PB0834 - Cross-reactivity of antiphospholipid antibodies with gut commensal proteins in antiphospholipid syndrome

Monday, June 24, 2024

13:45 – 14:45 ICT

Room: Exhibition Hall

Presenting Author(s)

Dagmar JM van Mourik, MSc

PhD student
Department of Thrombosis & Hemostasis, Leiden University Medical Center
Leiden, Zuid-Holland, Netherlands

Co-Author(s)

MB

Manon Balvers

PhD student
Department of Vascular Medicine, Amsterdam UMC location University of Amsterdam
Amsterdam, Noord-Holland, Netherlands
VJ

Valérie Jansen

PhD student
Department of Vascular Medicine, Amsterdam UMC location University of Amsterdam
Amsterdam, Noord-Holland, Netherlands
Michiel Coppens

MD, PhD
Department of Vascular Medicine, Amsterdam UMC location University of Amsterdam
Amsterdam, Noord-Holland, Netherlands
MN

Max Nieuwdorp

MD, Professor
Department of Vascular Medicine, Amsterdam UMC location University of Amsterdam
Amsterdam, Noord-Holland, Netherlands
Saskia Middeldorp, MD, PhD

Internist, Professor
Radboud university medical center
Nijmegen, Gelderland, Netherlands
Jeroen Eikenboom

MD, PhD, prof
Department of Thrombosis and Hemostasis, Leiden University Medical Center, Leiden, The Netherlands
Leiden, Zuid-Holland, Netherlands
JV

Jan Voorberg

Professor
Department of Molecular Hematology, Sanquin Research and Landsteiner Laboratory, Amsterdam, the Netherlands
Amsterdam, Noord-Holland, Netherlands
Tv

Thijs E. van Mens

MD, PhD
Department of Medicine - Thrombosis & Hemostasis, Leiden University Medical Center
Leiden, Zuid-Holland, Netherlands

Background: Antiphospholipid syndrome (APS) is a thrombotic autoimmune disease caused by persistent presence of antiphospholipid antibodies, mainly targeted against β2-glycoprotein 1 (β2GP1). Molecular mimicry between β2GP1 and gut commensal proteins leading to antibody and T cell cross-reactivity was recently shown. Previous APS molecular mimicry research focused on homology with one β2GP1 T cell epitope, while various other T cell epitopes are implicated in APS.

Aims: To examine molecular mimicry of gut commensal proteins as mechanism underlying APS antibody formation, with an expanded range of T cell epitopes, reflecting HLA diversity in APS patients.

Methods: Fecal microbial metagenome of 15 APS patients and 16 healthy controls was determined using shotgun sequencing. Metagenomic data were used to identify gut commensal proteins that share sequence homology with known β2GP1 B and T cell epitopes using an in-silico pipeline. Homologous proteins were considered for molecular mimicry when: present in at least four APS patients; containing an exact match of the immunodominant B cell epitope R39-R43 (RGGMR); and containing an ungapped alignment of at least seven amino acids with a literature derived T cell epitope using BLAST. Sequence read quality and adjacent amino acids were taken into account. Identified proteins were tested for cross-reactivity with plasma of 21 APS patients and 17 healthy controls in an in-house developed enzyme-linked immunosorbent assay.

Results: Six gut commensal proteins were identified (including the one published mimic) by the in-silico pipeline. One of the proteins showed significantly higher IgG reactivity using APS plasma (Figure). The previously published protein did not show cross-reactivity.

Conclusion(s): These preliminary results show modest cross-reactivity of IgG antibodies of APS patients with one newly identified gut commensal protein. IgM and IgA cross-reactivity is being examined, given the role of IgA in intestinal immunity. Insights into the origins of antibody formation may yield new therapeutic targets for improvement of APS treatment.