Study On The Immunoprotection Of P40and MIC6Genes Against Neospora Caninum Challenge

Neosporiasis is a kind of protozoal disease caused by Neospora canium parasitized in kindsof animal cells. Surface antigen protein and microneme protein of Neospora canium is theimportant proteins for adhesion and invasion to mammalian host cell. In this study, Theprokaryotic expression system pET-28a was applied to expressing P40in E.coli. Therecombinant protein of NcP40was about40KD after identified by SDS-PAGE. It can berecognized by positive serum anti-Neospora caninum after identified by Western blotting. TheDNA vaccine were also constructed using the eukaryotic expression vector pVAX1and theexpression were identified by Western blotting and IFA. Respectively，the subunit vaccine andDNA vaccine of NcP40and NcMIC6were immunized into BALB/c mice and analyzedantibodies and cytokine levels in serum. The decreased rate and the reduced active parasite ratewere measured to evaluate the protective efficacy from Neosporiasis.The result of the levels of IgG, IgG1and IgG2a in mice immunized protein vaccine wereelevated. The protein vaccine could elicit both Th1immune response with the elevated levels ofIL-4and Th2immune response with the elevated levels of IFN-γ. The mice in all groups werealive after challenged with tachyzoites of Neospora caninum. Compared with control, the resultshowed the decreased rate of parasites is65%and the reduced active parasite rate is62%inNcMIC6group、the decreased rate of parasites is79%and the reduced active parasite rate is78%in NcP40group、the decreased rate of parasites is81%and the reduced active parasite rateis85%in mixed group. The results indicated NcP40and NcMIC6had a protective efficacy toneosporosis and the protective efficacy of NcP40was better than NcMIC6as the subunitvaccine. The result of the levels of IgG, IgG1and IgG2a in mice immunized DNA vaccine wereelevated. The DNA vaccine could elicit both Th1immune response with the elevated levels ofIL-4and Th2immune response with the elevated levels of IFN-γ. The mice in all groups werealive after challenged with tachyzoites of Neospora caninum. Compared with control, the resultshowed the decreased rate of parasites is40%and the reduced active parasite rate is45%inNcMIC6group、the decreased rate of parasites is52%and the reduced active parasite rate is46%in NcP40group,the decreased rate of parasites is55%and the reduced active parasite rateis71%in mixed group. The results indicated NcP40and NcMIC6had a protective efficacy toneosporosis and the protective efficacy of NcP40was better than NcMIC6as the DNA vaccine.In all, Whether subunit vaccines or DNA vaccines, both NcP40and NcMIC6have some protective effects against infections, but the protective efficacy of recombinant NcP40vaccinewas better than recombinant NcMIC6vaccine. And the protective efficacy of combining NcP40and NcMIC6were better than the only one of recombinant vaccine.