Preliminary Characterization of Hia, an Auto-secreting Protein of Brucella abortus, A

Hia, a Type-V auto-secretion protein has been suggested as a possible marker for detecting brucellosis in cattle using a lateral flow-based assay system. Several studies have suggested that Hia may be important for the pathogenesis of brucellosis infection, so this project investigated various physical properties of the protein. Gel filtration chromatography and polyacrylamide electrophoresis gel suggest that the Hia monomer is a protein approximately 66-68 kDa in size. This study found that, while having the ability to form much larger aggregates, Hia preferentially forms dimers in a native state under physiological conditions. During preparation, Hia was enriched as either monomer or aggregate form and both were tested in a lateral flow device. Interestingly, reduced sensitivity was observed relative to a mixture of monomer and aggregates (POS control serum: 5/19 [26%] vs. 8/20 [40%]). Although not statistically different, this pattern of reduced sensitivity suggests that the complexed form of the protein may be less sensitive in the LFD than its monomeric form. Thus the higher the level of monomer, the more sensitive the assay. A better understanding of the properties of Hia may lead to an optimized assay for a disease with the potential to cause devastating effects livestock industries.