TAG HIV Basic Science, Vaccines, and Cure Project Blog

Slides & Abstracts from the 4th International Workshop on HIV Persistence during Therapy

Every other year since 2003, researcher Alain Lafeuillade has chaired a workshop on HIV persistence during therapy. The goal of the meeting is to work toward strategies for curing HIV infection, either by eradicating the virus or inducing long-term control of viral replication in the absence of ongoing treatment. The fourth meeting was held in December of 2009, and abstracts and selected slide presentations are now available on the IHL Press website. 

Final Program and Abstract Book

Selected Slide Presentations

 

Getting to the Guts of Immune Control

A new study from Barbara Shacklett’s research group investigates the contribution of mucosal HIV-specific CD4 T cell responses to immune control of viral replication. To the best of my knowledge, it is only the second study to measure HIV-specific CD4 T cells in the gut (a prior paper by Satya Dandekar’s group reported that the presence of these responses was associated with better gut CD4 T cell reconstitution on ART). The researchers find a significant association between the numbers of polyfunctional HIV-specific CD4 T cells in the gut and virological control in the absence of ART. Individuals with certain class II HLA genes mount particularly strong responses, and a correlation between the magnitude of the gut HIV-specific CD4 T cell response and HIV-specific CD8 T cell response is documented. The authors suggest that strategies to induce polyfunctional HIV-specific CD4 T cells in the gut might offer benefit in both the preventive and therapeutic vaccine context.  

J. Virol. doi:10.1128/JVI.00980-10

HIV Controllers HLA-DRB1*13 and HLA-DQB1*06 Have Strong, Polyfunctional Mucosal CD4+ T-cell Responses

April L. Ferre, Peter W. Hunt, Delandy H. McConnell, Megan M. Morris, Juan C. Garcia, Richard B. Pollard, Hal F. Yee Jr, Jeffrey N. Martin, Steven G. Deeks, and Barbara L. Shacklett

Department of Medical Microbiology and Immunology; Division of Gastroenterology; Division of Infectious Diseases, School of Medicine, University of California, Davis, CA; Positive Health Program, Department of Medicine; Division of Gastroenterology; Department of Epidemiology and Biostatistics San Francisco General Hospital, University of California, San Francisco, CA

Abstract

A small percentage of HIV-infected individuals, termed elite controllers, are able to spontaneously control HIV replication in blood. As the gastrointestinal mucosa is an important site of HIV transmission and replication, as well as CD4+ T-cell depletion, it is important to understand the nature of the immune responses occurring in this compartment. Although the role of the HIV-specific CD8+ T-cell responses in mucosal tissues has been described, few studies have investigated the role of mucosal HIV-specific CD4+ T-cells. In this study, we assessed HIV-specific CD4+ T-cell responses in the rectal mucosa of 28 "controllers" (VL<2,000 copies/mL), 14 "non-controllers" (VL<10,000 copies/mL), and 10 individuals on HAART (VL<50 copies/mL). Controllers had higher magnitude Gag-specific mucosal CD4+ T-cell responses than individuals on HAART (p<0.05), as measured by their ability to produce IFN, IL-2, TNF, and MIP-1. The frequency of polyfunctional mucosal CD4+ T-cells was also higher in controllers compared to non-controllers or individuals on HAART (p<0.05). Controllers with the strongest HIV-specific CD4+ T-cell responses possessed class II HLA alleles, HLA-DR*13 and/or HLA-DQ*06, previously associated with a non-progression phenotype. Strikingly, individuals with both HLA-DR*13 and HLA-DQ*06 had highly polyfunctional mucosal CD4+ T-cells compared to individuals with HLA-DQ*06 alone or other class II alleles. The frequency of polyfunctional CD4+ T-cells in rectal mucosa positively correlated with the magnitude of the mucosal CD8+ T-cell response (Spearman r=0.43, p=0.005), suggesting that increased CD4+ T-cell "help" may be important in maintaining strong CD8+ T-cell responses in the gut of HIV controllers.

Chloroquine May Temper Immune Activation

A newly published analysis of a small, 8-week study of the antimalarial drug chloroquine reports a significant decline in CD8 T cell activation (as measured by expression of CD38 and HLA-DR) and CD8 and CD4 T cell turnover (measured by the cell cycle marker Ki67). A slightly larger 30-person study involving 12 weeks of chloroquine treatment is now being conducted by the ACTG. Both studies involve people not receiving antiretroviral therapy (ART). Given that there is an association between persistent immune activation and poor immune reconstitution on ART, these results suggest chloroquine may also deserve evaluation in immunological non-responders who currently have few research options. In terms of the mechanism of action, the authors of the new paper note that chloroquine is known to inhibit signaling via several immune system proteins called toll-like receptors (TLR3, TLR7, TLR8, and TLR9) and they state that “it is plausible that suppression of intracellular TLR signaling resulted in the decrease in CD38+ HLA–DR+ CD8 T cells.”

J. Virol. doi:10.1128/JVI.01466-10

Reduction of Immune Activation during Chronic HIV Infection with Chloroquine Therapy

Shannon M Murray, Carrie M Down, David R Boulware, William M Stauffer, Winston P Cavert, Timothy W Schacker, Jason M Brenchley, and Daniel C Douek

National Institutes of Health, National Institute of Allergy and Infectious Diseases, Vaccine Research Center, Human Immunology Section, Bethesda, MD; Division of Infectious Diseases and International Medicine, Dept. of Medicine, University of Minnesota, Minneapolis, MN

Abstract

Increased levels of activated T cells are a hallmark of the chronic stage of human immunodeficiency virus (HIV) infection and are highly correlated with HIV disease progression. We evaluated chloroquine (CQ) as a potential therapy to reduce immune activation during HIV infection. We found that the frequency of CD38+ HLA-DR+ CD8 T cells, as well as Ki-67 expression in CD8 and CD4 T cells, were significantly reduced during CQ treatment. Our data indicate that treatment with CQ reduces systemic T cell immune activation and thus its use may be beneficial for certain groups of HIV-infected individuals.

Losing Immunological Naivete

The key cells of the adaptive immune system – CD4 T cells, CD8 T cells and B cells – are each divided into two vast pools in the body: naïve cells, which have not yet encountered an antigen to respond to, and memory cells, which are descendents of naïve cells that met an antigen and responded to it sometime in the past. As people age, naïve cell numbers decline and memory responses to the many different pathogens encountered over a lifetime accumulate. In addition to the decline in naïve cell numbers, there is evidence that remaining cells become less functionally competent in older individuals due to increased cell division (as less naïve cells are produced, extant cells divide more to maintain numbers).

Two recent papers discuss age-associated changes in naïve T cell homeostasis in the context of HIV infection and elderly uninfected individuals. Tammy Rickabaugh and Beth Jamieson note the striking similarity between the effects of HIV infection and aging on naïve T cell pools and hypothesize that this “may play a role in the development of age-inappropriate diseases in HIV-1+ individuals and contribute to poorer clinical outcomes observed in the older HIV+ population.” Their research group at UCLA is continuing to focus on this aspect of HIV pathogenesis.

In the pithily-named journal “Age,” Sara Ferrando-Martínez and colleagues describe a comparison of thymic function and naïve T cell parameters between individuals under 50 vs. over 50 years of age. The study is unusual in that it recruited individuals undergoing cardiac surgery in order to facilitate sampling of thymic tissue. The main findings echo data from mouse models, showing that decreased thymic output of naïve T cells is associated with increased proliferation of naïve T cells in the periphery. The increased levels of naïve T cell division were in turn linked to higher expression of the cellular senescence marker CD57 and shortened telomeres. The authors suggest that not only declining naïve cell numbers but also loss of function may contribute to poor immune responses in the elderly; however they stress that additional studies will be needed to confirm or refute this hypothesis.

In terms of the therapeutic implications of this research, Rickabaugh and Jamieson state: “Given the similarities in alterations of the T-cell compartment with aging and HIV-1 infection, the development of therapeutics to improve thymopoeisis, enhance peripheral T-cell function, and prevent or delay senescence may prove to be beneficial to both affected populations.”

Immunol Res. 2010 Aug 24. [Epub ahead of print]

A challenge for the future: aging and HIV infection.

Rickabaugh TM, Jamieson BD.

UCLA AIDS Institute and Department of Medicine, David Geffen School of Medicine, University of California, 10833 Le Conte Ave, Mail Code 174521, Los Angeles, CA, 90095-1745, USA.

Abstract

Older individuals (>/=50 years of age) are increasingly becoming a new at-risk group for HIV-1 infection and, together with those surviving longer due to the introduction of anti-retroviral therapy (ART), it is predicted that more than half of all HIV-1-infected individuals in the United States will be greater than 50 years of age in the year 2015. Older individuals diagnosed with HIV-1 are prone to faster disease progression and reduced T-cell reconstitution despite successful virologic control with anti-retroviral therapy (ART). There is also growing evidence that the T-cell compartment in HIV-1(+) adults displays an aged phenotype, and HIV-1-infected individuals are increasingly diagnosed with clinical conditions more commonly seen in older uninfected persons. As aging in the absence of HIV infection is associated with alterations in T-cell function and immunosenescence, the combined impact of both HIV-1 infection and aging may provide an explanation for poorer clinical outcomes observed in older HIV-1-infected individuals. Thus, the development of novel therapeutics to stimulate immune function and delay immunosenescence is critical and would be beneficial to both the elderly and HIV-1-infected individuals.

Age (Dordr). 2010 Aug 11. [Epub ahead of print]

Age-related deregulation of naive T cell homeostasis in elderly humans.

Ferrando-Martínez S, Ruiz-Mateos E, Hernández A, Gutiérrez E, Rodríguez-Méndez MD, Ordoñez A, Leal M.

Laboratory of Immunovirology, Biomedicine Institute of Seville (IBIS). Service of Infectious Diseases, Virgen del Rocío University Hospital, Avda. Manuel Siurot s/n, 41013, Seville, Spain.

Abstract

Immunosenescence is characterized by phenotypic and functional changes of effector memory T cells. In spite of the well-described senescent defects of these experienced T cells, immune responses to new pathogens are also deeply affected in elderly humans, suggesting that naive T cells could also show age-related defects. It has been reported in both, animal models and humans, alterations of the naive T cell turnover associated to advanced age or low thymic function. However, as far as we know, homeostatic mechanisms involved in the deregulation of naive T cell peripheral dynamics and their consequences are still not well understood. Thus, the aim of our study was to analyze homeostatic parameters of peripheral naive T cells and their relationship with thymic function in young and elderly humans. Our results show that lower naive T cell numbers were associated with a lower thymic function and higher activation and proliferating naive T cell levels. We then analyzed sjTREC numbers and relative telomere length from sorted naive T cells. Our results show that the aberrant activation and proliferation status was related to lower sjTREC numbers (a peripheral proliferation marker) and both, higher CD57 expression levels and shortened telomeres (replicative senescence-related markers). Elderly individuals show a greater contraction of the CD8 naive T cell numbers and all homeostatic alterations were more severe in this compartment. In addition, we found that low functional thymus show a CD4-biased thymocyte production. Taken together, our results suggest a homeostatic deregulation, affecting mostly the naive CD8 T cell subset, leading to the accumulation of age-associated defects in, otherwise, phenotypically naive T cells.

Searching for Signs of TB Activation

As eloquently described by Javid Syed in a chapter of TAG’s recent pipeline report, TB diagnostics remain woefully inadequate for addressing the challenges presented by the disease. One key goal for scientists is to find ways to better discriminate active from latent infection, and two recent papers describe possible progress in this effort.

In the journal Nature, Matthew Berry and colleagues use a systems biology approach to identify a gene expression pattern associated with active TB, and speculate that this pattern may be able to identify the individuals with latent infection most likely to develop disease; however, longitudinal studies will be needed to show whether this is indeed the case. The work is encouraging in that it suggests that new technologies may be able to address previously intractable problems in TB diagnosis, but translating these advances into something usable at the health posts where most people seek TB care will still be a daunting task. 

The second paper in PLoS One reports on a more traditional approach of measuring cytokine production in whole blood (as is currently done with interferon gamma-based assays) but analyzes a broader range of cytokines after 7 days of in vitro stimulation with TB antigens. The researchers report that a combined analysis of TNF-alpha, IL-12 and IL-17 production after stimulation with the TB10.4 antigen was better able to discriminate between active TB cases and latent infection than the use of interferon gamma alone.

Nature. 2010 Aug 19;466(7309):973-7.

An interferon-inducible neutrophil-driven blood transcriptional signature in human tuberculosis.

Berry MP, Graham CM, McNab FW, Xu Z, Bloch SA, Oni T, Wilkinson KA, Banchereau R, Skinner J, Wilkinson RJ, Quinn C, Blankenship D, Dhawan R, Cush JJ, Mejias A, Ramilo O, Kon OM, Pascual V, Banchereau J, Chaussabel D, O'Garra A.

Division of Immunoregulation, MRC National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, UK.

Abstract

Tuberculosis (TB), caused by infection with Mycobacterium tuberculosis, is a major cause of morbidity and mortality worldwide. Efforts to control it are hampered by difficulties with diagnosis, prevention and treatment. Most people infected with M. tuberculosis remain asymptomatic, termed latent TB, with a 10% lifetime risk of developing active TB disease. Current tests, however, cannot identify which individuals will develop disease. The immune response to M. tuberculosis is complex and incompletely characterized, hindering development of new diagnostics, therapies and vaccines. Here we identify a whole-blood 393 transcript signature for active TB in intermediate and high-burden settings, correlating with radiological extent of disease and reverting to that of healthy controls after treatment. A subset of patients with latent TB had signatures similar to those in patients with active TB. We also identify a specific 86-transcript signature that discriminates active TB from other inflammatory and infectious diseases. Modular and pathway analysis revealed that the TB signature was dominated by a neutrophil-driven interferon (IFN)-inducible gene profile, consisting of both IFN-gamma and type I IFN-alphabeta signalling. Comparison with transcriptional signatures in purified cells and flow cytometric analysis suggest that this TB signature reflects changes in cellular composition and altered gene expression. Although an IFN-inducible signature was also observed in whole blood of patients with systemic lupus erythematosus (SLE), their complete modular signature differed from TB, with increased abundance of plasma cell transcripts. Our studies demonstrate a hitherto underappreciated role of type I IFN-alphabeta signalling in the pathogenesis of TB, which has implications for vaccine and therapeutic development. Our study also provides a broad range of transcriptional biomarkers with potential as diagnostic and prognostic tools to combat the TB epidemic.

PLoS One. 2010 Aug 24;5(8). pii: e12365.

Production of TNF-alpha, IL-12(p40) and IL-17 Can Discriminate between Active TB Disease and Latent Infection in a West African Cohort.

Sutherland JS, de Jong BC, Jeffries DJ, Adetifa IM, Ota MO.

Bacterial Diseases Programme, Medical Research Council Laboratories, Banjul, The Gambia.

Abstract

BACKGROUND: Mycobacterium tuberculosis (MTb) infects approximately 2 billion people world-wide resulting in almost 2 million deaths per year. Determining biomarkers that distinguish different stages of tuberculosis (TB) infection and disease will provide tools for more effective diagnosis and ultimately aid in the development of new vaccine candidates. The current diagnostic kits utilising production of IFN-gamma in response to TB antigens can detect MTb infection but are unable to distinguish between infection and disease. The aim of this study was to assess if the use of a longer term assay and the analysis of multiple cytokines would enhance diagnosis of active TB in a TB-endemic population.

METHODS: We compared production of multiple cytokines (TNF-alpha, IFN-gamma, IL-10, IL-12(p40), IL-13, IL-17 and IL-18) following long-term (7 days) stimulation of whole-blood with TB antigens (ESAT-6/CFP-10 (EC), PPD or TB10.4) from TB cases (n = 36) and their Mycobacterium-infected (TST+; n = 20) or uninfected (TST-; n = 19) household contacts (HHC).

RESULTS AND CONCLUSIONS: We found that TNF-alpha production following EC stimulation and TNF-alpha and IL-12(p40) following TB10.4 stimulation were significantly higher from TB cases compared to TST+ HHC, while production of IFN-gamma and IL-13 were significantly higher from TST+ compared to TST- HHC following PPD or EC stimulation. Combined analysis of TNF-alpha, IL-12(p40) and IL-17 following TB10.4 stimulation resulted in 85% correct classification into TB cases or TST+ HHC. 74% correct classification into TST+ or TST- HHC was achieved with IFN-gamma alone following TB10.4 stimulation (69% following EC) and little enhancement was seen with additional cytokines. We also saw a tendency for TB cases infected with M. africanum to have increased TNF-alpha and IL-10 production compared to those infected with M. tuberculosis. Our results provide further insight into the pathogenesis of tuberculosis and may enhance the specificity of the currently available diagnostic tests, particularly for diagnosis of active TB.

Making Memories That Last a Lifetime

During the plague of Athens in 430 b.c., the Greek historian Thucydides made the first known reference to immunological memory when he observed that the “same man was never attacked twice.” More than two thousand years later, technological advances have allowed scientists to begin unraveling the molecular underpinnings of the phenomenon. It is now appreciated that the main components of the adaptive immune system--B cells, CD4 T cells and CD8 T cells--respond to infections by developing specialized abilities that can often mediate protection against re-infection or--in the case of pathogens that are controlled rather than eliminated from the body--disease. The long-lived B cells, CD4 T cells and CD8 T cells that perform these vital functions are known as “memory” cells.

The laboratory of Rafi Ahmed at Emory University has long been at the forefront of research into immunological memory, particularly as it pertains to CD8 T cells. In a new free-access paper in the journal International Immunology, Ahmed and colleagues review how changes in gene expression contribute to the enhanced infection-fighting functions of memory CD8 T cells, and outline how these functions are inherited by the progeny of memory cells via the wonders of epigenetics. The review concludes by suggesting that it may eventually become possible to correct memory cell dysfunction by targeting gene regulation mechanisms.

International Immunology Advance Access published online on August 23, 2010

International Immunology, doi:10.1093/intimm/dxq437

review-article

Making memories that last a lifetime: heritable functions of self-renewing memory CD8 T cells

Ben Youngblood1,2, Carl W. Davis1,2 and Rafi Ahmed1,2

1 Emory Vaccine Center, Atlanta, GA 30329, USA

2 Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, GA 30322, USA

Clonal expansion of virus-specific naive T cells during an acute viral infection results in the formation of memory CD8 T cells that provide the host with long-term protective immunity against the pathogen. Memory CD8 T cells display enhanced effector functions compared with their naive precursors, allowing them to respond more rapidly and effectively to antigen re-encounter. The enhanced functions of memory CD8 T cells are mediated by heritable changes in gene regulation. Expression of select transcription factors along with locus-specific epigenetic modifications are coupled to and are essential in the formation of memory-specific gene expression patterns. Here, we will review the changes in gene expression that accompany development of memory CD8 T cells and discuss chromatin modifications as a potential means for heritable propagation of these changes during homeostatic cell division of self-renewing memory CD8 T cells. Also, we will discuss therapies that manipulate heritable gene regulation as a potential mechanism to restore function to non-functional memory CD8 T cells to combat chronic viral infection.