Meeting Minutes - March 24, 2011

Office of AIDS Research Advisory Council
Thirty-second Meeting
March 24, 2011

National Institutes of Health
U.S. Department of Health and Human Services
5635 Fishers Lane Conference Center
Rockville, MD

Members Present: Dr. Sharon L. Hillier (Chair), Dr. Jack Whitescarver (Executive Secretary), Dr. Judith Auerbach, Ms. Dawn Averitt Bridge, Dr. David B. Clifford, Dr. Carrie E. Foote, Dr. Betsy C. Herold, Ms. Catalina Sol, Dr. Ronald Swanstrom, Dr. Irene S. Vernon, Dr. Paul Volberding, and Dr. Judith N. Wasserheit

Ex Officio Members Present: Dr. Ralph J. DiClemente, Dr. Carl W. Dieffenbach, Dr. John Douglas for Dr. Kevin Fenton, Dr. H. Kim Lyerly, Dr. Julie Ake for Dr. Nelson L. Michael, Dr. Christel H. Uittenbogaart, and Dr. Steven M. Wolinsky

Invited Speakers and Guests: Dr. Paula Cannon, Dr. Nicolas Chomont, Mr. Jeffrey Crowley, Dr. Steven G. Deeks, Dr. Warner C. Greene, Dr. H. Clifford Lane, Dr. David Margolis, Dr. John W. Mellors, Mr. Greg Millet, Dr. Rafick-Pierre Sékaly, Dr. Robert F. Siliciano, and Dr. Joseph K. Wong

Welcome and Meeting Overview

The National Institutes of Health (NIH) Office of AIDS Research Advisory Council (OARAC) convened its thirty-second meeting at 8:35 a.m. at the Fishers Lane Conference Center in Rockville, Maryland.  Dr. Sharon Hillier, Chair, welcomed the OARAC members, invited speakers, and guests. 

The topic of the meeting was research leading to a cure for HIV/AIDS.  Dr. Hillier noted that the presentations would focus on basic and clinical science related to HIV reservoirs.  The specific issues to be addressed were the persistence of HIV in anatomic reservoirs; immune-based therapeutics; immunological mechanisms of HIV persistence; the design of target-specific T cells to eradicate HIV; and novel approaches to HIV/AIDS therapeutics. 

Dr. Hillier said that the Office of AIDS Research (OAR) and the OARAC are approaching a transformative moment as discussion of a cure for HIV/AIDS is now possible after 30 years of the AIDS pandemic.  She noted that this OARAC meeting is one of a series of OAR-sponsored efforts on the topic which have led to the recent announcement by the International AIDS Society (IAS) of the beginning of a process to develop a global scientific strategy and enhanced research coordination toward a cure.  Dr. Hillier referred the OARAC members to IAS information provided in their meeting folders.  She noted that several speakers at the meeting are members of the international advisory board and scientific working group developing the IAS global strategy.  Following meetings and discussions over the next year, the global strategy will be formally launched in summer 2012 at a scientific symposium and other events co-sponsored by the OAR and IAS in conjunction with the IAS conference in Washington, D.C. 

Dr. Hillier commented that the intent of the new global strategy is to maximize precious and constrained resources in support of the highest-priority research conducted as efficiently as possible in a coordinated, cross-disciplinary way.  She noted that the OAR has taken steps to form a trans-NIH strategy of research toward a cure and has cited this area of research as a priority in its Fiscal Year (FY 2012) Congressional Justification.  OAR also has instituted a new budget code for tracking NIH-sponsored research toward a cure. 
 
The minutes of the November 9, 2010, OARAC meeting were approved as submitted.

Director’s Report

Dr. Jack Whitescarver, Director, OAR, thanked everyone for coming to address research toward a cure for HIV/AIDS.  He introduced Mr. Jeffrey Crowley, Director of the Office of National AIDS Policy (ONAP) at the White House and Mr. Greg Millett, Senior Policy Advisor, ONAP, who is on detail from the Centers for Disease Control and Prevention (CDC).

Dr. Whitescarver reported on a budget meeting convened earlier in the morning by Dr. Francis Collins, NIH Director, and attended by all of the NIH Institute and Center (IC) directors.  He noted that NIH continues to operate under a Continuing Resolution for FY 2011 until April 8 and that the Congress has not yet acted on the FY 2012 budget.  He said NIH is encouraging the ICOs to continue their levels of support for NIH program activities and that the funding of extramural research project grants (RPGs) will be maintained as possible. 

Dr. Whitescarver referred the OARAC members to the FY 2012 Congressional Justification provided in their meeting folders.  He said the FY 2012 President’s Budget request for NIH includes a 2.4 percent increase over the FY 2011 estimate and the NIH budget for AIDS research would grow at the same percent increase.  He noted that in FY 2012, the Secretary of Health and Human Services (HHS) will transfer 1 percent of each agency’s domestic AIDS budget to the Office of the Assistant Secretary for Health (ASH) to support implementation of the President’s National HIV/AIDS Strategy.  For the NIH AIDS program, this represents approximately $27 million.  With this transfer, the President’s Budget request would yield about a 1.5 percent increase in the NIH AIDS research program for FY 2012.

Dr. Whitescarver recognized three OARAC members whose terms will expire after the meeting -  Dr. Betsy C. Herold, Dr. Paul Volberding, and Ms. Dawn Averitt Bridge.  He thanked them for their long-time support of OAR and commitment to AIDS research and presented each with a certificate of appreciation from the Secretary, HHS.

UPDATE ON OARAC WORKING GROUPS FOR TREATMENT AND PREVENTION GUIDELINES

Dr. H. Clifford Lane, Clinical Director and Director, Division of Clinical Research and Special Projects, National Institute of Allergy and Infectious Diseases (NIAID), NIH, and Co-Chair of OARAC’s Adult and Adolescent Working Group, summarized recent updates of the treatment and prevention guidelines. 

Dr. Lane reported that the Guidelines for the Use of Antiretroviral Agents in HIV-1-Infected Adults and Adolescents were updated in January 2011.  Four key changes included:  1) less frequent monitoring (i.e., 6–12 months, instead of 3–6 months) of CD4+ counts for stable patients with viral suppression; 2) addition of the maraviroc (MVC)-based regimen as an “acceptable” initial antiretroviral treatment (ART) in treatment-naïve patients; 3) change of the saquinovir (SQV/r)-based regimen from “alternative” to “acceptable” initial ART, due to a recent warning by the Food and Drug Administration related to electrocardiogram changes; and 4) earlier initiation of ART in patients co-infected with tuberculosis (TB).  Dr. Lane highlighted the new HTML format of the guidelines launched in mid-March.  He noted that the new format allows for real-time updates; easier navigation, searching, and printing of separate sections; and tracking and generation of usage statistics per section.  He welcomed feedback on the change and anticipated that other guidelines will transition to the HTML format in the future.

Dr. Lane noted that the Prevention and Treatment of Opportunistic Infections in Adults and Adolescents Guidelines is currently being revised and will be available later this year.  The updated guidelines will be an online publication only.  He noted that major changes in the guidelines will include:  harmonization of the style, content, and rating system with those of the adult ART guidelines; segmentation of tables; and referencing within individual content chapters.  The guidelines will include an emphasis on when to start ART, with consideration of immune reconstitution inflammatory syndrome, as well as changes regarding co-infections including tuberculosis, human papillomavirus, hepatitis B virus, and hepatitis C virus.

Dr. Lane reported that a 2011 update of the Guidelines for the Prevention and Treatment of Opportunistic Infections among HIV-Exposed and HIV-Infected Children also is under way.  The final document is expected in the summer.

The Guidelines for the Use of Antiretroviral Agents in Pediatric HIV Infection is undergoing revision.  Dr. Lane noted that the criteria for when to start ART is being expanded to include initiating ART at all CD4+ T cell counts in children more than 1 year of age and for children more than 5 years of age when their counts have risen to 500 cells/uL.  The revisions include:  changes to the “what to start” section; addition of new toxicity sections; and updated information on drugs administered to children.

Dr. Lane reported that the Recommendations for Use of Antiretroviral Drugs in Pregnant HIV-1-Infected Women for Maternal Health and Interventions to Reduce Perinatal HIV Transmission in the United States will be updated later this year.  The updates will include reclassification of some antiretrovirals (ARVs) that are used in pregnancy including tenofovir, indinavir, and nelfinavir.  In addition, the revised guidelines will include a table on ARV drug use during pregnancy that includes dosing recommendations.  New sections will present information and recommendations pertaining to preconception care for HIV sero-discordant couples, acute HIV infection during pregnancy, HIV-2 infection during pregnancy, and neonatal prophylaxis when mothers are not receiving ARVs antepartum. 

INTRODUCTION TO MEETING TOPIC 

Dr. Paul Volberding, OARAC member, Professor of Medicine, University of California, San Francisco, and Chief of the Medical Service at the San Francisco Veterans Affairs Medical Center, introduced the meeting topic by noting that substantial research over the past 30 years has provided the scientific basis for being able to now address the possibility of a cure for HIV/AIDS.  Three main indications of having reached this point in time are:  availability of potent antiretrovirals that can suppress HIV below the limits of detection; powerful new technologies to identify the virus, viral latency, and viral reservoirs and potential gene activation to eradicate HIV in latently infected cells; and the report of a first-ever “cure” of HIV infection in a patient who has been referred to as “the Berlin patient”.  He noted that there is great momentum now to move beyond the limitations of bone marrow transplants to more promising and realistic strategies for HIV eradication.

Dr. Hillier thanked Dr. Volberding for helping to organize today’s meeting. 

BARRIERS TO HIV ERADICATION

Dr. Robert F. Siliciano, Professor of Medicine, Johns Hopkins University School of Medicine, and Investigator, Howard Hughes Medical Institute, discussed the promise of efforts to eradicate HIV infection and presented data on the dynamics of HIV replication.  He cited three steps for curing HIV infection:  halting HIV replication; identifying all reservoirs of non-replicating virus; and developing strategies to eliminate each HIV reservoir.  He noted that the first step has been achieved with ARVs, but that the second and third steps are more difficult.  He proposed that researchers will need to clarify the mechanisms of HIV persistence, discover new drugs and strategies for eradicating HIV, develop appropriate animal models, and conduct clinical trials of relevant strategies.  He commented that support for research collaboratories will be essential to conducting studies in this area.

Dr. Siliciano addressed the question of whether the persistence of HIV reflects ongoing viral replication or residual viremia in HIV reservoirs.  He presented clinical data showing the decline of plasma virus levels in patients started on highly active ART.  He noted that all of the ARVs used to treat HIV infection prevent new cells from being infected, but these anti-HIV drugs do not block virus production by cells that have integrated the provirus.  For a patient on ART, viremia declines to the limit of detection in a bi-phasic fashion with some infected cells decaying at a slower rate than others.  It is thought that these slower-decaying cells are latently infected resting CD4+ T cells—that can serve as a latent reservoir for HIV in which the virus persists unaffected by immune responses or ARVs.  If these transcriptionally silent cells are activated, they could begin to produce the virus. 

Dr. Siliciano noted that assay results show that all HIV-infected individuals have latently infected cells.  While this latency is a “rare” event, it cannot be eliminated by ART alone.  He suggested that stable HIV reservoirs, existing below the limit of detection of current clinical assays, prevent eradication of HIV and are predictive of a third phase of decay.  The residual viremia reflects release of HIV from these reservoirs rather than ongoing cycles of viral replication and the inability of intensified ART to have a measurable effect.  He suggested that the latent reservoir is replenished from HIV-infected memory T cells, not from HIV in the plasma of patients.

Dr. Siliciano emphasized that the complexity of residual viremia complicates identification of HIV reservoirs.  He cited research results that show residual viremia is dominated by a small number of viral clones that are underrepresented in resting CD4+ T cells. This suggests a second, major source of residual viremia and no evidence of HIV evolution. 

Dr. Siliciano noted that initial attempts to eliminate latent reservoirs are not selective for latent resting CD4+ T cells and are unacceptably toxic, as they induce global T cell activation.  He emphasized that in vitro models are needed to generate latently infected cells and to screen compounds that would activate latent HIV, but not T cells. 

Dr. Siliciano stated that there is a need to evaluate eradication strategies in animal models, develop and test new drug regimens, and develop methodologies to identify all viral reservoirs.  

CHARACTERISTICS OF RESIDUAL VIREMIA IN PATIENTS ON SUPPRESSIVE ANTIRETROVIRAL THERAPY

Dr. John W. Mellors, Professor of Medicine, Chief, Division of Infectious Diseases, and Director of the HIV/AIDS Program, University of Pittsburgh Medical Center, addressed persistent/residual viremia in HIV-infected patients on suppressive ART.  He presented on the dynamics of HIV replication, impact of ART intensification, genetic diversity in residual viremia, and relationship of viremia to immune activation. 

Dr. Mellors noted that eradication of HIV-1 will not be simple, as most patients treated for HIV-1 have residual viremia with HIV-1 RNA detected in the blood even when they received suppressive therapy for more than 4 years.  He commented that residual viremia in patients on ART correlates with their pretherapy levels of HIV-1 RNA and is independent of specific ART regimens.  Studies of patients on ART show that their HIV-1 levels decline over 4 years to reach a plateau that persists for years and it can be detected at 1 copy/ml.  Intensification of ART has no impact on this low-level residual viremia. 

Dr. Mellors reported that there is no evidence to date for evolution of the virus or emergence of drug-resistant variants.  He stated that studies on the genetic diversity of HIV-1 viremia using single-genome sequencing and sequence analyses before and during ART show no significant change in intra-patient diversity or structure of HIV cell population for up to 1 year of ART.  There also is no obvious change in HIV diversity over long-term suppression (10–15 years) by ART. 

Dr. Mellors noted that the focus of research has shifted to studying long-lived, chronically infected cells as the source of residual viremia and determining whether these are latently infected cells triggered to produce virus, or long-lived virus-producing cells, or both.  He noted that there may be many reservoirs for HIV-1 latency in blood.  He identified three key questions that warrant additional studies:  1) Are there isolated foci of ongoing, complete cycles of HIV-1 replication?  2) Which cells are long-lived or immortal HIV producers?  3) Where are the cells—in the liver, spleen, lymph nodes, gut, central nervous system, genital tract, or elsewhere? 

Dr. Mellors proposed that intervention strategies to eliminate long-lived, HIV-infected cells may include blocking ongoing replication with ART, activating HIV-1 expression from latently infected CD4+ memory T cells, and selectively killing cells that express HIV-1.  He suggested that additional research is needed on strategies to eliminate viral reservoirs including the use of the patients’ own stem cells.

HOW TO ROUSE A SLUMBERING HIV PROVIRUS

Dr. Warner C. Greene, Director, Gladstone Institute of Virology and Immunology, and Professor of Medicine, Microbiology, and Immunology, University of California, San Francisco, addressed the possibility of using a transcription factor, NF-kappa B, to stimulate reactivation of latent HIV.  He emphasized the need for appropriate models to study HIV latency.

Dr. Greene described the important role for NF-kappa B in HIV latency and activation of primary CD4+ T cells.  He described the steps by which the NF-kappa B pathway acts as an agonist of HIV-1 latency.  He suggested that NF-kappa B plays a key role in how activated cells can overcome the transcriptional interference that promotes a latent state.

Dr. Greene highlighted the need for physiologically relevant models (i.e., using CD4+ cells) to evaluate HIV latency.  While there are a number of promising cell models of HIV latency available, Dr. Greene stated that producing them is challenging.  An alternate model relies on latently infected CD4+ T cells generated ex vivo.  The advantages of this model include: production and analysis of cells within 6 days; effective assessment of viral reactivation; reproducibility; and ability to conduct detailed kinetic analyses. 

Dr. Greene summarized experimental data obtained with this model on HIV reactivation and kinetics as related to different HIV activators, donor CD4+ T cells, and inhibitors.  He noted that the model enables analyses of latency within the specific memory CD4+ T cell populations, where most researchers believe the HIV reservoir resides.  Using this model, CD4+ T cells can be purified unperturbed and HIV latency can be tested in central, transitional, and effector memory CD4+ T cells and in naïve CD4+ T cells. 

Dr. Greene proposed that there was a need for a research collaboratory on HIV latency that would engage NIH, academia, and the pharmaceutical industry to achieve scientific synergy needed in finding a cure for HIV/AIDS.  

DISCUSSION

OARAC members, speakers, and guests commented on the need to definitively distinguish viral replication from residual viremia existing in stable HIV reservoirs.  They noted that there is a critical need for collaborative research on HIV latency and eradication and that this could be conducted optimally in coordinated, intensive studies using a range of quantitative measures and agreed-upon measures of detection for different sites (e.g., gut, lymph nodes, and terminal ileum).  Viral activation and expression in the brain is a major research frontier.  Psychosocial research should address the areas of:  selection bias in enrollment of clinical trial patients; individual eligibility for treatment and attitudes toward treatment; and assurance of participation in intensive and multiple cycles of treatment. 

HIV PERSISTENCE IN ANATOMIC RESERVOIRS:  BEYOND PERIPHERAL BLOOD

Dr. Joseph K. Wong, Professor of Medicine, University of California, San Francisco, and Staff Physician, San Francisco Veterans Affairs Medical Center, addressed HIV persistence in anatomic reservoirs, focusing on the gut.  He noted the importance of the gut as a model for studying HIV persistence and expression at this site. 

Dr. Wong said that an estimated 60 percent or more of T lymphocytes reside in gut-associated lymphoid tissue (GALT), while only 2 percent are found in the blood, and the remaining reside elsewhere in the body.  He noted that the GALT is a good site for studying latent and active HIV reservoirs, as it is an activating environment with high levels of CCR5 gene expression and high levels of HIV replication prior to ART. 

Dr. Wong commented that reports of HIV in the GALT of patients on suppressive ART are conflicting.  He stated that some studies have shown HIV DNA to be present in the terminal ileum of 100 percent of HIV-infected patients and the frequency of infection was approximately five times greater than in the peripheral blood.  He reported on a two-phase study of CD4+ T cells in the gut of HIV-infected patients receiving ART.  Dr. Wong reported:  1) CD4+ T cell activation was greater in gut tissues than in peripheral blood and varied according to site; 2) the frequency of CD4+ T cells was up to tenfold higher in the GALT than in peripheral blood; and 3) HIV expression in gut sites other than the terminal ileum was surprisingly low despite the high frequency of markers of activation.  He also noted the differences in memory CD4+ T cell composition across gut sites likely contribute to the varied frequency of infected cells and viral expression patterns observed.  The level of drug concentration also varied across the different sites. 

Dr. Wong reported that intensification of treatment reduced HIV RNA levels and T cell activation in the terminal ileum, but it did not alter residual virus levels in the plasma.  He cautioned that “real-world” considerations, such as improved adherence by patients who enroll in clinical studies, may skew observations of the effects of intensification of treatment and need to be considered when evaluating interventions to eradicate HIV.

Dr. Wong emphasized the need to conduct studies on tissues other than blood when studying HIV persistence in anatomic reservoirs.  He suggested that the terminal ileum is an attractive target for research on residual HIV replication in humans.  He also noted that the sigmoid rectum region may provide a view of latent HIV infection in GALT.  The central nervous system also was suggested as important site for studying long-term viral persistence. 

RATIONALE FOR USING IMMUNE-BASED THERAPEUTICS TO CURE HIV INFECTION

Dr. Steven G. Deeks, Professor of Medicine, University of California, San Francisco, discussed host responses to HIV and their contribution to HIV persistence and the latent reservoir.  He described several studies relating inflammation and T cell activation, as well as several therapeutic and research approaches to pursue to cure HIV/AIDS.

Dr. Deeks noted that both HIV infection and HIV-associated inflammation persist in patients receiving ART and may coexist in a vicious cycle that is not eliminated by ART.  He commented that more than 80 percent of HIV-infected patients treated with ART have persistent low-level viremia.  He also noted that inflammatory markers are higher in HIV-infected patients on treatment than for individuals who are uninfected.  The result for HIV-infected patients is ongoing T cell activation, homeostatic proliferation, and lower HIV-specific T cell responses.  Dr. Deeks noted that early or late treatment has an incomplete effect; specifically, CD4+ T cell activation and cell-associated DNA and RNA levels after long-term ART are lower, but still not normal, in patients who start treatment early, compared with those who start late.

Dr. Deeks suggested that the inflammatory process could be harmful to HIV-infected patients receiving ART and it may contribute directly or indirectly to homeostatic proliferation and expansion of latently infected cells.  He noted that the immunological dysfunction that occurs may prevent clearance of HIV by reducing inhibiting HIV-specific T cells.  Dr. Deeks commented that there is an unexplained association between T cell activation and HIV persistence in tissues and that multiple mechanisms may account for this association including increased target susceptibility, increased homeostatic expansion, upregulation of a negative activator of T cell activation, and reduced clearance of HIV by host mechanisms. 

Dr. Deeks suggested that inflammation may “drive” HIV persistence and be a barrier to eradication.  Several non-mutually exclusive mechanisms of persistence (e.g., cell-to-cell transfer) are possible and could be altered or enhanced by the host response, particularly the inflammatory response.  He noted that not all inflammation is bad, i.e., if an immune response is needed during long-term ART, then having a functional HIV-specific T cell response would be useful.

Dr. Deeks noted that theoretical pathways to persistence can be studied easily in non-human primates and humans.  He proposed that researchers could link to ongoing Phase-1 or Phase-2 clinical trials for studies on inflammation and aging.  He also suggested that research on HIV eradication and T cell activation in aging would be complementary and mutually informative.

Dr. Deeks emphasized the need for combination therapy (including specific inhibitors, drugs, and/or vaccines) to activate and clear latently infected cells.  He suggested continued investigations of “natural models” of HIV cure based on HIV-treated individuals who become “elite controllers.”  He proposed an international effort to identify elite controllers and to study the mechanisms and consequences of their control of HIV infection, including the role of host responses and immune-based therapeutics.  He also suggested a continued priority for immune-based therapeutics including therapeutic vaccines.

IMMUNOLOGICAL MECHANISMS INVOLVED IN HIV PERSISTENCE

Dr. Nicolas Chomont, Assistant Member, Vaccine and Gene Therapy Institute of Florida, addressed several questions about HIV persistence including:  1) Where does HIV persist?  2) How does it persist?  3) Is it possible to interfere in the mechanisms of persistence?  His presentation focused on the role of the immune system and its components in HIV persistence.

Dr. Chomont described the localization of HIV reservoirs in CD4+ T cells.  He noted that CD4+ cells constitute more than 95 percent of these reservoirs and that viral DNA is rarely detected in non-CD4+ T cells.  He noted that the reservoir of T cell subsets is heterogeneous and comprises central, transitional, and effector memory cells, as well as terminally differentiated cells and naïve cells.  He suggested that this composition is likely the same across individuals who are uninfected or HIV-infected. 

Dr. Chomont reported on a study that showed two major HIV reservoirs in the central memory and transitional memory CD4+ T cells.  He emphasized that studies on delineating the mechanisms of persistence in these memory T cell subsets are important.  He noted that localization of the HIV reservoir depends on absolute CD4+ T cell count -- with most of the reservoir located in transitional memory T cells at low CD4+ cells counts and in central memory T cells at high CD4 T cell counts.  He emphasized that these two T cell subsets are phenotypically and functionally distinct.  Dr. Chomont suggested that research is needed on other cell types (e.g., macrophages) and tissues that may serve as viral reservoirs.

Dr. Chomont noted the three main mechanisms known to contribute to HIV persistence include viral replication, T cell survival (residual viremia), and homeostatic proliferation.  He described studies on the possible roles of interleukin (IL)-7 and IL-15 in HIV persistence.  He noted that IL-7 may contribute to HIV persistence by inducing homeostatic proliferation of reservoir cells. 

Dr. Chomont described the programmed death (PD)-1 protein, a negative regulator of T cell activation, as a potential pathway for interfering with mechanisms of persistence.  He reported on several studies that showed PD-1 is associated with the size of the HIV reservoir.  He suggested that PD-1 may contribute to HIV persistence during ART. 

Dr. Chomont proposed additional research is needed on the immunological mechanisms involved in HIV persistence.

DISCUSSION

OARAC members, presenters, and guests addressed the role of inflammation in HIV infection and persistence.  They discussed the mechanisms and pathways of inflammatory responses in HIV-infected patients.  They noted key differences in tissue-derived CD4+ T cells compared with blood-derived cells; the possibilities for blocking the cascade of events; and the relationship between HIV infection and inflammation, even in the presence of ART, to preserve the host immune system.  They proposed further research on HIV reservoirs in tissues other than blood. 

OARAC members and speakers also commented on alternative negative regulators that may play a role (similar to PD-1) in viral persistence.  They also discussed the ramifications of HIV reinfection of individuals who may be “cured” in the future.  Several presenters commented that research is under way to identify and target subsets of CD4+ T cells that are enriched with HIV.  They noted that this research must be part of a global effort to prevent, detect, treat, and eradicate HIV infection.  OARAC members noted that managing patients’ risks while pursuing the benefit of a global cure for HIV is a major ethical issue.

ENGINEERING CCR5-NEGATIVE T CELLS AND STEM CELLS

Dr. Paula Cannon, Associate Professor, Molecular Microbiology and Immunology, Kech School of Medicine, University of Southern California, described research toward achieving a functional cure for HIV-infected individuals by developing HIV-resistant versions of their own cells through ex vivo engineering of hematopoietic stem cells (HSCs).  This approach uses retroviral or lentiviral vectors to introduce anti-HIV genes into HSCs. 

Dr. Cannon reported that Phase-1 and Phase-2 gene therapy trials with HSCs have demonstrated the feasibility and safety of this strategy, but that the efficacy has yet to be proven.  She commented that obtaining bone marrow tissue from HIV-uninfected matched donors is an unrealistic approach for treating everyone who is HIV-infected.  She noted that this was the strategy used for the Berlin patient to treat his leukemia. 

Dr. Cannon described several studies that focused on the same CCR5 gene used with the Berlin patient.  These studies involve treating HSCs with zinc finger nucleases (ZFNs) engineered to disrupt CCR5 gene expression and effectively knocking out production of the CCR5 protein. In preclinical studies, this approach reduces HIV-1 to undetectable levels in both peripheral blood and tissues. 

Dr. Cannon noted that ongoing studies are testing this approach in a cohort of AIDS lymphoma patients who would be treated with fully ablative chemotherapy and then “rescued” by re-infusion of their modified HSCs.  She noted that two ongoing Phase-1 clinical trials are applying a similar strategy.  Interim data show that the technique is feasible and effective and that the treatment is well-tolerated by the majority of study patients with sustained increases in total CD4+ T cell counts after infusion and persistent normalization of CD4:CD8 ratios.  The ZFN-modified T cells engrafted, expanded, and persisted in peripheral blood and in the rectal mucosa.

Dr. Cannon commented on several aspects that could limit research toward a cure including animal models that are expensive and present technical challenges. She stated that collaboratory teams and approaches to ensure shared credit among researchers are needed.  Dr. Cannon suggested that cell-based therapies will contribute to a broad shift in medicine and yield critical information on the pathogenesis of HIV infection and T cell immunology.

TARGETING T-CELL MEMORY SURVIVAL AND PERSISTENCE AS A STRATEGY TO ERADICATE HIV

Dr. Rafick-Pierre Sékaly, Chief Scientific Officer and Co-Director, Vaccine and Gene Therapy Institute of Florida, reviewed the basic biology of T cells and described research to identify where memory T cells persist.  He also described the development of several strategies to eradicate HIV reservoirs.  His presentation focused on three topics:  signal transduction pathways leading to persistence of memory T cells; signal transduction pathways responsible for PD-1 inhibition of T cell activation and HIV latency; and the role of other negative regulators of T cell activation in establishing HIV reservoirs.

Dr. Sékaly noted that the maintenance of the HIV reservoir through homeostatic proliferation and self-renewal is an essential feature of T cell biology.  He presented a model for studying persistence and exhaustion of memory T cells utilizing a pathway for maintenance and survival of central memory T cells that appears to be critical.  This approach involves the forkhead box protein family (FOXO3a), a master regulator consisting of more than 100 genes.  A FOXO3a N-terminus mutant has been shown to increase persistence of central memory T cells in chronically HIV-infected individuals. 

Dr. Sékaly reported on a study of PD-1 activity in memory T cells from chronically HIV-infected individuals and macaques that showed:  1)  FOXO3a is associated with immune protection during HIV infection; and 2) interference with the FOXO3a pathway induces long-term survival of memory T cells in chronically infected patients.  He outlined research using specific inhibitors that interfere with the PD-1 signal that may represent a strategy that could contribute to HIV eradication while also rescuing the immune response.

Dr. Sékaly suggested additional research is needed to eradicate HIV by targeting multiple signal transduction pathways of viral persistence and self-renewal of memory T cells, as well as development and testing of strategies to rescue the immune response.

MODULATING PROVIRAL GENE EXPRESSION:  DEVELOPMENT AND TESTING OF THERAPIES TO TARGET LATENT HIV GENOMES

Dr. David Margolis, Professor of Medicine, Microbiology and Immunology, and Epidemiology, and Director, Program in Translational Clinical Research, Institute for Global Health and Infectious Diseases, University of North Carolina at Chapel Hill, presented several strategies for targeting latent HIV genomes based on molecular mechanisms of regulation and perturbation of HIV latency.  He summarized the studies to date that demonstrate:  stability of resting CD4+ T cell infection in HIV-infected patients on ART; persistent viral reservoirs in resting memory T cells; and specificity of latently infected cells and their probable generation.  He proposed the continued use of resting CD4+ cell outgrowth assays as the gold-standard method for quantifying latent HIV ex vivo and in culture with anti-HIV drugs. 

Dr. Margolis outlined three possibilities for modulating the regulation of latency including: interference with the virus integration site and host gene transcription; restriction at the initiation of mRNA transcription; and restriction of transcriptional elongation.  He also described the role of chromatin and histone deacetylase (HDAC)-1 inhibitor that stimulate the release of HIV from latent T cells and allow antiretrovirals to attack the re-emerged virus.  Dr. Margolis noted that continuing studies of HDACs indicate that Class I HDACs effect HIV-1 gene expression in resting CD4+ T cells.  He suggested that research focus on carefully measuring molecular events of latency using available assays while better and simpler assays are being developed. 

Dr. Margolis stated that there may be different levels of latency and that a quiescent provirus may be increasingly difficult to reawaken.  The challenge for researchers is to identify these obstacles and enable viral expression while not perturbing other cell functions (e.g., immunity) and causing toxicity in HIV-infected patients.  

Dr. Margolis suggested that there is a need for model systems to study various tissues, including the brain, which may serve as viral reservoirs.  He described research using immunedeficient, humanized mice that may allow testing of combined approaches and strategies that currently are difficult to do clinically. 

Dr. Margolis noted the broad range of research needed in the areas of:  basic biology on viral latency; in vitro and animal models to test new therapeutic strategies; and virologic and immunologic studies on persistent viremia and persistent provirus.  New and better methods also are needed to measure viral persistence in HIV-infected patients.  He proposed that infrastructure support is essential to rapidly translate basic discoveries to the clinic and that the future of HIV care must be a continuum of care.  He emphasized the critical need for collaborative research teams of researchers and clinicians. 

DISCUSSION

OARAC speakers noted that there will be no “magic bullet” in solving HIV latency, as it is a highly diverse, essentially rare event involving many different provirus states, sites of integration, pathways for activation, and mechanisms—all of which need to be characterized.  They noted that the concerted, multipronged effort needed can best be done in a research collaboratory that engages all partners and encourages sustained funding of researchers.  

NOVEL APPROACHES FOR HIV/AIDS THERAPEUTICS

Dr. H. Clifford Lane, described research on several novel approaches for HIV/AIDS therapeutics including the use of in vivo imaging of HIV reservoirs, enhancement of immunologic responses to HIV, and identification of the phenotypes of long-term non-progressors (LTNPs). 

Dr. Lane suggested that in vivo imaging techniques may be useful for assessing the extent of the residual HIV reservoir.  He noted that earlier research had shown indium (IN)-labeled anti-CD4+ monoclonal antibody could be used to study distribution of CD4+ T cells in mice.  This technique has been adapted to image, via single-photon emission computed tomography (SPECT), CD4+ counts in monkeys.  The results demonstrated that the intensity of anti-CD4+ staining in lymphoid tissues is proportional to the CD4+ T cell count in peripheral blood.  He described ongoing studies that are exploring the potential role of in vivo imaging to visualize HIV reservoirs, as well as approaches that combine SPECT and computed tomography to localize signals within anatomic structures.

Dr. Lane also reported on studies using the adoptive transfer of peripheral blood mononuclear cells (PBMCs) from LTNPs.  The LTNP phenotype has been shown to be highly associated with certain HLA genotypes and may represent immunologic control of HIV disease.  Studying this phenotype in other HIV-infected persons could be useful in developing a functional cure.  He described a unique feature among LTNPs— CD8+ T cells respond with aggressive clonal expansion when exposed to HIV antigens. 

Dr. Lane described the potential use of IL-15 to enhance immunity to HIV since IL-15 focuses on CD8+ cells.  Two NIH Institutes (NIAID and the National Cancer Institute) have organized a special development program for preclinical studies of IL-15 as an immunotherapy for HIV and cancer.  Preliminary findings in rhesus macaques have shown a significant increase in CD8+ T cell counts with the majority of these as effector memory cells.  Dr. Lane noted that further research on these and other novel approaches is needed.

FUTURE DIRECTIONS AND OPPORTUNITIES FOR RESEARCH LEADING TO A CURE

Dr. Paul Volberding summarized the speakers’ presentations and discussions.  He noted that significant progress has been made in clarifying whether residual viremia is viral release or replication—a central question in viral eradication.  He noted that additional research is needed on the nature of HIV reservoirs, which are more complex than previously thought and must be examined in tissues other than peripheral blood including the brain and GALT.  He also commented that HIV latency may vary—early latency may be relatively more amenable to therapeutic intervention compared with late latency, which may not be as manipulable.

Dr. Volberding noted that immune activation and the immune response may be an important component of HIV control and deserves increased consideration.  He noted that deciding on the targets for HIV eradication will be a complex process.  He proposed that HDAC and NF-kappa B inhibitors are two potential leads for therapeutic approaches that could be explored further.  The role of a local inflammatory state in immune activation associated with HIV infection may have particular importance for AIDS research and therapeutics.

Dr. Volberding commented that moving from current cell- and animal-based research on HIV eradication to human trials will present key challenges.  Attention will need to be given to the psychosocial aspects of discovering and implementing a cure for HIV.  He suggested that a particular concern is the possibility of re-infection and the challenges that re-infection poses to individuals and communities.

Dr. Volberding noted three main therapeutic approaches that were discussed (virological, immunological, and cellular), but none of these approaches, while promising, is sufficient for eradicating HIV.  He suggested that linking them together holds the greatest promise and that research collaboratories would foster this linkage.  He proposed that adequate funding for this area of research and clinical trials is critical.

DISCUSSION

OARAC members discussed the status of research toward a cure and the complexity of the research questions that are being addressed.  They noted the potential of this exciting research and that it is progressing rapidly.  Their comments on future needs are summarized by topic areas below.

Continuum of Prevention, Research, and Care.  AIDS research activities need to be combined and balanced across a continuum of prevention, research, and care.  Basic science is critical.  The research needed offers opportunities for creating multidisciplinary research teams working together across overlapping disciplines including virology, immunology, and cell biology. 

HIV Latency.  Additional research should be focused on defining all potential reservoirs of HIV, including the brain, and all cell types involved in HIV latency.  A better understanding is needed of the mechanisms of cell death and its relationship to viral latency.  Additional assays are needed to test the different cell types that may be potentially involved in HIV latency, as well as drug compounds that could be used therapeutically.  Animal models are needed to study HIV latency, reservoirs, and eradication.

Immune Activation.  Studies on strengthening the immune system to combat HIV infection and halt disease progression are an essential aspect of HIV latency and research toward a cure.  Research on the interaction of the immune system and HIV infection is important, including studies involving long-term non-progressors.

Participation of Women in AIDS Research.  Special efforts may be needed to encourage HIV-infected women to participate in research toward a cure.  Women’s immune systems may have unique attributes compared with men’s.  Research on HIV infection and treatment during pregnancy is needed.

Therapeutic Approaches.  Many novel approaches to HIV eradication and cure are being studied, and a consensus on productive ways to apply each of these is needed.  Maintaining a real-world perspective in this research is essential to ensure that the approaches that are developed are simple, safe, and effective.  Strategies toward a cure also should take into consideration their potential implementation in the developing world setting, where the burden of HIV and other diseases is highest and where appropriate approaches are needed. 

Behavioral, Psychosocial, and Ethical Aspects.  Behavioral and social scientists and the HIV affected community need to be involved in addressing the psychosocial issues associated with research toward a cure at both the individual and population levels.  Attention should be given to questions concerning the emphasis being placed on ART for HIV prevention or for HIV eradication/cure.  Specifically, does research or success in one obviate research on the other?  While the possibility of developing a cure for HIV may take many years, planning for a “post-cure era” should be under way and include discussions of individuals’ concerns about continued 
access to ART.  Research also should focus on psycho-social and ethical questions associated

with a cure including: 

• Who will be offered the cure?  Who will be able to afford it?  Is there an incentive or disincentive for patients responding well on antiretroviral therapy?

• How does one manage the risks to the patient of using potentially toxic drugs compared to the benefits to global society?

• What if the treatment does not work and the patient does not reach a “cure”? How does the patient cope if they are not “cured”?

• How does a “cure” impact the perceptions of persons living with HIV/AIDS and their risk behaviors?

Research Collaboratories.  Establishing a collaborative research enterprise is critical in order to accomplish the scientific agenda.  This agenda should include translational research to enhance uptake of strategies to eradicate HIV/AIDS.  Approaches are required to incentivize collaborations and sharing of ideas with special incentives to encourage industry participation.  Support is important for research collaboratories and incentives.  It was proposed that OAR should continue to play an important role in supporting this research area and working with the NIH Institutes, Centers, and Offices, other organizations, and collaboratories to ensure it is a priority.

Funding.  Research leading to a cure for HIV/AIDS is necessarily long-term and requires substantial and sustained resources.  It was acknowledged that now is the time to capitalize on the significant progress already made in the field and to accelerate this research by increasing support.

PUBLIC COMMENTS

No members of the public requested time to comment.

CLOSING COMMENTS

Dr. Hillier thanked the OARAC members, speakers, and guests for their participation and comments.  Dr. Whitescarver also thanked the participants.  He commented that OAR will continue to keep the momentum going in this high-priority research area.  He also noted that NIH will work in parallel with the International AIDS Society initiative in developing a global strategy for research toward a cure. 

The meeting was adjourned at 4:25 p.m. on March 24, 2011.

/Jack Whitescarver, Ph.D./

Jack Whitescarver, Ph.D., Executive Secretary

/Sharon L. Hillier, Ph.D./        
                                                
Sharon L. Hillier, Ph.D., Chair