Effective protection against PRRSV NADC30 by recombinant chimpanzee adenovirus vaccines expressing GP35 or M-GP5 fusion proteins

Porcine Reproductive and Respiratory Syndrome (PRRS) is one of the highly contagious infectious diseases caused by Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) that seriously harms the pig industry. Existing commercial inactivated and live attenuated PRRSV vaccines have very limited protective efficacy, with weak neutralizing antibody and cell-mediated immune responses, and risks of vaccine strain virulence reversion. PRRSV GP5, a key biological macromolecular antigen for neutralizing antibody induction, has complex immunogenicity and limited vaccine utility due to hypervariable regions, glycosylation changes, and narrow neutralizing epitopes. In contrast, the fusion antigen GP35 (GP3 and GP5) and M-GP5 (M and GP5) offer complementary improvements via expanded epitope coverage and stabilized GP5 conformation, respectively. In this study, we constructed two recombinant chimpanzee adenovirus vaccine candidates, rChAd-30-GP35 and rChAd-30-M-GP5, to express the GP35 or M-GP5 fusion proteins of the PRRSV NADC30-like strain. Vaccination with the recombinant adenovirus in both mouse and piglet models resulted in a potent antigen-specific immune response, including enhanced GP5-specific antibody production, neutralizing activity, and T-cell-mediated immunity. Furthermore, following viral challenge, the recombinant adenovirus vaccine elicited effective protection in piglets and outperformed a commercial inactivated vaccine in several critical efficacy parameters. Our results emphasize the importance and feasibility of recombinant chimpanzee adenovirus vector platforms in the development of novel genetic engineering vaccines for PRRSV. Collectively, this work provides a foundation for the development of next-generation safer and more effective PRRSV vaccines and offers a versatile platform for rapidly adapting vaccine designs to emerging field strains.