title: Humoral immune response against proteophosphoglycan surface antigens of Entamoeba histolytica elicited by immunization with synthetic mimotope peptides.
abstract: The protozoan parasite Entamoeba histolytica, which is responsible for intestinal amebiasis and amebic liver abscess, is causing significant morbidity and mortality worldwide. Proteophosphoglycans (PPGs, also known as lipophosphoglycans, LPGs, or lipopeptidophosphoglycans, LPPGs) are major surface components of E. histolytica. Passive immunization with a monoclonal antibody (EH5) directed against the PPGs protected severe combined immune-deficient mice from amebic liver abscess. The structure of the PPGs is very complex and only known in part. To find peptide mimics of E. histolytica PPG antigens, we had screened phage-displayed random peptide libraries with the antibody EH5. We identified various peptide mimics of E. histolytica PPGs, all sharing a consensus sequence Gly-Thr-His-Pro-X-Leu. Several of the phage clones induced a significant, specific IgG response against membrane antigens of E. histolytica after immunization of mice with whole phage particles. In the present work, in order to avoid the use of phage particles for immunization, we coupled two selected chemically synthesized peptides to keyhole limpet hemocyanin (KLH). The two KLH-conjugated peptides were immunogenic in mice and induced the production of high titers of anti-peptide antibodies, and one of the two peptides was also able to induce significant titers of antibodies against E. histolytica PPGs. Our results demonstrate that the KLH-conjugated peptides are able to mimic the EH5 epitope without the M13 phage sequences flanking the peptide inserts and independent of the structural framework of the phage.
authors.affiliation: Division of Specific Prophylaxis and Tropical Medicine, Department of Pathophysiology, University of Vienna, 1090 Vienna, Austria.
authors.forename: Helen
authors.initials: H
authors.lastname: Melzer
authors.forename: Karin
authors.initials: K
authors.lastname: Baier
authors.forename: Franco
authors.initials: F
authors.lastname: Felici
authors.forename: Bernd Ulrich
authors.initials: BU
authors.lastname: von Specht
authors.forename: Gerhard
authors.initials: G
authors.lastname: Wiedermann
authors.forename: Herwig
authors.initials: H
authors.lastname: Kollaritsch
authors.forename: Ursula
authors.initials: U
authors.lastname: Wiedermann
authors.forename: Michael
authors.initials: M
authors.lastname: Duchêne
mesh_terms: D000276:Adjuvants, Immunologic; D000595:Amino Acid Sequence; D000818:Animals; D000913:Antibodies, Protozoan / Q000097:blood*; D000953:Antigens, Protozoan / Q000276:immunology; D000954:Antigens, Surface / Q000276:immunology*; D004748:Entamoeba histolytica / Q000276:immunology*; D000939:Epitopes; D006433:Hemocyanins / Q000737:chemistry; D007114:Immunization; D051379:Mice; D008807:Mice, Inbred BALB C; D018716:Molecular Mimicry; D008969:Molecular Sequence Data; D010455:Peptides / Q000138:chemical synthesis / Q000737:chemistry / Q000276:immunology*; D011509:Proteoglycans / Q000276:immunology*; D016052:Protozoan Vaccines / Q000276:immunology*
chemical_list: D000276:Adjuvants, Immunologic; D000913:Antibodies, Protozoan; D000953:Antigens, Protozoan; D000954:Antigens, Surface; D000939:Epitopes; D010455:Peptides; D011509:Proteoglycans; D016052:Protozoan Vaccines; D006433:Hemocyanins; C032808:keyhole-limpet hemocyanin