TAG HIV Basic Science, Vaccines, and Cure Project Blog

The End of the Line for IL-2

Results from two large randomized studies of interleukin-2 (IL-2) have been published in the New England Journal of Medicine. The data were first presented earlier this year at CROI in Montreal. The trials were SILCAAT, which enrolled 1,695 people with CD4 counts between 50 and 299, and ESPRIT, which enrolled 4,111 people with CD4 counts over 300. In neither case did the addition of IL-2 offer any clinical benefits compared to antiretroviral therapy alone, despite increasing CD4 T cell counts. The results indicate that expanding CD4 T cell numbers with IL-2 does not confer added benefit beyond the increase in CD4 T cells caused by suppression of HIV replication. The researchers note that CD4 T cells induced by signaling through the IL-2 pathway may be functionally compromised and/or have a phenotype (e.g. suppressive) or specificity that is not clinically beneficial. An alternative or overlapping explanation is that the increased rate of adverse events associated with receipt of IL-2 counterbalanced any benefit from CD4 increases.

Although the results have been seen as a blow to immune-based therapy (IBT) development in HIV, they do not necessarily mean that other approaches to increasing CD4 T cell numbers (such as IL-7 or growth hormones) will suffer the same fate. The outcomes of SILCAAT and ESPRIT do however stress the need to evaluate IBTs for clinical benefit. As there are individuals who experience poor CD4 T cell reconstitution despite HIV suppression (sometimes called discordant responders) who remain at increased risk for illness, there is still a potential need for IBTs. Trials evaluating the clinical benefit of newer IBTs in this population should be feasible and would not necessarily require the large numbers involved in SILCAAT and ESPRIT.

New England Journal of Medicine, Volume 361:1548-1559, October 15, 2009, Number 16

Interleukin-2 Therapy in Patients with HIV Infection

The INSIGHT–ESPRIT Study Group and SILCAAT Scientific Committee

ABSTRACT

Background Used in combination with antiretroviral therapy, subcutaneous recombinant interleukin-2 raises CD4+ cell counts more than does antiretroviral therapy alone. The clinical implication of these increases is not known.

Methods We conducted two trials: the Subcutaneous Recombinant, Human Interleukin-2 in HIV-Infected Patients with Low CD4+ Counts under Active Antiretroviral Therapy (SILCAAT) study and the Evaluation of Subcutaneous Proleukin in a Randomized International Trial (ESPRIT). In each, patients infected with the human immunodeficiency virus (HIV) who had CD4+ cell counts of either 50 to 299 per cubic millimeter (SILCAAT) or 300 or more per cubic millimeter (ESPRIT) were randomly assigned to receive interleukin-2 plus antiretroviral therapy or antiretroviral therapy alone. The interleukin-2 regimen consisted of cycles of 5 consecutive days each, administered at 8-week intervals. The SILCAAT study involved six cycles and a dose of 4.5 million IU of interleukin-2 twice daily; ESPRIT involved three cycles and a dose of 7.5 million IU twice daily. Additional cycles were recommended to maintain the CD4+ cell count above predefined target levels. The primary end point of both studies was opportunistic disease or death from any cause.

Results In the SILCAAT study, 1695 patients (849 receiving interleukin-2 plus antiretroviral therapy and 846 receiving antiretroviral therapy alone) who had a median CD4+ cell count of 202 cells per cubic millimeter were enrolled; in ESPRIT, 4111 patients (2071 receiving interleukin-2 plus antiretroviral therapy and 2040 receiving antiretroviral therapy alone) who had a median CD4+ cell count of 457 cells per cubic millimeter were enrolled. Over a median follow-up period of 7 to 8 years, the CD4+ cell count was higher in the interleukin-2 group than in the group receiving antiretroviral therapy alone — by 53 and 159 cells per cubic millimeter, on average, in the SILCAAT study and ESPRIT, respectively. Hazard ratios for opportunistic disease or death from any cause with interleukin-2 plus antiretroviral therapy (vs. antiretroviral therapy alone) were 0.91 (95% confidence interval [CI], 0.70 to 1.18; P=0.47) in the SILCAAT study and 0.94 (95% CI, 0.75 to 1.16; P=0.55) in ESPRIT. The hazard ratios for death from any cause and for grade 4 clinical events were 1.06 (P=0.73) and 1.10 (P=0.35), respectively, in the SILCAAT study and 0.90 (P=0.42) and 1.23 (P=0.003), respectively, in ESPRIT.

Conclusions Despite a substantial and sustained increase in the CD4+ cell count, as compared with antiretroviral therapy alone, interleukin-2 plus antiretroviral therapy yielded no clinical benefit in either study.

Thai HIV Vaccine Trial Results Published

In tandem with the presentation of the data that took place today at the AIDS Vaccine 2009 conference in Paris, the results of the RV144 trial have been published online in the New England Journal of Medicine. Access to the paper and the accompanying editorial is free of charge. Three different analyses of the results are presented in sequence: the intent-to-treat analysis (ITT), which includes everyone enrolled and randomized to receive vaccine or placebo, a per protocol (PP) analysis limited to everyone who received all immunizations on schedule, and finally a modified ITT (mITT) analysis that excludes seven individuals who reportedly turned out to be HIV-infected at the time of their first immunization.

ITT: Total n=16,402. Cases of HIV infection: 76 placebo, 56 vaccine. Efficacy: 26.4% (95% confidence interval [CI], –4.0 to 47.9; P=0.08)

PP: Total n= 12,452. Cases of HIV infection: 50 placebo, 36 vaccine. Efficacy: 26.2% (95% CI, –13.3 to 51.9; P=0.16)

mITT: Total n=16,395. Cases of HIV infection: 74 placebo, 51 vaccine. Efficacy 31.2% (95% CI, 1.1 to 51.2; P=0.04)

The data suggests the possibility of a marginal protective effect, almost entirely concentrated during the first year of the study. Kaplan-Meier plots of the infection rate over time show a divergence initially, but the rates in the vaccine and placebo groups are superimposable from week 52 onwards. Subgroup data are also reported, but the statistics are uncorrected for multiple analyses and should be interpreted with great caution. With this caveat, there is a hint that the difference between vaccine an placebo was greatest among those at lowest risk of HIV exposure. The age group breakdown also indicates the difference between vaccine and placebo groups was concentrated in the 20-25 age group; there is no difference in the number of infections between the groups among those under 20, and very little difference among those over 26. Among the 20-25 age group, there were 20 infections in the vaccine group and 40 in placebo.

In terms of the viral load outcomes in people who acquired infection, the ITT analysis shows a trend in the wrong direction; viral load was higher on average among vaccine recipients (4.36 log vs. 4.21 log, p=0.09). However this trend disappears in both the PP and mITT analyses. There were no differences in post-infection CD4 T cell counts in any of the analyses.

As to why the only statistically significant result is reported last in the published paper (in contrast to the September 24 press announcement, in which the mITT was the only result given), it appears that the RV144 protocol specified that the primary analysis would be ITT. The paper states that the mITT analysis was used as the primary analysis for the interim efficacy evaluation (which was conducted by the Data Safety Monitoring Board in July of 2007) and then, five months before the study was unblinded, a decision was made to make the mITT the primary analysis. Reading between the lines, perhaps the reviewers of the manuscript were not satisfied that this late adoption of the mITT as the primary analysis justified listing the result first in the paper. It is currently unclear why the RV144 protocol did not specify the mITT as the primary efficacy analysis from the start. As the import of the trial results are mulled by the larger community, it will be important to gain some clarity as to exactly how these events played out.

So far, in the limited time observers have had to digest the data, the main issues that are being discussed are the suggestion of a transient, time-limited effect and what might explain it (vaccines generally work by the induction of immunological memory, which is typically long-lived) and the hint that vaccine-mediated protection might be easier to achieve in individuals with less frequent HIV exposure compared to those at high risk.

Regrettably, the release of the data today does not change the fact that it was an appalling and woefully short-sighted decision to only release the mITT analysis to the press on September 24. On the conference call hosted by AVAC that took place that day with investigator Merlin Robb and Peggy Johnston from NIAID, Robb explicitly stated that only 16,395 people had been enrolled into the trial. Not only was this not true, but it turns out that vaccine/placebo distribution of the 7 people excluded from the mITT was crucial to the attainment of statistical significance: five of these individuals were in the vaccine group and two in placebo. By cherry-picking the mITT to announce, the RV144 investigators have created suspicion and uncertainty in a field which they well know is already plagued by controversy. Their decision will only serve to complicate efforts to glean useful information from the trial data.

The webcast of the press conference about the trial results is now available online (scroll down to the bottom of the page to the Tuesday, 20 October press conference link). 

Published at www.nejm.org October 20, 2009 (10.1056/NEJMoa0908492)

Original Article

Vaccination with ALVAC and AIDSVAX to Prevent HIV-1 Infection in Thailand

Supachai Rerks-Ngarm, M.D., Punnee Pitisuttithum, M.D., D.T.M.H., Sorachai Nitayaphan, M.D., Ph.D., Jaranit Kaewkungwal, Ph.D., Joseph Chiu, M.D., Robert Paris, M.D., Nakorn Premsri, M.D., Chawetsan Namwat, M.D., Mark de Souza, Ph.D., Elizabeth Adams, M.D., Michael Benenson, M.D., Sanjay Gurunathan, M.D., Jim Tartaglia, Ph.D., John G. McNeil, M.D., Donald P. Francis, M.D., D.Sc., Donald Stablein, Ph.D., Deborah L. Birx, M.D., Supamit Chunsuttiwat, M.D., Chirasak Khamboonruang, M.D., Prasert Thongcharoen, M.D., Ph.D., Merlin L. Robb, M.D., Nelson L. Michael, M.D., Ph.D., Prayura Kunasol, M.D., Jerome H. Kim, M.D., for the MOPH–TAVEG Investigators

ABSTRACT

Background The development of a safe and effective vaccine against the human immunodeficiency virus type 1 (HIV-1) is critical to pandemic control.

Methods In a community-based, randomized, multicenter, double-blind, placebo-controlled efficacy trial, we evaluated four priming injections of a recombinant canarypox vector vaccine (ALVAC-HIV [vCP1521]) plus two booster injections of a recombinant glycoprotein 120 subunit vaccine (AIDSVAX B/E). The vaccine and placebo injections were administered to 16,402 healthy men and women between the ages of 18 and 30 years in Rayong and Chon Buri provinces in Thailand. The volunteers, primarily at heterosexual risk for HIV infection, were monitored for the coprimary end points: HIV-1 infection and early HIV-1 viremia, at the end of the 6-month vaccination series and every 6 months thereafter for 3 years.

Results In the intention-to-treat analysis involving 16,402 subjects, there was a trend toward the prevention of HIV-1 infection among the vaccine recipients, with a vaccine efficacy of 26.4% (95% confidence interval [CI], –4.0 to 47.9; P=0.08). In the per-protocol analysis involving 12,452 subjects, the vaccine efficacy was 26.2% (95% CI, –13.3 to 51.9; P=0.16). In the modified intention-to-treat analysis involving 16,395 subjects (with the exclusion of 7 subjects who were found to have had HIV-1 infection at baseline), the vaccine efficacy was 31.2% (95% CI, 1.1 to 51.2; P=0.04). Vaccination did not affect the degree of viremia or the CD4+ T-cell count in subjects in whom HIV-1 infection was subsequently diagnosed.

Conclusions This ALVAC-HIV and AIDSVAX B/E vaccine regimen may reduce the risk of HIV infection in a community-based population with largely heterosexual risk. Vaccination did not affect the viral load or CD4+ count in subjects with HIV infection. Although the results show only a modest benefit, they offer insight for future research. (ClinicalTrials.gov number, NCT00223080 [ClinicalTrials.gov] .)

Published at www.nejm.org October 20, 2009 (10.1056/NEJMe0909972)

Editorial

HIV Vaccine Trial Results — An Opening for Further Research

Raphael Dolin, M.D.

Thai HIV Vaccine Trial Update: Uncertainty Reigns

A slew of mainstream media articles have now picked up on Jon Cohen’s Science Insider piece from last week. As of right now, only one thing can be said with certainty: it would have been a good idea for the RV144 investigators to have mentioned the per protocol analysis in their initial announcement, even if only to state that it would be described in detail when the full results are presented (they have now added such a statement to the US Military HIV Research Program website). The lack of disclosure has understandably raised suspicions, but none of the additional information that has trickled out (from unnamed sources) really sheds light on the extent to which the per protocol analysis undermines the overall conclusion of marginal efficacy.

The article with the most additional information appeared in the Wall Street Journal on Monday. It reveals that an analysis described as “close to per protocol” reduces the number of HIV-infected trial participants that can be included from 125 to 96. A strict per protocol analysis reduces he number further, to 86. Statistical significance evaporates in both of these analyses, and efficacy is reduced to 30.9% and 26.2% respectively (the latter figure is now being extensively cited in news stories).

In the first instance, the similar efficacy estimate suggests that the result simply reflects the erosion of statistical power that inevitably comes when the number of endpoints (in this case, individuals who acquired HIV infection during the trial) is reduced. The number people eliminated from the per protocol analysis does seem quite large; although the subset of participants who became HIV-infected may not reflect the overall population, at worst it suggests close to a third of trial participants did not adhere entirely to the protocol. What appears to be most troubling observers is the apparent reduction in efficacy seen in the strict analysis; as articulated by Paul Sax in an article on Medscape: "the study subjects who followed the protocol most closely had less protection from the vaccine strategy."

However, the Wall Street Journal article lacks potentially important information, including whether the HIV-infected participants censored from these analyses are equally distributed between vaccine and placebo groups and the overall reduction in numbers in both arms. This information is critical for evaluating the impact of the per protocol analyses on the interpretation of the publicly reported intent-to-treat result.

The presentation of the data is scheduled to occur at the AIDS Vaccine 2009 conference in Paris next Tuesday, October 20 at 10am. The press conference discussing the results will occur at 1pm on the same day (schedule appended below), and live streaming will be available on the conference website. Press conference presentations will also be available for download an hour prior. The webcast of the conference session goes online at 10:50am (5:50am EST) on Wednesday October 21. It has also been reported that the paper describing the results may be published next week, possibly in the New England Journal of Medicine, but as far as I know this has not been confirmed.

PRESS CONFERENCE SCHEDULE

AIDS Vaccine 2009

All press conferences will be held in the St. German des Pres room, Marriott Rive Gauche Conference Center

Embargoes on research presented in AIDS Vaccine 2009 press conferences lift at the end of the press conference or at the end of the conference session in which the study is presented, whichever is earlier

Tuesday, 20 October, 1:00 – 2:00 pm (13.00 – 14.00) 

AIDS Vaccine Clinical Trials Update

CHAIRED BY: Alan Bernstein, Global HIV Vaccine Enterprise New York, NY, USA & Jean‐François Delfraissy, French National Agency for Research on AIDS and Viral Hepatitis (ANRS), Paris, France

Phase III trial of HIV prime‐boost vaccine combination in Thailand: result of final analysis (Abstract SS01‐05) 

Supachai Rerks‐Ngarm, Department of Disease Control, Ministry of Public Health Nonthaburi, Thailand

Nelson Michael, U.S. Military HIV Research Program, Rockville, MD, USA

Post‐infection cellular immune responses in recipients following ALVAC‐HIV® + AIDSVAX® B/E prime‐boost vaccination in the Thai phase III trial (Abstract OA04‐06 LB)

Jerome Kim, U.S. Military HIV Research Program, Rockville, MD, USA

Immunogenicity of ALVAC‐HIV® (vCP1521) and AIDSVAX® B/E prime boost vaccination in RV144, the Thai phase III HIV vaccine trial (Abstract OA07‐04 LB)

Mark de Souza, U.S. Military HIV Research Program/AFRIMS, Bangkok, Thailand

Recent immunologic findings from the Step and related HIV vaccine clinical trials  (Abstract SS01‐03)

Nicole Frahm, HIV Vaccine Trials Network, Fred Hutchinson Cancer Research Center and University of Washington, Seattle, WA, USA 

Did the World Get a "Fair Glimpse" of the Thai Vaccine Trial Data?

A new story by Jon Cohen - a longtime follower of the HIV vaccine field and author of an excellent book on the subject -  has just appeared on the Science Insider blog at Science Magazine, entitled "Unrevealed Analysis Weakens Claim of AIDS Vaccine 'Success.'" It suggests that, as some observers (including TAG) had feared, the very limited data from the Thai HIV vaccine trial that was announced on September 24th does not represent the whole story. Specifically, it appears that the statistically significant result that was announced was derived from what's called an "intent-to-treat" (ITT) analysis; this type of analysis includes data from all participants, whether or not they completed the full protocol-mandated series of immunizations. ITT is a standard and important way of analyzing data that typically avoids over-estimating the efficacy of an intervention. The less conservative type of data analysis is usually called a "per protocol" (PP) analysis; in this case only study participants who have completed the protocol as specified, including all immunizations, are included. Based on Cohen's report, it appears that the PP analysis of the Thai HIV vaccine trial also showed fewer HIV infections in the vaccine group, but the difference with placebo was not statistically significant. This seems odd, as PP analyses involving a successful intervention typically show a greater, not lesser, effect. Given the potential importance of the trial results, it is unconscionable that this discrepancy was not discussed when the initial announcement was made. 

Cohen closes his piece by citing an excellent and prescient "anticipating results" document about the Thai trial that was released by AVAC just a couple of weeks ago. Under the heading "Advocates' Guide to Statistical Terms" it says: 

"Other terms that might be used in discussion of initial results are per-protocol (PP) and intent-to-treat (ITT) analyses of results. PP results only include infections that occurred in those participants who received the full course of vaccinations . ITT results count every infection after trial enrollment, regardless of whether a participant completed the full regimen. ITT is considered a gold standard because it considers every randomized participant. Both approaches provide important information. The safest route is to report both PP and ITT and to analyze any difference. Advocates’ take-home message: no matter what the headlines say, a single number is not the full result."

New Screening Tool for Drugs that Reverse HIV Latency

The major obstacle to maximizing HIV elimination from the body is the existence of latently infected cells (for an excellent introduction to the topic, see this free access minireview from J. Virology). These cells harbor HIV DNA that has integrated into the chomosomal DNA, and virus particles are typically not produced unless the cell is stimulated in some way. Latently infected cells are thus invisible to the immune system, and while antiretrovirals can prevent any virus they produce from infecting other cells, the drugs cannot excise the integrated HIV DNA. This has led researchers to pursue new approaches to awakening dormant HIV, but the pursuit has been slowed by a reliance on cell lines, due to the lack of a physiologically relevant system for generating latently infected primary CD4 T cells.

In a new paper in the Journal of Clinical Investigation, Hung-Chih Yang and colleagues from Bob Siliciano’s laboratory at Johns Hopkins report the development of a new screening system for identifying latency-reversing drugs. The researchers introduced the survival gene Bcl-2 into CD4 T cells in vitro and this facilitated the generation of large numbers of long-lived latently infected cells. As a proof of concept, one compound (named 5HN) that potently reactivated latent HIV without activating the CD4 T cells was identified from a screen of several thousand drugs. The researchers note, however, that 5HN is likely too toxic for human use. Screens of other compounds are ongoing and the researchers hope to eventually identify candidates suitable for clinical testing.

J. Clin. Invest. doi:10.1172/JCI39199. 

Technical Advance

Small-molecule screening using a human primary cell model of HIV latency identifies compounds that reverse latency without cellular activation (free access to full text)

Hung-Chih Yang1, Sifei Xing1,2, Liang Shan1,2, Karen O’Connell1, Jason Dinoso1,2, Anding Shen3, Yan Zhou1, Cynthia K. Shrum1, Yefei Han1, Jun O. Liu2, Hao Zhang4, Joseph B. Margolick4 and Robert F. Siliciano1,5

1 Department of Medicine and 2 Department of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA. 3 Department of Biology, Calvin College, Grand Rapids, Michigan, USA. 4 Department of Molecular Microbiology and Immunology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, Maryland, USA. 5 Howard Hughes Medical Institute, Baltimore, Maryland, USA.

Published October 1, 2009

Received for publication March 16, 2009, and accepted in revised form July 29, 2009.

The development of highly active antiretroviral therapy (HAART) to treat individuals infected with HIV-1 has dramatically improved patient outcomes, but HAART still fails to cure the infection. The latent viral reservoir in resting CD4+ T cells is a major barrier to virus eradication. Elimination of this reservoir requires reactivation of the latent virus. However, strategies for reactivating HIV-1 through nonspecific T cell activation have clinically unacceptable toxicities. We describe here the development of what we believe to be a novel in vitro model of HIV-1 latency that we used to search for compounds that can reverse latency. Human primary CD4+ T cells were transduced with the prosurvival molecule Bcl-2, and the resulting cells were shown to recapitulate the quiescent state of resting CD4+ T cells in vivo. Using this model system, we screened small-molecule libraries and identified a compound that reactivated latent HIV-1 without inducing global T cell activation, 5-hydroxynaphthalene-1,4-dione (5HN). Unlike previously described latency-reversing agents, 5HN activated latent HIV-1 through ROS and NF-κB without affecting nuclear factor of activated T cells (NFAT) and PKC, demonstrating that TCR pathways can be dissected and utilized to purge latent virus. Our study expands the number of classes of latency-reversing therapeutics and demonstrates the utility of this in vitro model for finding strategies to eradicate HIV-1 infection.