Protection of BALB/c mice against Brucella melitensis 16 M infection induced by vaccination with live Escherchia coli expression Brucella P39 protein

The periplasmic binding protein (P39) antigen of Brucella melitensis 16 M was previously identified as Th1 dominant antigens. In this study, the potential for this antigen to function as vaccine against B. melitensis 16 M infection in BALB/c mice has been analyzed, and the humoral and cellular immune responses induced have been also characterized. Mice were injected intraperitoneally with live Escherichia coli alone or with that which express Brucella P39, two times at 4 weeks intervals. The live E. coli BL21 (DE3) pEt15b-p39 vaccine elicited a T-cell-proliferative response and also induced a gamma interferon production upon re-stimulation with either the bacterial extract or P39 as a specific antigen. Also the live E. coli BL21 (DE3) pEt15b-p39 vaccine has been found to induce a strong humoral response (IgG1 and IgG2a). Compared to the saline-inoculated control, vaccination of mice with E. coli BL21pEt15b-p39 at 3 weeks prior to the challenge infection, significantly reduced the number of strain 16 M bacteria in spleens at 4 and 8 weeks post-challenge infection in all vaccinated mice (p < 0.001).