Summary We report the primary analysis of the safety and efficacy of the MRKad5 gag/pol/nef HIV-1 sub-type B vaccine in South Africa (SA), where the major circulating clade is sub-type C. Methods This phase IIb double-blind, randomized test-of-concept study was conducted in sexually active HIV-1 sero-negative participants in SA. The co-primary endpoints were a vaccine-induced reduction in HIV-1 acquisition or viral-load setpoint. These were assessed independently in the modified intent-to-treat (MITT) cohort with two-tailed significance tests stratified by gender. Immunogenicity was assessed by interferon-gamma (IFNγ) ELISPOT in peripheral blood mononuclear cells. Following the lack of efficacy of the MRKAd5 HIV-1 vaccine in the Step study, enrollment and vaccination in this study was halted, treatment unblinding occurred and follow-up continued. This study is registered with the SA National Health Research Database (DOH-27-0207-1539) and ClinicalTrials.gov (NCT00413725). Results 801 of a scheduled 3000 participants were enrolled, of whom 360 (44.9%) were women, more than half (55.6%) had Ad5 titres > 200, and almost a third (29.3%) of men were circumcised. 62 MITT participants were diagnosed with HIV-1, 34 in the vaccine arm and 28 in the placebo arm, with infection rates of 4.54 and 3.70 per 100 person-years, respectively. There was no evidence of vaccine efficacy (VE); the hazard ratio adjusted for gender was 1.25 (95% CI: 0.76, 2.05). VE did not differ by Ad5 titre, gender, age, HSV-2 status, or circumcision. The geometric mean viral load setpoint was 20,483 copies/ml (N=33) in vaccinees and 34,032 copies/ml (N=28) in placebo recipients (p=0.39). The vaccine elicited IFNγ-secreting T cells recognizing both clade B (89.2%) and C (77.4%) antigens. Conclusion The MRKAd5 HIV-1 vaccine did not prevent HIV-1 infection or lower viral-load setpoint however early stopping likely compromised our ability to draw conclusions. The high incidence rates seen in SA highlight the critical need for intensified efforts to develop an efficacious vaccine.

Objective:To describe immunologic, virologic, and clinical HIV disease progression by HIV-1 subtype among Africans with well documented estimated dates of HIV infection (EDIs).Design:Prospective cohort.Methods:Adults and youth with documented HIV-1 infection in the past 12 months were recruited from seroincidence cohorts in East and Southern Africa and followed at 3–6 month intervals. Blood for lymphocyte subset and viral load determination was collected at each visit. Pol was sequenced from the first positive specimen to ascertain subtype. Preantiretroviral therapy disease progression was measured by three time-to-event endpoints: CD4+ cell count 350 cells/μl or less, viral load measurement at least 1 × 105 copies/ml, and clinical AIDS.Results:From 2006 to 2011, 615 participants were enrolled at nine research centers in Kenya, Rwanda, South Africa, Uganda, and Zambia; 579 (94.1%) had viral subtyping completed. Predominant subtypes were C (256, 44.2%), A (209, 36.1%), and D (84, 14.5%). After adjustment for age, sex, and human leukocyte antigen alleles in Cox regression analyses, subtype C-infected participants progressed faster than subtype A to all three endpoints [CD4+ hazard ratio 1.60, 95% (confidence interval) CI 1.16, 2.20; viral load hazard ratio 1.59, 95% CI 1.12, 2.25; and AIDS hazard ratio 1.60, 95% CI 1.11, 2.31). Subtype D-infected participants reached high viral load more rapidly (hazard ratio 1.61, 95% CI 1.01, 2.57) and progressed nearly twice as fast to AIDS compared to subtype A (hazard ratio 1.93, 95% CI 1.21, 3.09).Conclusion:Subtype-specific differences in HIV disease progression suggest that the local subtype distribution be considered when planning HIV programs and designing and defining clinical endpoints for HIV prevention trials.

Although regional differences exist, our data suggest that the incidence of HCV infection among injection drug users in the United States decreased from 1994 through 2004.

Interventions providing information, enhancing risk-reduction skills, and motivating behavior change through peer education training can reduce injection risk behaviors, although risk elimination might be necessary to prevent HCV transmission.