Characteristics and Outcomes of Initial Virologic Suppressors during Analytic Treatment Interruption in a Therapeutic HIV-1 gag Vaccine Trial

Background: In the placebo-controlled trial ACTG A5197, a trend favoring viral suppression was seen in the HIV-1-infected subjects who received a recombinant Ad5 HIV-1 $gag$ vaccine. Objective: To identify individuals with initial viral suppression (plasma HIV-1 RNA set point <3.0 $log_{10}$ copies/ml) during the analytic treatment interruption (ATI) and evaluate the durability and correlates of virologic control and characteristics of HIV sequence evolution. Methods: HIV-1 $gag$ and $pol$ RNA were amplified and sequenced from plasma obtained during the ATI. Immune responses were measured by flow cytometric analysis and intracellular cytokine expression assays. Characteristics of those with and without initial viral suppression were compared using the Wilcoxon rank sum and Fisher's exact tests. Results: Eleven out of 104 participants (10.6%) were classified as initial virologic suppressors, nine of whom had received the vaccine. Initial virologic suppressors had significantly less CD4+ cell decline by ATI week 16 as compared to non-suppressors (median 7 CD4+ cell gain vs. 247 CD4+ cell loss, P = 0.04). However, of the ten initial virologic suppressors with a pVL at ATI week 49, only three maintained pVL <3.0 log10 copies/ml. HIV-1 Gag-specific CD4+ interferon-γ responses were not associated with initial virologic suppression and no evidence of vaccine-driven HIV sequence evolution was detected. Participants with initial virologic suppression were found to have a lower percentage of CD4+ CTLA-4+ cells prior to treatment interruption, but a greater proportion of HIV-1 Gag-reactive CD4+ TNF-α+ cells expressing either CTLA-4 or PD-1. Conclusions: Among individuals participating in a rAd5 therapeutic HIV-1 $gag$ vaccine trial, initial viral suppression was found in a subset of patients, but this response was not sustained. The association between CTLA-4 and PD-1 expression on CD4+ T cells and virologic outcome warrants further study in trials of other therapeutic vaccines in development. Trial Registration: ClinicalTrials.gov NCT0008010

Interferon-Alpha Administration Enhances CD8+ T Cell Activation in HIV Infection

Type I interferons play important roles in innate immune defense. In HIV infection, type I interferons may delay disease progression by inhibiting viral replication while at the same time accelerating disease progression by contributing to chronic immune activation.To investigate the effects of type I interferons in HIV-infection, we obtained cryopreserved peripheral blood mononuclear cell samples from 10 subjects who participated in AIDS Clinical Trials Group Study 5192, a trial investigating the activity of systemic administration of IFNα for twelve weeks to patients with untreated HIV infection. Using flow cytometry, we examined changes in cell cycle status and expression of activation antigens by circulating T cells and their maturation subsets before, during and after IFNα treatment.The proportion of CD38+HLA-DR+CD8+ T cells increased from a mean of 11.7% at baseline to 24.1% after twelve weeks of interferon treatment (p = 0.006). These frequencies dropped to an average of 20.1% six weeks after the end of treatment. In contrast to CD8+ T cells, the frequencies of activated CD4+ T cells did not change with administration of type I interferon (mean percentage of CD38+DR+ cells = 2.62% at baseline and 2.17% after 12 weeks of interferon therapy). As plasma HIV levels fell with interferon therapy, this was correlated with a "paradoxical" increase in CD8+ T cell activation (p<0.001).Administration of type I interferon increased expression of the activation markers CD38 and HLA DR on CD8+ T cells but not on CD4+ T cells of HIV+ persons. These observations suggest that type I interferons may contribute to the high levels of CD8+ T cell activation that occur during HIV infection

HIV-1 Gag-specific CD4+ IFN-γ-producing T cells at weeks 8 and 38 categorized by initial virologic suppression and treatment arm.

<p>Panel A, CD4+ IFN-γ response 8 weeks after receiving the first vaccine dose. Number of cells quantified by the intracellular cytokine staining assay in response to pooled HIV Gag peptides. Panel B, CD4+ IFN-γ response 38 weeks after receiving the first vaccine dose and immediately prior to initiating the analytic treatment interruption. Statistical comparison not provided for participants in the “Suppressors (Placebo)” group as only two participants fell into this category.</p

Expression of HIV-1 Gag-specific CD4+ TNF-α+ T cells expressing either CTLA-4+ or PD-1+ by participants with and without initial virologic suppression.

<p>Panel A, Percentage of CD4+TNF-α+ T cells expressing CTLA-4 at week 38. Panel B, Percentage of CD4+TNF-α+ T cells expressing PD-1 at week 38.</p

Characteristics of initial viral suppressors.

<p>PID, patient identification number.</p

Viral load trends for individuals with ATI set point viral load <3.0 log10 copies/ml.

<p>The light yellow highlighted region encompass the HIV-1 viral load measurements used to calculate the viral set point (mean of the ATI weeks 12 and 16 HIV-1 RNA copies/ml). Pre-ARV, pre-antiretroviral therapy; PID, patient identification number.</p

Expression of HIV-1 CD4+ T cells expressing either CTLA-4+ or PD-1+ by participants with and without initial virologic suppression.

<p>Panel A, Percentage of CD4+ T cells expressing CTLA-4 at week 38 detected using flow cytometry. Panel B, Percentage of CD4+ T cells expressing PD-1 at week 38 detected using flow cytometry.</p

Patient Cohort from AIDS Clinical Trial Group Study 5192.

<p>Patient Cohort from AIDS Clinical Trial Group Study 5192.</p

Co-expression of CD38 and HLA-DR on CD4+ and CD8+ T cells.

<p>The percentage of CD4+ T cells (A) and CD8+ T cells (B) co-expressing CD38 and HLA-DR is shown over the course of interferon-alpha treatment during the ACTG 5192 Study. Week 0 corresponds to the patients' baseline cell counts before beginning Interferon-Alpha Therapy. Weeks 3 and 12 correspond to 3 weeks and 12 weeks of interferon-alpha Therapy. Interferon-Alpha therapy was stopped at Week 12, and therefore Week 18 corresponds to 6 weeks off therapy. The bar represents the median value.</p

CD4+ and CD8+ T cell counts.

<p>The CD4 Cell Count (A) and the CD8 Cell Count (B) are portrayed over the course of interferon-alpha treatment during the ACTG 5192 Study. Week 0 corresponds to the patients' baseline cell counts before beginning Interferon-Alpha Therapy. Weeks 3 and 12 correspond to 3 weeks and 12 weeks of interferon-alpha Therapy. Interferon-Alpha therapy was stopped at Week 12, and therefore Week 18 corresponds to 6 weeks off therapy.</p