Subunit vaccines are being developed as a potential therapy for preventing microbial pathogen infection. In this study, the immunogenicity of recombinant Brucella (B.) abortus Fe/Mn superoxide dismutase (rFe/Mn SOD) protein as a subunit vaccine against B. abortus was investigated in BALB/c mice model. Brucella Fe/Mn SOD gene was cloned into a pcold-TF DNA vector. The bacterial recombinant protein was expressed using the Escherichia coli DH5α strain with a size of 82.50 kDa. The western blotting assay showed that rFe/Mn SOD reacted with Brucella-positive serum, indicating the potential immunoreactivity of this recombinant protein. After the second and third vaccinations, the peripheral CD4+ T cell population was increased significantly in the rFe/Mn SOD-immunized mice group compared to the PBS control group. Moreover, immunization of this recombinant protein increased the CD4+ T cell population from the first vaccination to the third vaccination. Meanwhile, the CD8+ T cells were slightly enhanced after the second vaccination compared to the first vaccination and compared to control groups. Fourteen days after the bacterial infection, the splenomegaly and the number of bacteria in the spleen were evaluated. The result showed that both rFe/Mn SOD and positive control RB51 decreased the bacterial replication in the spleen and the splenomegaly compared to control groups. Altogether, these results suggested that rFe/Mn SOD could induce host immunity against B. abortus infection.

Abstract
INTRODUCTION
MATERIALS AND METHODS
    Bacterial strains and growth condition
    Recombinant protein expression and purification
    Mice immunization and bacterial challenge
    Quantitative measurement of CD4+ and CD8+ T cells
    Bacterial clearance efficiency
    Statistical analysis
RESULTS
    Protein purification and immunoreactivity of recombinantprotein
    rFe/Mn SOD induced the peripheral blood CD4+ andCD8+ T cell subsets proliferation
    rFe/Mn SOD induced the protective effect against B.abortus in mice
DISCUSSION
ACKNOWLEDGEMENT
CONFLICT OF INTEREST STATEMENT
REFERENCES

• Tran Xuan Ngoc Huy(Institute of Animal Medicine, College of Veterinary Medicine, Gyeongsang National University)
• Trang Thi Nguyen(Institute of Animal Medicine, College of Veterinary Medicine, Gyeongsang National University)
• Alisha Wehdnesday Bernardo Reyes(Institute of Animal Medicine, College of Veterinary Medicine, Gyeongsang National University)
• HeeJin Kim(Institute of Animal Medicine, College of Veterinary Medicine, Gyeongsang National University)
• WonGi Min(Institute of Animal Medicine, College of Veterinary Medicine, Gyeongsang National University)
• Hu Jang Lee(Institute of Animal Medicine, College of Veterinary Medicine, Gyeongsang National University)
• John Hwa Lee(College of Veterinary Medicine, Chonbuk National University)
• Suk Kim(Institute of Animal Medicine, College of Veterinary Medicine, Gyeongsang National University) Corresponding Author