90. Low ANCA IgG Sialylation Levels Enhance anti-MPO induced NCGN in a murine model
Creators: name: Doerte Lodka2
name: Rousselle2, Anthony
name: Bieringer3, Markus
name: Schneider4, Udo
name: Kettritz1, Ralph
name: Ebert2, Maximilian
name: Schreiber1, Adrian
Publisher: name: Zenodo
Year: 2022
Subjects: Vasculitis
ANCA
Abstracts
Giant Cell Arthritis
MPA
GPA
EGPA
Takayasu
IgA vasculitis

description: <strong>Background/Objective:</strong> ANCA induced vasculitides are induced by binding of anti-MPO or anti-PR3 IgG to the autoantigen expressed on the membrane of myeloid cells. However, ANCA titers only loosely correlate with disease activity in an individual ANCA patient. Glycosylation of IgG and especially of autoantibodies are an important regulator of the pathogenicity of autoantibodies. In AAV it has been described that glycosylation of ANCA IgG is changed in active AAV and that antibody glycosylation influences the binding ability to Fc receptors. However, only few publications show a direct connection of glycosylation pattern and cellular functionality in AAV-concerning processes. Our work aimed to understand the role of IgG sialylation in the pathogenicity of ANCA IgG. <strong>Methods</strong>: Flow cytometry was used to analyse the glycosylation status of patients-derived B cells compared to healthy controls. IgG isolated from patients with active disease were in vitro sialylated and desialylated. These modified antibodies were used in PMN stimulation assays to analyse the effect of the sialylation status on ROS production (Ferricytochrome C assay), NETs induction (Sytox, fluorescence microscopy) and IL-1b secretion (ELISA). Anti-MPO NCGN was induced in WT mice by passive transfer of IgG from MPO-immunized either MPO-deficient mice (normal IgG) or MPO/St6gal1-DKO mice (hyposialylated IgG). Histological evaluation of kidney sections as well as blood and kidney flow cytometry were performed. <strong>Results:</strong> Flow-cytometric analysis of the glycosylation status of B cells from active patients revealed a reduced level of sialic acid, terminal galactose and fucose compared to healthy controls. Sialylation of IgG derived from active patients resulted in reduced ROS-production of PMNs whereas desialylation did not further increase ROS-production compared to unmodified IgG. Furthermore, NETs formation was also reduced by sialylation. Finally, mice receiving IgG from MPO/St6gal1-DKO (hyposialylated IgG) had increased disease severity shown by elevated frequencies of crescentic or necrotic glomeruli compared to mice receiving IgG from MPO-KO mice. <strong>Conclusion:</strong> Glycosylation and especially sialylation of IgG influences disease severity in AAV. IgG sialylation had a protective effect, seen by reduced ROS production and NETs formation in sialylated IgG samples in vitro. Nevertheless, there seeto exist a certain threshold, where further lowering sialic acid frequency does not result in increase of PMN activity (ceiling effect). We finally found a profound impact of IgG sialylation on ANCA-induced NCGN severity in an animal model, where sialic acid-deficient anti-MPO IgG worsens disease. In summary, we here for the first time provide data, that IgG sialylation directly regulates severity of ANCA-induced NCGN. <strong>Disclosures:</strong> None.