Role of IgG glycans in severe COVID-19 inflammatory cytokine responses

Severe COVID-19 and multisystem inflammatory syndrome in children (MIS-C) are characterized by hyperinflammation. Severe COVID in adults is associated with development of afucosylated SARS-CoV-2 IgG that induce monocytes to secrete inflammatory cytokines. This study aimed to analyze the relationship between spike IgG Fc glycosylation and inflammatory markers during acute pediatric COVID or MIS-C or following COVID vaccination in adults. We assessed cross-sectional and longitudinal samples from 195 participants: Adult vaccinees, acute COVID patients, and healthy controls, as well as pediatric acute COVID patients, MIS-C patients, and healthy controls. We developed capillary electrophoresis (CE) methods to analyze bulk and spike IgG Fc glycans and measured ten relevant cytokines/chemokines by multiplexed assay. Analysis of healthy control bulk IgG by CE found 95.3–99.6% fucosylated, 2.7–6.9% bisected, 55.8–66.8% galactosylated, and 4.6–15.6% sialylated Fc glycans, compared to 99.8%, 6.7%, 45.4%, and 8.2% by mass spectrometry, respectively. IFN-γ, IL-10, CXCL10, and CCL3 were significantly increased in MIS-C compared to pediatric healthy controls; IL-10, CCL2, and TNF were only increased in severe adult COVID compared to healthy controls or less severe COVID. Initial results confirmed significantly more afucosylated spike IgG in adult severe COVID than afucosylated bulk IgG in controls. Our high-throughput methods for IgG Fc glycan profiling generated comparable results to mass spectrometry. Continued assessment will determine if COVID- or vaccine-induced spike IgG glycoforms correlate with inflammatory markers. Future mechanistic work will examine how modified glycosylation induces inflammatory cytokines. Supported by an IDCRC New Investigator Pilot Award to E.M.S. (NIH UM1AI148684), by the Centers for Disease Control and Prevention through a cooperative agreement with the Georgia Emerging Infection Program (grant no. U50CK000485), and by grant from NIH to P.A. (R24GM137782).