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

Following an increased understanding of the mechanisms of antigen processing and presentation for the generation of MHC-I restricted cytolytic T-lymphocyte (CTL) responses, the importance of cellular immunity became significant. The reasons for seeking to specifically generate CTLs include not just their activity of directly killing infected cells (versus directly killing the virus or bacteria) but also the fact that CTLs can focus on antigens that are not Figure 9 . Activity of CTLs in spleen and peripheral blood. Cytotoxicity was analyzed using the LDH release assay. The release of LDH which is directly proportional to CTL activity was monitored as a function of time over a period of 42 days. w: p,0.01 (highly significant) compared with PBS, pIRES treatment groups. doi:10.1371/journal.pone.0057468.g009 accessible to antibodies [25] . To elicit CTL responses, the antigen needs to be present in the cytoplasm of antigen-presenting cells (APCs). Then some of the newly synthesized proteins are processed in proteosomes with certain of the resultant peptides then binding to nascent MHC-I molecules for export via the Golgi to the cell surface [25] . Therefore, specific CTL activity could reflect the activity of the CD8+ T lymphocytes. In this study, the number of CD8+ T lymphocytes in peripheral blood and spleen reached the peak at 42 dpi and the number of CD8+ T cells from mice immunized with pIRES-(TGEV-S1-PEDV-S) was higher (p,0.05) than in the pIRES-(TGEV-S1-PEDV-S1) group, similar to the CD4+ T lymphocytes changes. The activity determined by the CTL assay showed that CTL function in the peripheral blood of the mice treated with pIRES-(TGEV-S1-PEDV-S1) was higher (P,0.05) than that of the PBS control, but significantly lower than in the pIRES-(TGEV-S1-PEDV-S) group (p,0.01). As with other studies, CTL functions in spleen cells were mirrored by a higher efficiency of the pIRES-(TGEV-S1-PEDV-S) group compared to the pIRES-(TGEV-S1-PEDV-S1) group.