Characterization of murine monoclonal antibodies to Escherichia coli J5

Twenty-eight independently derived monoclonal antibodies (MAb) directed against Escherichia coli J5 endotoxin were produced and characterized. Each MAb exhibited a specific titer by both radioimmunoassay and passive hemagglutination assay. Most of the MAb were of the immunoglobulin G isotype; however, several immunoglobulin M antibodies and one immunoglobulin A antibody were produced. When characterized for their capacity to cross-react with purified endotoxin preparations from several gram-negative bacteria, 22 MAb exhibited no cross-reactivity; 6 demonstrated a limited capacity to cross-react with other endotoxin preparations. When characterized for their capacity to react with the intact organism instead of the purified endotoxin the pattern of cross-reactivity was quite different. Most of the MAb were able to react with Salmonella minnesota Re595. Eighteen were able to react with E. coli O111:B4 (the parent strain of E. coli J5), 13 MAb reacted weakly with Pseudomonas aeruginosa, and 3 reacted weakly with Klebsiella pneumonia. The data imply that MAb generated against E. coli J5 endotoxin demonstrate greater cross-reactivity when assayed against the whole bacterium than when assayed against the corresponding purified endotoxin. We were unable to demonstrate that any of the 28 MAb could passively protect mice against lethal endotoxin challenge.