Identification of Brucella abortus (S19) immunogens using two- dimensional gel electrophoresis and westernblotting

Background & Objectives: : Brucellosis is one of the most important zoonotic disease caused by genus of Brucella. Lipopolysaccharides (LPSs), outer membrane proteins and several ribosomal or cytosolic proteins of Brucella have been considered for diagnostic and subunit vaccine purposes. The objective of this experiment  was to identify and compare immunogens of Brucella abortus(S19) in infected human and goat and immunized rabbit. Materials and  Methods: Brucella abortus(S19) was obtained from Pasture Institute of Iran. The bacterial proteins were extracted by lysozyme, urea and CHAPS, then analysed by two-dimensional gel electrophoresis. The resolved proteins were transfered to nitrocellulose membrane by tank blotting and their reactions with the sera preformed by immunoblotting. Results: The proteins of the (S19) strain were often acidic pI 4.5-5.7)  in range of 10-100 kDa . The most aboundant proteins which were immunogenic in goat and rabbit but not in human was  a group of 5-6 spots observed in acidic side  (pI 4.5-5.7 ) and  molecular mass of 32-34 kDa. In human a group of 4-5 proteins  with mass of 44 kDa and pI ranging from 4.5 to 5.5 and several low molecular weight proteins were immunogenic. Furthermore several proteins of Brucella had commom reactions with human , goat and rabbit sera. Discussion: Lipopolysaccharids of Brucella abortus(S 19) had remarkable reactivity against all of the sera;  but are  not  good candidates for diagnosis of brucellosis ,because of  structural  similarities with some gram negative bacteria  and remaining of anti-LPS antibodies in high levels in sera of many cases after recovery of brucellosis. In cotrast, some antigenic proteins can be candidated for accurate diagnosis, and recognition of active from inactives brucellosis in human and cattle. The resultes of this study suggested that a group of 4-5 proteins  of 44 kDa and pI 4.5-5.5 and several low molecular weight protein in human  and a group of 5-6 proteins with 32-34 KDa and  pI 4.5-5.7 in goat and rabbit as potential diagnostic candidates .