Oral Vaccination Approaches for Anti-SHIV Immunity.

We modified a Sabin Oral Poliovirus Vaccine (OPV) vector to permit secretion of the antigens of interest with the goal of improving anti-HIV Env humoral responses in a SHIV mucosal immunization composed of DNA and recombinant OPVs. We evaluated stimulation of systemic and mucosal cell-mediated and humoral immunity in Rhesus macaques by two regimens, both involving a prime with a SHIVBG505 DNA construct producing non-infectious particles formulated in lipid nanoparticles, administered in the oral cavity, and two different viral vector boostings, administered in the oral cavity and intestinally. Group 1 was boosted with rMVA-SHIVBG505, expressing SIV Gag/Pol and HIVBG505 Env. Group 2 was boosted with a SHIVBG505-OPV vaccine including a non-secreting SIVmac239CA-p6-OPV, expressing Gag CA, NC and p6 proteins, and a HIVBG505C1-V2-OPV, secreting the C1-V2 fragment of HIV EnvBG505, recognized by the broadly neutralizing antibody PG16. A time course analysis of anti-SHIV Gag and Env CD4+ and CD8+ T-cell responses in PBMC and in lymph node, rectal, and vaginal MNC was carried out. Both regimens stimulated significant cell-mediated responses in all compartments, with SHIVBG505-OPV immunization stimulating more significant levels of responses than rMVA- SHIVBG505. Boolean analysis of these responses revealed predominantly monofunctional responses with multifunctional responses also present in all tissues. Stimulation of antibody responses was disappointing in both groups with negative anti-SHIV IgG in plasma, and IgA in salivary, rectal and vaginal secretions being restricted to a few animals. After repeated rectal challenge with SHIVBG505, two Group 1 animals remained uninfected at challenge termination. No significant differences were observed in post-infection viral loads between groups. After the acute phase decline, CD4+ T cell percentages returned to normal levels in vaccinated as well as control animals. However, when compared to controls, vaccinate groups had more significant preservation of PBMC and rectal MNC Th17/Treg ratios, considered the strongest surrogate marker of progression to AIDS. We conclude that the vaccine platforms used in this study are insufficient to stimulate significant humoral immunity at the tested doses and schedule but sufficient to stimulate significant mucosal and systemic cell-mediated immunity, impacting the preservation of key Th17 CD4+ T cells in blood and rectal mucosa.

Construction and Immuno - biochemical Studies of Chimeric Polioviruses Expressing Multivalent V3 / PND - concatamers of Human Immunodeficiency Virus Type 1

Poliovirus Sabin 1 strain has its own special features that make it a particularly attractive live recombinant mucosal vaccine vehicle. Sabin 1 cDNA was manipulated to have multiple cloning site and viral specific 3C-protease cutting site at the N-terminal end of the polyprotein, named RPS-vax system HIV-1 V3- and principal neutralizing domain (PND)-concatamers were successfully cloned into the multiple cloning site of the vector system and produced expected chimeric viruses by transfection of their RNA transcripts into HeLa cells. These chimeric viruses have shown to express introduced HIV-1 subgenome concatamers efficiently during their replication in the infected HeLa cells. Expressed proteins were confirmed to retain the wild type structures at least in parts. Replication capacity of the chimeric viruses was slightly lower than that of wild type Sabin 1 likely to be due to delay in processing steps during their replication. Differing from the virulent Mahoney vectors, the rec-Sabin 1 chimeric viruses maintained the foreign gene stably during the serial passages. These chimeric viruses have also shown to be able to induce specific humoral immunity to the introduced vaccine proteins when inoculated into the poliovirus receptor-expressing transgenic (Tg-PVR) mice. Antiserum obtained from the immunized transgenic mice showed to have neutralizing capacity to HIV-1 in vitro. These results strongly suggest that the chimeric viruses expressing HIV-1 vaccine epitopes can be used as a good live mucosal vaccine candidate against AIDS.