FRI0524 HUMAN MONOCLONAL ACPAS INDUCE MOBILITY OF PRIMED SYNOVIAL FIBROBLAST IN A PAD-DEPENDENT PATHWAY
Authors: Meng Sun, Akilan Krishnamurthy, Alexandra Circiumaru, Marianne Engström, Johanna Steen, Philip Titcombe, Vivianne Malmström, Heidi Wähämaa, Lars Klareskog, Bence Réthi, Anca Catrina
Journal: Annals of the Rheumatic Diseases (2019)

<h3>Background</h3> Anti-citrullinated protein antibodies (ACPA) play an important role in rheumatoid arthritis (RA) pathogenesis. They recognize a wide number of citrullinated targets and show limited cross-reactivity to acetylated ones(<i>1</i>). <h3>Objectives</h3> We aimed to investigate the effect of monoclonal ACPAs with different binding patterns on RA synovial tissue derived fibroblasts (SF). <h3>Methods</h3> Synovial fibroblasts were isolated from synovial tissue of RA patients by enzymatic digestion. ACPA and control monoclonal antibodies (mAbs) were derived from single B cells isolated from RA patients. Two monoclonal ACPA (1325:01B09 and 1325:05C06) showed cross-reactivity to acetylated-targets while four of them (1325:04C03, 1325:07E07, 14CFCT2D09, 14CFCT2H12) did not(<i>1</i>). mAbs were tested in synovial fibroblast migration (Incucyte live time image analysis) and osteoclast formation (TRAP) assays. The role of mAbs cross-reactivity was tested in fibroblast migration assays using inhibitors of peptidylarginine deiminases (Cl-amidine), histone acetyltransferase (anacardic acid) and histone deacetylase (trichostatin A). Binding patterns of monoclonal ACPAs were tested in synovial biopsies obtained from both healthy donors and RA patients. <h3>Results</h3> One acetylation cross-reactive ACPA (1325:01B09) and two with no cross reactivity (14CFCT2D09 14CFCT2H12) significantly enhanced fibroblast migration (mean±SD fold increase of 1.9±0.5, 1.7±0.4 and 1.8±0.6, respectively) compared to control mAb 1362:01E02 (p&lt;0.05), while having no effect on osteoclast formation. In contrast, one acetylation non-cross-reactive ACPA (1325:04C03) promoted osteoclastogenesis (mean±SD fold increase of 1.6±0.05) compared to control mAb 1362:01E02 (p&lt;0.05), while having no effect on fibroblast migration. Cl-amidine completely abolished the effect of 1325:01B09, while neither anacardic acid nor trichostatin A had any effect. Moreover, the fibroblast-promoting ACPA (1325:01B09) but not the osteoclastogenic ACPA1325:04C03 co-localize with CD55-positive SF in the inflamed rheumatoid synovium. No detectable signals were found in healthy synovium. <h3>Conclusion</h3> Monoclonal ACPAs have distinct cellular effects on synovial fibroblasts and osteoclasts that are not related to cross reactivity towards acetylated targets <h3>References</h3> [1] K. A. Lloyd, G. Wigerblad, P. Sahlstrom, M. G. Garimella, K. Chemin, J. Steen, P. J. Titcombe, B. Marklein, D. Zhou, R. Stalesen, E. Ossipova, C. Lundqvist, O. Ekwall, J. Ronnelid, D. L. Mueller, M. C. I. Karlsson, M. J. Kaplan, K. Skriner, L. Klareskog, F. Wermeling, V. Malmstrom, C. Gronwall, Differential ACPA Binding to Nuclear Antigens Reveals a PAD-Independent Pathway and a Distinct Subset of Acetylation Cross-Reactive Autoantibodies in Rheumatoid Arthritis. Front Immunol9, 3033 (2018). <h3>Disclosure of Interests</h3> Meng Sun Grant/research support from: Yes, but not for presented project., Akilan Krishnamurthy: None declared, Alexandra Circiumaru: None declared, Marianne Engström: None declared, Johanna Steen: None declared, Philip Titcombe: None declared, Vivianne Malmström: None declared, Heidi Wähämaa: None declared, Lars Klareskog Grant/research support from: Yes, but not for the presented study., Bence Réthi: None declared, Anca Catrina Grant/research support from: Yes, but not for the presented study.