Development of canine parvovirus-2-based recombinant pseudoviruses expression system: a potential vaccine platform

Canine parvovirus-2 (CPV-2) and canine distemper virus (CDV) are two highly infectious and pathogenic pathogens that harm canids and various carnivores, and often cause co-infections in clinical settings. Although commercial attenuated live vaccines against CPV-2 and CDV have been widely used to prevent these viral infections, there are still issues of biosafety and insufficient protection against new variants, thus requiring novel vaccines. In this study, we developed a recombinant pseudovirus expression system based on the CPV-2 full-length infectious clone, and found that the recombinant CPV-2 pseudovirus expressing CDV H protein could efficiently protect dogs against both CPV-2 and CDV infections. We first designed a recombinant pseudovirus vector based on the CPV-2 backbone and established a stable cell system for the production of CPV-2 recombinant pseudoviruses carrying foreign genes. These pseudoviruses preserved the morphology and particle size of native CPV-2, while maintaining hemagglutination activity against porcine erythrocytes, and demonstrated the ability to effectively infect permissive cells to express the harbored foreign gene. Next, we produced a recombinant CPV-2 pseudovirus expressing CDV H protein, and the CPV-CDV recombinant pseudovirus induced effective cellular and humoral immune responses in dogs. The serum from CPV-CDV immunized dogs could effectively neutralize CPV-2 and CDV infections in susceptible cells. Importantly, CPV-CDV completely protected dogs against challenge with CPV-2 and CDV. In summary, we have successfully developed a stable production system of recombinant CPV-2 pseudoviruses, which has great potential for development as a vaccine platform.