Expression of the S glycoprotein of transmissible gastroenteritis virus (TGEV) in transgenic potato and its immunogenicity in mice

Transgenic plants have been tested as an alternative host for the production and delivery of experimental oral vaccines. Here, we developed transgenic potatoes that express the major antigenic sites A and D of the glycoprotein S from transmissible gastroenteritis coronavirus (TGEV-$S_{0.7}$) under three expression vector systems. The DNA integration and mRNA expression level of the TGEV-$S_{0.7}$ gene were confirmed in transgenic plants by PCR and northern blot analysis. Antigen protein expression in transgenic potato was determined by western blot analysis. Enzyme-linked immunosorbent assay results revealed that based on a dilution series of Escherichia coli-derived antigen, the transgenic line P-2 had TGEV-$S_{0.7}$ protein at levels that were 0.015% of total soluble proteins. We then examined the immunogenicity of potato-derived TGEV-$S_{0.7}$ antigen in mice. Compared with the wild-type potato treated group and synthetic antigen treated group, mice treated with the potato-derived antigen showed significantly higher levels of immunoglobulin (Ig) G and IgA responses.