Published June 27, 2025 | Version v1
Dataset Restricted

Anti-β2GPI IgG display a broad reactivity against different β2GPI domains beyond domain 1: results from the APS ACTION and multi-center Italian cohorts

Authors/Creators

  • 1. ROR icon IRCCS Istituto Auxologico Italiano
  • 2. Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, MO, USA
  • 3. Thrombosis Research Laboratory, Department of Cardio-Thoracic-Vascular Sciences and Public Health, University of Padova, Padova, Italy
  • 4. ROR icon Hospital Clínic de Barcelona
  • 5. ROR icon University of Milan
  • 6. Research and Development, Headquarters & Technology Center Autoimmunity, Werfen, San Diego, CA, USA
  • 7. Autoimmune Diseases Research Unit, Department of Internal Medicine, Biobizkaia Health Research Institute, Hospital Universitario Cruces, Spain
  • 8. Rheumatology and Clinical Immunology Unit, ASST Spedali Civili, Department of Clinical and Experimental Sciences, University of Brescia, ERN-Reconnect Member, Brescia, Italy
  • 9. Department of Clinical and Biological Sciences, University Center of Excellence on Nephrologic, Rheumatologic and Rare Diseases (ERK-Net, ERN-Reconnect and RITA-ERN Member) with Nephrology and Dialysis Unit and Center of Immuno- Rheumatology and Rare Diseases (CMID), Coordinating Center of the Interregional Network for Rare Diseases of Piedmont and Aosta Valley, San Giovanni Bosco Hub Hospital, University of Turin, Turin, Italy
  • 10. Hospital Universitario 12 de Octubre, Madrid, Spain
  • 11. ROR icon National and Kapodistrian University of Athens
  • 12. King's College London
  • 13. ROR icon University College London
  • 14. ROR icon Hospital for Special Surgery

Description

Dataset associated with the following paper DOI: 10.3389/fimmu.2026.1809192

This set of raw data cannot be made publicly available as including sensitive information, but might be available to interested researchers upon reasonable requests. Please, forward your request to: p.meroni@auxologico.it; c.grossi@auxologico.it.

APS ACTION discovery cohort raw data are available upon reasonable request to the APS ACTION committee (ErkanD@HSS.EDU)

Abstract

Background: Anti-β2glycoprotein I (β2GPI) antibodies are the hallmark of the antiphospholipid syndrome (APS). β2GPI consists of five domains, DI-DV. While DI is the primary target, the clinical relevance of antibodies against other domains remains uncertain. We analyzed two large anti-β2GPI IgG positive cohorts, to investigate whether different domain binding affects anti-β2GPI IgG assay testing and APS diagnosis.

Methods: The presence of anti-DI and anti-DIV/DV antibodies (by chemiluminescence (CLIA) and in-house ELISA, respectively) was searched in an APS ACTION (n.191) and Italian validation (n.105) cohorts. In the latter, we detected anti-β2GPI IgG reactivity by four assays (in-house and commercial ELISA, CLIA, and fluorescence enzyme immunoassay), and used a modified anti-β2GPI IgG in-house ELISA with recombinant single-domain-lacking β2GPI variants to evaluate domain-dependent reactivity.

Results: We confirmed anti-DI, anti-DIV/DV β2GPI IgG direct reactivity in classified and non-classifiable APS in the two cohorts, and found anti-DI/anti-DIV/DV double negative (38/191, 29/105) and anti-DIV/DV single-positive (6/191, 9/105) samples. Anti-β2GPI IgG discordant samples by the four methods had the highest presence of anti-DIV/DV single-positives and anti-DI/anti-DIV/DV double-negatives, compared to four-method concordant samples: 16% vs 2% and 45% vs 11% (p <0.0001), respectively. The single-domain molecule-based assay showed that the APS serum samples depended mainly on DI, DV, and DII, slightly on DIV, and not at all on DIII.

Conclusions: Serum IgG from both classified and non-classifiable APS may react with other β2GPI domains than DI and DIV/DV. Anti-β2GPI domain selectivity can explain discordant results among diagnostic assays.

Files

Restricted

The record is publicly accessible, but files are restricted. <a href="https://zenodo.org/account/settings/login?next=https://zenodo.org/records/15755268">Log in</a> to check if you have access.