[Construction of recombinant Bb(pGEX-OprF-I) vaccine of Pseudomonas aeruginosa and its protection elicited in mice].

Objective To construct and identify Bifidobacterium bifidum-vectored outer membrane protein F-I[rBb(pGEX-OprF-I)] vaccine of Pseudomonas aeruginosa and observe its protection against Pseudomonas aeruginosa infection in mice. Methods OprF and OprI genes were amplified by PCR, then the OprF-I fusion gene obtained by gene SOEing was digested and ligated into the vector pGEX-1λT to construct the recombinant plasmid pGEX-OprF-I. The plasmid was transformed into Bifidobacterium bifidum (Bb) by electroporation, and the rBb(pGEX-OprF-I) vaccine was constructed and identified by double enzyme digestion and PCR. Expression products of the vaccine induced by IPTG were analyzed and identified by SDS-PAGE and Western blot analysis. Twenty-one BALB/c mice were randomly divided into rBb(pGEX-OprF-I) vaccine group, Bb-pGEX-1λT empty vector group and Bb control group. The 5×10 ⁸ CFUs vaccine was intragastrically administered for 3 consecutive days per week for 3 weeks. All mice were challenged intranasally with 5×10 ⁷ CFUs of PA01 strain at the 4th week after the first immunization. At the 2nd week after the challenge, all mice were sacrificed to count the lung bacteria loads. IgG levels in sera from the mice before immunization, 4th week after the first immunization and 2nd week after the challenge were detected by routine ELISA. Results A total of 1289 bp OprF-I fusion gene was amplified by PCR. Double enzyme digestion and PCR identification confirmed that the gene was ligated into pGEX-1λT and transformed into Bb, and the rBb(pGEX-OprF-I) vaccine was successfully constructed. SDS-PAGE showed that the fusion protein with a relative molecular mass (M _r ) of about 68 000 could be expressed by IPTG-induced vaccine. Western blot analysis indicated that the protein could be specifically recognized by the sera of Pseudomonas aeruginosa-infected mice. The number of bacteria colonies in the lung of the mice immunized with rBb(pGEX-OprF-I) vaccine was significantly lower than that of the control group. The IgG levels in the sera of the immunized mice increased successively at 4th week after the first immunization and 2nd week after the challenge, and higher than that in the other control groups at the same time point. Conclusion The rBb(pGEX-OprF-I) vaccine has been successfully constructed, and it may take a certain protective effect on the mice against Pseudomonas aeruginosa infection.