E Asli - Department of Brucellosis, Razi Vaccine and Serum Research Institute. Agricultural, Research Education and Extension Organization (AREEO), Karaj, Iran
D. Hossaini - Department of Research and Development, Razi Vaccine and Serum Research Institute. Agricultural, Research Education and Extension Organization (AREEO), Arak, Iran
L Azimi - Department of Microbiology, Islamic Azad University, Karaj Branch, Karaj, Iran
A. Mobarez - Department of Medical Bacteriology, Faculty of Medical Sciences, Tarbiat University, Tehran, Iran
A.M. Behroozikhah - Department of Brucellosis, Razi Vaccine and Serum Research Institute. Agricultural, Research Education and Extension Organization (AREEO), Karaj, Iran

Introduction and Objectives: Brucellosis is a zoonotic disease of economic-hygienic importance caused by at least 12 different Brucella species. They cause infection in several animal species and humans. An effective and safer vaccine against human and animal brucellosis is in a pressing demand. Brucella melitensis is the global pathogenic species of Brucella. The recombinant outer membrane protein 31 KDa (Omp31) from B. melitensis is considered as a protective immunogen and an important candidate vaccine against human brucellosis. The objective of this study was to evaluate cellular immune responses of B. melitensis recombinant vaccine consisting of outer membrane protein conjugated with detoxified lipo-polysaccharide (D-LPS) in mice. It could be designed as an antigen candidate for development of prevention and diagnosis human brucellosis programs. Materials and Methods: In this study, groups of BALB/c mice were immunized and boosted (two weeks intervals) with the purified recombinant Omp 31 protein conjugated with detoxified LPS of B. melitensis. One control group was received PBS only. Prior to immunization, all mice were then sacrificed and their spleens were aseptically harvested for in vitro cytokine production using the ELISA method. Statistical analysis was used for evaluation of significant differences between the groups and a P value (P < 0.05) was considered to be statistically significant. Results: The results of this study showed both T cell populations CD4 and CD8 T-cells play a role in Brucella immunity. that the ratio concentration of IFN-γ to IL-4 in supernatant cell culture of immunized mice with recombinant Omp31 protein conjugated with D-LPS were higher than the control group. Conclusion: These results suggest that the rOMP31protein conjugated D-LPS may induce a specific CMI response in mice, particularly in the production of Th1-type cytokines such as IFN-γ. suggested that CD8+ T cells play a more critical role than CD4+ T cells in controlling brucellosis. It induces a strong Th1 dominated immune response with production of IFN-γ and CD8+ specific cytotoxic cells, but not IL-4 after immunization in mice. Further investigations and focusing on the efficacy of Omp31 against oral challenges are underway.

Omp31, D-LPS, Brucella melitensis, IL-4, IFN- γ