Immunological characteristics of the recombinant pseudorabies virus with chimeric PCV Cap protein in pigs

Porcine circovirus type 2 (PCV2) is one of the main pathogens causing porcine circovirus-associated diseases (PCVAD). We recently reported the immunogenicity of the recombinant PRV with an envelope-embedded Cap protein of PCV2 (PRV-Cap) in mice. Here, we further evaluated the immunoprotective efficacy of PRV-Cap virus in pigs. Following vaccination, the PRV-Cap stimulated the production of neutralizing antibodies against PRV and PCV2, along with protected piglets from the challenge of the lethal PRV, the virulent PCV2b and PCV2d. Peripheral blood mononuclear cells analysis revealed that PRV-Cap virus effectively induced proliferation and activation of CD4 and CD8 T cells, as well as an increase in T follicular helper cells, although γδ T and B cells did not show significant differences. Compared to DMEM control piglets, the expanded CD4 and CD8 T cells exhibited an effector memory T cell phenotype, and in vitro stimulation led to PRV- and PCV2-specific IFN-γ and TNF-α secretion, peaking at 21 days post-immunization. In summary, PRV-Cap virus effectively prevents PRV, PCV2b and PCV2d challenges in piglets by simultaneously inducing both PRV- and PCV2-specific humoral and cellular immunity, indicating that PRV-Cap virus is a promising and safe candidate vaccine for combined PRV and PCV2 immunization.