Recombinant fusion protein LpxC-ApxIVA elicits a protective immune response against Glaesserella parasuis and Actinobacillus pleuropneumoniae in mice.

Abstract

Glaesserella parasuis (GPS) and Actinobacillus pleuropneumoniae (APP) are often synergistically infected, posing a significant threat to the pig industry. Currently, there are no a broad-spectrum subunit vaccine that collectively targets these two pathogens. In this study, we employed fusion PCR to construct a recombinant DNA construct lpxC-apxIVA, incorporating the GPS lpxC gene and the APP apxIVA gene, and successfully expressed and purified the recombinant fusion protein LpxC-ApxIVA. Mice were immunized to assess the immunoprotective efficacy of subunit vaccine against GPS and APP challenges. The results demonstrated that mice immunized with the recombinant fusion protein LpxC-ApxIVA developed high levels of antibody titers, induced strong mixed Th1/Th2-type cytokine responses, and protected mice against challenges with GPS and APP. Notably, Adaptive immune responses were assessed in immunized mice to compare the immunogenicity and immunoprotective of the different immunization schemes. The results showed that immunization with the recombinant fusion protein LpxC-ApxIVA maintained high-titer antibodies, protected against GPS (serotype 5 and 13) and APP (serotype 1 and 7) infections in mice, and exhibited cross-protection. These results demonstrate that recombinant fusion protein LpxC-ApxIVA is a promising candidate for a subunit vaccine against co-infections caused by GPS and APP.