Down regulation of intimin expression during attaching and effacing enteropathogenic Escherichia coli adhesion

Enteropathogenic Escherichia coli (EPEC) produces attaching: and effacing (;VE) lesions in the intestinal mucosa. The intimate bacterial adhesion associated with A/E lesion formation is promoted by intimin, 3 94-kDa EPEC surface protein,, Anti-intimin antisera raised in rabbits by using the purified 280-amino-acid cell binding domain of intimin as the immunogen were employed in immunofluorescence and immunoelectron microscopical studies to investigate the expression of intimin by classical EPEC strain E2348/69 (O127:116) and defined E2348/69 derivatives during culture growth and NE bacterium adhesion to cultured HEp-2 cells, In stationary-phase broth cultures, only a small fraction of E2348/69 bacteria expressed intimin, and of those that did, immunolabelling revealed a uniform distribution of intimin over the bacterial surface; increased numbers of bacteria expressing intimin were detected when E2348/69 was grown in tissue culture medium, an effect not seen with strain JPN15, a virulence plasmid-cured derivative of E2348/69. Strain CVD206, an caeA mutant of E2348/69, did not stain with the anti-intimin antisera, but strain CVD206(pCVD438), containing a functional eaeA gene, stained uniformly, After a 3-h incubation of HEp-2 cells with strain E2348/69, double immunofluorescence Labelling of intimin and cellular actin revealed strong intimin expression by all NE bacteria, but after 6 h of incubation, intimin expression by most E2348/69 bacteria was greatly reduced or not detected, This effect on intimin expression,vas not observed with strain JPN15 but was restored for strain JPN15(pCVD450) harboring the virulence plasmid-encoded per genes, These results indicate that surface expression of intimin is regulated by environmental factors during bacterial growth and following IVE lesion formation and that virulence plasmid-encoded genes participate in these regulation processes.