The combined use of recombinant and pVAX-omp31 DNA Vaccine for immunological protection against pathogenic Brucellas melitesnsis in an experimental model of BALB/c Mice

Brucellosis is still an important zoonotic infection and evaluation of immunologic properties of various bacterial antigens along with different vaccination strategies helps in designing efficient vaccines against the disease. The aim of this study is to immunological evaluate the eukaryotic vector pVAX1, carrying the outer membrane protein gene of 31 kDa (Omp31) B.melitensis.
In this study which was carried out in 2014, whole sequence of omp31 of B. melitensis was inserted between BamHI and XhoI of pVAX1 plasmid vector. Female BALB/c mice aged 6-8 weeks (purchased from Pasteur Institute of Iran) were immunized intra-muscularly with 100μg of the construct, followed by either protein or plasmid boosters separately. The level of IL-4, IL-12, IFN-γ, total serum IgG, and specific IgG1 and IgG2a against recombinant Omp31 were evaluated. Finally the protective immune response following exposure to B. melitensis 16M was evaluated.
DNA-vaccine omp31 career with protein reminders Omp31, stimulate higher levels of IFN-γ, IL-12 and IgG2a compared to groups of DNA-vaccine or recombinant protein. Protective immunity was also significantly higher in mice which immunized with DNA vaccine– protein regimen.
Mice which immunized with DNA vaccine–protein regimen showed a significantly higher levels of IL-12 and IFN-γ along with serum IgG2a which together imply augmentation of T cell-mediated immune responses against Omp31. The latter was confirmed by significant protective response to B. melitensis 16M challenge.