Induction of mucosal immunity is critical for protection from enteric pathogens. We have developed a vaccine design that utilizes the unique property of the endoplasmic reticulum chaperon, heat shock protein (HSP) gp96, to bind antigenic peptides and deliver them to APCs.

The aim of our study was to evaluate safety and systemic and mucosal SIV-immunity with secreted gp96-Ig vaccines in non-human primates.

We have generated a secreted form gp96 by replacing the ER retention sequence KDEL with the IgG1-Fc tag. HEK-293 cells were transfected with gp96-Ig and with the cDNAs encoding the SIV antigens gag, pol, env and retanef (reassorted rev, tat, nef). Irradiated, transfected 293 cells that secrete 1, 5 or 50 micrograms gp96-Ig-SIV-peptide complexes in 24h, were injected intraperitoneally in Mamu-A*01+ macaques at 0, 4 and 24 weeks. The frequency of SIVGag- and SIVTat- tetramer+ cells in the rectal mucosa reached 30-50% in some macaques after the third immunization. Tetramer+ cells expressed appropriate functional (granzymeB) and migration markers (alpha4beta7, CD103). The cells secrete IL-2 and IFN-gamma in response to different peptide (gag, tat, env) stimulation.

We conclude that the cell secreted SIV-gp96-Ig vaccine is safe and can induce strong poly-specific, multifunctional CD8 responses in mucosal compartments that are thought to be critical for protection from SIV/HIV infection.