In vivo validation of the immunogenicity of recombinant Baumannii Acinetobactin Utilization A protein (rBauA)

Acinetobacter baumannii has become a tremendous challenge to modern healthcare as an antimicrobial resistant. Replication and persistence of A. baumannii within eukaryotes is based on iron acquisition functions including siderophore biosynthesis. Iron transport into the cytosol is mediated by specific membrane receptors which recognize the iron-siderophore complexes. Expression of this acinetobactin mediated Iron uptake system is vital for intracellular growth of A. baumannii. Baumannii acinetobactin utilization (BauA), is an outer membrane protein, acting out the siderophore-ferric complex receptor. This study was aimed at analysis of immunogenicity and specificity of BauA. The genomic bauA was amplified via PCR method and after digestion, bauA was ligated into pET28a. The recombinant gene was expressed in Escherichia coli BL21(DE3) and the product was analyzed by SDS-PAGE and purified by Ni-NTA affinity chromatography method. The recombinant BauA (rBauA) was confirmed by western blot analysis using anti-His antibodies and its immunogenicity was assessed by injecting the rBauA to BALB/c mice. Antibodies produced therein could effectively recognize and bind rBauA. The immunized mice challenged with bacterial doses higher than LD50 survived. The antibodies were highly specific to A. baumannii and its clinical isolates. Passive immunization using serum raised against BauA protected mice from infection. BauA can be nominated as an immunogen against A. baumannii.