Suppressor tRNA-mediated conditionally replicating live vaccine effectively protects pigs against Seneca Valley virus challenge.

Abstract

Seneca Valley virus (SVV) causes porcine idiopathic vesicular disease, severely endangering the economic benefits of the swine industry. Artificial control of viral replication via the introduction of premature termination codons (PTCs) into the viral genome using suppressor tRNAs (sup-tRNAs) is a promising strategy for developing efficient vaccines. In this study, optimization of the SVV 3D gene for the incorporation of multiple PTCs resulted in a progeny virus harboring three PTCs with high replicative capacity and genetic stability. In mouse and pig models, compared with inactivated vaccines, the SVV-PTC vaccination elicited high antibody titers at 14 days post-primary immunization and induced a stronger Th1-biased cellular immune response. We further validated the safety and protective efficacy of the SVV-PTC vaccine candidate in swine models, confirming its complete attenuation in vivo, absence of horizontal transmission, and protective efficacy comparable to that of the commercial inactivated SVV vaccine. In conclusion, the development of live but replication-incompetent attenuated vaccines using sup-tRNA is a promising prevention and control strategy, providing a new insight for the development of novel SVV vaccines.