OUTER-MEMBRANE PROTEIN-SPECIFIC AND ROUGH LIPOPOLYSACCHARIDE-SPECIFICMONOCLONAL-ANTIBODIES PROTECT MICE AGAINST BRUCELLA-OVIS

Brucella ovis, a naturally virulent rough Brucella species, is the aet iological agent of ram epididymitis. The identification of protective antigens is necessary to obtain a safe, specific subcellular vaccine. Monoclonal antibodies (MAbs) directed at both brucella outer-membrane proteins (OMPs) and rough lipopolysaccharide (R-LPS) in a mouse protec tion test were used to identify potential targets for humoral immunity . Mixtures of MAbs directed at the 165-, 25-27-, 31-34- and 36-38-kDa OMPs conferred significant protection 7 days after challenge with refe rence strain B. ovis 63/290 compared with controls receiving either sa line or an anti-brucella O-polysaccharide MAb. Furthermore, an anti-R- LPS MAb tested alone conferred protection at a level comparable with t hat obtained with the mixture of anti-OMP MAbs. The combination of pro tective OMP MAbs with the anti-R-LPS MAb was also strongly protective. One combination of OMP MAbs, which bound intensely to B. ovis in vitr o, was ineffective. These results indicate that B. ovis OMPs and R-LPS are targets for protective antibodies and that they can be regarded a s candidates for ram epididymitis subcellular vaccines.