P19-02. High protection of female macaques from repeated intravaginal challenges with SHIV-162P3 upon mucosal vaccination with Gp41 subunits-virosomes

Methods We have developed a mucosal vaccine candidate based on two complementary conserved gp41 subunit antigensa trimeric recombinant gp41 deleted in known immunodominant regions (rGp41) and the 35 amino acid peptide P1, this later adopting the 3D conformation of the gp41 MPER and target of HIV-neutralizing IgA in highly exposed but persistently seronegative individualsfor focusing the immune response on relevant neutralizing epitopes. Gp41 subunit antigens are grafted on virosomes, a market-approved vaccine carrier with intrinsic adjuvant properties. Female Macaca mulata were immunized 4 times with both rGp41and P1 peptide-virosomes, using either the sole intra-muscular or the combined intra-muscular/intra nasal routes. Five weeks post-vaccination, animals were challenged 13 times intra-vaginally with low dose of SHIV162p3 at a biweekly frequency. Results Up to 13 weeks post-challenge, 5/5 animals vaccinated by the combined intra muscular/intra nasal routes were fully protected against SHIV162p3 (undetectable viremia, antiHIV IgG seronegativity), as compared to the 6/6 infected control group, or the 5/6 infected animals vaccinated by only the intra muscular route. Protection was correlated to gp41-specific IgA in vaginal secretions with in vitro neutralizing activities against transcytosis and CD4+ cell infection.