MONOCLONAL-ANTIBODIES TO BRUCELLA ROUGH LIPOPOLYSACCHARIDE - CHARACTERIZATION AND EVALUATION OF THEIR PROTECTIVE EFFECT AGAINST B-ABORTUS

We characterized 4 monoclonal antibodies (mAb) specific for rough lipo polysaccharide (R-LPS) of Brucella. mAb were selected by enzyme-linked immunosorbent assay (ELISA) on whole B. abortus 45/20 rough cells and R-LPS from B. melitensis B115 rough cells. Specificity was confirmed by immunoblot analysis using R-LPS and smooth LPS (S-LPS) preparations . Anti-R-LPS revealed the low molecular mass R-LPS molecules below 20. 1 kDa in the R-LPS and S-LPS preparations as well as the typical A and M patterns in high molecular mass S-LPS molecules (between 21.5 and 6 6 kDa) in the S-LPS preparations. An O-polysaccharide-specific mAb rev ealed only high molecular mass S-LPS molecules in the S-LPS preparatio n. In ELISA the anti-R-LPS mAb bound better on rough than on smooth B. abortus 544 whole cells, and this was confirmed by immunoelectron mic roscopy. Protective activity of anti-R-LPS mAb of different isotypes w as tested on mice and compared with an S-LPS-specific mAb. Only the Ig G3 mAb reduced significantly the splenic infection but did not reach t he level of protection conferred by the S-LPS-specific mAb.