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

Transmissible gastroenteritis (TGE) and porcine epidemic diarrhea (PED) are both severe enteric diseases in newborn piglets which are characterized by extremely high mortality, as well as by devastating economic consequences for swine industry [3, 32, 35] . The etiologic agents responsible for these diseases are coronaviruses, TGEV and PEDV, respectively. TGEV was isolated for the first time in 1946 [8] . Japan and England reported the disease in 1956 and 1957 [12, 31] . The virus replicates in the cytoplasm of mature absorptive epithelial cells present on the tips of the villi in the small intestine. The functions of the coronavirus spike (S) protein are both attachment to the cell surface and fusion of the viral membrane with the cellular membrane [7, 36] . The S protein is the major inducer of TGEV-neutralizing antibodies [11, 15, 19] . Therefore, it is an excellent target protein candidate for vaccine development. The relevant epitopes for neutralization were mapped to the N-terminal domain of S protein, and four antigenic sites (A to D) were identified within the first 543 of the 1447 residues of the S protein [13, 20] . The first 37% of the polypeptide chain of the S protein appear to be more immunogenic than the rest of the sequence. This region would be located in the globular part of the peplomer, which is more exposed than the fibrillar, Cterminal portion of the S protein [13] . Previous reports show that the immunogenicity of the DNA vaccine comprising the main antigenic sites is superior to a vaccine containing the total length S gene [29] .