[Immunization with Bifidobacterium bifidum-vectored OprI vaccine of Pseudomonas aeruginosa enhances inhibitory effect on P. aeruginosa in mice].

Objective To study the pulmonary bacterial loads, splenocyte proliferation, distributions of T cell subsets and cell apoptosis in mice immunized with Bifidobacterium bifidum-vectored OprI (Bb-OprI) vaccine of Pseudomonas aeruginosa and challenged with P. aeruginosa PA01 strain. Methods BALB/c mice were immunized with 5×109 CFUs of vaccine by intragastric administration, 3 times a week for 3 weeks, and challenged intranasally with 5×106 CFUs of PA01 strain at the fourth week after the first immunization. At the second week after the challenge, all mice were sacrificed to separate their lungs and spleens, and the pulmonary bacterial loads were counted. The proliferation of the splenocytes was determined by MTT assay. The splenic CD4+, CD8+ T cell subsets and the apoptotic rate of splenocytes were detected by flow cytometry. Results The number of pulmonary bacterial colonies in the mice immunized with the vaccine and challenged with PA01 strain decreased, while the proliferation of splenocytes and the proportion of CD4+ T cells markedly increased, and the apoptosis of splenocytes was notably reduced. Conclusion The intragastric vaccination of recombinant Bb-OprI vaccine can increase the proportion of CD4+ T cells and enhance the inhibitory effect on P. aeruginosa.