Distribution of Salmonella paratyphi A ompA gene and immunological identification of the recombinant expressed product / 中华微生物学和免疫学杂志

ABSTRACT

Objective To construct a prokaryotic expression vector of Salmonella paratyphi A ompA gene, and to determine immunogenieity and immonuprotection of the recombinant expressed product rOmpA and carrying frequency of ompA gene in S. paratyphi A isolates. Methods ompA gene was amplified from a clinical S. paratyphi A strain JH01 by PCR, cloned into T-A cloning vector, and then the prokaryotic expression vector was constructed. The rOmpA expression was determined by SDS-PAGE. Antigenicity and immunoreactivity of rOmpA were determined by immunodiffusion test, Micro-Widal's test and Western blot assay, ompA gene exiting in 98 S. paratyphi A isolates was detected by PCR. By using immunoprotective effect of rOmpA against the challenge of S. paratyphi A strain 50001 in mice were determinded. Results Both the nucleotide and putative amino acid sequence identities of the cloned ompA gene were 100% com-pared to the reported corresponding sequences. The expression yield of rOmpA was approximately 65% of the total bacterial proteins, rOmpA was able to induce specific antibody in rabbits, and reacted efficiently with rabbit antisortm or the antiserum against whole cell of S. paratyphi A detected by Western blot. 94.9% (93/98) of the S. paratyphi A isolates had ompA gene. 41.7% (5/12) and 58.3% (7/12) of the mice im-murtized with 100 and 200 μg rOmpA were survival after lethal challenge with S. paratyphi A strain 50001. The titer of antibody to the H antigens of S. paratyphi spp in the sera from rOmpA immunized mice and sur-viral mice in the S. paratyphi A challenge detected by Micro-Widal's test was 15-140. Conclusion ompA gene has an extensive distribution in clinical isolates of S. paratyphi A. rOmpA possesses an immunogenicity and a certain immunoprotective effect, and can be used as the candidate antigen in genetic engineering vaccine.