| Porcine transmissible gastroenteritis virus (TGEV) and porcine epidemic diarrhea virus (PDEV) can cause porcine transmissible gastroenteritis (TGE) and porcine epidemic diarrhea (PED), respectively, which were characterized acute chordapsus, diarrhea and death in piglets. The effective prevention measure is vaccination. At present, there are some backwards in TGE and PED vaccine on stability, safety and efficacy; meanwhile, it is unclear that the pathogenesis for this two kinds of viruses. Therefore, it is important to develop effective vaccines against TGEV and PEDV. Spike protein (S) is an important surface glucoprotein of TGEV and PEDV, which can induce animal immune system to produce specific neutralization antibody,interact with the specific receptor on the host cell surface and be involved in membrane fusion process. It is a candidate immune protective antigen. Nucleic acid (DNA) vaccines are easy to produce and operate. They have a number of advantages over conventional vaccines, including the ability to induce a wider range of immune responses. Prevous study has shown that the N terminal half of TGEV S gene (2106bp), named TGEV S1, had better effect than the full-length S gene in terms of the immune efficacy in mouse model. In contrast, there is no report regarding immunological analysis of PEDV S gene. In this study, TGEV S gene and PEDV S1 or PEDV S gene were inserted into the eukaryotic expression vector, pIRES, resulting in recombinant plasmids, pIRES-T1-P1 and pIRES-T1-P2. The plasmids were transfected into BHK-21 cells and indirect fluorescence assay (IFA) showed that the transiently expressed S proteins were recognized by anti-TGEV or anti-PEDV antibody. Subseqently, 6-8 weeks old Kunming mice were inoculated with the both DNA plasmids. Spleens and blood of immunized mice were collected and subjected to lymphocyte proliferation assay, virus neutralization assay, IFN-γassay and CTL activity assay. TGEV/PEDV specific antibody responses were detected by indirect ELISA. Kinetic changes of T lymphocyte subgroups of the immunized mice were analyzed by flow cytometry. The results showed that the recombinant DNA plasmids increased the proliferation of T lymphocytes and the number of CD4+ and CD8+ T lymphocyte subgroups. In addition, the DNA vaccines induced the high level of IFN-γin the immunized mice. The specific CTL activity in the pIRES-T1-P2 group became significant at 42 days post-immunization. At 35 days post-immunization, the recombinant DNA plasmids stimulated higher level of specific antibody and neutralizing antibody in immunized mice. The study provides useful reference for further characterization of DNA vaccines bearing the S gens of TGE and PED. |
