Pushing HIV-1 Vaccine Protection to the Mucosal Barrier

Abstract Most gene-based vaccines are replication-defective mRNA, DNA, or adenovirus (Ad) vaccines. In each case, the vaccine delivers its one copy of an antigen gene and expresses "1X" of the antigens that are encoded by the vaccine. We developed single cycle Ad (SC-Ad) vaccines that replicate vaccine antigen genes up to 10,000-fold

in every cell to amplify antigen production but do not produce infectious progeny viruses. When RD-Ad and SC- Ad6 expressing HIV-1 antigens or SARS-CoV-2 spike are compared, SC-Ad produces 100 times more antigen than RD-Ad and generates significantly higher antibodies than RD-Ad-Spike or mRNA vaccines. When spike-

immunized animals were challenged 10.5 months after single immunization, SC-Ad reduced SARS-CoV-2 lung viral loads and damage and preserved body weights better than RD-Ad. During the COVID-19 pandemic, we tested SC-Ads expressing SIV gag and clade C HIV-1 Env in rhesus macaques by intramuscular (IM), intranasal (IN), and intravaginal (IVAG) routes of immunization in combination

with IM co-immunization with adjuvanted clade C SOSIP protein. When the macaques were challenged vaginally with clade C SHIV.CH505.375H.dCT 1.5-years after last vaccine, PBS, IN, and IM vaccinated animals became infected with similar kinetics with only one IN animal resisting infection. In contrast, 50% of the IVAG macaques

resisted vaginal challenge. These data suggest there are great merits to creating a mucosal barrier against incoming SHIV at the site of viral entry. Given this, this project will determine the reproducibility of this protection and examine how vaginal immunization drives local-regional immune responses in the female reproductive tract (FRT) and if these

responses might be amplified by co-immunization in this site. Proof of concept here for being able to “push” immune responses into the FRT in macaques will allow these approaches to be translated for humans, to protect not just women, but all sexes and gender identities from vaginal, rectal, or penile exposures to HIV-1.