Construction of an oral vaccine for transmissible gastroenteritis virus based on the TGEV N gene expressed in an attenuated Salmonella typhimurium vector.

This research aimed to develop an oral vaccine for transmissible gastroenteritis virus (TGEV) based on the TGEV N gene expressed in an attenuated Salmonella typhimurium vector and aimed to evaluate the vaccine's immune response in piglets. Recombinant plasmid pVAX-N was transformed into competent cells of attenuated S. typhimurium SL7207 via electroporation. After it was identified via RT-PCR and double digestion, the screened recombinant bacteria presenting pVAX-N were named SL7207 (pVAX-N). To evaluate the safety and stability of the developed vaccine, different dosages (5 × 10(8), 1 × 10(9), and 2 × 10(9) CFU/mice) of SL7207 (pVAX-N) were inoculated to 6-week-old mice. Piglets below 20 days of age were dosed with 1 × 10(12) CFU. Humoral (neutralization titer and specific IgG), cellular (interleukin-4, γ-interferon, and peripheral lymphocyte proliferation), and mucosal (sIgA) immune responses were detected and evaluated. The three immunizing dosages were determined to be safe for mice and were completely eliminated 8 weeks after the first inoculation. Results of antibody and cytokine detection indicated that SL7207 (pVAX-N) could significantly induce antibody-IgG, antibody-IgA, interleukin-4, and γ-interferon, whose value was maximized on the 6th week. Results confirmed that the recombinant vaccine increased the proliferation of peripheral T lymphocyte. In conclusion, the oral vaccine was developed successfully, and the vaccine could significantly induce humoral, cellular, and mucosal immune responses in piglets.