TAG HIV Basic Science, Vaccines, and Cure Project Blog

HIV Replication and Persistence in T Follicular Helper Cells

Following up on the recent post on T follicular helper cells (TFH), a study published on December 17 in the Journal of Experimental Medicine reports that TFH represent a major site of HIV replication and persistence. The finding is not necessariy surprising, because lymph node studies conducted in the late 1980s and early 1990s showed that CD4 T cells in areas named germinal centers bore a great burden of HIV infection, and it is now known that this is where TFH locate during an immune response. But it was not previously understood that these CD4 T cells comprise a discrete subset, and TFH are now becoming increasingly well characterized in terms of both identifying features (such as surface markers and cytokine secretion) and their function in providing help to B cells.

Matthieu Perreau and colleagues from the University of Lausanne investigated TFH in three different groups of HIV-positive individuals:

• 23 with untreated chronic infection and viral load >5,000 copies/mL
• 14 on antiretroviral therapy (ART) with viral load <20 copies/mL
• 3 long-term nonprogressors (LTNP) with low viral load (<1,000 copies/mL)

A control group of 13 HIV-negative individuals was also included. The study confirmed the prior finding that TFH are significantly expanded in the lymph nodes of people with HIV compared to controls and that this expansion correlates with alterations in B-cell subsets (a decline in long-lived resting naive and memory B cells and an increase in short-lived activated B cells). The percentage of TFH correlated significantly with peripheral blood HIV viral load (R = 0.6035, P = 0.002). Suppression of HIV replication by ART reduced TFH levels and shifted B-cell subsets back toward the distribution observed in controls. Echoing and extending the previous research by Madelene Lindqvist, a substantial proportion of the TFH were found to be specific for HIV, with responses to Gag and Pol proteins more commonly detected than those against Env (based on a test evaluating cytokine production after stimulation with Gag, Pol, or Env peptides).

An analysis of the different CD4 T-cell populations present in lymph nodes revealed that TFH contained the greatest amount of HIV DNA: assuming one HIV DNA copy per cell, approximately five percent of the TFH population was infected. After 72 weeks of ART there was a 1.5–2 log drop in the number of TFH containing HIV DNA, but a reservoir of infected cells remained detectable. Cell culture experiments showed that TFH were highly susceptible to HIV infection and replication compared to other CD4 T-cell subsets, with the difference being most notable among the LTNP. The expression of the proliferation marker Ki67 by TFH was found to correlate with HIV DNA levels and ability to support HIV replication in vitro. Consistent with the elevation in immune activation that occurs in HIV, the proportion of TFH expressing Ki67 was 50 percent higher in the untreated HIV-positive individuals than in HIV-negative controls.

The discussion section of the paper highlights several implications of the results, including:

• HIV itself—as opposed to other potential factors, like microbial translocation—appears to be the main driving force behind TFH activation and expansion, and the associated dysregulation of B cells.
• The preferential infection of TFH likely contributes to viral persistence, because germinal centers have been shown to offer limited access to CD8 T cells (which might otherwise kill HIV-infected cells). Follicular dendritic cells in lymph nodes have also long been known to be sites of extensive trapping of HIV virions, providing an ongoing source of viruses to infect TFH.
• The involvement of TFH in responses to new pathogens and vaccines offers an explanation for the reported association between intercurrent infections and vaccinations and transient HIV viral-load increases (activation of TFH by these stimuli provides additional targets for HIV replication).
• The expression of certain cell-surface markers (such as PD-1) by TFH may offer a means of targeting this population with interventions designed to reduce HIV persistence. A human trial of an antibody targeting PD-1 is currently in the works at the AIDS Clinical Trials Group (for more background, see this recent short review "Novel Approaches to Curing HIV" by the principal investigator for the trial, Hiroyu Hatano).

Journal of Experimental Medicine

Published December 17, 2012

The Rockefeller University Press, doi: 10.1084/jem.20121932

Article

Follicular helper T cells serve as the major CD4 T cell compartment for HIV-1 infection, replication, and production

Matthieu Perreau1, Anne-Laure Savoye1, Elisa De Crignis1, Jean-Marc Corpataux2, Rafael Cubas5, Elias K. Haddad5, Laurence De Leval3, Cecilia Graziosi1, and Giuseppe Pantaleo1,4

1Divisions of Immunology and Allergy and 2Thoracic Surgery, 3Institute of Pathology, and 4Swiss Vaccine Research Institute, Lausanne University Hospital, University of Lausanne, CH-1011 Lausanne, Switzerland

5Vaccine and Gene Therapy Institute of Florida, Port St. Lucie, Florida

M. Perreau and A.-L. Savoye contributed equally to this paper.

ABSTRACT

In the present study, we have investigated the distribution of HIV-specific and HIV-infected CD4 T cells within different populations of memory CD4 T cells isolated from lymph nodes of viremic HIV-infected subjects. Four memory CD4 T cell populations were identified on the basis of the expression of CXCR5, PD-1, and Bcl-6: CXCR5−PD-1−Bcl-6−, CXCR5+PD-1−Bcl-6−, CXCR5−PD-1+Bcl-6−, and CXCR5+PD-1+Bcl-6+. On the basis of Bcl-6 expression and functional properties (IL-21 production and B cell help), the CXCR5+PD-1+Bcl-6+ cell population was considered to correspond to the T follicular helper (Tfh) cell population. We show that Tfh and CXCR5−PD-1+ cell populations are enriched in HIV-specific CD4 T cells, and these populations are significantly increased in viremic HIV-infected subjects as compared with healthy subjects. The Tfh cell population contained the highest percentage of CD4 T cells harboring HIV DNA and was the most efficient in supporting productive infection in vitro. Replication competent HIV was also readily isolated from Tfh cells in subjects with nonprogressive infection and low viremia (<1,000 HIV RNA copies). However, only the percentage of Tfh cells correlated with the levels of plasma viremia. These results demonstrate that Tfh cells serve as the major CD4 T cell compartment for HIV infection, replication, and production.

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

Behavior and Circumcision Status Do Not Explain Increased Risk of HIV Acquisition Associated with Ad5-Based Vaccine

In September 2007, the HIV vaccine field received an unexpected setback when it was announced that the phase IIb efficacy trial of a candidate developed by Merck was being stopped early due to lack of efficacy. The trial was conducted by the HIV Vaccine Trials Network (HVTN) and was referred to as the STEP study. The Merck vaccine aimed to stimulate T cell immunity against HIV, and used a novel attenuated adenovirus serotype 5 (Ad5) vector to deliver the HIV antigens Gag, Pol and Nef. The Ad5 approach was selected because it induced unprecedented levels of HIV-specific CD8 T cell responses in phase I and II trials, with >70-80% of recipients responding (the previous best was a dismal 20-30% of recipients showing low-level CD8 T cell responses after immunization with an ALVAC vector). Although HIV-specific CD8 T cell responses were not anticipated to protect against acquisition of HIV infection, evidence indicated that they might be able to suppress HIV replication and thereby increase the chances of vaccine recipients becoming elite controllers if they became HIV-infected.

The STEP study was stopped after an interim analysis by the Data Safety Monitoring Board revealed that this hoped-for salutary outcome was not being observed. Furthermore, it transpired that certain subgroups of the trial population experienced a significantly increased risk of HIV acquisition associated with receipt of the vaccine. In the overall results, this finding represented a strong trend that did not quite reach statistical significance. However, in a pre-specified analysis that evaluated results based on baseline levels of antibodies to Ad5, there was a stepwise increase in the risk associated with vaccination as anti-Ad5 antibody titers increased, strongly suggesting a real biological effect. Subsequent post-hoc studies revealed that the effect appeared entirely concentrated among uncircumcised men who have sex with men. To their great credit, the HVTN engaged in a massive and extremely transparent effort to investigate this outcome, involving both investigators affiliated with the network and the solicitation of input from external scientists with relevant expertise.

In the time since, a variety of investigations have been conducted but so far no causative mechanism has been identified to explain the STEP results. Unfortunately, along the way, some figures in leadership roles in the HIV vaccine field mistakenly attempted to suggest that the adenovirus vector had been absolved from having any role in enhancing HIV acquisition risk. For example, in 2009, Alan Bernstein (then head of the Global HIV/AIDS Vaccine Enterprise) had this to say to The Scientist:

"[This] result really rules out the possibility that it was the vaccine itself, and the fact that we used Adeno5, that was somehow increasing susceptibility to acquiring [HIV] in those volunteers."

The erroneousness of Bernstein’s public claim—and similar but less public assertions made by some scientists and policymakers in conference hallways—is highlighted by a new paper published in JAIDS. After many careful analyses, the researchers (from the HVTN and Merck) found that no potential confounder could account for the increased risk of HIV acquisition associated with receipt of the Ad5 vector. The HVTN has continued to be forthright about the issue, and it was these as-yet-unpublished analyses that led the network’s principal investigator Lawrence Corey to state in 2010:

“Even though we don’t have a mechanism [for Adeno5-mediated enhancement of HIV acquisition risk], we’re pretty sure this is a real biologic effect”

Continued efforts to understand the mechanism are important because while Merck’s Ad5-based HIV vaccine has been discontinued, adenovirus vectors from an array of different serotypes continue to be studied as potential vaccines against HIV, TB, malaria and hepatitis C, and it is currently uncertain if they might also have the potential to increase HIV acquisition risk.

The most commonly cited hypothesis to explain the STEP outcome was that the vaccine had boosted numbers of Ad5-specific CD4 T cells, thereby increasing the pool of cells potentially susceptible to HIV. But several papers have reported data that is inconsistent with this idea: blood levels of Ad5-specific CD4 T cells did not associate with acquisition risk, and these responses were also rapidly induced in study participants who lacked anti-Ad5 antibodies at baseline (yet these participants experienced no increase in risk). Another notion was that perhaps anti-Ad5 antibodies levels correlate with HIV risk for unknown reasons, but an analysis of the Multi-AIDS Center Cohort (MACS) study did not find an association, and this finding is echoed in a new Journal of Infectious Diseases paper looking at participants in several vaccine trials (abstract and link below). A study just published in PLoS One even finds the opposite: the inability of some STEP participants to make neutralizing antibodies against certain Ad5 components appeared to reflect generally weaker immunity and was associated with a greater risk of becoming HIV-infected independent of vaccination (abstract and link also below).

One remaining possibility that has yet to be thoroughly explored is that the STEP results related to something happening at the mucosal site of exposure, specifically the foreskin of the uncircumcised individuals that experienced the increased HIV acquisition risk. This idea is a subtle variant of the hypothesis related to Ad5-specific CD4 T cells. It is possible that Ad5 antibody titers in STEP were linked to the presence of persistent Ad5 infection, and that vaccination did not boost Ad5-specific CD4 T cell responses in blood but rather at mucosal sites of Ad5 antigen expression. One such site is known to be the gut, but because there are already huge numbers of CCR5-expressing CD4 T cells in that location it would be unlikely that a small additional influx would alter susceptibility to HIV (and this would be consistent with the risk associated with vaccination in STEP being seen in individuals reporting insertive anal intercourse but not receptive, as reported in the new JAIDS paper).

To the best of my knowledge, it is not known whether persistent Ad5 antigen expression can be detected in the foreskin, which would likely be a prerequisite for causing vaccine-boosted Ad5-specific CD4 T cell responses to traffic to—and be retained at—that site, potentially increasing susceptibilty to HIV. This type of scenario was suggested as a possible explanation of the STEP results by the research group of Steven Patterson in the discussion section of their PNAS paper in 2009, but still requires further investigation (there is one study that attempted to investigate the possibility in macaques, but because they are not susceptible to natural Ad5 the relevance of the results to humans is unclear). Of particular concern, CD4 T cells targeting adenoviruses cross-react with multiple serotypes (and simian adenoviruses), so the safety of vectors derived from variants other than Ad5 will remain uncertain until the issue is resolved.

JAIDS Journal of Acquired Immune Deficiency Syndromes:

POST ACCEPTANCE, 14 March 2012

doi: 10.1097/QAI.0b013e31825325aa

Sexual risk behaviors, circumcision status and pre-existing immunity to adenovirus type 5 among men who have sex with men participating in a randomized HIV-1 vaccine efficacy trial: Step Study

Koblin, Beryl A. PhD; Mayer, Kenneth H. MD; Noonan, Elizabeth MS; Wang, Ching-Yun PhD; Marmor, Michael PhD; Sanchez, Jorge MD, MPH; Brown, Stephen J. MD; Robertson, Michael N. MD; Buchbinder, Susan P. MD

Published Ahead-of-Print

Abstract

Background: The Step Study found that men who had sex with men (MSM) who received an adenovirus type 5 (Ad5) vector-based vaccine and were uncircumcised or had prior Ad5 immunity had a higher HIV incidence than MSM who received placebo. We investigated whether differences in HIV exposure, measured by reported sexual risk behaviors, may explain the increased risk.

Methods: Among 1,764 MSM in the trial, 724 were uncircumcised, 994 had prior Ad5 immunity and 560 were both uncircumcised and had prior Ad5 immunity. Analyses compared sexual risk behaviors and perceived treatment assignment among vaccine and placebo recipients, determined risk factors for HIV acquisition and examined the role of insertive anal intercourse in HIV risk among uncircumcised men.

Findings: Few sexual risk behaviors were significantly higher in vaccine vs. placebo recipients at baseline or during follow-up. Among uncircumcised men, vaccine recipients at baseline were more likely to report unprotected insertive anal intercourse with HIV negative partners (25.0% vs. 18.1%; p=0.03). Among uncircumcised men who had prior Ad5 immunity, vaccine recipients were more likely to report unprotected insertive anal intercourse with partners of unknown HIV status (46.0% vs. 37.5%; p=0.05). Vaccine recipients remained at higher risk of HIV infection compared to placebo recipients (HR =2.8; 95% CI:1.7, 6.8) controlling for potential confounders.

Interpretation: These analyses do not support a behavioral explanation for the increased HIV infection rates observed among uncircumcised men in the Step Study. Identifying biologic mechanisms to explain the increased risk is a priority.

J Infect Dis. (2012)

doi: 10.1093/infdis/jis285

First published online: April 5, 2012

Preexisting Adenovirus Seropositivity is Not Associated with Increased HIV-1 Acquisition in Three HIV-1 Vaccine Efficacy Trials

Kathryn E. Stephensona, John Huralb, Susan P. Buchbinderc, Faruk Sinangild and Dan H. Barouch*,a,e

aDivision of Vaccine Research, Beth Israel Deaconess Medical Center, Boston MA

bFred Hutchinson Cancer Research Center, Seattle, WA

cSan Francisco Department of Public Health, San Francisco, CA

dGlobal Solutions for Infectious Diseases, South San Francisco, CA

eRagon Institute of MGH, MIT, and Harvard, Boston MA

The Step study of a recombinant adenovirus serotype 5 (Ad5)-based HIV-1 vaccine revealed an increased risk of HIV-1 acquisition in vaccinees who were Ad5 seropositive at baseline. We therefore investigated whether preexisting Ad seropositivity to seven different Ad serotypes was associated with increased risk of HIV-1 infection in three HIV-1 vaccine efficacy trials. In a case-control study involving 1,570 adults enrolled in the VAX003 and VAX004 trials of a recombinant protein subunit HIV-1 vaccine and in the Step study, we observed that preexisting seropositivity to multiple Ad serotypes was not intrinsically associated with increased risk of HIV-1 acquisition.

PLoS ONE 7(4): e33969. doi:10.1371/journal.pone.0033969

Decreased Pre-existing Ad5 Capsid and Ad35 Neutralizing Antibodies Increase HIV-1 Infection Risk in the Step Trial Independent of Vaccination

Cheng Cheng1, LingShu Wang1, Jason G. D. Gall3, Martha Nason2, Richard M. Schwartz1, M. Juliana McElrath4,5, Steven C. DeRosa4,5, John Hural4,5, Lawrence Corey4,5, Susan P. Buchbinder5,6, Gary J. Nabel1

1 Vaccine Research Center, National Institute of Allergy and Infectious Diseases, National Insititutes of Health, Bethesda, Maryland, United States of America, 2 Biostatistics Research Branch, National Institute of Allergy and Infectious Disease, National Institutes of Health, Bethesda, Maryland, United States of America, 3 GenVec, Inc., Gaithersburg, Maryland, United States of America, 4 Vaccine and Infectious Disease Division, Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America, 5 HIV Vaccine Trials Network, Seattle, Washington, United States of America, 6 HIV Research Section, San Francisco Department of Public Health, San Francisco, California, United States of America

Abstract

Background

The Step trial raised the possibility that uncircumcised men with pre-existing Ad5 neutralizing antibodies carried an increased risk of HIV infection after vaccination. Thus, understanding Ad seropositivity in humans is important to the development of an AIDS vaccine. Here, we analyze the impact of different Ad5-specific neutralizing antibodies on immune function and clinical outcome.

Methods and Findings

Ad seropositivity in the Step trial volunteers was analyzed using chimeric rAd5/35 vectors to characterize their specificity for Ad5 fiber and non-fiber external (capsid) proteins. Immune responses and HIV seropositivity were correlated with the specificity of Ad5-neutralizing antibodies. Neutralizing antibodies induced by the vaccine in Ad5 seronegative subjects were directed preferentially to Ad5 capsid proteins, although some fiber-neutralizing antibodies could be detected. Pre-vaccination Ad5 serostatus did not affect the capsid-directed response after three vaccinations. In contrast, anti-fiber antibody titers were significantly higher in volunteers who were Ad5 seropositive prior to vaccination. Those Ad5 seropositive subjects who generated anti-capsid responses showed a marked reduction in vaccine-induced CD8 responses. Unexpectedly, anti-vector immunity differed qualitatively in Ad5 seropositive participants who became HIV-1 infected compared to uninfected case controls; Ad5 seropositive participants who later acquired HIV had lower neutralizing antibodies to capsid. Moreover, Ad35 seropositivity was decreased in HIV-infected subjects compared with uninfected case controls, while seroprevalence for other serotypes including Ad14, Ad28 and Ad41 was similar in both groups.

Conclusions

Together, these findings suggest that the case subjects were less immunologically responsive prior to infection. Subjects infected during the Step trial had qualitative differences in immunity that increased their risk of HIV-1 infection independent of vaccination.

Mycoplasma genitalium, Schistosoma haematobium, and HIV Acquisition Risk

Previously on the blog I’ve covered studies addressing the under-researched role of genital tract immune activation in increasing the risk of HIV acquisition, and the potential link between this phenomenon and global variation in HIV prevalence. A related issue is the impact of genital infections on the probability of acquiring HIV. Several recent papers (abstracts and links below) draw attention to the specific contributions of Mycoplasma genitalium and Schistosoma haematobium in this regard, highlighting the importance of considering these factors in the context of HIV prevention, and also emphasizing the need to better understand their contribution to the increased risk of heterosexual HIV transmission in sub-Saharan Africa.

AIDS. 2011 Dec 29. [Epub ahead of print]

The association between Mycoplasma genitalium and HIV-1 acquisition among women in Zimbabwe and Uganda.

Mavedzenge SN, Van der Pol B, Weiss HA, Kwok C, Mambo F, Chipato T, Van der Straten A, Salata R, Morrison C.

aWomen's Global Health Imperative, RTI International, San Francisco, California, USA bLondon School of Hygiene & Tropical Medicine, Department of Infectious Disease Epidemiology, London, UK cIndiana University School of Public Health, Division of Epidemiology & Biostatistics, Bloomington, IN, United States dBiostatistics Department, FHI, Durham, NC, United States eAMPATH Reference Laboratory, Eldoret, Kenya fUniversity of Zimbabwe, Harare, Zimbabwe gCenter for AIDS Prevention Studies, Department of Medicine, University of California San Francisco, CA, United States hCase Western Reserve University, Cleveland, Ohio, United States iClinical Sciences, FHI, Durham, NC, United States. 

Abstract

OBJECTIVE: Mycoplasma genitalium is an emerging sexually transmitted infection (STI) and has been associated with reproductive tract infections, and with HIV in cross-sectional studies. In this longitudinal study, we assess whether M. genitalium is associated with risk of acquiring HIV-1 infection.

DESIGN: Nested case-control study within a large prospective study in Zimbabwe and Uganda

METHODS: A total of 190 women who seroconverted to HIV-1 during follow-up ("cases") were matched with up to two HIV-negative controls. M. genitalium testing was performed by PCR-ELISA, using archived cervical samples from the HIV-1 detection visit and the last HIV-negative visit for cases, and equivalent visits in follow-up time for controls. Risk factors for HIV-1 acquisition were analyzed using conditional logistic regression, with M. genitalium as the primary exposure.

RESULTS: M. genitalium was a common infection in these populations (14.8% and 6.5% prevalence among cases and controls, respectively, at the visit prior to HIV-1 detection), and more prevalent than other non-viral STIs. We found a greater than two-fold independent increased risk of HIV-1 acquisition among women infected with M. genitalium at the visit prior to HIV-1 acquisition (AOR=2.42; 95%CI:1.01-5.80), and at time of HIV-1 acquisition (AOR = 2.18; 95%CI:0.98-4.85). An estimated 8.7% (95%CI:0.1-12.2%) of incident HIV-1 infections were attributable to M. genitalium.

CONCLUSIONS: This is the first longitudinal study to assess the relationship between M. genitalium and HIV-1 acquisition. If findings from this research are confirmed, M. genitalium screening and treatment among women at high-risk for HIV-1 infection may be warranted as part of an HIV-1 prevention strategy.

J Infect Dis. 2012 Jan;205(2):289-96. Epub 2011 Nov 18.

Prevalence and Correlates of Mycoplasma genitalium Infection Among Female Sex Workers in Kampala, Uganda.

Vandepitte J, Muller E, Bukenya J, Nakubulwa S, Kyakuwa N, Buvé A, Weiss H, Hayes R, Grosskurth H.

MRC/UVRI Uganda Research Unit on AIDS, Entebbe.

Abstract

Background. The importance of Mycoplasma genitalium in human immunodeficiency virus (HIV)-burdened sub-Saharan Africa is relatively unknown. We assessed the prevalence and explored determinants of this emerging sexually transmitted infection (STI) in high-risk women in Uganda.

Methods. Endocervical swabs from 1025 female sex workers in Kampala were tested for Mycoplasma genitalium using a commercial Real-TM polymerase chain reaction assay. Factors associated with prevalent Mycoplasma genitalium, including sociodemographics, reproductive history, risk behavior, and HIV and other STIs, were examined using multivariable logistic regression.

Results. The prevalence of Mycoplasma genitalium was 14% and higher in HIV-positive women than in HIV-negative women (adjusted odds ratio [OR], 1.64; 95% confidence interval [CI], 1.12-2.41). Mycoplasma genitalium infection was less prevalent in older women (adjusted OR, 0.61; 95% CI, .41-.90 for women ages 25-34 years vs <25 years; adjusted OR, 0.32; 95% CI, .15-.71 for women ≥35 years vs those <25 years) and in those who had been pregnant but never had a live birth (adjusted OR, 2.25; 95% CI, 1.04-4.88). Mycoplasma genitalium was associated with Neisseria gonorrhoeae (adjusted OR, 1.84; 95% CI, 1.13-2.98) and with Candida infection (adjusted OR, 0.41; 95% CI, .18-.91), and there was some evidence of association with Trichomonas vaginalis (adjusted OR, 1.56; 95% CI, 1.00-2.44).

Conclusions. The relatively high prevalence of Mycoplasma genitalium and its association with prevalent HIV urgently calls for further research to explore the potential role this emerging STI plays in the acquisition and transmission of HIV infection.

Am J Trop Med Hyg. 2011 Dec;85(6):1060-4. 

HIV Target Cells in Schistosoma haematobium-Infected Female Genital Mucosa.

Jourdan PM, Holmen SD, Gundersen SG, Roald B, Kjetland EF. 

Centre for Imported and Tropical Diseases, Department of Infectious Diseases, Oslo University Hospital Ulleval, Oslo, Norway; Faculty of Medicine, University of Oslo, Oslo, Norway; Research Unit, Sorlandet Hospital HF, Kristiansand, Norway; Centre for Development Studies, University of Agder, Kristiansand, Norway; Centre for Paediatric and Pregnancy Related Pathology, Department of Pathology, Oslo University Hospital Ulleval, Oslo, Norway.

Abstract

The parasite Schistosoma haematobium frequently causes genital lesions in women and could increase the risk of human immunodeficiency virus (HIV) transmission. This study quantifies the HIV target cells in schistosome-infected female genital mucosa. Cervicovaginal biopsies with and without schistosomiasis were immunostained for quantification of CD4(+) T lymphocytes (CD3, CD8), macrophages (CD68), and dendritic Langerhans cells (S100 protein). We found significantly higher densities of genital mucosal CD4(+) T lymphocytes and macrophages surrounding schistosome ova compared with cervicovaginal mucosa without ova (P = 0.034 and P = 0.018, respectively). We found no increased density of Langerhans cells (P = 0.25). This study indicates that S. haematobium may significantly increase the density of HIV target cells (CD4(+) T lymphocytes and macrophages) in the female genitals, creating a beneficial setting for HIV transmission. Further studies are needed to confirm these findings and to evaluate the effect of anti-schistosomal treatment on female genital schistosomiasis.

PLoS Negl Trop Dis 5(12): e1396. doi:10.1371/journal.pntd.0001396

Examining the Relationship between Urogenital Schistosomiasis and HIV Infection

Pamela Sabina Mbabazi1, Olivia Andan1, Daniel W. Fitzgerald2, Lester Chitsulo1, Dirk Engels1, Jennifer A. Downs2

1 Department of Control of Neglected Tropical Diseases, World Health Organization, Geneva, Switzerland, 2 Center for Global Health, Division of Infectious Diseases, Weill Cornell Medical College, New York, New York, United States of America

Abstract

Background

Urogenital schistosomiasis, caused by infection with Schistosoma haematobium, is widespread and causes substantial morbidity on the African continent. The infection has been suggested as an unrecognized risk factor for incident HIV infection. Current guidelines recommend preventive chemotherapy, using praziquantel as a public health tool, to avert morbidity due to schistosomiasis. In individuals of reproductive age, urogenital schistosomiasis remains highly prevalent and, likely, underdiagnosed. This comprehensive literature review was undertaken to examine the evidence for a cause-effect relationship between urogenital schistosomiasis and HIV/AIDS. The review aims to support discussions of urogenital schistosomiasis as a neglected yet urgent public health challenge.

Methodology/Principal Findings

We conducted a systematic search of the literature including online databases, clinical guidelines, and current medical textbooks. We describe plausible local and systemic mechanisms by which Schistosoma haematobium infection could increase the risk of HIV acquisition in both women and men. We also detail the effects of S. haematobium infection on the progression and transmissibility of HIV in co-infected individuals. We briefly summarize available evidence on the immunomodulatory effects of chronic schistosomiasis and the implications this might have for populations at high risk of both schistosomiasis and HIV.

Conclusions/Significance

Studies support the hypothesis that urogenital schistosomiasis in women and men constitutes a significant risk factor for HIV acquisition due both to local genital tract and global immunological effects. In those who become HIV-infected, schistosomal co-infection may accelerate HIV disease progression and facilitate viral transmission to sexual partners. Establishing effective prevention strategies using praziquantel, including better definition of treatment age, duration, and frequency of treatment for urogenital schistosomiasis, is an important public health priority. Our findings call attention to this pressing yet neglected public health issue and the potential added benefit of scaling up coverage of schistosomal treatment for populations in whom HIV infection is prevalent.

Author Summary

Urogenital schistosomiasis is a parasitic infection caused by a worm, Schistosoma haematobium, which lives in the bloodstream of infected individuals. It affects at least 112 million people, mostly in sub-Saharan Africa, and has been suggested to be a risk factor for becoming infected with HIV. We reviewed publications in order to examine whether it seems likely that this parasitic infection could be a risk factor for HIV. Evidence from many types of studies supports the hypothesis that urogenital schistosomiasis does increase a person's risk of becoming infected with HIV. Studies also suggest that individuals who have both urogenital schistosomiasis and HIV have a more aggressive HIV infection and can more easily transmit HIV to their sexual partners. Praziquantel is an oral, nontoxic, inexpensive medication that is safe in pregnancy and is recommended for treatment of schistosomiasis. In areas where both infections co-exist, regular administration of praziquantel both to young girls and to sexually-active women may be an important approach to reducing HIV transmission. Our findings support the importance of making praziquantel more available to people who live in areas of the world where both urogenital schistosomiasis and HIV infection are widespread.

The Lancet, Volume 378, Issue 9809, Pages 2069 - 2070, 17 December 2011

doi:10.1016/S0140-6736(11)61897-7

Neglected tropical diseases and the HIV prevention agenda

Jennifer Manne a b, Karolina Maciag c d

a Department of Global Health and Population, Harvard School of Public Health, Boston, MA 02115, USA

b Boston University School of Medicine, Boston, MA, USA

c Harvard—Massachusetts Institute of Technology Division of Health Sciences and Technology, Harvard Medical School, Boston, MA, USA

d Broad Institute, Cambridge, MA, USA

We applaud Nancy Padian and colleagues (July 16, p 269)[1] for their thorough Review of the HIV prevention research agenda. Although Padian and colleagues address many crucial ways to break the transmission cycle, we point out one important omission: the intersection between HIV transmission and neglected tropical diseases (NTDs). With increasing evidence that infections such as female urogenital schistosomiasis (FUS) and helminthiases substantially increase the risk of HIV infection and speed disease progression,[2] it is essential that we no longer ignore the importance of the NTDs in the context of the HIV epidemic.

Specifically, preliminary research[3] has shown a three-fold increase in sexual transmission and incidence of HIV/AIDS in women with genital ulcers caused by FUS, as well as a substantial geographical overlap between areas of high HIV prevalence and regions where FUS is endemic.[4] Evidence also suggests that deworming reduces HIV viral load[5] and that maternal helminth infection increases risk of mother-to-child HIV transmission.[4]

Mounting evidence supports the addition of this intersection between HIV/AIDS and NTDs to the HIV prevention research agenda. Since treatments for several NTDs are cheaply available,[4] integration of NTD and HIV/AIDS delivery platforms offers a rare and substantial opportunity for efficiency and savings, particularly in the face of escalating financial constraints to the maintenance and escalation of HIV/AIDS treatment. Finally, increased research to establish the population-level effects of NTDs on HIV/AIDS will offer an avenue for better understanding, prevention, and treatment of both HIV and several long-neglected infections of the “bottom billion”.

We declare that we have no conflicts of interest.

References

1 Padian N, McCoy SI, Abdool Karim SS, et al. HIV prevention transformed: the new prevention research agenda. Lancet 2011; 378: 269-278.

2 Sawers L, Stillwaggon E, Hertz T. Cofactor infections and HIV epidemics in developing countries: implications for treatment. AIDS Care 2008; 20: 488-494.

3 Downs JA, Mguta C, Kaatano GM, et al. Urogenital schistosomiasis in women of reproductive age in Tanzania's Lake Victoria region. Am J Trop Med Hyg 2011; 84: 364-369.

4 Hotez PJ, Mistry N, Rubinstein J, Sachs JD. Integrating neglected tropical diseases into AIDS, tuberculosis, and malaria control. N Engl J Med 2011; 364: 2086-2089.

5 Walson JL, Herrin BR, John-Stewart G. Deworming helminth co-infected individuals for delaying HIV disease progression. Cochrane Database Syst Rev 2009; 3. CD006419.

 

Maxed Out: Treatment Intensification Studies Report No Effect on Residual HIV Levels or Immune Activation

Scientists continue to wrestle with the question of whether combination antiretroviral therapy (ART) completely suppresses HIV replication in most recipients. The development of ultra-sensitive “single copy” viral load tests (which can measure down to 0.3 HIV RNA copies in a milliliter of blood) has revealed that most individuals with levels below 50 copies show evidence of persistent residual viral RNA. There are two potential (non-exclusive) sources: long-lived, chronically infected cells containing integrated viral DNA which produce RNA copies either intermittently or continuously—such cells would be impervious to the effects of current antiretroviral therapies—or low-level HIV replication, in which new RNA copies are produced which go on to infect other cells. In the latter case, intensifying ART with additional drugs would be predicted to reduce the amount of residual viral load and the number of cells containing integrated HIV DNA.

A slew of new papers (abstracts below) describe the results obtained in several different treatment intensification trials. The results add to the evidence that, in the majority of individuals, ongoing low-level HIV replication is not the source of residual HIV RNA, and nor is it the major driver of immune activation in individuals on ART. Most prior studies of treatment intensification have produced similar results, with just a couple of notable exceptions. In one small trial involving intensification with raltegravir there was a transient increase in a piece of HIV’s genetic code called a 2-LTR circle in around 1/3 of participants, which suggests the drug may have been blocking new rounds of infection in these individuals. Another similar trial produced evidence that the addition of raltegravir may have reduced HIV replication and immune activation in a specific part of the gut (the terminal ileum). But the preponderance of evidence now favors chronically infected cells as the primary source of residual viral load on ART, highlighting the importance of designing strategies to identify, target and eliminate this persistent HIV reservoir.

J Infect Dis. (2011) doi: 10.1093/infdis/jir667

First published online: October 21, 2011

Raltegravir Treatment Intensification Does Not Alter Cerebrospinal Fluid HIV-1 Infection or Immunoactivation in Subjects on Suppressive Therapy

Viktor Dahl1, Evelyn Lee2, Julia Peterson2, Serena S. Spudich2,a, Idris Leppla2, Elizabeth Sinclair3, Dietmar Fuchs4, Sarah Palmer1 and Richard W. Price2

1Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet and Swedish Institute for Infectious Disease Control, Stockholm, Sweden

2Department of Neurology

3Department of Medicine, University of California, San Francisco

4Division of Biological Chemistry, Biocentre, Innsbruck Medical University, Austria

Abstract

Background. Despite suppression of plasma human immunodeficiency virus type 1 (HIV-1) RNA by antiretroviral therapy to levels below clinical assay detection, infection and immune activation may persist within the central nervous system and possibly lead to continued brain injury. We hypothesized that intensifying therapy would decrease cerebrospinal fluid (CSF) infection and immune activation.

Methods. This was a 12-week, randomized, open-label pilot study comparing addition of the integrase inhibitor raltegravir to no treatment augmentation, with an option for rollover to raltegravir. CSF and plasma were analyzed for HIV-1 RNA using a single-copy assay. CSF and blood immune activation was assessed by neopterin concentrations and CD4+ and CD8+ T-cell surface antigen expression.

Results. Primary analysis compared 14 intensified (including rollovers) to 9 nonintensified subject experiences. Median HIV-1 RNA levels in all samples were lower in CSF (<.3 copies/mL) than in plasma (<.9 copies/mL; P < .0001), and raltegravir did not reduce HIV-1 RNA, CSF neopterin, or CD4+ and CD8+ T-cell activation.

Conclusions. Raltegravir intensification did not reduce intrathecal immunoactivation or alter CSF HIV-1 RNA levels in subjects with baseline viral suppression. With and without raltegravir intensification, HIV RNA levels in CSF were very low in the enrolled subjects. 

Clin Infect Dis. (2011) doi: 10.1093/cid/cir721

First published online: October 19, 2011

Short-course Raltegravir Intensification Does Not Increase 2 Long Terminal Repeat Episomal HIV-1 DNA in Patients on Effective Antiretroviral Therapy

Guillaume J. Besson1, Deborah McMahon1, Frank Maldarelli2, and John W. Mellors1

1Division of Infectious Diseases, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania

2National Cancer Institute, Frederick, Maryland

TO THE EDITOR—Controversy exists about whether human immunodeficiency virus type 1 (HIV-1) replication persists in patients receiving effective antiretroviral therapy. Residual viremia can often be detected in such patients by sensitive quantitative polymerase chain reaction assays, but the source of this viremia is unknown [1]. Possibilities include ongoing cycles of HIV-1 replication, long-lived HIV-1–infected cells that continuously or intermittently produce virus, or both. If residual plasma viremia is derived from ongoing HIV-1 replication, intensification of an effective regimen with another potent antiretroviral drug should lower viremia. Such treatment intensification studies have been conducted with different classes of antiretroviral agents (nucleoside reverse-transcriptase inhibitors, nonnucleoside reverse-transcriptase inhibitors, protease inhibitors, and the integrase inhibitor raltegravir), and none has shown reduction in residual viremia [ …

JAIDS Journal of Acquired Immune Deficiency Syndromes:

POST ACCEPTANCE, 11 November 2011

doi: 10.1097/QAI.0b013e31823fd1f2

No Effect of Raltegravir Intensification on Viral Replication Markers in the Blood of HIV-1-infected Patients Receiving Antiretroviral Therapy

Gandhi, Rajesh T.; Coombs, Robert W.; Chan, Ellen S.; Bosch, Ronald J.; Zheng, Lu; Margolis, David M.; Read, Sarah; Kallungal, Beatrice; Chang, Ming; Goecker, Erin A.; Wiegand, Ann; Kearney, Mary; Jacobson, Jeffrey M.; D'Aquila, Richard; Lederman, Michael M.; Mellors, John W.; Eron, Joseph J.; for the AIDS Clinical Trials Group (ACTG) A5244 team

Published Ahead-of-Print

Abstract

Background: Controversy continues regarding the extent of ongoing viral replication in HIV-1-infected patients on effective antiretroviral therapy (ART). Adding an additional potent agent, such as raltegravir, to effective ART in patients with low-level residual viremia may reveal whether there is ongoing HIV-1 replication.

Methods: We previously reported the outcome of a randomized, placebo-controlled study of raltegravir intensification in patients on ART with HIV-1 RNA <50 copies/mL that showed no effect on residual viremia measured by single copy assay (SCA). We now report the effects of raltegravir intensification in that trial on other potential measures of ongoing HIV-1 replication: 2-LTR HIV-1 circles, total cellular HIV-1 DNA and T cell activation.

Results: Of 50 patients tested, 12 (24%) had 2-LTR-circles detected at baseline. Patients who were 2-LTR-positive had higher plasma HIV-1 RNA and HIV-1 DNA levels than 2-LTR-negative individuals. At week 12 of raltegravir intensification, there was no change from baseline in 2-LTR circles, in total HIV-1 DNA or in the ratio of 2-LTR circles to total HIV-1 DNA. There was also no change in markers of T cell activation.

Conclusions: In HIV-1-infected individuals on effective antiretroviral therapy, we find no evidence of ongoing viral replication in the blood that is suppressible by raltegravir intensification. The results imply that raltegravir intensification alone will not eradicate HIV-1 infection.

AIDS:

POST ACCEPTANCE, 14 November 2011

doi: 10.1097/QAD.0b013e32834e8955

Effect of raltegravir intensification on HIV proviral DNA in the blood and gut mucosa of men on long-term therapy: a randomized control trial

Chege, Duncan; Kovacs, Colin; La Porte, Charles; Ostrowski, Mario; Raboud, Janet; Su, Desheng; Kandel, Gabor; Brunetta, Jason; Kim, Connie; Sheth, Prameet M.; Kaul, Rupert; Loutfy, Mona R.

Published Ahead-of-Print

Abstract

Background: Highly active antiretroviral therapy (HAART) dramatically reduces plasma HIV-1 viremia. However, despite completely suppressive HAART, it has been suggested that low-levels of viral replication may persist in the gut mucosa and elsewhere in individuals on long-term HAART.

Objective: We conducted a double-blind randomized, placebo-controlled trial (RCT) evaluating whether intensification of HAART in long-term virologically suppressed individuals with raltegravir is associated with a reduction in the level of proviral HIV-1 DNA in CD4+ T cells in blood and the sigmoid colon (gut).

Methods: Long-term (>4 years) virologically suppressed HIV-infected individuals on standard HAART were randomized 1:1 in a double-blind fashion to receive raltegravir (400mg twice/day) or placebo for 48 weeks. After week 48, all participants were treated with raltegravir to week 96. Blood and sigmoid biopsies were sampled and the frequency of CD4+ T cells carrying HIV-1 proviral DNA was determined.

Results: 24 study patients were recruited. At 48 weeks, no difference was apparent between participants receiving raltegravir or placebo in blood HIV-1 proviral levels (p=0.62), CD4+ T cell counts (p=0.25) and gut proviral loads (p=0.74). Similarly, prolonged raltegravir intensification up to week 96 had no further effect on both blood and gut HIV-1 proviral loads and blood CD4+ T cell counts.

Conclusion: In long-term virologically suppressed patients on standard HAART, intensification with raltegravir did not result in further decay of CD4+ T cells carrying HIV-1 proviral DNA in either the blood or gut after 48 or 96 weeks of therapy, or in any increase in CD4+ T cell counts.

Open Access Articles on HIV in Cold Spring Harbor Perspectives

The journal Cold Spring Harbor Perspectives is offering several free review articles on HIV research, see abstracts and links below.

doi: 10.1101/cshperspect.a007252

Vaccine Design for CD8 T Lymphocyte Responses

Richard A. Koup and Daniel C. Douek

Immunology Laboratory, Vaccine Research Center, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892

Abstract

Vaccines are arguably the most powerful medical intervention in the fight against infectious diseases. The enormity of the global human immunodeficiency virus type 1 (HIV)/acquired immunodeficiency syndrome (AIDS) pandemic makes the development of an AIDS vaccine a scientific and humanitarian priority. Research on vaccines that induce T-cell immunity has dominated much of the recent development effort, mostly because of disappointing efforts to induce neutralizing antibodies through vaccination. Whereas T cells are known to limit HIV and other virus infections after infection, their role in protection against initial infection is much less clear. In this article, we will review the rationale behind a T-cell-based vaccine approach, provide an overview of the methods and platforms that are being applied, and discuss the impact of recent vaccine trial results on the future direction of T-cell vaccine research.

doi: 10.1101/cshperspect.a007096

HIV Latency

Robert F. Siliciano1 and Warner C. Greene2

1Department of Medicine, Johns Hopkins University School of Medicine, Howard Hughes Medical Institute, Baltimore, Maryland 21205

2Gladstone Institute of Virology and Immunology, Department of Medicine, Microbiology and Immunology, University of California, San Francisco, California 94158

Abstract

HIV-1 can establish a state of latent infection at the level of individual T cells. Latently infected cells are rare in vivo and appear to arise when activated CD4+ T cells, the major targets cells for HIV-1, become infected and survive long enough to revert back to a resting memory state, which is nonpermissive for viral gene expression. Because latent virus resides in memory T cells, it persists indefinitely even in patients on potent antiretroviral therapy. This latent reservoir is recognized as a major barrier to curing HIV-1 infection. The molecular mechanisms of latency are complex and include the absence in resting CD4+ T cells of nuclear forms of key host transcription factors (e.g., NFκB and NFAT), the absence of Tat and associated host factors that promote efficient transcriptional elongation, epigenetic changes inhibiting HIV-1 gene expression, and transcriptional interference. The presence of a latent reservoir for HIV-1 helps explain the presence of very low levels of viremia in patients on antiretroviral therapy. These viruses are released from latently infected cells that have become activated and perhaps from other stable reservoirs but are blocked from additional rounds of replication by the drugs. Several approaches are under exploration for reactivating latent virus with the hope that this will allow elimination of the latent reservoir.

doi: 10.1101/cshperspect.a007278

Rational Design of Vaccines to Elicit Broadly Neutralizing Antibodies to HIV-1

Peter D. Kwong, John R. Mascola and Gary J. Nabel

Vaccine Research Center, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892

Abstract

The development of a highly effective AIDS vaccine will likely depend on success in designing immunogens that elicit broadly neutralizing antibodies to naturally circulating strains of HIV-1. Although the antibodies induced after natural infection with HIV-1 are often directed to strain-specific or nonneutralizing determinants, it is now evident that 10%–25% of HIV-infected individuals generate neutralizing antibody responses of considerable breadth. In the past, only four broadly neutralizing monoclonal antibodies had been defined, but more than a dozen monoclonal antibodies of substantial breadth have more recently been isolated. An understanding of their recognition sites, the structural basis of their interaction with the HIV Env, and their development pathways provides new opportunities to design vaccine candidates that will elicit broadly protective antibodies against this virus.

doi: 10.1101/cshperspect.a006841

Origins of HIV and the AIDS Pandemic

Paul M. Sharp1 and Beatrice H. Hahn2

1Institute of Evolutionary Biology and Centre for Immunity, Infection and Evolution, University of Edinburgh, Edinburgh EH9 3JT, United Kingdom

2Departments of Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104

Abstract

Acquired immunodeficiency syndrome (AIDS) of humans is caused by two lentiviruses, human immunodeficiency viruses types 1 and 2 (HIV-1 and HIV-2). Here, we describe the origins and evolution of these viruses, and the circumstances that led to the AIDS pandemic. Both HIVs are the result of multiple cross-species transmissions of simian immunodeficiency viruses (SIVs) naturally infecting African primates. Most of these transfers resulted in viruses that spread in humans to only a limited extent. However, one transmission event, involving SIVcpz from chimpanzees in southeastern Cameroon, gave rise to HIV-1 group M—the principal cause of the AIDS pandemic. We discuss how host restriction factors have shaped the emergence of new SIV zoonoses by imposing adaptive hurdles to cross-species transmission and/or secondary spread. We also show that AIDS has likely afflicted chimpanzees long before the emergence of HIV. Tracing the genetic changes that occurred as SIVs crossed from monkeys to apes and from apes to humans provides a new framework to examine the requirements of successful host switches and to gauge future zoonotic risk.

Published in Advance September 14, 2011, doi: 10.1101/cshperspect.a007385

Microbicides: Topical Prevention against HIV

Robin J. Shattock1 and Zeda Rosenberg2

1Centre for Infection and Immunity, Division of Clinical Sciences, St George’s, University of London, Cranmer Terrace, London SW17 0RE, United Kingdom

2International Partnership for Microbicides, 8401 Colesville Road, Suite 200, Silver Spring, Maryland 20910

Abstract

Microbicides represent a potential intervention strategy for preventing HIV transmission. Vaginal microbicides would meet the need for a discreet method that women could use to protect themselves against HIV. Although early-generation microbicides failed to demonstrate efficacy, newer candidates are based on more potent antiretroviral (ARV) products. Positive data from the CAPRISA 004 trial of tenofovir gel support use in women and represent a turning point for the field. This article reviews current progress in development of ARV-based microbicides. We discuss the consensus on selection criteria, the potential for drug resistance, rationale for drug combinations, and the use of pharmacokinetic (PK)/pharmacodynamic (PD) assessment in product development. The urgent need for continued progress in development of formulations for sustained delivery is emphasized. Finally, as the boundaries between different prevention technologies become increasingly blurred, consideration is given to the potential synergy of diverse approaches across the prevention landscape.

Published in Advance September 7, 2011, doi: 10.1101/cshperspect.a007153

Nonpathogenic Simian Immunodeficiency Virus Infections

Nichole R. Klatt1, Guido Silvestri2 and Vanessa Hirsch1

1Laboratory of Molecular Microbiology, NIAID, NIH, Bethesda, Maryland 20892

2Department of Pathology and Laboratory Medicine, Emory University School of Medicine, and Yerkes National Primate Research Center, Atlanta, Georgia 30322

Abstract

The simian immunodeficiency viruses (SIVs) are a diverse group of viruses that naturally infect a wide range of African primates, including African green monkeys (AGMs) and sooty mangabey monkeys (SMs). Although natural infection is widespread in feral populations of AGMs and SMs, this infection generally does not result in immunodeficiency. However, experimental inoculation of Asian macaques results in an immunodeficiency syndrome remarkably similar to human AIDS. Thus, natural nonprogressive SIV infections appear to represent an evolutionary adaptation between these animals and their primate lentiviruses. Curiously, these animals maintain robust virus replication but have evolved strategies to avoid disease progression. Adaptations observed in these primates include phenotypic changes to CD4+ T cells, limited chronic immune activation, and altered mucosal immunity. It is probable that these animals have achieved a unique balance between T-cell renewal and proliferation and loss through activation-induced apoptosis, and virus-induced cell death. A clearer understanding of the mechanisms underlying the lack of disease progression in natural hosts for SIV infection should therefore yield insights into the pathogenesis of AIDS and may inform vaccine design.

HIV Replication in CCR5-Expressing T Cells

A new study from the laboratory of Elizabeth Connick at the University of Colorado takes a detailed look at HIV replication in activated T cells. The study demonstrates that the chemokine receptor CCR5 is highly expressed by CD4 T cells displaying dual activation markers, HLA-DR and CD38, and that these cells are the major source of virus in lymph node samples from infected individuals. Importantly, there were differences observed between viral replication studied in lab culture conditions (in vitro) compared to the lymph node samples: the bulk of the CD4 cells replicating HIV in vitro were CD38+ but lacked HLA-DR and did not preferentially express CCR5.

The researchers also extend the findings of prior studies suggesting that CD4 downregulation is common among activated, HIV-infected cells. The DR+CD38+ T cells could be sorted into the following subsets:

• CD4-CD8- T cells (contributing a median of 48% of the total HIV RNA copies detected)
• CD4+CD8- T cells (median HIV RNA copies, 15%)
• CD4+CD8+ T cells (median HIV RNA copies, 29%)
• CD4-CD8+ T cells (HIV RNA copies, 8%)

Thus the bulk of HIV RNA in the lymph node samples was coming from cells that had downregulated their CD4 receptors, similar to the previously reported results obtained from the blood of untreated HIV-positive individuals. CD4 cells co-expressing CD8 are an unusual subset and the authors note they need further study; whether the observed CD8 expression is stable or a transient activation-related phenomena is unclear. The amount of HIV RNA produced by each of the DR+CD38+ T cell subsets correlated with the amount of CCR5 they expressed. 

The importance of CCR5 expression in facilitating viral replication is also underscored by a recent Nature Medicine paper from Miko Paiardini and colleagues. The researchers document that non-pathogenic SIV infection of sooty mangabeys is associated with greatly reduced CCR5 expression on long-lived central memory CD4 T cells. A consequence of the reduced CCR5 expression is that the amount of SIV found in central memory CD4 T cells in sooty mangabeys is a log lower than in rhesus macaques, whereas there is no significant difference when SIV infection of short-lived effector memory CD4 T cells is compared. The authors argue that this sparing of central memory CD4 T cell allows sooty mangabeys to co-exist peacefully with SIV, because the short-lived effector memory CD4 T cells the virus does infect are relatively dispensable.

JVI Accepts, published online ahead of print on 3 August 2011

J. Virol. doi:10.1128/JVI.02529-10

HLA-DR+CD38+CD4+ T Lymphocytes Have Elevated CCR5 Expression and Produce the Majority of R5-tropic HIV-1 RNA in Vivo

Amie L. Meditz1, Michelle K. Haas1, Joy M. Folkvord1, Kelsey Melander1, Russ Young1, Martin McCarter3, Samantha MaWhinney4, Thomas B. Campbell1, Yolanda Lie5, Eoin Coakley5, David N. Levy7, and Elizabeth Connick1

1 Division of Infectious Diseases, Department of Medicine, University of Colorado Denver, Aurora, CO

3 Department of Surgery, University of Colorado Denver, Aurora, CO

4 Department of Biostatistics and Informatics, University of Colorado Denver, Aurora, CO

5 Monogram Biosciences, South San Francisco, CA

7 New York University, College of Dentistry, New York City, NY

ABSTRACT

Percentages of activated T-cells correlate with HIV-1 disease progression, but underlying mechanisms are not fully understood. We hypothesized that HLA-DR+CD38+ (DR+38+) CD4+ T-cells produce the majority of HIV-1 due to elevated expression of CCR5 and CXCR4. In PHA-stimulated CD8-depleted PBMC infected with HIV-1 GFP reporter viruses, DR-38+ T-cells constituted the majority of R5-tropic (median, 62%) and X4-tropic HIV-1-producing cells (median, 61%), although cell surface CCR5 and CXCR4 were not elevated on this subset. In lymph nodes from untreated individuals infected with R5-tropic HIV-1, percentages of CCR5+ cells were elevated in DR+38+CD4+ T-cells (median, 36.4%) compared to other CD4+ T-cell subsets (median, DR-38- 5.7%; DR+38- 19.4%; DR-38+ 7.6%; n=18; p<0.001). In sorted CD8- lymph node T-cells, median HIV-1 RNA copies/105 cells was higher for DR+38+ (1.8x106) compared to DR-38- (0.007x106), DR-38+ (0.064x106), and DR+38- (0.18x106) subsets (n=8; p<0.001 for all). After adjusting for percentages of subsets, a median of 87% of viral RNA was harbored by DR+38+ cells. Percentages of CCR5+ CD4+ T-cells and concentrations of CCR5 molecules among subsets predicted HIV-1 RNA levels among CD8- DR/38 subsets (p<0.001 for both). Median HIV-1 DNA copies/105 cells was higher in DR+38+ (5, 360) compared to DR-38- (906), DR-38+ (814), and DR+38- (1, 984) subsets (n=7, p<=0.031). Thus, DR+38+CD4+ T-cells in lymph nodes have elevated CCR5 expression, are highly susceptible to infection with R5-tropic virus, and produce the majority of R5-tropic HIV-1. PBMC assays failed to recapitulate in vivo findings, suggesting limited utility. Strategies to reduce numbers of DR+38+CD4+ T-cells may substantially inhibit HIV-1 replication.

Nat Med. 2011 Jun 26;17(7):830-6. doi: 10.1038/nm.2395.

Low levels of SIV infection in sooty mangabey central memory CD4(+) T cells are associated with limited CCR5 expression.

Paiardini M, Cervasi B, Reyes-Aviles E, Micci L, Ortiz AM, Chahroudi A, Vinton C, Gordon SN, Bosinger SE, Francella N, Hallberg PL, Cramer E, Schlub T, Chan ML, Riddick NE, Collman RG, Apetrei C, Pandrea I, Else J, Munch J, Kirchhoff F, Davenport MP, Brenchley JM, Silvestri G.

Abstract

Naturally simian immunodeficiency virus (SIV)-infected sooty mangabeys do not progress to AIDS despite high-level virus replication. We previously showed that the fraction of CD4(+)CCR5(+) T cells is lower in sooty mangabeys compared to humans and macaques. Here we found that, after in vitro stimulation, sooty mangabey CD4(+) T cells fail to upregulate CCR5 and that this phenomenon is more pronounced in CD4(+) central memory T cells (T(CM) cells). CD4(+) T cell activation was similarly uncoupled from CCR5 expression in sooty mangabeys in vivo during acute SIV infection and the homeostatic proliferation that follows antibody-mediated CD4(+) T cell depletion. Sooty mangabey CD4(+) T(CM) cells that express low amounts of CCR5 showed reduced susceptibility to SIV infection both in vivo and in vitro when compared to CD4(+) T(CM) cells of rhesus macaques. These data suggest that low CCR5 expression on sooty mangabey CD4(+) T cells favors the preservation of CD4(+) T cell homeostasis and promotes an AIDS-free status by protecting CD4(+) T(CM) cells from direct virus infection.

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.

Lymphocyte Production Capacity in HIV: Links to Immune Activation & Immune Reconstitution on ART

A number of studies have documented that the body’s machinery for producing new immune system cells is impaired by HIV infection. In a new paper in the journal Blood, Delphine Sauce and colleagues delve into the issue further by analyzing circulating CD34+ hematopoietic progenitor cells (HPC) in over one hundred HIV positive individuals at various stages of disease, compared to both age-matched and elderly (75-96 years old) uninfected controls. The research reveals significant correlations between the number of HPC and multiple types of immune cells including CD4 T cells, CD8 T cells, B cells, natural killer cells and neutrophils (the strongest correlation being between circulating HPC and CD4 T cells). The number of HPC is found to decline over the course of HIV disease progression such that middle-aged HIV-positive individuals with CD4 T cell counts less than 200 had similar levels of circulating HPCs to the elderly uninfected controls.

Additional analyses show that markers of immune activation such as CD38 expression on CD8 T cells are inversely associated with HPCs; the higher the levels of immune activation, the lower the HPC counts. The researchers demonstrate that among elite controllers with declining CD4 T cell counts, HPC numbers and functional capacity are diminished despite persistently low viral load, consistent with the link between immune activation and CD4 T cell loss that has been reported in this population. HIV-positive individuals with poor CD4 T cell recovery despite antiretroviral therapy (ART) also show reduced HPC numbers and functional capacity compared to individuals with better immune reconstitution.

The study authors conclude that preservation of lymphocyte production capacity (lymphopoiesis) is important for preventing HIV disease progression and that strategies for enhancing lymphopoiesis should be evaluated in the setting of poor CD4 T cell recovery on ART. One approach that is currently under evaluation in a clinical trial for people on ART with CD4 T cell counts less than 250 is TXA127 (angiotensin 1-7), a drug formulation of a naturally occurring substance that may stimulate production of HPCs.

Published online before print March 24, 2011, doi: 10.1182/blood-2011-01-331306

Blood March 24, 2011 blood-2011-01-331306

HIV disease progression despite suppression of viral replication is associated with exhaustion of lymphopoiesis

Delphine Sauce1, Martin Larsen2, Solene Fastenackels1, Michele Pauchard3, Hocine Ait-Mohand4, Luminita Schneider3, Amelie Guihot1, Faroudy Boufassa5, John Zaunders6, Malika Iguertsira7, Michelle Bailey6, Guy Gorochov2, Claudine Duvivier8, Guislaine Carcelain9, Anthony D Kelleher10, Anne Simon7, Laurence Meyer11, Dominique Costagliola3, Steven G Deeks12, Olivier Lambotte13, Brigitte Autran1, Peter W Hunt12, Christine Katlama3, and Victor Appay1,*

1 INSERM UMR S 945, Infections and Immunity, Avenir Group, Universite Pierre et Marie Curie-Paris6, Hopital Pitie-Salpetriere, Paris, France;

2 Immunoregulation and Immunotherapy, INSERM UMR S 945, Universite Pierre et Marie Curie-Paris6, Hopital Pitie-Salpetriere, Paris, France;

3 INSERM UMR S 943, Universite Pierre et Marie Curie-Paris6, Hopital Pitie-Salpetriere, Paris, France;

4 AP-HP, Groupe hospitalier Pitie-Salpetriere, Service des Maladies Infectieuses et Tropicales, Paris, France;

5 INSERM U81018, University Paris-Sud, Hopital Bicetre, Le Kremlin-Bicetre, France;

6 St Vincent's Centre for Applied Medical Research and University of New South Wales, Sydney, NSW, Australia;

7 AP-HP, Groupe hospitalier Pitie-Salpetriere, Service de Medecine Interne, Paris, France;

8 Institut Pasteur, Centre Medical de l'Institut Pasteur; Centre d'Infectiologie Necker-Pasteur, Departement Infection et Epidemiologie, Paris, France;

9 AP-HP, Groupe hospitalier Pitie-Salpetriere, Laboratoire d'Immunologie Cellulaire et Tissulaire, Paris, France;

10 St. Vincent's Centre for Applied Medical Research and University of New South Wales, Sydney, NSW, Australia;

11 AP-HP, Service d'Epidemiologie et de Sante Publique, Hopital Bicetre, Le Kremlin-Bicetre, France;

12 HIV/AIDS Division, Department of Internal Medicine, University of California, San Francisco, San Francisco, CA, United States;

13 AP-HP, Department of Internal Medicine and Infectious Diseases, Hopital Bicetre, Le Kremlin-Bicetre, France

Abstract

The mechanisms of CD4+ T cell count decline, the hallmark of HIV disease progression, and its relationship to elevated levels of immune activation are not fully understood. Massive depletion of CD4+ T cells occurs during the course of HIV-1 infection, so that maintenance of adequate CD4+ T cell levels likely depends primarily on the capacity to renew depleted lymphocytes, i.e. the lymphopoiesis. We performed here a comprehensive study of quantitative and qualitative attributes of CD34+ hematopoietic progenitor cells directly from the blood of a large set of HIV infected individuals compared with uninfected donors, in particular elderly. Our analyses underline a marked impairment of primary immune resources with the failure to maintain adequate lymphocyte counts. Systemic immune activation emerges as a major correlate of altered lymphopoiesis, which can be partially reversed with prolonged antiretroviral therapy. Importantly, HIV disease progression despite elite control of HIV replication or virological success on antiretroviral treatment is associated with persistent damage to the lymphopoietic system, or exhaustion of lymphopoiesis. These findings highlight the importance of primary hematopoietic resources in HIV pathogenesis and the response to antiretroviral treatments.

Jostling Latent HIV from Slumber

A study in the new issue of the Journal of Immunology suggests that triggering a cell surface molecule called toll-like receptor 8 (TLR8) may be a means to activating latent HIV infection. Erika Schlaepfer and Roberto Speck report that, in vitro, targeting TLR8 with the drug resiquimod (aka R-848) prompted HIV activity in latently infected cells of myeloid-monocytic origin (which include monocytes, macrophages, dendritic cells, microglial cells, and hematopoietic stem cells) and also had an activating effect on HIV in latently infected CD4 T cells, by causing production of the cytokine TNF-alpha. The researchers took a very preliminary look at whether individuals on HAART might be able to respond to such an approach, and found that--solely based on TNF-alpha production--their monocytes reacted to TLR8 stimulation comparably to those from HIV negative controls. 

The conclusion from the findings is that “TLR8 agonists, in combination with HAART, are intriguing compounds for purging HIV from its latent reservoirs and sanctuary sites.” Schlaepfer and Speck caution, however, that “we believe that compounds, and, in particular, TLR8 agonists, acting on the latent reservoir should be given in cycles, because a longer-term administration of any such compound might be too toxic.” Resiquimod has been studied in humans with hepatitis C infection and appeared quite potent in terms of inducing alpha interferon production (and associated side effects). The manufacturer, 3M, does not appear to be developing it further but has recently offered it to the pharmaceutical industry for license. Development of a TLR7 agonist as a hepatitis C treatment was stopped in 2007 due to toxicology studies showing "intense immune stimulation in animals."

The Journal of Immunology, April 1, 2011, vol. 186 no. 7 4314-4324

TLR8 Activates HIV from Latently Infected Cells of Myeloid-Monocytic Origin Directly via the MAPK Pathway and from Latently Infected CD4+ T Cells Indirectly via TNF-α

Erika Schlaepfer and Roberto F. Speck

Division of Infectious Diseases and Hospital Epidemiology, University Hospital of Zurich, University of Zurich, 8091 Zurich, Switzerland

Abstract

We previously showed that the TLR7/8 agonist, R-848, activated HIV from cells of myeloid-monocytic origin. In this work, we show that this effect was solely due to triggering TLR8 and that NF-κB was involved in the TLR8-mediated activation of HIV from latently infected cells of myeloid-monocytic origin. Inhibition of Erk1/2 or p38α resulted in attenuation of TLR8-mediated activation of NF-κB. Western blots confirmed that TLR8 triggering activated Erk1/2 and p38α but, surprisingly, not JNK. Although the Erk1/2 inhibitors resulted in a less attenuated TLR8-mediated NF-κB response than did p38α inhibitors, they had a more pronounced effect on blocking TLR8-mediated HIV replication, indicating that other transcription factors controlled by Erk1/2 are involved in TLR8-mediated HIV activation from latently infected cells. TNF-α, which was secreted subsequent to TLR8 triggering, contributed to the activation of HIV from the latently infected cells in an autocrine manner, revealing a bimodal mechanism by which the effect of TLR8 triggering can be sustained. We also found that TNF-α secreted by myeloid dendritic cells acted in a paracrine manner in the activation of HIV from neighboring latently infected CD4+ T cells, which do not express TLR8. Notably, monocytes from highly active antiretroviral therapy-treated HIV+ patients with suppressed HIV RNA showed a robust TNF-α secretion in response to TLR8 agonists, pointing to a functional TLR8 signaling axis in HIV infection. Thus, triggering TLR8 represents a very promising strategy for attacking the silent HIV from its reservoir in HIV+ patients treated successfully with highly active antiretroviral therapy.