The primary therapeutic approach for Brucella species infections has mainly been based on antibiotic treatment. However, the development of vaccines for brucellosis control remains controversial. Furthermore, there is currently no licensed vaccine available for human brucellosis. This study aims to evaluate the effect of a combination of recombinant protein vaccines against Brucella (B.) abortus infection using a mouse model. Two B. abortus genes, namely dapB and gpm, were cloned and expressed in competent Escherichia (E.) coli DH5α using the pCold-TF vector. Successfully cloned vectors were subjected to PCR amplification using specific primer pairs. The apparent sizes of dapB and gpm were detected at 807 bp and 621 bp, respectively. Besides, the purified recombinant proteins dapB and gpm were detected using SDS-PAGE electrophoresis with correct sizes of 82.86 kDa and 87.61 kDa, respectively. These recombinant proteins were used to immunize mice as a combined subunit vaccine (CSV) to elicit host immunity against B. abortus infection. Mice immunized with CSV exhibited increased proliferation of CD4+ and/or CD8+ T cells at week 7th and 9th before sacrifice, in comparison to the control group. Notably, CSV immunization showed a significant decrease in bacterial burden in the spleen compared to the control group. Altogether, CSV using dapB and gpm induced host adaptive immune response against Brucella infection, suggesting its potential as an effective new subunit vaccine candidate.

INTRODUCTION
MATERIALS AND METHODS
    Animals and bacterial strains
    Recombinant plasmid construction
    Recombinant protein expression and purification
    Mice immunization and bacterial challenge
    Statistical analysis
RESULTS
    Cloning and expression of recombinant proteins
    Peripheral blood CD4+ and CD8+ T cell subsetsproliferation
    Protective effects of vaccination against B. abortus inmice
DISCUSSION
ACKNOWLEDGEMENTS
REFERENCES

• Tran Xuan Ngoc Huy(Institute of Animal Medicine, College of Veterinary Medicine, Gyeongsang National University, Jinju, 52828, Korea)
• Alisha Wehdnesday Bernardo Reyes(Department of Veterinary Paraclinical Sciences, College of Veterinary Medicine, University of the Philippines Los Baños, Laguna 4031, Philippines)
• 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