Characterization of virulence marker antigen of Shigella spp. and enteroinvasive Escherichia coli

Antisera produced in rabbits immunized with an enteroinvasive O143 strain of Escherichia coli were absorbed with an avirulent derivative of the same strain. The resulting sera have been previously shown to recognize enteroinvasive pathogens when used in an enzyme-linked immunosorbent assay. In the current study, Western blots (immunoblots) showed that such an absorbed rabbit antiserum recognized two proteins (IpaB and IpaC) which are encoded by a large, virulence-associated plasmid. These proteins are the apparent constituents of the virulence marker antigen which is expressed by shigellae and enteroinvasive E. coli.