Short report: identification of B-cell epitopes in the serine-rich Entamoeba histolytica protein

The serine-rich Entamoeba histolytica protein (SREHP) has been shown to be a protective antigen in animal models of amebic liver abscess when delivered by either parenteral or oral routes of immunization, and antibodies to SREHP can prevent amebic liver abscess in severe combined immunodeficient mice. To identify B cell epitopes of the SREHP molecule that could serve as the basis for a peptide-based vaccine, we synthesized overlapping peptides spanning the amino acid sequence of SREHP, and looked at the reactivity of serum samples from five individuals with amebic liver abscess to the overlapping peptides. We found that most of the epitopes recognized by serum samples from patients with amebic liver abscess map to the hydrophilic dodecapeptide or octapeptide repeats of SREHP, but there was no universal epitope recognized by all five serum samples. In addition, we show that synthetic peptides that include the epitopes of SREHP recognized in the mapping study are immunogenic in animals and can generate antibodies that recognize SREHP.