IRO-203: a novel intranasal COVID-19 vaccine showing immunogenicity and viral suppression in African green monkey challenge study.

This study indicates that IRO-203, a novel intranasal Coronavirus Disease 2019 vaccine based on a non-transmissible Sendai virus (nT-SeV) vector induces measurable humoral and cellular immune responses and shows signs of protective potential in a non-human primate challenge model. Immunogenicity was evaluated in both BALB/cA mice and African green monkeys (AGMs). Intranasal administration of IRO-203 led to the production of spike protein-specific IgG and IgA antibodies in serum and mucosal samples. Enzyme-Linked ImmunoSpot assays revealed increased IL-2 and IFN-γ secretion, indicating activation of cellular immunity. Neutralizing antibody titers were significantly boosted by repeated immunizations in both species. In the challenge study, AGMs vaccinated with IRO-203 and subsequently challenged via intranasal and intratracheal administration of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) exhibited statistically significant reductions in SARS-CoV-2 RNA levels in nasal and throat swabs at certain time points compared to controls, suggesting partial attenuation of viral replication. Although clinical symptoms were not assessed in this study, and further investigation is needed to determine the extent of protection conferred by IRO-203, these findings highlight the ability of IRO‑203 to induce measurable immune responses and to partially reduce viral RNA levels in a non‑human primate challenge model. Furthermore, they suggest that the nT-SeV vector represents an attractive platform for developing vaccines against other respiratory infectious diseases.