Extensive research and testing continue to be conducted for the development of vaccines targeting zoonotic diseases such as brucellosis. In this study, the potential of the DapB as a recombinant protein vaccine to effectively combat Brucella abortus 544 infection in BALB/c mice was evaluated. Western blotting assay results showed that recombinant protein DapB reacted with Brucella-positive serum, indicating its potential immunoreactivity. In vivo results showed that the peripheral blood CD4+ and CD8+ T cell population significantly increased in the DapB-immunized mice group after the first, second and third blood collection, compared to the control group that received PBS. Additionally, at the fourth blood collection, an increase in CD4+ T cell activation was observed in three vaccination groups compared to PBS negative control group. These results indicate the potential of DapB in stimulating cellular immunity. Fourteen days after infection, the bacterial load in the spleen was evaluated. The reduction in bacterial replication in the spleen by both DapB and RB51 highlights their protective efficacy against Brucella infection. These findings contribute to the ongoing efforts in developing effective vaccines against brucellosis and provide valuable insights for further research in this field.

INTRODUCTION
MATERIALS AND METHODS
    Bacterial strains and growth condition
    Recombinant protein expression and purification
    Western blotting for immunoreactivity of recombinantproteins
    Mice immunization and bacterial challenge
    Samples collection and protection level analysis in vivo
    Quantitative measurement of CD4+ and CD8+ T cells
    Statistical analysis
RESULTS
    Protein purification and immunoreactivity of recombinantproteins
    Peripheral blood CD4+ and CD8+ T cell subsetsproliferation
    Protective effects of vaccination against B. abortus inmice
DISCUSSION
ACKNOWLEDGEMENTS

• Tran Xuan Ngoc Huy(Institute of Animal Medicine, College of Veterinary Medicine, Gyeongsang National University, Jinju, 52828, Korea)
• Ched Nicole Turbela Aguilar(Institute of Animal Medicine, College of Veterinary Medicine, Gyeongsang National University, Jinju, 52828, Korea)
• Trang Thi Nguyen(Institute of Animal Medicine, College of Veterinary Medicine, Gyeongsang National University, Jinju, 52828, Korea)
• Said Abdi Salad(Institute of Animal Medicine, College of Veterinary Medicine, Gyeongsang National University, Jinju, 52828, Korea)
• Hu Jang Lee(Institute of Animal Medicine, College of Veterinary Medicine, Gyeongsang National University, Jinju, 52828, Korea)
• Jin Hur(College of Veterinary Medicine, Chonbuk National University, Iksan, 54596, Korea)
• Dong-Kwan Lee(College of Veterinary Medicine, Chungnam National University, Daejeon, 34134, Korea)
• Suk Kim(Institute of Animal Medicine, College of Veterinary Medicine, Gyeongsang National University, Jinju, 52828, Korea) Corresponding Author