Summary Background In the Step Study, the MRKAd5 HIV-1 gag/pol/nef vaccine did not
reduce plasma viraemia after infection, and HIV-1 incidence was higher in vaccine-treated
than in placebo-treated men with pre-existing adenovirus serotype 5 (Ad5) immunity. We
assessed vaccine-induced immunity and its potential contributions to infection risk. Methods
To assess immunogenicity, we characterised HIV-specific T cells ex vivo with validated
interferon-γ ELISPOT and intracellular cytokine staining assays, using a case–cohort design …

Abstract Background—In the Step Study, the MRKAd5 HIV-1 gag/pol/nef vaccine did not
lower postinfection plasma viremia, and HIV-1 incidence was higher in vaccine-treated than
placebo-treated males with pre-existing adenovirus serotype 5 (Ad5) immunity. We
evaluated vaccine-induced immunity and its potential contributions to infection risk. Methods—
To assess immunogenicity, HIV-specific T-cells were characterized ex vivo using validated
IFN-γ ELISpot and intracellular cytokine staining (ICS) assays, employing a case-cohort …