Pre-Existing Adenovirus Immunity Modifies a Complex Mixed Th1 and Th2 Cytokine Response to an Ad5/HIV-1 Vaccine Candidate in Humans

The results of the recent Step Study highlight a need to clarify the effects of pre-existing natural immunity to a vaccine vector on vaccine-induced T-cell responses. To investigate this interaction, we examined the relationship between pre-existing Ad5 immunity and T-cell cytokine response profiles in healthy, HIV-uninfected recipients of MRKAd5 HIV-1 gag vaccine (HVTN 050, ClinicalTrials.gov #NCT00849732). Participants were grouped by baseline Ad5 neutralizing antibody titer as either Ad5-seronegative (titer ≤18; n = 36) or Ad5-seropositive (titer >200; n = 34). Samples from vaccine recipients were analyzed for immune responses to either HIV-1 Gag peptide pools or Ad5 empty vector using an ex vivo assay that measures thirty cytokines in the absence of long-term culture. The overall profiles of cytokine responses to Gag and Ad5 had similar combinations of induced Th1- and Th2-type cytokines, including IFN-γ, IL-2, TNF-α, IP-10, IL-13, and IL-10, although the Ad5-specific responses were uniformly higher than the Gag-specific responses (p<0.0001 for 9 out of 11 significantly expressed analytes). At the peak response time point, PBMC from Ad5-seronegative vaccinees secreted significantly more IP-10 in response to Gag (p = 0.008), and significantly more IP-10 (p = 0.0009), IL-2 (p = 0.006) and IL-10 (p = 0.05) in response to Ad5 empty vector than PBMC from Ad5-seropositive vaccinees. Additionally, similar responses to the Ad5 vector prior to vaccination were observed in almost all subjects, regardless of Ad5 neutralizing antibody status, and the levels of secreted IFN-γ, IL-10, IL-1Ra and GM-CSF were blunted following vaccination. The cytokine response profile of Gag-specific T cells mirrored the Ad5-specific response present in all subjects before vaccination, and included a number of Th1- and Th2-associated cytokines not routinely assessed in current vaccine trials, such as IP-10, IL-10, IL-13, and GM-CSF. Together, these results suggest that vector-specific humoral responses may reduce vaccine-induced T-cell responses by previously undetected mechanisms

Effects of partnership change on microbicide gel adherence in a clinical trial (HPTN 035).

Use of HIV prevention methods may vary for women by types of sexual partners. In a microbicide safety and effectiveness trial (HPTN 035) differences in adherence to a microbicide study gel were compared between women with new versus ongoing partnerships over time. 1,757 women in the three HPTN 035 trial's arms completed the Follow-up Partner Status (FPS) questionnaire at their last study visit. Women married at baseline were asked if they had the same husband, new husband or new partner. Unmarried women were asked if they had changed partners or married. Self-reported gel adherence during the last sex act was compared at each quarterly visit between women with ongoing versus new partners. High gel adherence was compared with low gel adherence (85-100 vs. &lt;85 % of last vaginal sex acts reported with gel use, respectively) in multivariable models to assess associations with partner change. Overall 7 % of women (n = 123) reported a new partner and 41 % (51) of those reported a new husband. Median gel adherence was reported to be 100 % in women with ongoing partners and 75 % for women with new partners (p &lt; 0.001). In women reporting no gel use in their last sex act, only 12.5 % of the women with a new partner and none of those with an ongoing partner reported using condoms (p &lt; 0.001). Fewer women with new partners reported using both the gel and condom during the last sex act as compared to women with ongoing partners (median 50 vs. 71.4 %, p &lt; 0.001). After adjusting for age, site, education level, and sexual frequency, women with ongoing partners were more likely to report high gel adherence than those with new partners (AOR 2.5, 95 % CI 1.6, 3.9). This pattern persisted when gel use over time was compared between women with new versus ongoing partners. In the HPTN 035 trial, women with new partners had higher HIV incidence and reported less gel use and higher condom use. Specific counseling and support are needed to help women use potential HIV prevention methods, including microbicides, when they are changing partners