Michael G. Hudgens

Administration of vorinostat disrupts HIV-1 latency in patients on antiretroviral therapy

Despite antiretroviral therapy, proviral latency of human immunodeficiency virus type 1 (HIV-1) remains a principal obstacle to curing the infection. Inducing the expression of latent genomes within resting CD4+ T cells is the primary strategy to clear this reservoir. Although histone deacetylase inhibitors such as suberoylanilide hydroxamic acid (also known as vorinostat, VOR) can disrupt HIV-1 latency in vitro, the utility of this approach has never been directly proven in a translational clinical study of HIV-infected patients. Here we isolated the circulating resting CD4+ T cells of patients in whom viraemia was fully suppressed by antiretroviral therapy, and directly studied the effect of VOR on this latent reservoir. In each of eight patients, a single dose of VOR increased both biomarkers of cellular acetylation, and simultaneously induced an increase in HIV RNA expression in resting CD4+ cells (mean increase, 4.8-fold). This demonstrates that a molecular mechanism known to enforce HIV latency can be therapeutically targeted in humans, provides proof-of-concept for histone deacetylase inhibitors as a therapeutic class, and defines a precise approach to test novel strategies to attack and eradicate latent HIV infection directly.

Correlation between immunologic responses to a recombinant glycoprotein 120 vaccine and incidence of HIV-1 infection in a phase 3 HIV-1 preventive vaccine trial

BACKGROUND An objective of the first efficacy trial of a candidate vaccine containing recombinant human immunodeficiency virus (HIV) type 1 envelope glycoprotein 120 (rgp120) antigens was to assess correlations between antibody responses to rgp120 and the incidence of HIV-1 infection. METHODS Within the randomized trial (for vaccinees, n=3598; for placebo recipients, n=1805), binding and neutralizing antibody responses to rgp120 were quantitated. A case-cohort design was used to study correlations between antibody levels and HIV-1 incidence. RESULTS Peak antibody levels were significantly inversely correlated with HIV-1 incidence. The relative risk (RR) of infection was 0.63 (95% confidence interval, 0.45-0.89) per log(10) higher neutralization titer against HIV-1(MN), and the RRs of infection for second-, third-, and fourth-quartile responses of antibody blocking of gp120 binding to soluble CD4 versus first-quartile responses (the lowest responses) were 0.35, 0.28, and 0.22, respectively. CONCLUSIONS Despite inducing a complex, robust immune response, the vaccine was unable to reduce the incidence of HIV-1. Two interpretations of the correlative results are that the levels of antibodies (i) caused both an increased (low responders) and decreased (high responders) risk of HIV-1 acquisition or (ii) represented a correlate of susceptibility to HIV-1 but had no causal effect on susceptibility. Although the data cannot definitively discriminate between these 2 explanations, (ii) appears to be more likely.

Toward Causal Inference with Interference

A fundamental assumption usually made in causal inference is that of no interference between individuals (or units); that is, the potential outcomes of one individual are assumed to be unaffected by the treatment assignment of other individuals. However, in many settings, this assumption obviously does not hold. For example, in the dependent happenings of infectious diseases, whether one person becomes infected depends on who else in the population is vaccinated. In this article, we consider a population of groups of individuals where interference is possible between individuals within the same group. We propose estimands for direct, indirect, total, and overall causal effects of treatment strategies in this setting. Relations among the estimands are established; for example, the total causal effect is shown to equal the sum of direct and indirect causal effects. Using an experimental design with a two-stage randomization procedure (first at the group level, then at the individual level within groups), unbiased estimators of the proposed estimands are presented. Variances of the estimators are also developed. The methodology is illustrated in two different settings where interference is likely: assessing causal effects of housing vouchers and of vaccines.

Obesity is associated with impaired immune response to influenza vaccination in humans

Background:Obesity is an independent risk factor for morbidity and mortality from pandemic influenza H1N1. Influenza is a significant public health threat, killing an estimated 250 000–500 000 people worldwide each year. More than one in ten of the worlds adult population is obese and more than two-thirds of the US adult population is overweight or obese. No studies have compared humoral or cellular immune responses to influenza vaccination in healthy weight, overweight and obese populations despite clear public health importance.Objective:The study employed a convenience sample to determine the antibody response to the 2009–2010 inactivated trivalent influenza vaccine (TIV) in healthy weight, overweight and obese participants at 1 and 12 months post vaccination. In addition, activation of CD8+ T cells and expression of interferon-γ and granzyme B were measured in influenza-stimulated peripheral blood mononuclear cell (PBMC) cultures.Results:Body mass index (BMI) correlated positively with higher initial fold increase in IgG antibodies detected by enzyme-linked immunosorbent assay to TIV, confirmed by HAI antibody in a subset study. However, 12 months post vaccination, higher BMI was associated with a greater decline in influenza antibody titers. PBMCs challenged ex vivo with vaccine strain virus, demonstrated that obese individuals had decreased CD8+ T-cell activation and decreased expression of functional proteins compared with healthy weight individuals.Conclusion:These results suggest obesity may impair the ability to mount a protective immune response to influenza virus.

Chemoprophylaxis with Tenofovir Disoproxil Fumarate Provided Partial Protection against Infection with Simian Human Immunodeficiency Virus in Macaques Given Multiple Virus Challenges

We examined the efficacy of tenofovir disoproxil fumarate (TDF) in blocking simian human immunodeficiency virus (SHIV) infection in Chinese rhesus macaques. Once weekly for 14 weeks or until a macaque became infected, 12 male macaques were inoculated intrarectally with amounts of SHIV(SF162P3) (10 median tissue culture infective doses; 3.8 x 10(5) virus particles) that were approximately 5-fold higher than the human immunodeficiency virus type 1 RNA levels noted in human semen during an acute infection. Of the 12 macaques, 4 received oral TDF daily, 4 received oral TDF once weekly, and 4 (control animals) received no TDF. The control animals became infected after receiving a median of 1.5 virus inoculations; macaques receiving TDF daily (1 macaque remained uninfected after 14 inoculations) and those receiving TDF weekly became infected after a median duration of 6.0 and 7.0 weeks, respectively. Although infection was delayed in treated macaques, compared with control macaques, the differences were not statistically significant (P=.315); however, the study was limited by the small numbers of animals evaluated and the variability in blood levels of TDF that resulted from oral dosing. These data demonstrate that treatment with oral TDF provided partial protection against SHIV infection but ultimately did not protect all TDF treated animals against multiple virus challenges.

Immune and Genetic Correlates of Vaccine Protection Against Mucosal Infection by SIV in Monkeys.

A vaccine protecting monkeys against mucosal infection by simian immunodeficiency virus sheds light on immune and genetic correlates of protection. Unraveling Immune Correlates of Vaccine Protection Developing an effective vaccine against HIV-1, the virus that causes AIDS, has been a huge challenge that has stymied AIDS researchers for several decades. A key problem for HIV vaccine trials has been the lack of immune correlates that indicate which antibody and T cell responses in the vaccinees correlate directly with a protective effect. The only HIV vaccine trial to date that has shown a protective effect is the RV144 trial carried out in Thailand between 2003 and 2006, with the final results reported in 2009. In this trial of 16,400 Thai volunteers, those vaccinated with a prime-boost HIV vaccine showed a reduction in the rate of infection by HIV-1 of 31% compared to volunteers given a placebo. The protective effect was seen for up to 3 years after the initial vaccination, but the immune correlates of protection by this vaccine are still not known. In an effort to learn more about possible immune correlates of HIV vaccine protection, Letvin and colleagues used a prime/boost vaccine regimen in monkeys that was similar to that used in the RV144 trial. Monkeys were vaccinated with a plasmid DNA prime/recombinant adenovirus serotype 5 (rAd5) boost vaccine regimen and then were challenged with intrarectal doses of one of two isolates of the simian immunodeficiency virus (SIV) every week for 12 weeks. Although the vaccine had no impact on acquisition of the SIVmac251 isolate (which is tough for the monkey immune system to neutralize), the vaccine provided a 50% reduction in infection with the SIVsmE660 isolate (which more readily undergoes neutralization). The authors then examined a variety of immune responses in the protected vaccinated monkeys including cellular, antibody, and innate immune responses; they also examined whether protective host alleles were present in the protected animals. They found that low levels of neutralizing antibodies and a CD4+ T cell response against the HIV envelope (Env) protein correlated with the protective effect. In addition, monkeys that expressed two TRIM5 alleles that help to restrict SIV replication in host cells were protected by the vaccine, whereas monkeys expressing one TRIM5 allele that is permissive for SIV replication were not. This study begins to unravel the immune and genetic correlates of protection in nonhuman primates and highlights the need to scrutinize these types of correlates in future trials of HIV vaccines in human volunteers. The RV144 vaccine trial in Thailand demonstrated that an HIV vaccine could prevent infection in humans and highlights the importance of understanding protective immunity against HIV. We used a nonhuman primate model to define immune and genetic mechanisms of protection against mucosal infection by the simian immunodeficiency virus (SIV). A plasmid DNA prime/recombinant adenovirus serotype 5 (rAd5) boost vaccine regimen was evaluated for its ability to protect monkeys from infection by SIVmac251 or SIVsmE660 isolates after repeat intrarectal challenges. Although this prime-boost vaccine regimen failed to protect against SIVmac251 infection, 50% of vaccinated monkeys were protected from infection with SIVsmE660. Among SIVsmE660-infected animals, there was about a one-log reduction in peak plasma virus RNA in monkeys expressing the major histocompatibility complex class I allele Mamu-A*01, implicating cytotoxic T lymphocytes in the control of SIV replication once infection is established. Among Mamu-A*01–negative monkeys challenged with SIVsmE660, no CD8+ T cell response or innate immune response was associated with protection against virus acquisition. However, low levels of neutralizing antibodies and an envelope-specific CD4+ T cell response were associated with vaccine protection in these monkeys. Moreover, monkeys that expressed two TRIM5 alleles that restrict SIV replication were more likely to be protected from infection than monkeys that expressed at least one permissive TRIM5 allele. This study begins to elucidate the mechanisms of vaccine protection against immunodeficiency viruses and highlights the need to analyze these immune and genetic correlates of protection in future trials of HIV vaccine strategies.

Sensitivity analysis for the assessment of causal vaccine effects on viral load in HIV vaccine trials

Vaccines with limited ability to prevent HIV infection may positively impact the HIV/AIDS pandemic by preventing secondary transmission and disease in vaccine recipients who become infected. To evaluate the impact of vaccination on secondary transmission and disease, efficacy trials assess vaccine effects on HIV viral load and other surrogate endpoints measured after infection. A standard test that compares the distribution of viral load between the infected subgroups of vaccine and placebo recipients does not assess a causal effect of vaccine, because the comparison groups are selected after randomization. To address this problem, we formulate clinically relevant causal estimands using the principal stratification framework developed by Frangakis and Rubin (2002, Biometrics 58, 21-29), and propose a class of logistic selection bias models whose members identify the estimands. Given a selection model in the class, procedures are developed for testing and estimation of the causal effect of vaccination on viral load in the principal stratum of subjects who would be infected regardless of randomization assignment. We show how the procedures can be used for a sensitivity analysis that quantifies how the causal effect of vaccination varies with the presumed magnitude of selection bias.

Moving to Human Immunodeficiency Virus Type 1 Vaccine Efficacy Trials: Defining T Cell Responses As Potential Correlates of Immunity

There is evidence in both simian immunodeficiency virus and human immunodeficiency virus (HIV) type 1 infection that class I major histocompatibility complex-restricted CD8(+) cytotoxic T lymphocytes play a pivotal role in controlling infection and, potentially, in protecting by immunization. Progress has been made in designing strategies to elicit these responses with HIV-1 vaccines, but methods to reproducibly quantify them have posed difficulties. An interferon-gamma enzyme-linked immunospot assay, using peptide pools spanning the HIV-1 genes, was developed and standardized. This method is rapid (2 days), sensitive (threshold of detection, > or =0.005%), quantitative, feasible using cryopreserved cells, and able to define epitope specificities. When this assay was applied to 36 HIV-1-seropositive and 10 HIV-1-seronegative subjects, it proved to be robust (specificity, 100%). When responses in natural infection were compared with vaccine-induced responses, vaccine recipient responses were > or =1 log lower, which confirms the importance of using this sensitive assay as an initial screen in vaccine protocols.

Evaluation of oncogenic human papillomavirus RNA and DNA tests with liquid-based cytology in primary cervical cancer screening: the FASE study

The APTIMA® HPV Assay (AHPV) allows detection of 14 high‐risk human papillomavirus (HPV) RNA types in cervical specimens. Until present, the assay has been compared to HPV DNA tests only in triage settings. Herein, we compare AHPV with a DNA assay (Hybrid Capture® 2; HC2) and liquid‐based cytology (LBC; using PreservCyt® ThinPrep liquid Pap) in a screening setting (French APTIMA screening evaluation [FASE] study). Women (N = 5,006) aged 20–65 were screened by gynecologists in 17 private practices in Paris, France. One cervical specimen was collected and tested with LBC, AHPV and HC2 assays. Women were referred to colposcopy if they were ASC‐US+ in LBC or HPV positive in either HPV assay. To control for verification bias, a random group (14%) with normal LBC and dually HPV negative tests underwent colposcopy. Data from 4,429 women were analyzed. Sensitivity, specificity and predictive values were calculated for the three tests. AHPV and HC2 were highly sensitive for CIN2+ (92.0% and 96.7%) and CIN3+ (95.7% and 95.3%) detection and much more sensitive than LBC (69.1% for CIN2+ and 73.3% for CIN3+). Specificity of AHPV was higher than that of HC2, but similar to that of LBC (p < 0.001). Combining LBC with either HPV test slightly increased sensitivity but compromised specificity. AHPV assay is both specific and sensitive for the detection of high‐grade precancerous lesions and may be considered as an option for routine cervical cancer screening for women over 20 years of age.

Safety and immunogenicity of a high-titered canarypox vaccine in combination with rgp120 in a diverse population of HIV-1-uninfected adults: AIDS vaccine evaluation group protocol 022A

&NA; To test the safety and immunogenicity of a high‐titered preparation of ALVAC‐HIV vCP205 in both high‐risk and low‐risk persons and to evaluate variations in dosing schedule, we conducted a multicenter, randomized, double‐blind trial of this vector in combination with recombinant subunit gp120 in 150 HIV‐1‐seronegative volunteers. The high‐titered ALVAC vaccine was well tolerated; adverse events were minimal and not influenced by dosing. At day 728, the cumulative probability of a cytotoxic T‐lymphocyte (CTL) response was 76% (95% confidence interval [CI]: 64%‐89%) among volunteers receiving vaccine, and the net amount attributable to vaccination was 50% (CI: 16%; 74%). The net probability of a repeated positive CTL response by day 728 was 50% (CI: 21%; 64%). There was a significant difference in CTL response at day 182 between volunteers who had received four doses versus three doses of vCP205 (42% vs. 24%, p = .052). The CTL response was similar in high‐risk volunteers and vaccinia‐naive volunteers compared with vacciniaimmune volunteers. Neutralizing antibody responses were detected in 95% of vaccinees at day 287, with higher geometric mean titers in recipients of sequential versus simultaneous dosing of the two vaccines and in vaccinia‐naive volunteers. This hightitered preparation of ALVAC‐HIV vCP205 in combination with gpl20 was safe and immunogenic in a diverse group of HIV‐1‐seronegative volunteers.