Abstract
BACKGROUND: HLA strongly influences human immunodeficiency virus type 1 (HIV-1) disease progression. A major contributory mechanism is via the particular HLA-presented HIV-1 epitopes that are recognized by CD8(+) T-cells. Different populations vary considerably in the HLA alleles expressed. We investigated the HLA-specific impact of the MRKAd5 HIV-1 Gag/Pol/Nef vaccine in a subset of the infected Phambili cohort in whom the disease-susceptible HLA-B*58:02 is highly prevalent. METHODS: Viral loads, CD4(+) T-cell counts, and enzyme-linked immunospot assay-determined anti-HIV-1 CD8(+) T-cell responses for a subset of infected antiretroviral-naive Phambili participants, selected according to sample availability, were analyzed. RESULTS: Among those expressing disease-susceptible HLA-B*58:02, vaccinees had a lower chronic viral set point than placebo recipients (median, 7240 vs 122 500 copies/mL; P = .01), a 0.76 log10 lower longitudinal viremia level (P = .01), and slower progression to a CD4(+) T-cell count of <350 cells/mm(3) (P = .02). These differences were accompanied by a higher Gag-specific breadth (4.5 vs 1 responses; P = .04) and magnitude (2300 vs 70 spot-forming cells/10(6) peripheral blood mononuclear cells; P = .06) in vaccinees versus placebo recipients. CONCLUSIONS: In addition to the known enhancement of HIV-1 acquisition resulting from the MRKAd5 HIV-1 vaccine, these findings in a nonrandomized subset of enrollees show an HLA-specific vaccine effect on the time to CD4(+) T-cell count decline and viremia level after infection and the potential for vaccines to differentially alter disease outcome according to population HLA composition. CLINICAL TRIALS REGISTRATION: NCT00413725, DOH-27-0207-1539.