Mucosal antibody responses to vaccines targeting SIV protease cleavage sites or full-length Gag and Env proteins in Mauritian cynomolgus macaques

Abstract

HIV mutates rapidly and infects CD4+ T cells, especially when they are activated. A vaccine targeting conserved, essential viral elements while limiting CD4+ T cell activation could be effective. Learning from natural immunity observed in a group of highly HIV-1 exposed seronegative Kenyan female sex workers, we are testing a novel candidate HIV vaccine targeting the 12 viral protease cleavage sites (PCSs) (the PCS vaccine), in comparison with a vaccine targeting full-length Gag and Env (the Gag/Env vaccine) in a Mauritian cynomolgus macaque/SIV model. In this study we evaluated these vaccines for induction of mucosal antibodies to SIV immunogens at the female genital tract. Bio-Plex and Western blot analyses of cervicovaginal lavage samples showed that both the PCS and Gag/Env vaccines can elicit mucosal IgG antibody responses to SIV immunogens. Significantly higher increase of anti-PCS antibodies was induced by the PCS vaccine than by the Gag/Env vaccine (p<0.0001). The effect of the mucosal antibody responses in protection from repeated low dose pathogenic SIVmac251 challenges is being evaluated.

Cervico-Vaginal Inflammatory Cytokine and Chemokine Responses to Two Different SIV Immunogens

“…Generation of rVSVpcs and rVSVgag/env, as well as packaging of the different SIVmac239 immunogens in nanoparticles were performed as previously described ( 25 , 26 ). Briefly, nucleotide sequences of SIVmac239 (Los Alamos National Laboratory HIV database) encoding 20 amino acids overlapping 12 PCS were previously cloned in pATX VSV-G (rVSV vector), and packaged into rVSVpcs virus.…”

“…The freeze-dried nanoparticle formulations were stored at 4°C, and reconstituted in sterile water just before the immunization. SIVmac239 full-length Gag and Env coding sequences were previously prepared and packaged into rVSVgag and rVSVenv viruses (rVSVgag/env), as previously described ( 25 ). Separate DNA constructs coding for full-length Gag or Env (pVAX1-Gag and pVAX1-Env) were packaged into separate nanoparticles made of chitosan and tripolyphosphate to form the NANOgag/env formulation.…”

“…MHC (major histocompatibility complex) typing was performed by the Wisconsin Non-human Primate Research Centre Genetics Services as described previously ( 25 ). Those with the same MHC haplotypes were grouped to form several MHC-based subgroups.…”

“…Immunization was performed as previously described ( 25 ). Briefly, these monkeys were divided into 3 groups of 8 monkeys: the PCS vaccine group received rVSVpcs and NANOpcs; the Gag/Env vaccine group received rVSVgag/env and NANOgag/env; and the Control group received VSV virus vector and sterile water boosts ( Figure 1 ).…”

“…Cytokines/chemokines were quantified using a custom 14-plex assay based on a previously published Bio-Plex assay method with some modifications ( 25 , 27 ). Bio-Plex® Amine Coupling Kit (Bio-Rad, Canada) was used to couple 20 μg of capture antibody for each cytokine/chemokine to 1.25 × 10 7 Bio-Plex Pro™ fluorescently-dyed magnetic COOH Beads, diluted to a stock concentration of 5 × 10 6 beads/ml.…”