Demonstration of antibodies against Brucella melitensis 16M lipopolysaccharide and native hapten in human sera by enzyme-linked immunosorbent assay

An enzyme-linked immunosorbent assay (ELISA) for the detection and quantification of human immunoglobulin G (IgG), IgA, and IgM antibodies against Brucella melitensis 16M by using lipopolysaccharide (LPS) and native hapten (NH) as antigens is described. The results obtained with the LPS ELISA were compared with the results of the NH ELISA. A good statistically significant correlation was established between the antibody titers of the IgG class against both antigens. A total of 104 (99%) of the 105 serum samples of patients with brucellosis exhibited specific anti-NH antibodies by the ELISA technique. In 52 (50%) of these positive samples, antibodies against NH were detected by radial immunodiffusion (RID). In 100% of these RID-positive sera, the antibody titers of the IgG class with ELISA-determined anti-NH specificity were equal to or greater than 160. These results point to a higher sensitivity of the ELISA technique as compared with RID. Inhibition experiments revealed that the assay was specific for LPS and NH from B. melitensis 16M