Studies on in vitro expression and in vivo immunogenicity of a recombinant MVA HIV vaccine

Here we conduct dose-response studies for in vitro expression and in vivo immunogenicity for a recombinant modified vaccinia Ankara (MVA) vaccine that expresses HIV Gag, Pol, and Env proteins. The dose-response studies for in vitro expression used fluorescent-activated cell sorting to score Gag- and Env-expressing cells and showed good increases for antigen expression with increasing MVA dose. In these studies, a 1000-fold increase in the dose of MVA resulted in a 300-fold increase in the frequency of antigen-expressing cells. In contrast, dose-response studies for in vivo immunogenicity showed <10-fold increases in elicited T cells and Ab for 100-1000-fold increases in the dose of inoculated MVA. These studies used intracellular cytokine assays to enumerate responding CD8 and CD4 T cells and an ELISA to score anti-Env Ab. The shallow dose-response curves for immunogenicity were observed post priming as well as post boosting of an MVA or a DNA prime.