Antigenic Cross-reactivity of Major Outer Membrane Proteins in Enterobacteriaceae Species

Abstract

The protein constituents in the outer membrane (OM) of several serotypes of Escherichia coli and some other Enterobacteriaceae cross-reacted antigenically. Solubilized OM preparations of these bacteria were applied in interfacial precipitin tests to antisera elicited in rabbits against whole bacterial cells, absorbed with their appropriate lipopolysaccharide before testing. The resulting immunecomplexes were analyzed on polyacrylamide gels. Protein profiles of the immunoprecipitates showed a considerable antigenic cross-reactivity of OM proteins between most E. coli serotypes. Cross-reactivity, though substantially lower, was also found with OM from 3 other Enterobacteriaceae species, but was not detectable with Pseudomonas aeruginosa OM. When OM preparations were solubilized at room temperature, the peptidoglycan-bound proteins in the MW range 37,000-41,000 predominated in the protein profiles of the immunecomplexes. In profiles of immunecomplexes obtained with boiled OM preparations, a heat-modifiable protein (MW 33,000) predominated. The major OM proteins of the gram-negative bacterium may play a role as common surface antigens of the family of Enterobacteriaceae.