RESUMEN
The use of liposome as an adjuvant and a vaccine carrier has been cited previously in the literature. It has also been shown to be effective in enhancing the immunogenicity of vaccine candidates. BALB/c mice immunized subcutaneously with outer membrane protein [OMP] of Brucella abortus S19 vaccine strain entrapped in a commercial cationic liposome [S19-OMP-liposome] for vaccine delivery, showed enhanced protection [P<0.05] compared to groups of mice inoculated with S19 OMP alone, S19 live B. abortus vaccine and liposome alone, when challenged intra-peritoneally with virulent B. abortus strain 544 at 30 days post-immunization [DPI]. The S19-OMP-liposome preparation was found to be safer compared to the live B. abortus S19 vaccine at 15 days post challenge [DPC], as evidenced by the significant difference in spleen weight between S19-OMP-liposome, S19 OMP and S19 live as well as the liposome control groups [P<0.01]. Antibody isotype response profiles of the experimental groups indicated that the immune response was Th1 cell mediated. The protective advantage conferred to mice immunized with S19-OMP entrapped in liposome over those immunized with the live B. abortus S19 version, could probably be related to the significantly different response of IgG2b at 30 DPI [P<0.01], IgG2a [P<0.01], IgG2b [P<0.01] and IgG3 [P<0.05] at the DPC stages, respectively