Immunochemical Specificity of Human Antibodies to Lipopolysaccharide from the J5 Rough Mutant of Escherichia coli O111:B4

Abstract

Antibody to the core region of lipopolysaccharide (LPS) of Escherichia coli O111:B4 (J5) is reported to cross-react with LPS from other gram-negative bacteria. We used an enzyme-linked immunosorbent assay to test various LPSs and their constituents for their ability to inhibit binding of human IgG antibody to J5 LPS to J5 LPS. Results were expressed as the concentration of inhibitor required to cause 50% inhibition of binding (I50). I50 values of antibody to J5 LPS for J5 LPS ranged from 5 x 10(-7) M to 8 x 10(-9) M. I50 values for Salmonella minnesota (Rc) were higher (2 x 10(-4) M to 2 x 10(-7) M). Other rough LPS failed to inhibit to 50% (up to 2 x 10(-4) M). J5 lipid A and core oligosaccharide inhibited, with I50 values ranging from 2 x 10(-5) M to 3 x 10(-8) M. Fifty percent inhibition was not achieved by smooth LPS (8 x 10(-5) M), heterologous lipid A (3 x 10(-4) M), or core LPS constituents (5 x 10(-3) M). These data suggest that IgG J5 LPS antibodies are specific for the Rc chemotype of the core of LPS.