Effect Of Porcine Interleukin-12 And Porcine Interleukin-18 On Immune Responses In Mice Immunized With The Spike Gene Of Transmissible Gastroenteritis Virus

Porcine transmissible gastroenteritis(TGE) is caused by transmissible gastroenteritis virus(TGEV). TGE is a highly infectious enteritic disease. Vaccination is one effective way for the prevention of TGE. In this study, TGEV S and porcine IL-12 genes were inserted into the eukaryotic expression vector, pVAX1, resulting in recombinant plasmids, pVAX1-TGEV S1 and pVAX1-pIL-12,respectively. The plasmids were transfected into BHK cells and the transient expression of both genes was recoginzied by respective antibody. Experimental mice were divided into 9 groups. They were blank control group, PBS control group, pVAX1 control group, pIL-12 group, pIL-12+ pIL-18 group, TGEV group, TGEV+pIL-12 group, TGEV+ pIL-12+pIL-18 group, vaccine group. Lymphocyte proliferative assay, enzyme linkered immunosorbent assay(ELISA), flow cytometry, specificity CTL activity assay, virus neutralization test and cytokine detection by ELISA were used to analyze the immune responses in the immunized mice.The results showed that the general immune responses of six immunized groups were higher than those of the control groups. Especially, the mice inoculated with the S gene and adjuvant group had higher immune response than other groups in terms of the T lymphocyte proliferative function, the valence of antibody, the levels of IFN-γand IL-4 in peripheral blood, the specific CTL activity and the number of CD4+ and CD8+ in peripheral blood and spleen. ELISA and virus neutralization test results showed the antibody titer of vaccine group was higher than other group. The flow cytometry and cytokine detection assay showed that the adjuvant group was able to enhance the immune responses of the mice.At the same time, we amplified two truncated pIL-12(p40) genes with deletion of the N-terminal 22 aa signal peptide. The maximum expression of the pIL-12(p40) was determined after cloning and expression of the genes in E.coli. The pIL-12(p40) protein was used as an immunogen to inoculate a rabbit for generation of specific polyclonal antiserum. ELISA results showed that both the pIL-15 reacted well with its antiserum.In summary, we for the first time, used pIL-12gene and pIL-18 genes as adjuvants for immunization in mice inoculated with TGEV S gene. Our results indicated that pIL-12 gene alone or pIL-12 united with pIL-18 enhanced both humoral and cellular immune responses in the immunized mice. The current study provides the basis for further investigation on the adjuvant effect of pIL-12 and pIL-18 on DNA immunization.