Study of the immunogenicity of outer membrane protein A (ompA) gene from Acinetobacter baumannii as DNA vaccine candidate in vivo

Acinetobacter baumannii is one the most dangerous opportunistic pathogens in hospitalized infections. This bacterium is resistant to 90% of commercial antibiotics. Therefore, developing new strategies to cure A. baumannii-infections is urgent. The DNA vaccines new approach in which the immunogen can be directly expressed inside the target cells through cloning of immunogen into an expression vector. The outer membrane protein A(OmpA) is one the critical factors in pathogenicity of A. baumannii which has been repeatedly described as a powerful immunogen to trigger the immune responses. As the pure form of the OmpA is insoluble, vaccine delivery is very hard. We previously cloned the ompA gene from A. baumannii into the eukaryotic expression vector pBudCE4.1 and observed that the OmpA protein has been considerably expressed in eukaryotic cell model. In current study, the immunogenic potential of pBudCE4.1-ompA has been evaluated in mice model of experimental. The serum levels of IgM, IgG, IL-2, IL-4, IL-12 and INF-γ were measured by enzyme-linked immunosorbent assay (ELISA) after immunization with ompA-vaccine. The protective efficiency of the designed-DNA vaccine was evaluated following intranasal administration of mice with toxic dose of A. baumannii. Obtained data showed the elevated levels of IgM, IgG, IL-2, IL-4, IL-12 and INF-γ in serum following the vaccine administration and mice who immunized with recombinant vector were survived more than control group. These findings indicate ompA-DNA vaccine is potent to trigger humoral and cellular immunity responses although further experiments are needed.