Decreased adherence of enterohemorrhagic Escherichia coli to HEp-2 cells in the presence of antibodies that recognize the C-terminal region of intimin

Antiserum raised against intimin from enterohemorrhagic Escherichia coli (E HEC) O157:H7 strain 86-24 has been shown previously by our laboratory to in hibit adherence of this strain to HEp-2 cells. In the present study, we sou ght to identify the region(s) of intimin important for the effect of anti-i ntimin antisera on EHEC adherence and to determine whether antisera raised against intimin from an O157:H7 strain could reduce adherence of other stra ins. Compared to preimmune serum controls, polyclonal sera raised against t he histidine-tagged intimin protein RIHisEae (intimin(O157)) or against His -tagged C-terminal fragments of intimin from strain 86-24 reduced adherence of this strain. Furthermore, an antibody: fraction purified from the anti- RIHisEae serum that contained antibodies to the C-terminal third of intimin , the putative receptor-binding domain, also reduced adherence of strain 86 -24, but a purified fraction containing antibodies to the N-terminal two-th irds of intimin did not inhibit adherence. The polyclonal anti-intimin(O157 ) serum raised against RIHisEae inhibited, to different degrees, the adhere nce of another O157:H7 strain, an EHEC O55:H7 strain, one of two independen t EHEC O111:NM isolates tested, and one of two EHEC O26:H11 strains tested. Adherence of the other O26:H11 and O111:NM strains and an EPEC O127:H6 str ain was not reduced. Finally, immunoblot analysis indicated a correlation b etween the antigenic divergence in the C-terminal third of intimins from di fferent strains and the capacity of anti-intimin(O157) antiserum to reduce adherence of heterologous strains. Taken together, these data suggest that intimin(O157) could be used as an immunogen to elicit adherence-blocking an tibodies against O157:H7 strains and closely-related EHEC.