The Escherichia coli O157:H7 cattle immunoproteome includes outer membrane protein A (OmpA), a modulator of adherence to bovine rectoanal junction squamous epithelial (RSE) cells

Building on previous studies, we defined the repertoire of proteins comprising the immunoproteome (IP) of Escherichia coli O157:H7 (O157) cultured in DMEM supplemented with norepinephrine (O157 IP), a β‐adrenergic hormone that regulates E. coli O157 gene expression in the gastrointestinal tract, using a variation of a novel proteomics‐based platform proteome mining tool for antigen discovery, called “proteomics‐based expression library screening” (PELS; Kudva et al., 2006). The E. coli O157 IP (O157‐IP) comprised 91 proteins, and included those identified previously using proteomics‐based expression library screening, and also proteins comprising DMEM and bovine rumen fluid proteomes. Outer membrane protein A (OmpA), a common component of the above proteomes, and reportedly a contributor to E. coli O157 adherence to cultured HEp‐2 epithelial cells, was interestingly found to be a modulator rather than a contributor to E. coli O157 adherence to bovine rectoanal junction squamous epithelial cells. Our results point to a role for yet to be identified members of the O157‐IP in E. coli O157 adherence to rectoanal junction squamous epithelial cells, and additionally implicate a possible role for the outer membrane protein A regulator, TdcA, in the expression of such adhesins. Our observations have implications for the development of efficacious vaccines for preventing E. coli O157 colonization of the bovine gastrointestinal tract.