Phenotypic and kinetic analysis of effective simian-human immunodeficiency virus-specific T cell responses in DNA--and fowlpox virus-vaccinated macaques.

Although T cell immunity is important in the control of HIV-1 infection, the characteristics of effective HIV-specific T cell responses are unclear. We previously observed protection from virulent SHIV challenges in macaques administered priming with DNA vaccines and boosting with recombinant fowlpox viruses expressing shared SIV Gag antigens. We therefore performed a detailed kinetic and phenotypic study of the T cell immunity induced by these vaccines prior to and following SHIV challenge utilizing intracellular cytokine staining. Pigtail macaques vaccinated intramuscularly with DNA/recombinant fowlpox virus exhibited a coordinated induction of first Gag-specific CD4 T cell responses and then a week later Gag-specific CD8 T cell responses following the fowlpox virus boost. Overall, the magnitude and timing of the peak CD8 T cell responses following challenge was significantly associated with reductions in SHIV viremia following pathogenic challenge. After pathogenic lentiviral challenge, virus-specific effector memory T cells derived from animals controlling SHIV infection recognized a broad array of epitopes, expressed multiple effector cytokines and rapidly recognized virus-exposed cells ex vivo. These results shed light on some of the requirements for T cells in the control of pathogenic lentiviral infections.