A proteomic map of thromboinflammatory signatures in antiphospholipid syndrome: Results from Antiphospholipid Syndrome Alliance for Clinical Trials and International Networking (APS ACTION) Registry

Alexander Pine^1,2Ayesha Butt^1,2Laura Andreoli³Jason S Knight⁴MARIA GEROSA⁵Irene Cecchi⁶D Ware Branch^7,8Rosario Lopez-Pedrera⁹Michael Belmont¹⁰Nina Kello¹¹Michelle Petri¹²Ricard Cervera¹³Vittorio Pengo¹⁴Pier Luigi Meroni⁵Hannah Cohen¹⁵Rohan Willis¹⁶Maria Laura Bertolccini^17,18George Goshua^1,2Sean Gu^1,19John Hwa^1,19Alfred I Lee^1,2Doruk Erkan^20,21Anish Vaibhav Sharda^1,2*

• ¹Yale School of Medicine, New Haven, United States
• ²Yale University Yale Cancer Center, New Haven, United States
• ³Universita degli Studi di Brescia, Brescia, Italy
• ⁴University of Michigan, Ann Arbor, United States
• ⁵Universita degli Studi di Milano, Milan, Italy
• ⁶Universita degli Studi di Torino, Turin, Italy
• ⁷Intermountain Health, Salt Lake City, United States
• ⁸University of Utah Health, Salt Lake City, United States
• ⁹Instituto Maimonides de Investigacion Biomedica de Cordoba, Córdoba, Spain
• ¹⁰NYU Langone Health, New York, United States
• ¹¹Donald and Barbara Zucker School of Medicine at Hofstra/Northwell, Hempstead, United States
• ¹²Johns Hopkins Medicine Division of Rheumatology, Baltimore, United States
• ¹³Hospital Clinic de Barcelona, Barcelona, Spain
• ¹⁴Universita degli Studi di Padova, Padua, Italy
• ¹⁵University College London, London, United Kingdom
• ¹⁶The University of Texas Medical Branch at Galveston Store, Galveston, United States
• ¹⁷St Thomas' Hospital, London, United Kingdom
• ¹⁸King's College London, London, United Kingdom
• ¹⁹Yale School of Medicine Section of Cardiovascular Medicine, New Haven, United States
• ²⁰Hospital for Special Surgery, New York, United States
• ²¹Weill Cornell Medicine, New York, United States

Antiphospholipid syndrome (APS) is an autoimmune disease with thromboembolic and obstetric morbidity arising via a model of immunothrombosis. Individuals with APS may present with thrombotic (TAPS), obstetric (OAPS), or microvascular (MAPS) disease, while many have circulating antiphospholipid antibodies (aPL) without APS classification (NoAPS). Multiple pathophysiologic mechanisms have been proposed in APS, including activation by aPL of platelets, endothelial and immune cells, as well as complement and coagulation pathways; however, the pathophysiology of APS, particularly transition of clinical APS from aPL remains unclear. Seeking to define the inflammatory signature of APS, we carried out an unbiased proteomic screen of persistently aPL-positive patients with different clinical phenotypes from the international APS Alliance for Clinical Trials and International Networking (ACTION) Registry and compared them to 10 healthy controls. 6398 unique proteins were estimated using an DNA aptamer-based assay. Subsequently, we validated our findings in 34 additional patients. Our data show that the mere presence of aPL confers a distinct thromboinflammatory signature characterized by the activation of coagulation, complement, innate and adaptive immune response pathways shared by all APS subtypes. Pathway enrichment analysis revealed increasing enrichment with rising statistical significance of thrombosis, complement, neutrophil and other innate and adaptive immune activation, as well as extracellular matrix (ECM) organization with increasing clinical severity, suggesting a model of progressive thromboinflammation in evolution of APS from NoAPS to TAPS and MAPS. Our findings provide novel insights into the pathogenesis of APS and identify potential novel targets for diagnostic and therapeutic intervention in APS across its entire spectrum.