OA05-03. Efficacy study of a T-cell-based DNA vaccine delivered by intradermal electrotransfer in macaques

Abstract

Results Before challenge, all animals raised SIV-specific T-cells as evidenced by IFN-γ ELISPOT (110 ± 42, 921 ± 310 and 905 ± 252 spots/106 cells in the ID only, ID+EP and ID+EP+genetic-adjuvant groups, respectively). Weak and transient antibody responses were detected. All animals were intrarectally challenged with pathogenic SIVmac251. T-cell responses increased in both ID+EP groups as early as week 1 post-challenge (3,898 ± 395 and 3,031 ± 893 spots, respectively), and up to 12,000 spots by week 2. Macaques immunized ID only raised delayed and lower responses remaining earlier and higher than in controls. At peak of viremia, plasma viral load was significantly reduced (p = 0.0104) in the ID+EP group. Interestingly, no reduction of plasma viral load was observed by that time in the genetic-adjuvant group despite high anamnestic responses. Differences in anti-Gag responses may explain this observation. Viremia was not reduced in the ID only group. At set-point, although similar plasma viral load in all groups, reduction of SIV-DNA copies in rectal biopsies was observed in the vaccinated animals.