Abstract：Porcine transmissible gastroenteritis (TGE) is one important causative enteric infection caused by Transmissible gastroenteritis virus(TGEV). The S and N genes of TGEV have important immunological function respectively, a DNA vaccine co-expressing S and N gene will provide better immune efficacy for controlling. In this research, the S gene fragment (2.1 kb, including A, B, C and D antigenic sites of the S protein) and the full-length N gene(1.2 kb) of TGEV were amplified by RT-PCR, respectively. The N and S genes were respectively inserted into the multiple cloning sites (MCS) of the dural-promoter eukaryotic vector pVAXD to construct the recombinant plasmid pVAXD-N and pVAXD-S firstly. The N gene was subsequently inserted into the recombinant plasmid pVAXD-S to construct the dural-promoter eukaryotic plasmid pVAXD-N/S. The plasmid pVAXD-N/S and the control plasmids(pVAX-S, pVAX-N and pVAXD) were transfected into COS-7 cells to express. The transcription of the S and N genes could be detected by RT-PCR from transfected COS-7 cells. The expression of pVAXD-N/S in COS-7 cells could react with the rabbit anti-S protein serum、the rabbit anti-N protein serum and the rabbit anti-TGEV serum, respectively, by indirect immunofluorescence assay(IFA), the fluorescence intensity detected from the pVAXD-N/S transfected COS-7 cells was consistent with that detected from the pVAXD-N group and pVAXD-S group. The results indicated that the dural-promoter eukaryotic vector pVAXD-N/S could express the S protein and N protein at the same time. Six-weeks-old BALB/c mice(Mus musculus) were immunized with the plasmid pVAXD-N/S and the control groups(pVAXD-N, pVAXD-S and pVAXD). The serum IgG antibody was measured by indirect ELISA. The result showed that specific anti-TGEV serum IgG antibody could be detected at day 14 post-immunization, and the antibody peak was detected at day 35 post-immunization. The IgG antibody level induced by pVAXD-N/S was significantly higher than that induced by the pVAXD-N group or pVAXD-S group(P<0.5), and was consistent with that induced by the group(pVAXD-N+pVAXD-S). This study provides a basic materials for developing a bivalent DNA vaccine of TGEV.
