SARS-CoV-2 animal vaccine with cross-protection against Wuhan strain and delta variant.

The increasing number of reverse zoonotic transmission cases, in which pathogens are transmitted from humans to companion animals, has raised substantial concerns in both veterinary and public health fields. The emergence of novel viral strains through interspecies transmission poses a potential threat to the health of animals and humans. In response to the growing incidence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections in companion animals, a SARS-CoV-2 vaccine candidate was developed and evaluated for use in these species to mitigate the risks associated with viral transmission. The Delta variant (B.1.617.2) of SARS-CoV-2 emerged as one of the most concerning variants during the COVID-19 pandemic due to its heightened transmissibility, increased pathogenicity, and partial immune evasion. In this study, a subunit vaccine candidate composed of the spike (S) and receptor-binding domain (RBD) proteins of the Wuhan strain was developed, and its cross-protective efficacy against both the Wuhan strain and the Delta variant was assessed. To evaluate vaccine efficacy and safety, experimental infection studies were conducted in beagles, and a field clinical trial was performed in companion animals. The results demonstrated that the vaccine induced a robust immune response while maintaining an acceptable safety profile. Vaccinated animals exhibited high levels of neutralizing antibodies, significant inhibition of viral shedding and marked alleviation of clinical symptoms during experimental challenge with the Delta variant. The development of a SARS-CoV-2 vaccine candidate for companion animals represents a proactive 'One Health' strategy to limit viral transmission and ensure both animal and human health during pandemic events.