title: The murine B cell repertoire is severely selected against endogenous cellular prion protein.
abstract: Abs to the prion protein (PrP) can protect against experimental prion infections, but efficient Ab responses are difficult to generate because PrP is expressed on many tissues and induces a strong tolerance. We previously showed that immunization of wild-type mice with PrP peptides and CpG oligodeoxynucleic acid overcomes tolerance and induces cellular and humoral responses to PrP. In this study, we compared Ab and T cell repertoires directed to PrP in wild-type and PrP knockout (Prnp o/o) C57BL/6 mice. Animals were immunized with mouse PrP-plasmid DNA or with 30-mer overlapping peptides either emulsified in CFA or CpG/IFA. In Prnp o/o mice, Abs raised by PrP-plasmid DNA immunization recognized only N-terminal PrP peptides; analyses of Ab responses after PrP peptide/CFA immunization allowed us to identify six distinct epitopes, five of which were also recognized by Abs raised by PrP peptides/CpG. By contrast, in wild-type mice, no Ab response was detected after PrP-plasmid DNA or peptide/CFA immunization. However, when using CpG, four C-terminal peptides induced Abs specific for distinct epitopes. Importantly, immune sera from Prnp o/o but not from wild-type mice bound cell surface PrP. Abs of IgG1 and IgG2b subclasses predominated in Prnp o/o mice while the strongest signals were for IgG2b in wild-type mice. Most anti-PrP Th cells were directed to a single epitope in both Prnp o/o and wild-type mice. We conclude that endogenous PrPC expression profoundly affects the Ab repertoire as B cells reactive for epitopes exposed on native PrPC are strongly tolerized. Implications for immunotherapy against prion diseases are discussed.
authors.affiliation: Institut National de la Santé et de la Recherche Médicale Unité 712 and Université Pierre et Marie Curie, Hôpital Saint-Antoine, Paris, France.
authors.forename: Sylvie
authors.initials: S
authors.lastname: Grégoire
authors.forename: Anne Sophie
authors.initials: AS
authors.lastname: Bergot
authors.forename: Cécile
authors.initials: C
authors.lastname: Féraudet
authors.forename: Claude
authors.initials: C
authors.lastname: Carnaud
authors.forename: Pierre
authors.initials: P
authors.lastname: Aucouturier
authors.forename: Martine Bruley
authors.initials: MB
authors.lastname: Rosset
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001323:Autoantibodies / Q000096:biosynthesis; D001402:B-Lymphocytes / Q000276:immunology*; D018604:Epitope Mapping; D000939:Epitopes / Q000235:genetics; D005260:Female; D007108:Immune Tolerance; D007114:Immunization; D007074:Immunoglobulin G / Q000096:biosynthesis; D007167:Immunotherapy; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008969:Molecular Sequence Data; D017096:Prion Diseases / Q000276:immunology / Q000628:therapy; D011328:Prions / Q000235:genetics / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology
chemical_list: D001323:Autoantibodies; D000939:Epitopes; D007074:Immunoglobulin G; D011328:Prions