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

The PEDV S protein also plays an important role in induction of neutralizing antibodies, specific receptor binding and cell membrane fusion [10] . The S protein is not cleaved into S1 and S2 subunits by furin-like proteases, due to the lack of appropriate cleavage sites. The S1 domain (residues 1-789) and the S2 domain are artificially defined on the S protein (residues 790-1.383) [10, 34] . Previous reports have shown that the main neutralizing epitopes are located on the S1 domain that is thought to form the globular part of S protein [34, 39] . Sun et al. (2007) reported that the epitope region designated S1D (aa 636,789) on the S1 domain of PEDV S protein is highly conserved across PEDV isolates and that this region has the capacity to induce the production of virus neutralization antibodies. Moreover, the immune serum against S1D showed the binding ability to the native S protein of PEDV. The S1D5 (aa 744-759) and S1D6 (aa 756-771) are two linear epitope domains. Furthermore, the SS2 (-748 YSNIGVCK 755-) and SS6 (-764 LQDGQVKI 771-) are two core epitope domains on S1D5 and S1D6, respectively, located on the S protein of PEDV [40] . According to the sequence information for the neutralizing epitope of the transmissible gastroenteritis virus (TGEV), the neutralizing epitope domain COE (aa 499-638) that is responsible for inducing virus neutralizing antibodies on the S1 domain of PEDV S protein was identified. It is highly conserved in PEDV strains [17, 41] . A novel antigenic domain -1368GPRLQPY1347-motif has excellent immunogenicity has been identified on the C-terminal portion of the S protein, which elicited a strong antibody response and induced neutralizing antibodies [5] .