Immunogens of Brucella Abortus S19 Identified By Two-Dimensional Gel Electrophoresis and Immunoblotting

Lipopolysaccharides (LPSs) and several antigenic proteins of Brucella have been considered for preparation of diagnostic reagents and subunit vaccines. The objective of this study was to identify and compare immunogens of B. abortus S19 which induce humoral immune responses in human, goat and rabbit. The bacterial whole cell extract was prepared in extraction buffer and resolved using two-dimensional gel electrophoresis (2-DE). The resolved antigens were reacted against human, goat and rabbit sera using western blotting. At least 19, 14 and 16 immunogenic proteins were recognized in western blotting with human, goat and rabbit sera, respectively. The most abundant proteins of the bacterium with immunogenic properties in goat and rabbit but not in human, were a group of 5-6 proteins with molecular masses of 32-34 KDa and isoelectric point (pI) ranging from 4.5 to 5.7. In contrast, a group of 5 proteins with molecular weight of 45 KDa and pI in the range of 4.5 to 5.4 as well as several low molecular weight proteins were immunogenic in human. Furthermore several proteins of Brucella had similar reactions against all sera. These results showed that some of the antigenic proteins of Brucella could be candidates for more accurate diagnosis of Brucellosis in humans and domestic animals.