title: Epitope-specific antibody and suppression of autoantibody responses against a hybrid self protein.
abstract: This study addresses the relationship of epitope-specific Ab responses and alternative autoantibody responses in a model system in which an antigenized self protein serves as the carrier for a defined heterologous B cell epitope. Ubiquitin, a nonimmunogenic self protein, was engineered to present heterologous B and T cell epitopes in the recombinant molecule. Fusion to the C terminus introduced a universal T cell epitope from a Mycobacterium tuberculosis Ag. The B cell epitope was created by inserting a 12-residue loop sequence of HIV-1 gp120 at a surface-exposed position of ubiquitin. These modifications preserved the ubiquitin fold, allowing a new conformational epitope to be presented among native self epitopes. Mice immunized with the hybrid protein bearing only the mycobacterial T cell epitope elicited a strong autoantibody response to native ubiquitin. In contrast, antisera elicited against hybrid ubiquitin presenting the HIV B cell epitope reacted specifically with the foreign epitope but not with native ubiquitin. Absence of autoantibody in the response was attributed to poor competition of autoreactive B cells for limiting T cell help. Both types of responses were associated with Th responses to defined epitopes of the ubiquitin hybrid protein. These results may have implications for a tolerance mechanism dependent on B-T cell cooperation.
authors.affiliation: Proteinix Company, Gaithersburg, MD 20877, USA.
authors.forename: G L
authors.initials: GL
authors.lastname: Lohnas
authors.forename: S F
authors.initials: SF
authors.lastname: Roberts
authors.forename: A
authors.initials: A
authors.lastname: Pilon
authors.forename: A
authors.initials: A
authors.lastname: Tramontano
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000907:Antibodies, Bacterial / Q000096:biosynthesis* / Q000276:immunology; D000942:Antigens, Bacterial / Q000235:genetics / Q000276:immunology*; D001323:Autoantibodies / Q000096:biosynthesis* / Q000276:immunology; D000939:Epitopes / Q000276:immunology*; D005260:Female; D015699:HIV Envelope Protein gp120 / Q000235:genetics / Q000276:immunology*; D015497:HIV-1 / Q000235:genetics / Q000276:immunology; D007114:Immunization; D051379:Mice; D008807:Mice, Inbred BALB C; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D009169:Mycobacterium tuberculosis / Q000235:genetics / Q000276:immunology; D010446:Peptide Fragments / Q000235:genetics / Q000276:immunology; D011487:Protein Conformation; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000276:immunology*; D013045:Species Specificity; D014452:Ubiquitins / Q000235:genetics / Q000276:immunology*
chemical_list: D000907:Antibodies, Bacterial; D000942:Antigens, Bacterial; D001323:Autoantibodies; D000939:Epitopes; D015699:HIV Envelope Protein gp120; D010446:Peptide Fragments; D011993:Recombinant Fusion Proteins; D014452:Ubiquitins