[Construction of a recombinant strain expressing SpaA and CbpB of and evaluation of the strain immunogenicity in a mouse model].

To construct a recombinant strain expressing SpaA and CbpB of for oral administration, we constructed the recombinant plasmid pDG1730-CBJA by fusion PCR and seamless cloning. The plasmid was introduced into . KC strain by natural transformation, and the recombinant strain KC-- was screened out on the plate containing spectinomycin () and confirmed by PCR and starch degradation test. The SpaA and CbpB expressed by KC-- were detected by Western blotting and indirect immunofluorescence assay, and the genetic stability of the recombinant strain in mice was determined. The plasmid pMAD-∆ with knockout of was constructed and transformed into KC-. The -deleted mutant strain KC--: : ∆ was screened and identified, and its immunogenicity in a mouse model was evaluated by oral immunization. The results showed that the recombinant strain KC-- was stable in mice, expressing SpaA on the cell surface and CbpB on the spore surface. KC--: : ∆ expressed SpaA and CbpB. The mice vaccinated with the spores of KC--: : ∆ had higher levels of SpaA and CbpB-specific IgG in the serum that those vaccinated with the wild-type spores 42 days after vaccination by gavage ( < 0.01). The protective rate of mice immunized with the recombinant spores was 67.5%. The results indicated that a recombinant . strain expressing SpaA and CbpB of . was successfully constructed, and the recombinant strain laid a foundation for the development of oral live vector vaccines for swine erysipelas.