Characterization of monoclonal antibodies against Shiga-like toxin from Escherichia coli.

Three monoclonal antibodies, designated MAb 16E6, MAb 13C4, and MAb 19G8, were produced which recognize Shiga-like toxin (SLT) from Escherichia coli. All three monoclonal antibodies neutralized the cytotoxicity of E. coli SLT and were able to immunoprecipitate intact labeled toxin with Staphylococcus aureus protein A. The three antibodies were of the G1 heavy and kappa light chain classes. MAb 16E6 bound to the B subunit of SLT in Western blots and also neutralized the lethality of the toxin for mice and the enterotoxicity of the toxin in ligate rabbit ileal loops. The ability of MAb 16E6 to neutralize the cytotoxicity, lethality, and enterotoxicity of E. coli confirms the hypothesis that all three activities are associated with a single toxin. MAb 16E6 and MAb 13C4 also neutralized the cytotoxicity of purified Shiga toxin from Shigella dysenteriae type 1 and Shiga-like toxic activities in crude cell extracts from Shigella flexneri, Vibrio cholerae, Vibrio parahaemolyticus, and Salmonella typhimurium. Thus, Shiga toxin and the SLTs from E. coli, Shigella flexneri, V. cholerae, V. parahaemolyticus, and Salmonella typhimurium share a common B subunit epitope that is involved in neutralization. MAb 13C4 has been successfully used in a colony blot assay for the detection of bacterial colonies which produce high levels of SLT. Sixty-two different strains of bacteria were tested by both the cytotoxicity and colony blot assays for the presence of SLT. The colony blot assay detected all strains of bacteria which produce greater than or equal to 10(5) 50% cytotoxic doses of SLT per ml of sonic lysate. There were no false-positive results among the 62 samples tested.