title: Identification of discrete epitopes of Ro52p200 and association with fetal cardiac conduction system manifestations in a rodent model.
abstract: Congenital heart block (CHB) is a potentially lethal condition characterized by a third-degree atrioventricular block (AVB). Despite anti-Ro52 antibodies being detected in nearly 90% of mothers of affected children, CHB occurs in only 1-2% of anti-Ro/Sjögren's-syndrome-related antigen A (SSA) autoantibody-positive pregnancies. Maternal antibodies have been suggested to bind molecules crucial to fetal cardiac function; however, it remains unknown whether a single antibody profile associates with CHB or whether several specificities and cross-reactive targets exist. Here, we aimed to define further the reactivity profile of CHB-associated antibodies towards Ro52p200 (amino acid 200-239). We first analysed reactivity of a monoclonal anti-Ro52 antibody shown to induce AVB in rats (7.8C7) and of sera from anti-Ro52p200 antibody-positive mothers of children with CHB towards a panel of modified Ro52p200 peptides, and subsequently evaluated their potential to induce AVB in rats upon transfer during gestation. We observed that CHB maternal sera displayed a homogeneous reactivity profile targeting preferentially the C-terminal part of Ro52p200, in contrast to 7.8C7 that specifically bound the p200 N-terminal end. In particular, amino acid D233 appeared crucial to maternal antibody reactivity towards p200. Despite low to absent reactivity towards rat p200 and different binding profiles towards mutated rat peptides indicating recognition of different epitopes within Ro52p200, immunoglobulin (Ig)G purified from two mothers of children with CHB could induce AVB in rats. Our findings support the hypothesis that several fine antibody specificities and cross-targets may exist and contribute to CHB development in anti-Ro52 antibody-positive pregnancies.
authors.affiliation: Department of Medicine, Rheumatology Unit, University of Padua, Padua, Italy.|Department of Medicine, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden.
authors.forename: A
authors.initials: A
authors.lastname: Hoxha
authors.affiliation: Department of Medicine, Rheumatology Unit, University of Padua, Padua, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Ruffatti
authors.affiliation: Department of Medicine, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden.
authors.forename: A
authors.initials: A
authors.lastname: Ambrosi
authors.affiliation: Department of Medicine, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden.
authors.forename: V
authors.initials: V
authors.lastname: Ottosson
authors.affiliation: Department of Medicine, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden.
authors.forename: M
authors.initials: M
authors.lastname: Hedlund
authors.affiliation: Department of Medicine, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden.
authors.forename: L
authors.initials: L
authors.lastname: Ottosson
authors.affiliation: Department of Medical Biophysics, Linköping University, Linköping, Sweden.
authors.forename: M
authors.initials: M
authors.lastname: Anandapadamanaban
authors.affiliation: Department of Medical Biophysics, Linköping University, Linköping, Sweden.
authors.forename: M
authors.initials: M
authors.lastname: Sunnerhagen
authors.affiliation: Department of Women's and Children's Health, Karolinska Institutet, Stockholm, Sweden.
authors.forename: S-E
authors.initials: SE
authors.lastname: Sonesson
authors.affiliation: Department of Medicine, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden.
authors.forename: M
authors.initials: M
authors.lastname: Wahren-Herlenius
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D001323:Autoantibodies / Q000097:blood / Q000276:immunology; D002648:Child; D002675:Child, Preschool; D004195:Disease Models, Animal; D000939:Epitopes / Q000737:chemistry / Q000276:immunology*; D005260:Female; D006327:Heart Block / Q000151:congenital* / Q000175:diagnosis / Q000276:immunology; D006329:Heart Conduction System; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology; D010446:Peptide Fragments / Q000276:immunology; D011485:Protein Binding / Q000276:immunology; D051381:Rats; D012261:Ribonucleoproteins / Q000737:chemistry / Q000276:immunology*; D000099207:SS-A Antigen
chemical_list: D000911:Antibodies, Monoclonal; D001323:Autoantibodies; D000939:Epitopes; D007074:Immunoglobulin G; D010446:Peptide Fragments; D012261:Ribonucleoproteins; D000099207:SS-A Antigen
keywords: AV block; SSA; anti-Ro52 antibodies; congenital heart block; neonatal lupus erythematosus