CD4 count, CD8 count and nadir CD4. Multivariate analyses (adjusted for age, sex, nadir CD4, proximal CD4 count, year of ART initiation and ART duration) confirmed the independent association of a low CD4/CD8 ratio with the risk of non-AIDS morbidity (per CD4/CD8 ratio quartile decrease, OR, 2.9; 95% CI, 1.3–6.2) and non-AIDS mortality (OR, 2.8; 95% CI, 1.5–5.3).

Conclusions

The CD4/CD8 ratio provides additional information to the CD4 counts and nadir CD4 in treated HIV-infected individuals, since it is independently associated with the risk of non-AIDS-related morbidity and mortality. This association is robust and maintained within different subgroups of patients.

The Journal of Immunology

Published online before print February 3, 2014, doi: 10.4049/​jimmunol.1302596

Multiparametric Bioinformatics Distinguish the CD4/CD8 Ratio as a Suitable Laboratory Predictor of Combined T Cell Pathogenesis in HIV Infection

Marcus Buggert, Juliet Frederiksen, Kajsa Noyan, Jenny Svärd, Babilonia Barqasho, Anders Sönnerborg, Ole Lund, Piotr Nowak, and Annika C. Karlsson

Abstract

HIV disease progression is characterized by numerous pathological changes of the cellular immune system. Still, the CD4 cell count and viral load represent the laboratory parameters that are most commonly used in the clinic to determine the disease progression. In this study, we conducted an interdisciplinary investigation to determine which laboratory parameters (viral load, CD4 count, CD8 count, CD4 %, CD8 %, CD4/CD8) are most strongly associated with pathological changes of the immune system. Multiparametric flow cytometry was used to assess markers of CD4+ and CD8+ T cell activation (CD38, HLA-DR), exhaustion (PD-1, Tim-3), senescence (CD28, CD57), and memory differentiation (CD45RO, CD27) in a cohort of 47 untreated HIV-infected individuals. Using bioinformatical methods, we identified 139 unique populations, representing the “combined T cell pathogenesis,” which significantly differed between the HIV-infected individuals and healthy control subjects. CD38, HLA-DR, and PD-1 were particularly expressed within these unique T cell populations. The CD4/CD8 ratio was correlated with more pathological T cell populations (n = 10) and had a significantly higher average correlation coefficient than any other laboratory parameters. We also reduced the dimensionalities of the 139-unique populations by Z-transformations and principal component analysis, which still identified the CD4/CD8 ratio as the preeminent surrogate of combined T cell pathogenesis. Importantly, the CD4/CD8 ratio at baseline was shown to be significantly associated with CD4 recovery 2 y after therapy initiation. These results indicate that the CD4/CD8 ratio would be a suitable laboratory predictor in future clinical and therapeutic settings to monitor pathological T cell events in HIV infection.

Reviewing Strategies for Draining HIV Reservoirs

The April issue of Human Vaccines & Immunotherapeutics features an excellent open access review by Thomas Rasmussen and colleagues describing approaches to eliminating HIV reservoirs that are advancing into clinical trials.

Prominently featured are histone deacetylase (HDAC) inhibitors, which have emerged as lead candidates for liberating latent HIV from cellular lockdown. The paper offers detailed descriptions of the various HDAC inhibitors being studied—or considered for study—and notes that the authors, who are based at the University of Aarhus in Denmark, have launched a phase I trial of one such drug, panobinostat, in people with HIV. Also cited is their companion study in the January issue of the same journal (now available open access) that compares the activity of several HDAC inhibitors in clinical development. Among the less-discussed aspects of HDAC inhibitors that are highlighted in the review are the potential for both pro- and anti-inflammatory effects depending on the individual compound (the latter effect could conceivably be beneficial in HIV infection).

Since the review was published, additional relevant data has emerged from CROI: as mentioned in a previous post, results from Sharon Lewin’s trial of vorinostat were presented, and George Wei from Gilead Sciences gave a glimpse at the first in vitro data on romidepsin, reporting that it is 500 times more potent at reactivating latent HIV than vorinostat (the ACTG is now planning a phase I trial). Not all the news was positive, however: as discussed in an April 4th Nature Medicine news article by Elie Dolgin, Antony Cillo described study results indicating that HDAC inhibitors may only induce a small fraction of latently infected cells to produce viral proteins, possibly meaning that combinations of anti-latency approaches will be needed to comprehensively target HIV reservoirs.

Potentially supplementing the armamentarium are immune-based strategies such as those targeting toll-like receptors (TLRs). TLRs are involved in the recognition of pathogenic organisms and, as the review by Rasmussen and colleagues explains, there is evidence that compounds that stimulate TLRs (TLR agonists) can induce HIV expression by latently infected cells. They reference their own study of a TLR9 agonist named CPG 7909 as a pneumococcal vaccine adjuvant in people with HIV, that—in an example of scientific kismet—allowed them the opportunity to go back and investigate its effect on the latent HIV reservoir. The results were reported at CROI and, while exploratory, showed a significant mean reduction in HIV DNA levels of 12.6% after each immunization. The decline in HIV DNA correlated with an increase in HIV-specific CD8 T cells expressing CD107a (a marker for their release of cell-killing substances) and the chemokine MIP1β. This study was subsequently published on April 26 in the journal PLoS One. 

Other research groups are also looking at the anti-latency properties of TLR agonists. At CROI, Camille Novis from the laboratory of Alberto Bosque presented a poster showing that Pam3CSK4, which targets TLR2/1, was able to reactivate HIV from latently infected CD4 T cells without causing T cell activation. Romas Geleziunas has cited plans to study GS-9620, a TLR7 agonist, in several presentations describing the Gilead Sciences HIV eradication program (further details are included in his slides from the 2012 International Symposium HIV & Emerging Infectious Diseases).

The review by Rasmussen et al mentions the cytokine IL-7 as a possible immunotherapy to reduce HIV reservoirs, under evaluation in a trial named Eramune 01 at the time the paper was written. Results debuted at CROI in a poster and, disappointingly, IL-7 added to intensified antiretroviral therapy (ART) was not successful in reducing HIV DNA levels (there was some evidence it may have slightly increased levels due to causing transient proliferation of latently infected CD4 T cells). Despite this outcome, IL-7 had a beneficial impact on CD4 and CD8 T cell counts, as seen in prior studies, and remains the lead candidate for enhancing immune reconstitution in individuals with poor CD4 recovery despite HIV suppression by ART (in this population, the increased risk of morbidity and mortality is a far greater concern than small changes in HIV DNA levels).

The topic of targeting HIV reservoirs is the subject of another recent review by Christine Katlama and colleagues in The Lancet, but this paper is not open access and requires a subscription (although it may eventually appear in PubMed’s full text archive).  

Update 4/20/13: The April issue of Clinical Pharmacology & Therapeutics includes a free commentary on HIV cure research by Christine Durand and Charles Flexner, and the journal has also made a review on the subject from the January issue (by Kirston Barton, Brandon Burch, Natalia Soriano-Sarabia and David Margolis) available open access. Abstracts and links added below.  

Update 4/29/13: Sadly, it seems that one of the authors of the Human Vaccines & Immunotherapeutics review, Dr. Ole Søgaard, has rather shot himself in the foot by contributing to a wildly irresponsible article in the UK newspaper the Daily Telegraph regarding his group's ongoing research. The article misstates the mechanism of action of HDAC inhibitors (stating that they "strip" HIV DNA from latently infected cells when, at best, they prompt the HIV DNA into transcribing proteins) and uncritically reports Dr. Søgaard's apparent confidence in the ability of panobinostat to reactivate latent HIV; as noted in the Nature Medicine news article linked to above, there are many outstanding questions regarding the ability of HDAC inhibitors to accomplish this task.

The Telegraph also mentions the use of immune-based therapies to prompt the killing of latently infected cells (assuming the cells are successfully induced to express HIV); my best guess is that, in the case of Dr. Søgaard's group, this is a reference to their data on the TLR9 agonist CPG 7909, although the article is unconscionably vague on this point. Also cited, again vaguely, are plans by Lucy Dorrell's research group in the UK to conduct a trial in which HDAC inhibition is combined with therapeutic vaccination. This research is undoubtedly very important but for the article to suggest that it means that scientists are on the brink of an HIV cure is shockingly erroneous and misleading. The promise of these approaches can only be evaluated when the results of the studies become available. Since the trials combining HDAC inhibitors and immune-based therapies (whether TLR agonists or therapeutic vaccines) have yet to start it is extremely unlikely that the data will be available in "months" as the subhead of the article claims.

Inevitably, the Daily Telegraph piece has triggered the media equivalent of a game of telephone in which other outlets rehash the story while managing to mangle the facts further (e.g. see the Daily Mail, which elevates the mistatement about how HDAC inhibitors work into a subhead: "Danish scientists using a technique which strips HIV virus from human DNA"). 

Update 5/2/13: The Daily Telegraph article has now been edited to correct the erroneous and misleading statements in the subhead and the body of the story (the title, however, currently remains). For example, "expecting results" in the opening para has been changed to "hoping for results," and several quotes have been modified to highlight the uncertainty regarding what proportion of the latent HIV reservoir can be activated by HDAC inhibitors. The suggestion that participants in the panobinostat trial might be cured of HIV infection has also been removed. 

Additonally, Dr. Søgaard has kindly posted a comment below that addresses the article and clarifies the views of his research group. 

Update 5/3/13: Hopefully the last update on this, the Aarhus University Hospital has now issued a formal correction to the Telegraph story. And the Telegraph has changed the title of the article to "Scientists' hope for HIV cure."

Hum Vaccin Immunother. 2013 Apr 1;9(4). [Epub ahead of print]

Eliminating the latent HIV reservoir by reactivation strategies: Advancing to clinical trials.

Rasmussen TA, Tolstrup M, Winckelmann A, Ostergaard L, Søgaard OS.

Department of Infectious Diseases; Aarhus University Hospital; Denmark.

Abstract

Combination antiretroviral therapy (cART) has transformed HIV from a deadly to a chronic disease, but HIV patients are still burdened with excess morbidity and mortality, long-term toxicities from cART, stigmatization, and insufficient access to cART worldwide. Thus, a cure for HIV would have enormous impact on society as well as the individual. As the complexity and mechanisms of HIV persistence during therapy are being unraveled, new therapeutic targets for HIV eradication are discovered. Substances that activate HIV production in the latently infected cells have recently received much attention. By turning on expression of latent HIV proviruses, reactivation strategies could contribute to the eradication HIV infection. Compounds that are currently being or soon to be tested in clinical trials are emphasized. The results from these trials will provide important clues as to whether or not reactivating strategies could become significant components of a cure for HIV.

Lancet. 2013 Mar 28. pii: S0140-6736(13)60104-X. doi: 10.1016/S0140-6736(13)60104-X. [Epub ahead of print]

Barriers to a cure for HIV: new ways to target and eradicate HIV-1 reservoirs.

Katlama C, Deeks SG, Autran B, Martinez-Picado J, van Lunzen J, Rouzioux C, Miller M, Vella S, Schmitz JE, Ahlers J, Richman DD, Sekaly RP.

Department of Infectious Diseases, Pierre and Marie Curie University, Pitié-Salpêtriere Hospital, Paris, France.

Abstract

Antiretroviral therapy for HIV infection needs lifelong access and strict adherence to regimens that are both expensive and associated with toxic effects. A curative intervention will be needed to fully stop the epidemic. The failure to eradicate HIV infection during long-term antiretroviral therapy shows the intrinsic stability of the viral genome in latently infected CD4T cells and other cells, and possibly a sustained low-level viral replication. Heterogeneity in latently infected cell populations and homoeostatic proliferation of infected cells might affect the dynamics of virus production and persistence. Despite potent antiretroviral therapy, chronic immune activation, inflammation, and immune dysfunction persist, and are likely to have important effects on the size and distribution of the viral reservoir. The inability of the immune system to recognise cells harbouring latent virus and to eliminate cells actively producing virus is the biggest challenge to finding a cure. We look at new approaches to unravelling the complex virus-host interactions that lead to persistent infection and latency, and discuss the rationale for combination of novel treatment strategies with available antiretroviral treatment options to cure HIV.

Clinical Pharmacology & Therapeutics (2013); 93 5, 382–384. doi:10.1038/clpt.2013.22

Commentaries

HIV Cure: Knocking on the Door

C M Durand1 and C Flexner1,2

1Division of Infectious Diseases, Department of Medicine, Johns Hopkins University School of Medicine and Bloomberg School of Public Health, Baltimore, Maryland, USA

2Division of Infectious Diseases, Department of Medicine, and Division of Clinical Pharmacology, Department of Pharmacology and Molecular Sciences and Department of International Health, Johns Hopkins University School of Medicine and Bloomberg School of Public Health, Baltimore, Maryland, USA

Abstract

Although major advances in drug development and public health are helping to control the HIV/AIDS epidemic, there is a strong rationale for pursuing a more definitive cure. Several bold but unproven strategies for HIV eradication are reviewed in this issue of CPT, including novel drugs, gene therapy, and bone marrow transplantation (BMT). Early results, including one probable case of HIV eradication in a leukemia patient, are intriguing but raise many questions.

Clinical Pharmacology & Therapeutics (2013); 93 1, 46–56. doi:10.1038/clpt.2012.202

State of the Art

Prospects for Treatment of Latent HIV

K M Barton1, B D Burch2, N Soriano-Sarabia2 and D M Margolis1,2,3

1Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA

2Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA

3Department of Epidemiology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA

Abstract

Recent advances in antiretroviral therapy (ART) have drastically improved the quality of life for people with HIV infection. However, owing to the persistence of latent HIV in the presence of therapy, patients must remain on therapy indefinitely. Currently, the solution to the HIV pandemic rests on the prevention of new infections and many decades of ART for the steadily expanding number of people infected worldwide. ART is costly, requires ongoing medical care, and can have side effects, thereby preventing its universal availability. Therefore, to escape the ironic burdens of therapy, efforts have begun to develop treatments for latent HIV infection. Current approaches propose either complete eradication of infection or induction of a state of stringent control over viral replication without ART. This review will discuss these strategies in detail and their potential for clinical development.

Lymph Node Fibrosis, CD4 T Cells, and Immune Reconstitution

One of the less well-publicized consequences of the persistent immune activation caused by HIV infection is a type of scarring damage to lymph tissues described as fibrosis. Some early studies of lymph nodes from HIV-infected individuals reported evidence of this problem, but it wasn’t until the publication of a study by the research group of Ashley Haase in 2002 that a connection was made between the extent of fibrosis (as measured by deposition of collagen) and maintenance of CD4 T-cell numbers. Haase and colleagues showed that there was an inverse correlation between lymph node fibrosis and the number of CD4 T cells measurable in the same node. Importantly, they also found that the degree of fibrosis was significantly associated with the magnitude of CD4 T-cell increases after initiation of antiretroviral therapy, with greater fibrosis linked to poorer CD4 T-cell recovery.

In the subsequent years, Haase’s group has delved further into the mechanisms underlying these findings. In 2011, they reported that fibrosis disrupts the fibroblastic reticular cell (FRC) network, which forms pathways along which T cells travel on their journey through lymph tissue. The FRC network provides fuel for maintaining T-cell health in the form of the cytokine IL-7, and fibrotic damage to FRCs was found to inhibit the ability of T cells to access IL-7, leading to cell death. The study also identified the cytokine lymphotoxin-β as critical for maintaining FRCs, and suggested that loss of CD4 T cells was linked to a decline in lymphotoxin-β production, further exacerbating the problem created by the fibrosis.

In an important paper published last summer that I neglected to write about at the time, the researchers confirm that CD4 T cells are the major source of lymphotoxin-β, thus demonstrating that fibrosis creates a vicious cycle by depleting factors needed for CD4 T-cell survival, leading to CD4 T-cell loss, which in turn removes a critical source of factors needed to maintain the FRC network that provides sustenance to CD4 T cells. The study offers evidence that this problem is relevant to not just HIV infection but also CD4 depletion after chemotherapy and irradiation in individuals with cancer. 

In an accompanying editorial, Steve Deeks from UCSF notes that the research suggests possible interventions that could be evaluated in the context of HIV-induced persistent immune activation and CD4 T-cell depletion: “These experimental interventions include drugs that remove pro-inflammatory pathogens and microbial products (eg, valganciclovir for CMV, rifaximin for gut microbes, sevelamer for lipopolysaccharide), drugs that directly prevent fibrosis (eg, angiotensin II receptor antagonists* and ACE inhibitors), and drugs that have more broad effects in reducing inflammation (eg, statins, nonsteroidal antinflammatory drugs, methotrexate, and mesalamine).” Deeks also points out that the best way of avoiding fibrotic damage to the lymph nodes is to suppress HIV replication as soon as possible after infection.

A more recent study, published in the Journal of Infectious Diseases this past October, offers further support for the conclusions of Haase et al. Researchers led by Brian Tabb from the laboratory of Jacob Estes at NCI–Frederick report that blocking the inflammatory cytokine TNF alpha in early SIV infection reduced lymphoid-tissue fibrosis and was associated with better preservation of CD4 T-cell numbers in macaques (without affecting SIV viral load). The authors conclude: “This initial study highlights the importance of early inflammatory responses to lentiviral infections and underscores the need for additional studies to ascertain the potential clinical benefits of adjunctive therapies to attenuate these responses and to improve patient outcomes.”

*TAG’s new HIV project director, Tim Horn, has recently led an effort to support AIDS Clinical Trial Group investigators seeking to obtain the angiotensin II receptor antagonist telmisartan (trade name: Micardis) from the manufacturer, Boehringer Ingelheim, for a study in people with HIV. Unfortunately, the company remains unwilling to provide drug for the planned trial, citing regulatory concerns. This situation highlights issues that will likely arise again in the future as investigators attempt to conduct exploratory studies of these types of potential adjunctive treatments in HIV infection: many of the candidate interventions are already indicated for other uses and are off-patent or toward the end of their patent life; additionally, the research is at such an early stage that it is probing questions of disease pathogenesis rather than carving a clear path toward an FDA-approved HIV indication. Activists are continuing to discuss possible approaches to addressing these issues in order to ensure that needed research can proceed.

Blood August 30, 2012 vol. 120 no. 9 1753-1754

HIV infection, lymphoid fibrosis, and disease

Steven G. Deeks

In this issue of Blood, Zeng and colleagues demonstrate in SIV-infected macaques and HIV-infected humans that CD4+ T cells actively maintain the fibroblastic reticular cell network in lymphoid tissues and that this network in turn is needed to maintain normal T-cell homeostasis and function.

Blood August 30, 2012 vol. 120 no. 9 1856–1867

Critical role of CD4 T cells in maintaining lymphoid tissue structure for immune cell homeostasis and reconstitution

Ming Zeng1, Mirko Paiardini2, Jessica C. Engram3, Greg J. Beilman4, Jeffrey G. Chipman4, Timothy W. Schacker5, Guido Silvestri2, and Ashley T. Haase1 

1Department of Microbiology, Medical School, University of Minnesota, Minneapolis, MN;

2Yerkes National Primate Research Center and Emory University, Atlanta, GA;

3University of Pennsylvania School of Medicine, Philadelphia, PA;

4Department of Surgery, University of Minnesota, Minneapolis, MN; and

5Department of Medicine, Medical School, University of Minnesota, Minneapolis, MN 

ABSTRACT

Loss of the fibroblastic reticular cell (FRC) network in lymphoid tissues during HIV-1 infection has been shown to impair the survival of naive T cells and limit immune reconstitution after antiretroviral therapy. What causes this FRC loss is unknown. Because FRC loss correlates with loss of both naive CD4 and CD8 T-cell subsets and decreased lymphotoxin-β, a key factor for maintenance of FRC network, we hypothesized that loss of naive T cells is responsible for loss of the FRC network. To test this hypothesis, we assessed the consequences of antibody-mediated depletion of CD4 and CD8 T cells in rhesus macaques and sooty mangabeys. We found that only CD4 T-cell depletion resulted in FRC loss in both species and that this loss was caused by decreased lymphotoxin-β mainly produced by the CD4 T cells. We further found the same dependence of the FRC network on CD4 T cells in HIV-1–infected patients before and after antiretroviral therapy and in other immunodeficiency conditions, such as CD4 depletion in cancer patients induced by chemotherapy and irradiation. CD4 T cells thus play a central role in the maintenance of lymphoid tissue structure necessary for their own homeostasis and reconstitution. 

J Infect Dis. (2012)

doi: 10.1093/infdis/jis643

First published online: October 19, 2012

Reduced Inflammation and Lymphoid Tissue Immunopathology in Rhesus Macaques Receiving Anti-TNF Treatment During Primary SIV Infection

Brian Tabb1,7, David R. Morcock1, Charles M. Trubey1, Octavio A. Quiñones2, Xing Pei Hao3, Jeremy Smedley4, Rhonda Macallister4, Michael Piatak Jr1, Levelle D. Harris5, Mirko Paiardini6, Guido Silvestri6, Jason M. Brenchley5, W. Gregory Alvord2, Jeffrey D. Lifson1 and Jacob D. Estes1 

1AIDS and Cancer Virus Program, SAIC-Frederick, Inc., Frederick National Laboratory for Cancer Research, Frederick, MD

2Statistical Consulting, Data Management Services, Inc., Frederick National Laboratory for Cancer Research, Frederick, MD

3Pathology and Histotechnology Laboratory, SAIC-Frederick, Inc., Frederick National Laboratory for Cancer Research, Frederick, MD

4Laboratory Animal Science Program, SAIC-Frederick, Inc., Frederick National Laboratory for Cancer Research, Frederick, MD

5Immunopathogenesis Unit, Lab of Molecular Microbiology, NIAID, NIH, Bethesda, MD

6Yerkes National Primate Research Center, Emory University, Atlanta, Georgia

7Present address: XYZ, Memphis, TN 

Abstract 

Background. HIV/SIV infections induce robust, generalized inflammatory responses that begin during acute infection and lead to pathological systemic immune activation, fibrotic damage of lymphoid tissues (LTs) and CD4+ T cell loss, pathogenic processes that contribute to disease progression.

Methods. To better understand the contribution of TNF, a key regulator of acute inflammation, to lentiviral pathogenesis, rhesus macaques (RMs) newly infected with SIVmac239 were treated for 12 weeks in a pilot study with adalimumab (Humira), a human anti-TNF mAb.

Results. Adalimumab did not affect plasma SIV RNA levels or measures of T-cell immune activation (CD38 or Ki67) in peripheral blood or lymph node T cells. However, compared to untreated RMs, adalimumab-treated RMs showed attenuated expression of pro-inflammatory genes, decreased infiltration of polymorphonuclear cells into the T cell zone (TZ) of LTs and weaker anti-inflammatory regulatory responses to SIV infection (i.e. fewer presumed alternatively activated (CD163+) macrophages, IL-10+ and TGFβ+ cells), along with reduced LT fibrosis and better preservation of CD4+ T cells.

Conclusions. While HIV/SIV replication drives pathogenesis, these data emphasize the contribution of the inflammatory response to lentiviral infection to overall pathogenesis, and suggest that early modulation of the inflammatory response may help attenuate disease progression.

J Infect Dis. first published online October 24, 2012

doi:10.1093/infdis/jis648

EDITORIAL:

Cooling off the Host Immune Response to Acute SIV Infection—Is Less More?

Nelson L. Michael

Immune Activation, Inflammation, and HIV Acquisition Risk

The geographic variation in the risk of HIV acquisition among heterosexuals has prompted extensive speculation and debate as to the underlying causes. The lack of a clear explanation has even fueled conspiracy theories, playing a prominent role in Thabo Mbeki’s disastrous embrace of AIDS denialism in South Africa and driving a campaign that insists—in the face of a mountain of evidence to the contrary—that nonsexual transmission is the answer. It has not helped that much of the research on the subject has focused on behavior, with hypotheses such those based on concurrent sexual partnerships being aggressively promoted by certain individuals even though many view the evidence supporting them as slim to non-existent (for a recent critique, see “HIV, logic and sex in Africa” by Lucy Allais and Francois Venter). Relatively speaking, biological explanations have received less attention, despite the fact that it is well known that the immunological environment in which HIV finds itself has a huge impact on its ability to replicate and thrive. Only a handful of published studies have looked at how geographic location can impact levels of immune activation, finding that background levels are significantly higher in locations on the African continent compared to Europe and the US. The first such study to specifically analyze immune activation in the genital tract (comparing women in Kisumu, Kenya and San Francisco, USA) was published only two years ago.

Several new papers report data potentially relevant to this topic. Researchers involved in the CAPRISA 004 trial, an evaluation of the preventive efficacy of a gel form of the antiretroviral tenofovir, describe results from an analysis of immune activation and HIV acquisition risk among trial participants (44 who acquired HIV infection and 37 who remained HIV-negative). Elevated systemic innate immune activation was a significant risk factor for HIV infection (odds ratio 11.27, 95% CI 1.84-69.09, p=0.009) while a quiescent innate immunity profile was associated with reduced risk (odds ratio 0.06, 95%CI 0.013-0.33, p=0.001). The data echo similar findings from a study of genital tract inflammation among CAPRISA 004 participants, which were presented at CROI in 2011 and further discussed at CROI this year by Quarraisha Abdool Karim. In those analyses, women with genital track inflammation were 14 times more likely to acquire HIV infection than those without. The researchers argue that strategies for dampening immune activation and inflammation should be considered in the context of biomedical HIV prevention research.  

Among the potential causes of genital tract inflammation and immune activation, sexually transmitted diseases obviously stand out, and many STDs have been reported to significantly increase HIV acquisition risk (including HSV-2, gonorrhoea, chlamydial infection, trichomoniasis, and bacterial vaginosis). A more recent addition to this list is Mycoplasma genitalium, and a study just published online by the journal Infection and Immunity suggests that, unsurprisingly, this effect is likely mediated by increased inflammation.

The question of whether human papilloma virus (HPV) has a role in enhancing HIV acquisition has not been clearly answered, but a review and meta-analysis in the journal AIDS finds that the available evidence is consistent with a doubling in risk (although no associations with specific genotypes were detectable). The authors stress that the findings require validation, but note that three of the studies they reviewed contained sufficient data to estimate the proportion of HIV infections that may have been attributable to the presence of HPV infection at baseline: in women in Zimbabwe and South Africa, the figures were 21% and 37%, respectively, and in heterosexual men in Kenya the estimate was 28%. A recommendation that emerges from these analyses is that the effect of HPV vaccination programs on HIV incidence should be evaluated, particularly as vaccine coverage of HPV genotypes improves.

Unfortunately, unlike HPV, no vaccine exists for other STDs. At one time it was hoped that syndromic treatment of STDs could significantly reduce HIV acquisition risk but promising results from an initial randomized controlled trial were not confirmed by subsequent studies. Similarly, suppression of HSV-2 with acyclovir did not prove efficacious in reducing HIV incidence. More recently, compelling evidence has emerged that inflammation and immune activation are critical factors underlying these apparent disconnects. In the case of HSV-2, a detailed study revealed that numbers of CCR5-expressing CD4 T cells and DC-SIGN-expressing dendritic cells are elevated in the genital tract of infected individuals, and that acyclovir treatment does not significantly alter this environment.

In the July 1, 2012 issue of the Journal of Infectious Diseases, researchers in South Africa report that symptomatic vaginal discharge, a criteria for syndromic STD diagnosis, is in fact a poor predictor of inflammation and the presence of laboratory-diagnosed STDs. Furthermore, levels of inflammation were significantly elevated among women with laboratory-diagnosed STDs regardless of whether they were symptomatic or asymptomatic. The latter paper prompted a commentary from Myron Cohen entitled “Classical Sexually Transmitted Diseases Drive the Spread of HIV-1: Back to the Future.” Cohen concludes: “the ‘hidden epidemic’ of classical STDs is squarely blocking optimal prevention of HIV-1 transmission. These STDs—symptomatic or asymptomatic—simply cannot be ignored. As we commit to combination HIV-1 prevention, we must redouble our efforts to think of every possible way to recognize and treat classical STDs. Surely this problem is no more impossible to attack or less important than any other part of the HIV-1 pandemic.”

J Infect Dis. (2012)

doi: 10.1093/infdis/jis465

First published online: July 24, 2012

Innate Immune Activation Enhances HIV Acquisition in Women, Diminishing the Effectiveness of Tenofovir Microbicide Gel

Vivek Naranbhai1,2, Salim S. Abdool Karim1,3, Marcus Altfeld2,4, Natasha Samsunder1, Raveshni Durgiah2, Sengeziwe Sibeko1, Quarraisha Abdool Karim1,3, William H. Carr2,4 and the CAPRISA004 TRAPS team

1CAPRISA – Centre for the AIDS Programme of Research in South Africa

2HIV Pathogenesis Programme, Nelson R. Mandela School of Medicine, Doris Duke Medical Research Institute, University of KwaZulu-Natal, Durban, South Africa

3Department of Epidemiology, Mailman School of Public Health, Columbia University, New York

4Ragon Institute of Massachusetts General Hospital, Massachusetts Institute of Technology and Harvard, Boston, Massachusetts

Abstract

The antiretroviral agent, tenofovir, formulated as a vaginal microbicide gel, reduces human immunodeficiency virus (HIV) acquisition by 39% in women. This study assessed the role of preexisting immune activation in HIV acquisition in women from the CAPRISA 004 trial, to identify potential strategies to increase the effectiveness of tenofovir gel. Systemic cytokine and cellular immune mediators (platelets and natural killer [NK] cells) were assessed in women at high risk for HIV assigned to either tenofovir or placebo gel in the CAPRISA 004 trial. Notwithstanding tenofovir gel use, women who acquired HIV had significantly higher systemic innate immune activation prior to infection than women who remained uninfected. Activation of both soluble (cytokine) and cellular (NK cells) immune mediators were associated with HIV acquisition, individually or in combination. Hence, an innate immune activation suppressant could be added to tenofovir gel as a potential combination gel strategy in developing the next generation of higher efficacy antiretroviral microbicides.

Infection and Immunity Published ahead of print 20 August 2012, doi: 10.1128/​IAI.00819-12

Persistent Mycoplasma genitalium infection of human endocervical epithelial cells elicits chronic inflammatory cytokine secretion

Chris L. McGowin1,#, Rochelle S. Annan1, Alison J. Quayle2, Sheila J. Greene2, Liang Ma1, Miriam M. Mancuso1, David Adegboye3 and David H. Martin1

1Department of Medicine; Section of Infectious Diseases, Louisiana State University Health Sciences Center, New Orleans, Louisiana, USA

2Department of Microbiology, Immunology and Parasitology, Louisiana State University Health Sciences Center, New Orleans, LA, USA

3Southern University at New Orleans, New Orleans, Louisiana, USA

ABSTRACT

Infection with Mycoplasma genitalium has been associated with male and female urogenital disease syndromes including urethritis, cervicitis, pelvic inflammatory disease (PID) and tubal-factor infertility. Basic investigations of mucosal cytotoxicity, microbial persistence and host immune responses are imperative to understanding these inflammatory urogenital syndromes, particularly in females considering the potential severity of upper tract infections. Herein, we report that M. genitalium can establish long-term infection of human endocervical epithelial cells that results in chronic inflammatory cytokine secretion and increased responsiveness to secondary toll-like receptor (TLR) stimulation. Using a novel quantitative PCR assay, M. genitalium was shown to replicate from 0-80 d post-inoculation (PI) during which, at most time points, the median ratio of M. genitalium organisms to host cells was ≤ 10 indicating that low organism burdens are capable of eliciting chronic inflammation in endocervical epithelial cells. This observation is consistent with clinical findings in women. Persistently-secreted cytokines predominately consisted of potent chemotactic and/or activating factors for phagocytes including IL-8, MCP-1 and MIP-1β. Despite persistent cytokine elaboration, no host cell cytotoxicity was observed except with super-physiologic loads of M. genitalium suggesting persistent infection occurs with minimal direct damage to the epithelium. However, it is hypothesized that chronic chemokine secretion with leukocyte trafficking to the epithelium could lead to significant inflammatory sequelae. Therefore, persistent M. genitalium infection could have important consequences for acquisition and/or pathogenesis of other STI, and perhaps explain the positive associations between this organism and Human Immunodeficiency Virus (HIV) shedding.

AIDS: POST ACCEPTANCE, 7 August 2012

doi: 10.1097/QAD.0b013e328358d908

HPV infection and increased risk of HIV acquisition. A systematic review and meta-analysis

Houlihan, Catherine F.; Larke, Natasha L.; Watson-Jones, Deborah; Smith-McCune, Karen K.; Shiboski, Stephen; Gravitt, Patti E.; Smith, Jennifer S.; Kuhn, Louise; Wang, Chunhui; Hayes, Richard

Abstract

Objectives: Human papillomavirus (HPV), one of the commonest sexually transmitted infections, may be a cofactor in HIV acquisition. We systematically reviewed the evidence for an association of HPV infection with HIV acquisition in women, heterosexual men and men who have sex with men (MSM).

Design: Systematic review and meta-analysis.

Methods: Studies meeting inclusion criteria in Pubmed, Embase and conference abstracts up to 29/07/2011 were identified. Random effects meta-analyses were performed to calculate summary hazard ratios (HR). Publication bias and statistical heterogeneity were evaluated and population attributable fractions (PAFs) calculated.

Results: Eight papers were included, with previously unpublished data from five authors. Seven studies found an association between prevalent HPV and HIV acquisition. Risk of HIV acquisition in women doubled with prevalent HPV infection with any genotype (HR = 2.06 (95%CI = 1.44-2.94), I2 = 0%), although adjustment for confounders was often inadequate. The effect was similar for high-risk (HR = 1.99 (95%CI = 1.54-2.56), I2 = 8.4%) and low-risk (HR = 2.01 (95%CI = 1.27-3.20), I2 = 0%) HPV genotypes with weak evidence of publication bias (P = 0.06). Two studies in men were identified: both showed an association between HPV infection and HIV acquisition. Unpublished data from one of two studies in women indicated an association between genotypes targeted by HPV vaccines and HIV acquisition. PAFs for HIV attributable to infection with any HPV genotype ranged between 21% and 37%.

Conclusion: If further studies validate the association between HPV infection and HIV acquisition, HPV vaccines may reduce HIV incidence in high HPV prevalence populations, in addition to preventing cervical cancer. HIV surveillance studies during implementation of HPV vaccine programmes are warranted.

J Infect Dis. (2012) 206 (1): 6-14.

doi: 10.1093/infdis/jis298

Symptomatic Vaginal Discharge Is a Poor Predictor of Sexually Transmitted Infections and Genital Tract Inflammation in High-Risk Women in South Africa

Koleka Mlisana1,2,3, Nivashnee Naicker1, Lise Werner1, Lindi Roberts4, Francois van Loggerenberg1, Cheryl Baxter1, Jo-Ann S. Passmore1,4,5, Anneke C. Grobler1, A. Willem Sturm6, Carolyn Williamson1,4,5, Katharina Ronacher7, Gerhard Walzl7 and Salim S. Abdool Karim1,8

1Centre for the AIDS Programme of Research in South Africa

2Department of Medical Microbiology, University of KwaZulu-Natal, Durban

3National Health Laboratory Service, Durban

4Institute of Infectious Diseases and Molecular Medicine, Faculty of Health Sciences, University of Cape Town

5National Health Laboratory Service, Cape Town

6Department of Infection Prevention and Control, University of KwaZulu-Natal, Durban

7Faculty of Health Sciences, University of Stellenbosch Medical School, Tygerberg, Cape Town, South Africa

8Department of Epidemiology, Columbia University, New York, New York

Abstract

Background. Diagnosis and treatment of sexually transmitted infections (STIs) is a public health priority, particularly in regions where the incidence of human immunodeficiency virus (HIV) infection is high. In most developing countries, STIs are managed syndromically. We assessed the adequacy of syndromic diagnosis of STIs, compared with laboratory diagnosis of STIs, and evaluated the association between STI diagnosis and the risk of HIV acquisition in a cohort of high-risk women. 

Methods. HIV-uninfected high-risk women (n = 242) were followed for 24 months. Symptoms of STIs were recorded, and laboratory diagnosis of common STI pathogens was conducted every 6 months. Forty-two cytokines were measured by Luminex in cervicovaginal lavage specimens at enrollment. Human immunodeficiency virus type 1 (HIV-1) infection was evaluated monthly.

Results. Only 12.3% of women (25 of 204) who had a laboratory-diagnosed, discharge-causing STI had clinically evident discharge. Vaginal discharge was thus a poor predictor of laboratory-diagnosed STIs (sensitivity, 12.3%; specificity, 93.8%). Cervicovaginal cytokine concentrations did not differ between women with asymptomatic STIs and those with symptomatic STIs and were elevated in women with asymptomatic STIs, compared with women with no STIs or bacterial vaginosis. Although laboratory-diagnosed STIs were associated with increased risk of HIV infection (hazard ratio, 3.3 [95% confidence interval, 1.5–7.2)], clinical symptoms were not.

Conclusions. Syndromic STI diagnosis dependent on vaginal discharge was poorly predictive of laboratory-diagnosed STI. Laboratory-diagnosed STIs were associated with increased susceptibility to HIV acquisition, while vaginal discharge was not.

J Infect Dis. (2012) 206 (1): 1-2.

doi: 10.1093/infdis/jis303

Classical Sexually Transmitted Diseases Drive the Spread of HIV-1: Back to the Future

Myron S. Cohen

Departments of Medicine, Microbiology and Immunology, and Epidemiology, The Schools of Medicine and Public Health, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina

Exercise as Immune-Based Therapy

Many studies have reported that regular exercise confers health benefits and that, conversely, a sedentary lifestyle is a major risk factor for morbidity and mortality (particularly from cardiovascular disease). In recent years, researchers have begun to look more specifically at the immunological effects of exercise. The scientist Richard Simpson, formerly at Napier University in Edinburgh and now based at the University of Houston in Texas, has pioneered the exploration of the intersection between exercise and immune senescence. This research is potentially relevant to HIV infection because, as reported in some prior blog posts (see the immunosenescence category), senescent immune cells—particularly CD8 T cells—accumulate over time and may persist despite antiretroviral therapy. Simpson’s recent work suggests that exercise mobilizes senescent immune system cells from the tissues into the blood and increases their death by apoptosis; if confirmed this may offer both a more practical approach to addressing senescence than the idea of physically removing cells, and could also explain some of the positive contributions of exercise to healthy aging that have been described in the literature.

Exercise may also have a beneficial impact on inflammation, another problem common to both aging and HIV infection. In Nature Reviews Immunology, Mike Gleeson and colleagues from Loughborough University in the UK review the mechanisms by which exercise may reduce inflammation, and highlight some of the questions that remain to be answered about which mechanisms are most important in producing beneficial health outcomes.

Finally, in a paper in press at the Journal of the Association of Nurses in AIDS Care, Anella Yahiaoui and colleagues review the literature in an attempt to offer evidence-based exercise recommendations for older individuals with HIV. They conclude that:

“Combined moderate to vigorous aerobic and resistance exercise for 20-40 minutes, 3 times per week, is safe and effective in older adults and has many benefits to decrease symptom burden, decrease disease progression, and increase quality of life.”

Additional specifics are included in the paper. The authors also recommend the basic "Exercise Tips for Older Americans" offered on the website of the American Heart Association.

Brain Behav Immun. 2011 Jul 19. [Epub ahead of print]

Aerobic fitness is associated with lower proportions of senescent blood T-cells in man.

Spielmann G, McFarlin BK, O'Connor DP, Smith PJ, Pircher H, Simpson RJ.

Laboratory of Integrated Physiology, Department of Health and Human Performance, University of Houston, 3855 Holman Street, Houston, TX 77204, USA; Biomedicine and Sports Science Research Group, School of Life Sciences, Edinburgh Napier University, 10 Colinton Road, Edinburgh, EH10 5DT, UK.

Abstract

Senescent T-cells accumulate with age, lowering the naïve T-cell repertoire and increasing host infection risk. As this response is likely to be influenced by certain lifestyle factors, we examined the association between aerobic fitness (V˙O(2max)) and the age-related accumulation of senescent T-cells. Blood lymphocytes from 102 healthy males (18-61yr) were analyzed for KLRG1, CD57, CD28, CD45RA, CD45RO surface expression on CD4+ and CD8+ T-cells by 4-color flow cytometry. Advancing age (yr) was positively associated with the proportion (%) of senescent (KLRG1+/CD57+; KLRG1+/CD28-) CD4+ (B=1.00; 1.02) and CD8+ (B=0.429; 1.02) T-cells and inversely associated with naïve (KLRG1-/CD28+) CD4+ (B=-1.000) and CD8+ (B=-0.993) T-cells. V˙O(2max) was inversely associated with senescent CD4+ (B=-0.97) and CD8+ (B=-0.240). Strikingly, age was no longer associated with the proportions of senescent or naïve T-cells after adjusting for V˙O(2max), while the association between V˙O(2max) and these T-cell subsets withstood adjustment for age, BMI and percentage body fat. Ranking participants by age-adjusted V˙O(2max) revealed that the highest tertile had 17% more naïve CD8+ T-cells and 57% and 37% less senescent CD4+ and CD8+ T-cells, respectively, compared to the lowest tertile. V˙O(2max) was not associated with latent cytomegalovirus (CMV), Epstein-Barr virus (EBV) or herpes simplex virus-1 (HSV-1) infection, indicating that the moderating associations of V˙O(2max) were not confounded by persistent viral infections. This is the first study to show that aerobic fitness is associated with a lower age-related accumulation of senescent T-cells, highlighting the beneficial effects of maintaining a physically active lifestyle on the aging immune system.

Exerc Sport Sci Rev. 2011 Jan;39(1):23-33.

Aging, persistent viral infections, and immunosenescence: can exercise "make space"?

Simpson RJ.

Laboratory of Integrated Physiology, Department of Health and Human Performance, University of Houston, Houston, TX 77204, USA.

Abstract

Overcrowding the immune space with excess clones of viral-specific T cells causes the naïve T-cell repertoire to shrink, which increases infection susceptibility to novel pathogens. Physical exercise preferentially mobilizes senescent T cells from the peripheral tissues into the blood, which might facilitate their subsequent apoptosis and create "vacant space" for newly functional T cells to occupy and expand the naïve T-cell repertoire.

Exerc Immunol Rev. 2010;16:40-55.

Senescent phenotypes and telomere lengths of peripheral blood T-cells mobilized by acute exercise in humans.

Simpson RJ, Cosgrove C, Chee MM, McFarlin BK, Bartlett DB, Spielmann G, O'Connor DP, Pircher H, Shiels PG.

Laboratory of Integrated Physiology, Department of Health and Human Performance, University of Houston, 3855 Holman Street, Houston, Texas 77204, USA.

Abstract

Acute bouts of aerobic exercise are known to mobilize antigen-experienced CD8+ T-cells expressing the cell surface marker of senescence, KLRG1, into the blood. It is not known; however if this is due to a selective mobilization of terminally differentiated T-cells (i.e., KLRG1 +/CD28-/CD57+) or a population of effector memory T-cells (i.e., KLRG1+/CD28+/CD57-) that have not reached terminal differentiation. The aim of this study was to further characterize KLRG1 + T-cells mobilized by acute exercise by assessing the co-expression of KLRG1 with CD28 or CD57 and to determine telomere lengths in the CD4+ and CD8+ T-cell subsets. Nine moderately trained male subjects completed an exhaustive treadmill running protocol at 80%. Blood lymphocytes isolated before, immediately after and 1h after exercise were labelled with antibodies against KLRG1, CD28 or CD57, CD4 or CD8 and CD3 for 4-color flow cytometry analysis. Telomere lengths in CD3+, CD4+ and CD8+ T-cells were determined using Q-PCR. The relative proportion of KLRG1 + cells among the CD8+ T-cells increased by 40% immediately after exercise, returning to baseline 1h later. This was due to a mobilization of KLRG1+/CD28- (61% increase), KLRG1+/CD57+ (56% increase) and to a lesser extent, KLRG1+/CD57- cells (24% increase). Telomeres in CD8+ T-cells displayed an increased relative length immediately after exercise, whereas no change occurred for CD4+ or the overall CD3+ T-cells. In conclusion, the increased frequency of KLRG1 +/CD8+ T-cells in blood after acute exercise is predominantly due to a selective mobilization of terminally differentiated T-cells. The increased relative telomere length in CD8+ T-cells after exercise might indicate that KLRG1+ cells mobilized by exercise are under stress or aberrant signaling-induced senescence (STASIS). We postulate that a frequent mobilization of these cells by acute exercise might eventually allow naïve T-cells to occupy the "vacant" immune space and increase the naïve T-cell repertoire.

Nat Rev Immunol. 2011 Aug 5. doi: 10.1038/nri3041. [Epub ahead of print]

The anti-inflammatory effects of exercise: mechanisms and implications for the prevention and treatment of disease.

Gleeson M, Bishop NC, Stensel DJ, Lindley MR, Mastana SS, Nimmo MA.

Inflammation, Exercise and Metabolism Research Group, School of Sport, Exercise and Health Sciences, Loughborough University, Ashby Road, Loughborough, Leicestershire LE11 3TU, UK.

Abstract

Regular exercise reduces the risk of chronic metabolic and cardiorespiratory diseases, in part because exercise exerts anti-inflammatory effects. However, these effects are also likely to be responsible for the suppressed immunity that makes elite athletes more susceptible to infections. The anti-inflammatory effects of regular exercise may be mediated via both a reduction in visceral fat mass (with a subsequent decreased release of adipokines) and the induction of an anti-inflammatory environment with each bout of exercise. In this Review, we focus on the known mechanisms by which exercise - both acute and chronic - exerts its anti-inflammatory effects, and we discuss the implications of these effects for the prevention and treatment of disease.

J Assoc Nurses AIDS Care. 2011 Jul 29. [Epub ahead of print]

Development of Evidence-Based Exercise Recommendations for Older HIV-Infected Patients.

Yahiaoui A, McGough EL, Voss JG.

Abstract

Advances in antiretroviral therapy (ART) have decreased HIV-related morbidity and mortality and contributed to rapidly increasing numbers of older people living with HIV. Successful management of ART-related side effects (metabolic syndrome) and age-related comorbidities (frailty) are major challenges for patients and providers. Exercise has proven beneficial for younger HIV-infected patients, but we know little about which exercise regimens to recommend to the elderly. Our goal was to develop age-appropriate, evidence-based exercise recommendations for older HIV-infected adults (age > 50). We reviewed randomized controlled trials on the effects of physical exercise for: (a) HIV-infected young adults, (b) frail older adults, and (c) elderly individuals with metabolic syndrome. We recommend a combination of endurance and resistance exercises 3 times per week for at least 6 weeks to improve cardiovascular, metabolic, and muscle function. Further research is warranted to study the benefits and risks of physical exercise in older HIV-infected patients.