A semi-replicating VSV (srVSV)-based platform for developing broad-spectrum mucosal vaccines against influenza A viruses.

Influenza A viruses (IAVs) are significant respiratory pathogens characterized by high mutation rates and frequent genetic reassortments, underscoring the need for vaccines that can induce robust and broadly protective mucosal immunity. While replication-competent vesicular stomatitis virus (VSV) vectors have the potential to elicit mucosal immunity, their neurovirulence raises significant safety concerns. Herein, we report that a semi-replicating VSV (srVSV) vector, composed of one VSV with the glycoprotein (G) gene deleted (rVSVΔG) and another with the L gene deleted (rVSVΔL), has improved safety. Using srVSV, we constructed a monovalent vaccine (srVSV-N1), expressing the neuraminidase 1 (N1) of IAV. A single intranasal dose of srVSV-N1 elicited both systemic and mucosal immune responses against N1, and provided sterilizing immunity against homologous influenza virus. We further generated a bivalent IAV vaccine (srVSV-N1/N2), co-expressing N1 and N2. A single intranasal dose of srVSV-N1/N2 conferred 80% protection against heterologous IAVs (H1N1 and H3N2). Notably, low-dose priming immunization followed by a high-dose boost with srVSV-N1/N2 fully protected mice against lethal heterologous IAV challenges. These findings demonstrate the potential of the srVSV platform for developing mucosal vaccines against IAVs and other respiratory viruses.