Elevated Fab glycosylation of autoantibodies maintained during B cell depletion therapy

Several chronic autoimmune diseases are characterized by elevated autoantibody Fab glycosylation. Whether Fab glycans link to disease state or development remains unclear, yet may serve as a marker thereof. Many autoimmune diseases are treated with B cell depletion therapies that particularly result in a decline of autoantibodies. The question arises whether B cell depletion therapy may have an impact on Fab glycosylation. Here, we investigated the longitudinal effects of B cell depletion therapy on Fab glycosylation of total IgG and IgG autoantibodies in rheumatoid arthritis (RA), pemphigus vulgaris (PV), ANCA-associated vasculitis (AAV), and multiple sclerosis (MS). Baseline Fab glycosylation was compared to 6-12 months into therapy by lectin affinity chromatography, determining Fab sialylation as an estimate of Fab glycosylation. We observed a modest decrease in Fab glycosylation of total IgG for RA (median 13.8%[IQR 11.7-16.3] - 9.1%[IQR8-11]) and PV (16.4%[IQR14.9-17.5] - 13.01%[IQR10.8-15.5]) after 6 months, whereas for AAV Fab glycosylation slightly increased (11.6%[IQR7.4-15] - 14.9%[IQR11.4-19.3]), and no changes were found for MS. Autoantibody titers (anti-CCP, anti-PR3, anti-Dsg3) had declined following B cell depletion therapy, yet their elevated Fab glycosylation levels were maintained. Taken together, Fab glycosylation levels of autoantibodies do not decrease upon B cell depletion therapy, thereby retaining their predictive potential as biomarker.