Vaccine-specific CD8+ T cell proliferation
Results for CD8+ T cell assays were valid in 149 samples. CD8+ HIV-specific T-cell proliferation was detected in AIDSVAX recipients at higher frequencies compared to placebo recipients (, 15/87 [17.2%)] and1/62 [1.6%], respectively, p-value <0.05). In addition, HIV-specific responses were more frequently detected among vaccine recipients in the high-risk (N=34) compared to low-risk (N=53) groups (26.5% and 11.3%, respectively) although this did not reach statistical significance (OR 2.8, 95% CI [0.9–9.3], p-value=0.075).
Surprisingly, the frequency of responses was significantly higher in vaccine recipients who subsequently acquired HIV infection compared to individuals who remained HIV seronegative (, 34.8% and 10.9%, respectively, OR 4.3, 95% CI [1.4–14.3], p-value=0.01). This difference remains statistically significant after adjusting for risk score (OR 4.0, 95% CI [1.2–13.6], p-value=0.02).
To assess whether race or gender played a role in the above finding, similar analyses were performed in a subset of white, male vaccine recipients, who constituted the majority of the study population (). The responses rate in white male vaccinees remains significantly higher in individuals who subsequently acquired HIV infection compared to those who remained HIV negative (8/20 and 7/52, respectively, OR 4.29, 95% CI [1.30, 14.68], p-value=0.017), similar to the overall population, suggesting that race or gender did not contribute significantly to our findings
No difference in the frequency of HCMV-specific proliferation was observed among all subgroups (, p>0.05), suggesting that the finding were vaccine specific among vaccine and placebo recipients, regardless of outcome.
Figure 2 CMV-specific CD4+ and CD8+ proliferation in VAX004 samples. CFSE- labeled PBMC were stimulated with HCMV peptides then assessed for proliferation after 5 days. No significant difference between the frequency of responses in CD4− and CD8− (more ...)
Vaccine-specific CD4+ T cell proliferation
Results for CD4+ T cell proliferation were valid in 166 samples. Vaccine-specific CD4+ proliferation was significantly higher in individuals who received the vaccine compared to placebo recipients (13/94 [13.8%] and 1/72 [2.8%], respectively, p<0.05) placebo recipients. The response rate was significantly different between vaccine volunteers who subsequently acquired HIV infection compared to individuals who remained HIV seronegative (7/31 and 6/63 respectively, OR 5.4, 95% CI [1.5–25.4], p=0.02). However, when adjusted for risk score, no significant difference was seen in the CD4+ response rate between vaccine recipients who eventually acquired HIV infection compared to those who did not (OR 2.77, 95%CI [0.84, 9.45], p-value=0.093). The odds ratio of a positive response among white, male vaccine recipients who eventually became HIV infected versus never infected vaccinees, adjusted for risk score, is3.43 (95%CI [0.86, 15.43], p-value= 0.087). The lack of differences in findings between male vaccine recipients subanalyis and the total vaccine recipients indicate that race or gender do not play a role in the above findings.
T cell profile of vaccine responders
We next determined the level of intracellular cytokine production and immune activation in vaccine recipients who demonstrated evidence of T cell proliferation. Low levels of Env-specific IFN-γ and TNF-α were detected in 3 out of 20 evaluated responders (representative plot in ). In contrast, CMV-specific responses included simultaneous production of multiple cytokines, including IFN-γ and TNF-α as well as CD107 surface expression. No Nef-specific responses were detected, supporting the fact that HIV-specific immune responses were attributable to AIDSVAX immunization.
Figure 3 Representative plots of antigen-specific CD8+ T cells in a vaccine responder. PBMC were stimulated with Env or CMV peptides then stained with anti-CD107a PE, anti-IFN-γ FITC, anti-TNF-α PE-CY7, anti-CD4 PerCP-Cy5.5 anti-IL-2 APC, anti-CD3 (more ...)
CD4+ and CD8+ T cell activation was also assessed and analyzed by HIV infection outcome. We observed a significantly higher immune activation in CD4+ T cells in vaccine responders who subsequently acquire HIV infection compared to those who remain uninfected (Wilcoxon test, p=0.05). We also found significantly higher CD8 T cell activation in vaccine responders who subsequently became HIV positive (, p=0.014).
Figure 4 Immune activation in CD4+ and CD8+ lymphocyte subsets in vaccine responders based on subsequent HIV infection status. PBMC were stained with HLADR FITC, CD38 PE, CD3 AmCyan, CD4 APC-CY7, and CD8 PerCP-Cy5.5, and analyzed by flow cytometry. Immune activation (more ...)