ABSTRACT
TNX-1800 is a synthetically derived live chimeric Horsepox Virus (rcHPXV) vaccine expressing Wuhan SARS-CoV-2 spike (S) protein. The primary objective of this study was to evaluate the immunogenicity and efficacy of TNX-1800 in two nonhuman primate species challenged with USA-WA1/2020 SARS-CoV-2. TNX-1800 vaccination was well tolerated, as indicated by the lack of serious adverse events or significant changes in clinical parameters. A single dose of TNX-1800 generated robust humoral responses in African Green Monkeys and Cynomolgus Macaques, as measured by the total binding anti-SARS-CoV-2 S IgG and neutralizing antibody titers against the USA-WA1/2020 strain. In Cynomolgus Macaques, a single dose of TNX-1800 induced a strong interferon-gamma (IFN-{gamma}) mediated T cell response, promoting both pathogen clearance in the upper and lower airways and generation of systemic neutralizing antibody response against WA strain SARS-CoV-2. Future studies will assess the efficacy of TNX-1800 against newly emerging variants and demonstrate its safety in humans.