Evaluation on the Efficacy and Immunogenicity of Recombinant DNA Plasmids Expressing Spike Genes from Porcine Transmissible Gastroenteritis Virus and Porcine Epidemic Diarrhea Virus

Meng, Fandan; Ren, Yudong; Suo, Siqingaowa; Sun, Xuejiao; Li, Xunliang; Li, Pengchong; Yang, Wei; Li, Guangxing; Li, Lu; Schwegmann-Wessels, Christel; Herrler, Georg; Ren, Xiaofeng

Most exogenous proteins and even inactivated pathogens are internalized and processed via the endolysosomal pathway; the resulting degradation of proteins yields peptides that are associated with MHC-II molecules. They not only may stimulate antibody responses but also the production of helper T cells, which are necessary for the specificity of antibodies and CTLs production. Activated CD 4 + T cells can be classified into at least two subgroups, Th1 and Th2. The Th1-like phenotype is predominantly associated with interleukin-2 (IL-2) and interferon-c (IFN-c) [30, [43] [44] [45] [46] ; The Th2-like phenotype, characterized by increased levels of interleukin-4 (IL-4), interleukin-5 (IL-5), and interleukin-6 (IL-6), is associated with improving humoral response and mucosal immune response [21, 38] . In this study, the number of CD 4 + T lymphocytes in peripheral blood and spleen reached the peak at 42 dpi and the number of CD 4 + T cells from mice immunized with pIRES-(TGEV-S1-PEDV-S) was higher (p,0.05) than pIRES-(TGEV-S1-PEDV-S1) group. Changes in serum IFN-c and IL-4 levels in immunized mice were analyzed. The results showed that the levels of IFN-c in mice treated with DNA vaccine were significantly higher. In addition, the levels of IFN-c induced by pIRES-(TGEV-S1-PEDV-S) were higher than other groups (p,0.05). However, the levels of IL-4 in all treatment groups were fluctuant, especially, in pIRES-(TGEV-S1-PEDV-S1) and pIRES-(PEDV-S1) group the IL-4 level even much lower (P,0.05) than PBS and pIRES control. This result may be explained by the high level of IFN-c promoting the Th1 cell differentiation, at the same time, restraining the Th2 cell differentiation by down-regulating IL-4 and humoral immune response. This tendency is consistent with the IgG antibody changes in 42 dpi. Several reports also suggested that the level of antigen presentation can affect Th1/ Th2 profiles [4] .