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Background & Objective: One of the most common diseases between zoonosis - especially in developing countries -- is brucellosis. Identification of Brucella cell antigen combinations in terms of the amount and type of immune response in infected hosts, are important in vaccine design. 31kDa Brucella cell surface protein (BCSP31) is shared among all Brucellae. We aimed to define specific immune responses to BCSP31 which are elicited during infection of murine host with B. abortus. Surface protein of 31 kDa (BCSP31) is present in all strains, and here, the host immune response during murine infection with Brucella abortus which are formed in proportion to the proteins are studied. Materials & Methods: Recombinant BCSP31 (rBCSP31) of B. abortus was produced and purified. One group of BALB/c mice were infected with pathogenic B. abortus 544 and maintained for 60 days; a no-infected group of mice also was considered. Specific serum antibodies directed to rBCSP31 was evaluated through ELISA. Splenocytes of mice were cultured and stimulated with rBCSP31; thereafter, IL-4, IL-12 and IFN-γ cytokine responses of spleen lymphocytes were assessed. Results: We detected a remarkable IgG titer along with IgG1 and IgG2a specific to recombinant BCSP31 in serum samples from infected mice. Significant titers of IgG, IgG1 and IgG2a antibodies than BCSP31 in the the serum of mice infected with the virulent strain were observed. The Evaluation of Splenocytes responses to rBCSP31 also showed a significant IL-12 and IFN-γ production along with remarkable IL-4 production in infected mice. All responses were significantly different from that of non-infected mice (p<0.05). Conclusion: These findings suggest that specific humoral and cell-mediated responses to BCSP31 is formed during murine host infection with B. abortus. Based on these findings, rBCSP31 can be used in further design of immunogenic strategies for vaccination against brucellosis. [ABSTRACT FROM AUTHOR]