The current
brucellosis serodiagnostic assays are chiefly based on detecting anti-LPS (
lipopolysaccharide)
antibodies. However, cross-reaction with some gram-negative bacteria can occasionally induce due to similar O-
polysaccharide (OPS) structure. Therefore, the aim of the present study was to identify new candidate
antigens from Brucella abortus RB51, a mutant strain lacking the LPS portion, which might be valuable in
brucellosis diagnosis. To detect potential
antigens, immobilized pH gradients (IPG) strips with three ranges (
pH 3-5.6, 4-7 and 6-11) were applied. After separating the insoluble
proteins of B. abortus RB51 using two-dimensional electrophoresis (2-DE), their immunogenicity was evaluated by western blotting using four types of
antisera - B. abortus, Yersinia enterocolitica O:9 and Escherichia coli O157:H7-positive, and B. abortus-negative bovine sera. Among the several immunogenic spots, the spots showing specific reactivity with only the B. abortus-positive
antisera, were considered as candidate
antigens. Overall, eleven immuno-reactive
proteins were identified, as follows:
Cu/Zn superoxide dismutase,
histidinol dehydrogenase,
chaperonin DnaK,
chaperonin GroES,
beta-ketoadipyl CoA thiolase, two-component response regulator, the cell-division
protein FtsZ,
aldehyde dehydrogenase, 50s ribosomal protein L10 and invasion
protein B. These selected highly immunogenic
protein spots might be useful as alternative
antigens for
brucellosis and helpful in reducing the cross-reactivity.