Conclusions
These findings suggest NDV-vectored PCVcap-TMCT vaccine candidate, expressing the cap gene of PCV2 along with the TMCT domain, offers a promising alternative for protecting against PCV2 infection, potentially addressing the challenges posed by emerging PCV2 strains in the swine industry.
Methods
Six-week-old BALB/c mice were divided into five groups and immunized intramuscularly three times at 14-day intervals with various vaccine candidates, namely rNDV-R2B-PCVcap-TMCT, rNDV-R2B-PCVcap, and CircoFLEX commercial vaccine, along with controls. Following immunization and PCV2d virus challenge, multiple assays assessed the immune responses in animal trials. In the pig animal trial, pigs were divided into four groups: a control group (PBS), NDV-vectored PCVcap-TMCT group, NDV-vectored-PCVcap group, and CircoFLEX vaccine group. Pigs were immunized intramuscularly twice at 28-day intervals. Blood samples were collected at regular intervals over 70 days to evaluate the humoral and cell-mediated immune responses.
Results
Both mice and pigs' trials indicated that the NDV-vectored PCV2 cap-TMCT vaccine candidate elicited superior immune responses. In mice, the rNDV-R2B-PCVcap-TMCT group showed enhanced humoral and cellular immunity, increased PCV2-specific antibody levels, higher CD4+/CD8+ ratio, elevated IFN-γ and TNF-α levels, decreased IL-10 levels, reduced viral loads, and minimal histopathological changes. In pigs, the NDV-vectored PCVcap-TMCT group demonstrated better antibody responses, cytokine profiles (IFN-γ and IL-10), and higher levels of PCV2-specific neutralizing antibodies against the PCV2a, PCV2b and PCV2d genotypes when compared to other groups. Conclusions: These findings suggest NDV-vectored PCVcap-TMCT vaccine candidate, expressing the cap gene of PCV2 along with the TMCT domain, offers a promising alternative for protecting against PCV2 infection, potentially addressing the challenges posed by emerging PCV2 strains in the swine industry.