IN-VITRO INTERACTIONS OF LAWSONIA-INTRACELLULARIS WITH CULTURED ENTEROCYTES

Strains of the obligately intracellular bacterium Lawsonia intracellul aris, the etiologic agent of porcine proliferative enteropathy, were c o-cultured in rat enterocyte cell cultures (IEC-18) and examined ultra structurally. No regular surface arrays typical of surface or S-layers were visible on any bacterial strain, with or without Triton-X-100 de tergent treatment. In separate experiments, there was no difference in the ability of L. intracellularis to attach and enter enterocytes wit h or without the presence of added bovine plasma fibronectin, or the p eptide Arg-Gly-Ser. Interestingly, there was an increase in the invasi veness of L. intracellularis in the presence of the peptide Arg-Gly-As p (RGD), in a dose-related manner. A reduction was observed in the abi lity of L. intracellularis to invade enterocytes in the presence of mo novalent fragments of IgG monoclonal antibodies to an outer surface co mponent of L. intracellularis. This neutralization showed an antibody concentration-dependent titration effect and was not apparent with co- cultures incorporating control antibodies. The exact nature of ligand and cell receptor interactions for L. intracellularis remain to be det ermined.