Cross-reactive immunoprotective antibodies to Escherichia coli O111 rough mutant J5.

The potential immunoprotective role of antiserum to an Escherichia coli J5 mutant derived from E. coli O111:B4 was demonstrated in an experimental mouse model. Overwhelming bacterial inocula masked the effects of cross-reactive immunoprotection due to antiserum to strain J5. Enhanced bacterial clearance was observed in mice receiving antiserum to strain J5 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 J5 in lethal infection. Pretreatment of mice with antiserum to strain J5 did not protect against lethal doses of endotoxin. The protective factor was demonstrated by exhaustive adsorption experiments to be an antibody specific for strain J5 lipopolysaccharide. The protective activity of antiserum to strain J5 was abolished only after adsorption with strain J5 lipopolysaccharide but not with Salmonella typhimurium mutants with or without enterobacterial common antigen.