Identification of a novel linear epitope on EspA from enterohemorrhagic E. coli using a neutralizing and protective monoclonal antibody.

Enterohemorrhagic E. coli (EHEC) causes severe diseases in humans and animals via the production of Shiga toxins, and injection of effectors into epithelia using type III secretion system (TTSS). E. coli secreted protein A (EspA) forms the filamentous conduits of TTSS, which extends into the translocation pore embedded in host cell membranes and aids in the transportation of bacterial effectors. In addition, EspA is closely associated with initial bacterial adhesion and the formation of biofilms. EspA in its various forms elicits protective immune responses, although the epitope responsible has not to be identified. Here we report the presence of a linear, immunogenic, conserved and partially protective epitope E07 (100Lys-120Val) on EspA, which is recognized by the novel monoclonal antibody 1H10. This antibody blocks EHEC-induced actin polymerization and confers protection in mice. These findings provide a better understanding of EspA-induced immune responses and could lead to epitope-based vaccines and antibody-based therapies.