Vaccine immunogenicity and efficacy in the rhesus macaque/SHIV model

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Project 2 seeks to test virosomal vaccine immunogenicity and efficacy in the rhesus macaque (RM)/SHIV model. Mymetics has improved virosomal vaccines built from empty influenza virus-like particles that display an elongated HIV gp41 peptide on their surface (virosome-P1) or recombinant truncated HIV gp41 (virosome- rgp41). Earlier, Chinese RMs given two intramuscular (IM) primes followed by two intranasal (IN) boosts were 100% protected from persistent systemic infection and did not seroconvert to SIV Gag after low-dose intravaginal SHIV challenges. A follow-up study in Indian RMs showed 78% to 87% protection as long as the SHIV dose was ~7x104 times the median HIV inoculum in human male-to-female HIV transmission, but when the SHIV inoculum was ~105x greater, protection was lost. In these NHP studies, unadjuvanted, liquid formulations of the combination of virosome-P1 + virosome-rgp41 were used. To improve immunogenicity, Mymetics embedded the toll-like receptor (TLR)7/8 adjuvant 3M-052 directly into virosome membranes and developed solid, cold-chain independent vaccine formulations that can be administered needle-free. The powdered virosome forms can be given as IN spray, sublingual (SL) tablets, or packaged into oral capsules (PO). Our overall hypothesis is that the cold-chain independent, needle-free adjuvanted solid virosome forms are significantly more immunogenic than their earlier liquid form in RMs and will induce higher mucosal fluid Ab levels after mucosal priming/mucosal boosting via different routes. Mymetics has performed pilot tests in small animals with the IN and SL forms; vaccine delivery via oral capsules needs to be optimized in RMs. The Specific Aims for Project 2 are to: 1. Optimize vaccine delivery to the ileum via enteric-coated capsules; a) monitor passage of capsules containing 99mTc or 64Cu by scans; b) attach fluorescent labels to the virosomal vaccines for detection in the near-infrared spectrum. Tissues collected at necropsy will be tested by fluorescent microscopy. 2. Test the immunogenicity of different routes of the novel adjuvanted virosomes through a prime/boost approach. We will test their relative immunogenicity via IN, SL and PO routes; boosts will be given via a different mucosal route, a novel approach. Controls will be immunized IM with the soluble virosomal vaccine. 3. Test the efficacy of the cold-chain independent, needle-free, adjuvanted virosomal vaccines against repeated low-dose intrarectal (IR) clade B SHIV (SHIV-B) challenges. The most immunogenic mucosal prime/mucosal boost regimen (see Aim 2) will be used to immunize a group of 12 RMs; control (n=12) will receive empty virosomes. All RMs will undergo ~10 weekly low-dose IR challenges with the tier 2, R5 clade B SHIVSF162P3. 4. Test whether RMs that resisted multiple SHIV-B challenges will be protected against cross-clade challenge with the tier 2 R5 clade C SHIV. Protected RMs will be used to determine correlates of protection. These innovations are highly significant for the developing world, where our novel vaccine will be a major plus to combat the AIDS epidemic.