title: Characteristics of guinea-pig immune sera elicited by a synthetic diphtheria toxin oligopeptide.
abstract: Several oligopeptides of different lengths contained within the Cys 186-Cys 201 first disulfide loop of the diphtheria toxin molecule have been synthesized by a solid-phase method. 125I-labeled rabbit antibodies raised against diphtheria toxin reacted specifically with oligopeptides linked to m-nitrobenzhydrylamine resin when the amino acid chain length was equal to or greater than 10 residues. The synthetic tetradecapeptide (STDP) corresponding to the sequence Gly 188-Cys 201 was used to immunize guinea-pigs. The immune sera obtained reacted with the whole diphtheria toxin molecule as judged by an antigen-linked immunosorbent assay. Anti-STDP sera exhibited a clear, albeit limited, neutralizing effect against the lethal action of diphtheria toxin on cultivated Vero cells. The anti-STDP sera were also able to partially block the ADP-ribosylation of elongation factor 2 mediated by whole diphtheria toxin. In contrast, anti-STDP sera were almost inactive on the enzymic activities of either toxin fragment A or crm 45, a mutant protein which lacks the 15,000 mol. wt C-terminal sequence of the toxin molecule. On the basis of the results obtained, a possible localization of the Cys 188-Cys 201 loop region on the toxin molecule is proposed.
mesh_terms: D000818:Animals; D000906:Antibodies / Q000032:analysis; D002478:Cells, Cultured; D004167:Diphtheria Toxin / Q000138:chemical synthesis / Q000276:immunology* / Q000378:metabolism / Q000494:pharmacology; D004168:Diphtheria Toxoid / Q000276:immunology; D004797:Enzyme-Linked Immunosorbent Assay; D006168:Guinea Pigs; D006736:Horses; D007106:Immune Sera / Q000276:immunology*; D009842:Oligopeptides / Q000138:chemical synthesis / Q000276:immunology*; D010446:Peptide Fragments / Q000378:metabolism; D014176:Protein Biosynthesis; D011817:Rabbits
chemical_list: D000906:Antibodies; D004167:Diphtheria Toxin; D004168:Diphtheria Toxoid; D007106:Immune Sera; D009842:Oligopeptides; D010446:Peptide Fragments; C029795:diphtheria toxin fragment A