Brucella melitensis, as a pathogenic gram-negative intracellular bacterium, causes brucellosis in animals and humans. According to literature, the B. melitensis outer membrane protein 31 (Omp31) is considered as an important vaccine candidate against brucellosis. The aim of the current study was to compare three different expression constructs containing B. melitensis Omp31 antigen using bioinformatics analysis approaches to facilitate choosing the best immunogenic construct. The coding sequence of Omp31 gene was PCR amplified, TA cloned and sequenced. The obtained DNA sequence was in silico cloned in pcDNA3.1/Hygro (+), pcDNA3.1/His A and pSecTag2/Hygro mammalian expression vectors using CLC Main Workbench 5.5 software. The Omp31 gene was successfully cloned into the pTZ57R/T vector, and recombination was confirmed by colony PCR and sequencing. Comparison of the obtained Omp31 sequence with other Omp31 gene sequences showed high similarities. Bioinformatics analysis of three different mammalian expression vectors harboring Omp31 gene made it possible to choose the best immunogenic structure for further studies in order to design effective DNA vaccines against brucellosis.

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