A candidate inactivated chimeric vaccine PCV1-2 constructed based on PCV1 and PCV2 isolates originating in China and its evaluation in conventional pigs in regard to protective efficacy against PCV2 infection

A chimeric PCV1-2 clone containing the PCV2 capsid gene cloned into the backbone of the nonpathogenic PCV1 genome was recently generated based on PCV2 and PCV1 strains isolated in China. The efficacy of this available candidate inactivated vaccine was evaluated by subjecting conventional pigs to intramuscular immunization with the inactivated chimeric PCV1-2 virus, followed by challenge with wild-type PCV2 strain. By 35 days post-vaccination (DPV), all vaccinated pigs had developed seroconversion, having high indirect immunofluorescence assay (IFA) titers of antibody and neutralizing antibody against PCV2. By 21 days post-challenge, gross and microscopic lesions of lymph nodes and lungs in non-vaccinated but challenged pigs were significantly more severe than those found in the vaccinated group. PCV2 viral copy loads detected in the tracheobronchial lymph nodes or serum samples of vaccinated pigs were significantly smaller than those in non-vaccinated but challenged pigs (P ≤ 0.05). The results suggest that inactivated PCV1-2 is effective in inducing protective immunity against PCV2 infection.