Paul A. Monach, Alvise Berti, Wayel H. Abdulahad, Peter Heeringa, Carol A. Langford, Divi Cornec, Peter A. Merkel, Tobias Peikert, Amber M. Hummel, Fernando C. Fervenza, E. William St. Clair, Kristina Harris, John H. Stone, Jacques-Olivier Pers, Eva M. Carmona, Ulrich Specks, Philip Seo, and Robert Spiera
Background: We recently reported that, in a small number of subjects, the proportion of proteinase 3 (PR3)-specific B cells was higher in patients with PR3-ANCA-associated vasculitis (AAV) compared to healthy controls (HCs). Objectives: The objectives of this work were to replicate our previous findings on a larger number of subjects, including myeloperoxidase (MPO)-AAV patients as disease controls, and to study the association of PR3-specific B cell proportions with clinical and biological features in patients with PR3-AAV. Methods: We analyzed frozen PBMCs from 166 patients who participated in the RAVE trial, including 113 patients with PR3-AAV and 53 patients with MPO-AAV, as well as 27 HCs. We measured the proportion of PR3-specific B cells and subsets among PBMCs using a multi-color flow cytometry panel including CD19, IgD, CD27, CD38, CD24, and a biotinylated PR3 revealed by fluorescent streptavidin. In parallel, one million PBMCs from each sample were cultivated in vitro for 12 days and stimulated by CpG, BAFF, and IL-21. PR3-ANCAs were quantified in the culture supernatants and in the serum. Results: The mean (SD) proportion of PR3-specific B cells was higher in patients with PR3-AAV compared to patients with MPO-AAV and to HCs: 2.78% (2.64) vs 1.97% (1.2) vs 1.24% (0.49) respectively, p Conclusion: The proportion of circulating PR3-specific B cells is higher in patients with PR3-AAV than in patients with MPO-AAV and HCs, and importantly, their repartition is shifted towards a memory phenotype. Further studies are ongoing to characterize the dynamics of the PR3-specific B cells after therapy, and to understand the differences of these autoreactive B cells between patients with PR3-AAV and HCs. Reference [1] Cornec D, Berti A, Hummel A, Peikert T, Pers JO, Specks U. Identification and phenotyping of circulating autoreactive proteinase 3-specific B cells in patients with PR3-ANCA associated vasculitis and healthy controls. J Autoimmun. 2017Nov;84:122-131. Disclosure of Interests: Divi Cornec: None declared, Alvise Berti: None declared, Amber Hummel: None declared, Eva Carmona: None declared, Tobias Peikert: None declared, Carol Langford: None declared, Paul Monach: None declared, Peter Merkel: None declared, Philip Seo: None declared, Robert Spiera Grant/research support from: Roche-Genentech, GlaxoSmithKline, Bristol-Myers Squibb, Boehringer Ingelheim, Cytori, Chemocentryx, Corbux, Consultant for: Roche-Genentech, GlaxoSmithKline, CSL Behring, Sanofi Aventis, E. William St. Clair Grant/research support from: Bristol-Myers Squibb, Consultant for: Bristol-Myers Squibb, Fernando Fervenza: None declared, Kristina Harris: None declared, John H. Stone Grant/research support from: F. Hoffmann-La Roche, Genentech, Xencor, Consultant for: Chugain, F. Hoffmann-La Roche, Genentech, Xencor, Jacques-Olivier Pers: None declared, Peter Heeringa: None declared, Wayel Abdulahad: None declared, Ulrich Specks: None declared