Serological relationships between Escherichia coli and Salmonella smooth- and rough-mutant lipopolysaccharides as revealed by enzyme-linked immunosorbent assay for human immunoglobulin G antiendotoxin antibodies

Abstract

Reactions of sera from healthy blood donors to smooth and rough mutant lipopolysaccharides (LPS) from Escherichia coli O111:B4 and Salmonella minnesota which had been complexed with polymyxin B were determined by enzyme-linked immunosorbent assay. Relative enzyme-linked immunosorbent assay reactivities were examined for prima facie evidence of cross-reactivity by analyses of correlation and relative scatter. Patterns of reactivity were interpreted in relation to published structures. Evidence was obtained for two dominant epitopes associated with the lipid A-2-keto-3-deoxyoctulosonic acid and heptose regions of the LPS core. Sera demonstrated apparent exclusive antibody homogeneity in that given sera showed only one of the two possible specificities, which occurred with equal frequency. Cross-reactivity was found in the lipid A-2-keto-3-deoxyoctulosonic acid region for all LPS. Cross-reactivity was found in the heptose region for larger rough mutant S. minnesota LPS and smooth S. minnesota LPS and for E. coli O111:B4 LPS but not for E. coli rough mutant J5 LPS, whose heptose region appears to be different from those of the other organisms.