Characterization of transmissible gastroenteritis coronavirus S protein expression products in avirulent S. typhimurium Δcya Δcrp: persistence, stability and immune response in swine

Abstract

The spike protein from transmissible gastroenteritis virus (TGEV) was expressed in attenuated S. typhimurium delta cya delta crp delta asd chi 3987. Three partially overlapping fragments of TGEV S gene, encoding the amino-terminal, intermediate, and carboxy-terminal end of the protein, as well as the full length gene were inserted into the asd+ plasmid pYA292 to generate recombinant plasmids pYATS-1, pYATS-2, pYATS-3, and pYATS-4, respectively, which were transformed into S. typhimurium chi 3987. Recombinant S. typhimurium chi 3987 (pYATS-1) and chi 3987 (pYATS-4) expressing constitutively a 53 kDa amino-terminal fragment of the S protein and the full length protein (144 kDa), respectively, showed high stability. After 50 generations in vitro 60% and 20% of the bacteria transformed with pYATS-1 and pYATS-4, respectively, expressed the S-protein antigen. Since S. typhimurium chi 3987 (pYATS-1) showed a better level of expression and stability in vitro, this recombinant strain was selected as a potential bivalent vector to induce both immunity to Salmonella and TGEV in swine. In order to study colonization of swine tissues by S. typhimurium delta cya delta crp, a gene conferring resistance to rifampicin was cloned into the chromosome of S. typhimurium chi 3987, generating chi 4509 strain. Both S. typhimurium chi 4509 (pYA292) and chi 4509 (pYATS-1) colonized the ileum of orally inoculated swine with clearance of bacteria between days 10-20 post-infection. The expression of the amino-terminal fragment of the S protein diminished the ability of S. typhimurium chi 4509 (pYATS-1) to colonize deep tissues. The recombinant strain S. typhimurium chi 3987 (pYATS-1) induced TGEV specific antibodies in both serum and saliva of orally inoculated swine.

Intragastric administration of Lactobacillus casei expressing transmissible gastroentritis coronavirus spike glycoprotein induced specific antibody production

“…Therefore, it is likely that to be effective, an oral TGEV vaccine will have to induce a specific intestinal IgA response. The recombinant LcS was shown to be able to elicit both mucosal and systemic humoral responses after oral immunization in mice, which is in agreement with a study conducted by Enjuanes and coworkers [33]. Likewise, Enjuanes and coworkers developed an attenuated strain of Salmonella typhimurium expressing the amino terminus of TGEV S protein.…”

Intragastric administration of attenuated Salmonella typhimurium harbouring transmissible gastroenteritis virus (TGEV) DNA vaccine induced specific antibody production

“…Thus, new developments have focused on the production and delivery of the S protein through oral immunization. Several systems have been used to express the full-length or truncated TGEV S proteins such as Salmonella [9][10][11], Lactobacillus casei [12] and plants [13][14][15][16][17]. However, the expression level of antigen protein in transgenic plants is generally low and will lose its bioactivity due to the degradation of stomach acid [13,18].…”

Enhanced immune responses to viral epitopes by combining macrophage-inducible expression with multimeric display on a Salmonella vector

“…New developments focused on the production and delivery of the S protein. S glycoprotein antigen produced in baculovirus [13,14], or adenovirus [15] and Salmonella vectors expressing full-length or truncated S protein [16,17] were investigated. Moreover, both purified chimeric CS31 and 987P fimbriae carrying TGEV C and/or A epitopes [18,19] and Salmonella vaccine strains expressing chimeric 987P fimbriae carrying the TGEV C and A epitopes have been developed and shown to be immunogenic [20].…”