Enteropathogenic Escherichia coli (EPEC) and enterohemorrhagic E. coli (EHEC) possess a filamentous type III secretion system (TTSS) employed to deliver effector proteins into host cells. EspA is a type III secreted protein which forms the filamentous extension to the TTSS and which interacts with host cells during early stages of attaching and effacing (A/E) lesion formation. By immunofluorescence, a polyclonal antibody previously raised to EspA from EPEC strain E2348/69 (0127:H6) stained similar to12-nm-diameter EspA filaments produced by this strain but did not stain similar filaments produced by EHEC serotype 0157:H7. Similarly, an antibody that we subsequently raised to EHEC strain 85-170 (0157:H7) EspA stained similar to12-nm-diameter EspA filaments produced by strain 85-170 but did not stain E2348/69 EspA filaments. Given such heterogeneity between EPEC and EHEC EspA filaments, we examined polymorphisms of functional EspA filaments among different SPEC and EHEC serotypes. With use of the EPEC EspA antiserum, EspA filaments were observed only with EPEC serotypes 0127:H6 and 055:H6, serotypes which encode an identical EspA protein. When stained with the EHEC EspA antiserum, EspA filaments were detected only on EHEC strains belonging to serotype 0157:H7; the EHEC antiserum did, however, stain EspA filaments produced by the closely related SPEC serotype 055:H7 but not filaments of any other EPEC serotype tested. Such polymorphisms among functional EspA filaments of EPEC and EHEC would be expected to have important implications for the development of broad-range EspA-based vaccines.
|Number of pages||5|
|Journal||Infection and Immunity|
|Publication status||Published - 1 Jan 2003|