Cross-Reactive Immunoprotective Antibodies to Escherichia coli 0111 Rough Mutant J5

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Abstract
The potential immunoprotective role of antiserum to an Escherichia coli 15 mutant derived from E. coli 0111:B4 was demonstrated in an experimental mouse model. Overwhelming bacterial inocula masked the effects of cross-reactive immunoprotection due to antiserum to strain 15. Enhanced bacterial clearance was observed in mice receivingantiserum to strain 15 in sublethal infections but not from lethal doses. Incorporation of hemoglobin with the bacterial inocula decreased the 50% lethal dose of challenge organisms, allowing the demonstration of protective activity of antiserum to strain 15 in lethal infection. Pretreatment of mice with antiserum to strain 15 did not protect against lethal doses of endotoxin. The protective factor was demonstrated by exhaustive adsorption experiments to be an antibody specific for strain 15 lipopolysaccharide. The protective activity of antiserum to strain 15 was abolished only after adsorption with strain 15 lipopolysaccharide but not with Salmonella typhimurium mutants with or without enterobacterial common antigen.