Immune reactivity of sera obtained from brucellosis patients and vaccinated-rabbits to a fusion protein from Brucella melitensis

Brucella spp. are facultative intracellular pathogens which can stay alive and multiply in professional and nonprofessional phagocytes. Immunity against Brucella melitensis involves antigen-specific CD4(+) and CD8(+) T-cells activation and humoral immune responses. Due to negative aspects of live attenuated vaccines, much attention has been focused on finding Brucella-protective antigens to introduce them as potential subunit vaccine candidates. A chimeric gene encoding trigger factor (TF), Omp31(48-74) and BP26(87-111) fragments (TOB) from B. melitensis was successfully cloned, expressed in Escherichia coli BL21-DE3 and purified by Ni-NTA agarose column. Antibodies to recombinant TOB (rTOB) have been investigated in Brucella-infected human sera and a pool serum prepared from B. melitensis-vaccinated rabbits. Our results showed that the immunized rabbit pool serum strongly reacted with rTOB. In addition, antibodies against rTOB were detectable in 76.5% of sera obtained from infected patients. These findings suggest that rTOB may provide a potential immunogenic candidate which could be considered in future vaccine studies.