Identification of Campylobacter jejuni surface proteins that bind to Eucaryotic cells in vitro

To understand the role of Campylobacter jejuni surface proteins in the interaction of C. jejuni with cultured mammalian cell lines in vitro, we developed a ligand-binding assay. This procedure allowed us to antigenically identify C. jejuni outer membrane proteins (OMPs) that attach to intact host cell membranes. OMPs isolated from an invasive strain and a less invasive strain were antigenically indistinguishable. However, we found that proteins with molecular masses of 28 and 32 kilodaltons (kDa) from just the invasive strain bound to HEp-2 cell monolayers. Binding of the 32-kDa OMP was cell line specific and correlated directly with the ability of the invasive C. jejuni strain to penetrate. Such a correlation was probably also true for the 28-kDa OMP. We also investigated the binding of glycine acid extracts with cell line HEp-2. We identified four proteins with apparent molecular masses of 28, 32, 36, and 42 kDa in the invasive strain extracts that bound to HEp-2 cells. In contrast, only the 36-kDa protein from the less invasive strain bound to HEp-2 cells. Our data suggest that binding of these surface exposed proteins may play a key role in C. jejuni-host cell interactions and ultimate invasion.