title: Lupus anti-ribosomal P autoantibody proteomes express convergent biclonal signatures.
abstract: Lupus-specific anti-ribosomal P (anti-Rib-P) autoantibodies have been implicated in the pathogenesis of neurological complications in systemic lupus erythematosus (SLE). The aim of the present study was to determine variable (V)-region signatures of secreted autoantibody proteomes specific for the Rib-P heterocomplex and investigate the molecular basis of the reported cross-reactivity with Sm autoantigen. Anti-Rib-P immunoglobulins (IgGs) were purified from six anti-Rib-P-positive sera by elution from enzyme-linked immunosorbent assay (ELISA) plates coated with either native Rib-P proteins or an 11-amino acid peptide (11-C peptide) representing the conserved COOH-terminal P epitope. Rib-P- and 11-C peptide-specific IgGs were analysed for heavy (H) and light (L) chain clonality and V-region expression using an electrophoretic and de-novo and database-driven mass spectrometric sequencing workflow. Purified anti-Rib-P and anti-SmD IgGs were tested for cross-reactivity on ELISA and their proteome data sets analysed for shared clonotypes. Anti-Rib-P autoantibody proteomes were IgG1 kappa-restricted and comprised two public clonotypes defined by unique H/L chain pairings. The major clonotypic population was specific for the common COOH-terminal epitope, while the second shared the same pairing signature as a recently reported anti-SmD clonotype, accounting for two-way immunoassay cross-reactivity between these lupus autoantibodies. Sequence convergence of anti-Rib-P proteomes suggests common molecular pathways of autoantibody production and identifies stereotyped clonal populations that are thought to play a pathogenic role in neuropsychiatric lupus. Shared clonotypic structures for anti-Rib-P and anti-Sm responses suggest a common B cell clonal origin for subsets of these lupus-specific autoantibodies.
authors.affiliation: Department of Immunology, Flinders Medical Centre and Flinders University, SA Pathology.
authors.forename: M A
authors.initials: MA
authors.lastname: Al Kindi
authors.affiliation: Flinders Proteomic Facility, Flinders University, SA, Australia.
authors.forename: A D
authors.initials: AD
authors.lastname: Colella
authors.affiliation: Department of Immunology, Flinders Medical Centre and Flinders University, SA Pathology.
authors.forename: D
authors.initials: D
authors.lastname: Beroukas
authors.affiliation: Flinders Proteomic Facility, Flinders University, SA, Australia.
authors.forename: T K
authors.initials: TK
authors.lastname: Chataway
authors.affiliation: Department of Immunology, Flinders Medical Centre and Flinders University, SA Pathology.
authors.forename: T P
authors.initials: TP
authors.lastname: Gordon
mesh_terms: D000328:Adult; D000368:Aged; D000595:Amino Acid Sequence; D000918:Antibody Specificity; D001323:Autoantibodies / Q000096:biosynthesis / Q000097:blood / Q000737:chemistry* / Q000145:classification; D001324:Autoantigens / Q000737:chemistry / Q000276:immunology; D016022:Case-Control Studies; D002999:Clone Cells; D003429:Cross Reactions; D004797:Enzyme-Linked Immunosorbent Assay; D000939:Epitopes / Q000737:chemistry / Q000276:immunology; D005260:Female; D015870:Gene Expression; D006801:Humans; D007074:Immunoglobulin G / Q000096:biosynthesis / Q000097:blood / Q000737:chemistry* / Q000145:classification; D008180:Lupus Erythematosus, Systemic / Q000097:blood / Q000175:diagnosis* / Q000276:immunology / Q000473:pathology; D008875:Middle Aged; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry / Q000276:immunology; D020543:Proteome / Q000096:biosynthesis / Q000737:chemistry* / Q000145:classification; D012269:Ribosomal Proteins / Q000737:chemistry* / Q000276:immunology; D012270:Ribosomes / Q000737:chemistry / Q000276:immunology
chemical_list: D001323:Autoantibodies; D001324:Autoantigens; D000939:Epitopes; D007074:Immunoglobulin G; D010455:Peptides; D020543:Proteome; D012269:Ribosomal Proteins
keywords: mass spectrometry; ribosomal P; systemic lupus erythematosus