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Anti-Idiotype scFv Localizes an Autoepitope in the Globular Domain of C1q. Int J Mol Sci 2021; 22:ijms22158288. [PMID: 34361054 PMCID: PMC8347764 DOI: 10.3390/ijms22158288] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2021] [Revised: 07/29/2021] [Accepted: 07/29/2021] [Indexed: 11/16/2022] Open
Abstract
We addressed the issue of C1q autoantigenicity by studying the structural features of the autoepitopes recognized by the polyclonal anti-C1q antibodies present in Lupus Nephritis (LN) sera. We used six fractions of anti-C1q as antigens and selected anti-idiotypic scFv antibodies from the phage library "Griffin.1". The monoclonal scFv A1 was the most potent inhibitor of the recognition of C1q and its fragments ghA, ghB and ghC, comprising the globular domain gC1q, by the lupus autoantibodies. It was sequenced and in silico folded by molecular dynamics into a 3D structure. The generated 3D model of A1 elucidated CDR similarity to the apical region of gC1q, thus mapping indirectly for the first time a globular autoepitope of C1q. The VH CDR2 of A1 mimicked the ghA sequence GSEAD suggested as a cross-epitope between anti-DNA and anti-C1q antibodies. Other potential inhibitors of the recognition of C1q by the LN autoantibodies among the selected recombinant antibodies were the monoclonal scFv F6, F9 and A12.
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Csorba K, Schirmbeck LA, Tuncer E, Ribi C, Roux-Lombard P, Chizzolini C, Huynh-Do U, Vanhecke D, Trendelenburg M. Anti-C1q Antibodies as Occurring in Systemic Lupus Erythematosus Could Be Induced by an Epstein-Barr Virus-Derived Antigenic Site. Front Immunol 2019; 10:2619. [PMID: 31787984 PMCID: PMC6853867 DOI: 10.3389/fimmu.2019.02619] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2019] [Accepted: 10/21/2019] [Indexed: 01/08/2023] Open
Abstract
Previous infection with Epstein-Barr virus (EBV) is believed to trigger autoimmunity and to drive autoantibody generation as occurring in patients with systemic lupus erythematosus (SLE). Complement C1q and autoantibodies targeting it (anti-C1q) are also considered to be involved in the pathogenesis of SLE, independently of the impact of environmental insults. Still, the circumstances under which these autoantibodies arise remain elusive. By studying a major antigenic site of C1q targeted by anti-C1q (A08), we aimed to determine environmental factors and possible mechanisms leading to the development of anti-C1q. First, we determined antigenic residues of A08 that were critical for the binding of anti-C1q; importantly, we found the binding to depend on amino-acid-identity. Anti-C1q of SLE patients targeting these critical antigenic residues specifically cross-reacted with the EBV-related EBNA-1 (Epstein-Barr virus nuclear antigen 1)-derived peptide EBNA348. In a cohort of 180 SLE patients we confirmed that patients that were seropositive for EBV and recognized the EBNA348 peptide had increased levels of anti-A08 and anti-C1q, respectively. The correlation of anti-EBNA348 with anti-A08 levels was stronger in SLE patients than in matched healthy controls. Finally, EBNA348 peptide-immunization of C1q−/− mice induced the generation of cross-reactive antibodies which recognized both the A08 epitope of C1q and intact C1q. These findings suggest that anti-C1q in SLE patients could be induced by an EBV-derived epitope through molecular mimicry, thereby further supporting the pathogenic role of EBV in the development of SLE. Considering the role of C1q and anti-C1q, modifying the anti-EBV response might be a promising strategy to improve the course of the disease.
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Affiliation(s)
- Kinga Csorba
- Clinical Immunology, Department of Biomedicine and Division of Internal Medicine, University and University Hospital Basel, Basel, Switzerland
| | - Lucia A Schirmbeck
- Clinical Immunology, Department of Biomedicine and Division of Internal Medicine, University and University Hospital Basel, Basel, Switzerland
| | - Eylul Tuncer
- Clinical Immunology, Department of Biomedicine and Division of Internal Medicine, University and University Hospital Basel, Basel, Switzerland
| | - Camillo Ribi
- Immunology and Allergy, Department of Internal Medicine, University Hospital Lausanne, Lausanne, Switzerland
| | - Pascale Roux-Lombard
- Division of Immunology and Allergy, Department of Medicine, University Hospital and University of Geneva, Geneva, Switzerland
| | - Carlo Chizzolini
- Division of Immunology and Allergy, Department of Medicine, University Hospital and University of Geneva, Geneva, Switzerland
| | - Uyen Huynh-Do
- Division of Nephrology and Hypertension, University Hospital Bern, Bern, Switzerland
| | - Dominique Vanhecke
- Clinical Immunology, Department of Biomedicine and Division of Internal Medicine, University and University Hospital Basel, Basel, Switzerland
| | - Marten Trendelenburg
- Clinical Immunology, Department of Biomedicine and Division of Internal Medicine, University and University Hospital Basel, Basel, Switzerland
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