In silico analysis and recombinant expression of BamA protein as a universal vaccine against Escherichia coli in mice

Colibacillosis, caused by pathogenic Escherichia coli, is a common disease in animals and human worldwide with extensive losses in breeding industry and with millions of people death annually. There is thus an urgent need for the development of universal vaccines against colibacillosis. In this study, the BamA protein was analyzed in silico for sequence homology, physicochemical properties, allergenic prediction, and epitopes prediction. The BamA protein (containing 286 amino acids) clusters in E. coli were retrieved in UniProtKB database, in which 81.7 % sequences were identical (Uniref entry A7ZHR7), and sequences with 94.82 % identity were above 93.4 %. Moreover, BamA was highly conserved among Salmonella and Shigella and has no allergenicity to mice and human. The epitopes of BamA were located principally in periplasm and extracellular domain. Surf_Ag_VNR domain (at position 448-810 aa) of BamA was expressed, purified, and then used for immunization of mice. Titers of the rBamA sera were 1:736,000 and 1:152,000 against rBamA and E. coli and over 1:27,000 against Salmonella and Shigella. Opsonophagocytosis result revealed that the rBamA sera strengthened the phagocytic activity of neutrophils against E. coli. The survival rate of mice vaccinated with rBamA and PBS was 80 and 20 %, respectively. These data indicated that BamA could serve as a promising universal vaccine candidate for the development of a protective subunit vaccine against bacterial infection. Thus, the above protocol would provide more feasible technical clues and choices for available control of pathogenic E. coli, Salmonella, and Shigella.