Comparison of intradermal and intramuscular delivery followed by in vivo electroporation of SIV Env DNA in macaques.

A panel of SIVmac251 transmitted Env sequences were tested for expression, function and immunogenicity in mice and macaques. The immunogenicity of a DNA vaccine cocktail expressing SIVmac239 and three transmitted SIVmac251 Env sequences was evaluated upon intradermal or intramuscular injection followed by in vivo electroporation in macaques using sequential vaccination of gp160, gp120 and gp140 expressing DNAs. Both intradermal and intramuscular vaccination regimens using the gp160 expression plasmids induced robust humoral immune responses, which further improved using the gp120 expressing DNAs. The responses showed durability of binding and neutralizing antibody titers and high avidity for>1 y. The intradermal DNA delivery regimen induced higher cross-reactive responses able to neutralize the heterologous tier 1B-like SIVsmE660_CG7V. Analysis of cellular immune responses showed induction of Env-specific memory responses and cytotoxic granzyme B(+) T cells in both vaccine groups, although the magnitude of the responses were ~10x higher in the intramuscular/electroporation group. The cellular responses induced by both regimens were long lasting and could be detected ~1 y after the last vaccination. These data show that both DNA delivery methods are able to induce robust and durable immune responses in macaques.