Construction of Specifically Targeted Chimeric Canine Parvovirus DNA Vaccine and Its Efficacy Assessment

To design chimeric DNA vaccine targeted to antigen-presenting cells with enhanced efficacy to induce immunization.The plasmid containing the gene encoding the extracelluar domain of canine cytotoxic T-lymphocyte antigen 4(CTLA-4₁₂₅),was directly fused to the gene fragment for major antigenic epitopes of VP2(VP2₂₂₈) by molecular engineering technology.The plasmid containing VP2₂₂₈ alone was also constructed to serve as control and transfection of COS-7 cells with the two resultant plasimds was performed respectively,followed by assay of Western blotting.The mice were immunized with the constructed two plasimds,respectively.After immunization,the antibodies anginst CPV in the immunized mice at different times were measured by HI.The spleen lymphocyte proliferation response was determined by lymphocyte proliferation assay,and the interferon-γ (IFN-γ) expression level of the mouse lymphocytes were measured by ELISA.The eukaryotic expression plasimds of CTLA-4₁₂₅-VP2₂₂₈ fusion protein or VP2₂₂₈ alone were cloned.Western blotting showed that the two recombinant proteins could be expressed.Immunization results showed that the antibody levels in serum of CTLA-4₁₂₅-VP2₂₂₈-immunized mice were significantly higher than that of VP2₂₂₈-immunized mice (P<0.05).The lymphocyte stimulation indexes and secreted IFN-γ levels of the CTLA-4₁₂₅-VP2₂₂₈-immunized mice were significantly higher than that of VP2₂₂₈-immunized mice (P<0.05 and P<0.01),respectively.CTLA-4₁₂₅-VP2₂₂₈ chimeric DNA vaccine stimulates strong immune response in mice,making it possible for further exploration into chimeric DNA that target the antigen to APCs.