Protection conferred on mice by combinations of monoclonal antibodies directed against outer-membrane proteins or smooth lipopolysaccharide of Brucella.

The effect of monoclonal antibodies (MAbs) injected alone or in combination on brucella splenic infection in CD-1 mice was tested 7 and 21 days after a challenge with virulent Brucella abortus 544. Passive immunisation of mice with anti-25-27-kDa MAb alone, or mixed with protective anti-16.5 and anti-36-38-kDa MAbs, or with MAbs of the same specificity which were previously demonstrated to have no activity on CD-1 mice, produced a significant reduction of spleen counts of B. abortus (p less than 0.01). Other combinations of MAbs did not reduce splenic infection in comparison with the untreated control group. BALB/c mice were used to test the possible interference of the immune response of CD-1 mice against MAbs that were produced in BALB/c mice. No reduction of splenic infection was shown with anti-25-27- or -36-38-kDa MAbs, whereas anti-lipopolysaccharide (LPS) MAb which was produced in CBA mice was effective. Combination of anti-protein MAbs with the anti-LPS MAb produced only the effect of the anti-LPS MAb at 7 and 21 days after challenge.