Immunoglobulin G1 Fc glycosylation as an early hallmark of severe COVID-19

Abstract

BackgroundImmunoglobulin G1 (IgG1) effector functions are impacted by the structure of fragment crystallizable (Fc) tail-linked N-glycans. Low fucosylation levels on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein specific (anti-S) IgG1 has been described as a hallmark of severe coronavirus disease 2019 (COVID-19) and may lead to activation of macrophages via immune complexes thereby promoting inflammatory responses, altogether suggesting involvement of IgG1 Fc glycosylation modulated immune mechanisms in COVID-19.MethodsIn this prospective, observational single center cohort study, IgG1 Fc glycosylation was analyzed by liquid chromatography – mass spectrometry following affinity capturing from serial plasma samples of 159 SARS-CoV-2 infected patients.FindingsAt baseline close to disease onset, anti-S IgG1 glycosylation was highly skewed when compared to total plasma IgG1. A rapid, general reduction in glycosylation skewing was observed during the disease course. Low anti-S IgG1 galactosylation and sialylation as well as high bisection were early hallmarks of disease severity, whilst high galactosylation and sialylation and low bisection were found in patients with low disease severity. In line with these observations, anti-S IgG1 glycosylation correlated with various inflammatory markers.InterpretationAssociation of low galactosylation, sialylation as well as high bisection with disease severity suggests that Fc-glycan modulated interactions contribute to disease mechanism. Further studies are needed to understand how anti-S IgG1 glycosylation may contributes to disease mechanism and to evaluate its biomarker potential.FundingThis project received funding from the European Commission’s Horizon2020 research and innovation program for H2020-MSCA-ITN IMforFUTURE, under grant agreement number 721815.Research in contextEvidence before this studyAntibody glycosylation against the spike (S) protein of patients infected with severe acute respiratory syndrome SARS-CoV-2 has been reported as a potentially important determinant of COVID-19 disease severity. Studies have hitherto focused on afucosylation, a modification on immunoglobulin G1 (IgG) Fc-tail-linked N-glycans that enhances effector functions. Most of these studies featured limited sample numbers or were imperfectly matched with respect to demographic and other important confounding factors. Our lab has contributed to some of these studies, and we additionally searched for research articles on PubMed and Google Scholar from January 2020 to October 2021. To date, only two groups studied anti-S IgG1 glycosylation, which resulted in overall three publications found. However, none of these groups found a severity marker between hospitalized non-ICU and ICU patients or studied dynamic changes. Instead, exclusively fucosylation at the first available timepoint has been associated with disease severity between severely ill inpatients and mild outpatients.Added value of this studyIn this prospective, observational single center cohort study, we investigated the severity marker potential of anti-S IgG1 glycosylation in severe and mild hospitalized COVID-19 cases, and correlated these findings with numerous inflammation and clinical markers. Our study reveals low galactosylation and sialylation as well as high bisection on anti-S IgG1 as early hallmarks of severe COVID-19, after correction for age and sex effects. In line with these observations, anti-S IgG1 glycosylation correlated with many inflammatory markers. As days since onset is one of the major confounders of anti-S IgG1 glycosylation due to its highly dynamic nature, we additionally confirmed our findings in time-matched patient subgroups. We believe anti-S IgG1 glycosylation may be applicable for patient stratification upon hospitalization.Implications of all the available evidenceDemographic factors as well as temporal differences should be taken into consideration when analyzing IgG1 glycosylation of COVID-19 patients. Anti-S IgG1 glycosylation is highly dynamic, but is a promising early severity marker in COVID-19.

The BNT162b2 mRNA SARS-CoV-2 vaccine induces transient afucosylated IgG1 in naive but not antigen-experienced vaccinees

“…2B patients, as previously described (Fig. 2B) (2,30). A high level of IgG galactosylation boosted the classical complement pathway activation capacity through enhanced C1q-binding, which was in line with previous reports (Fig.…”

“…Anti-S IgG Abs were affinity-captured from plasma or sera using recombinant, in-house produced trimerized spike protein-coated plates (Thermo Fisher Scientific, Roskilde, Denmark) followed by a 100 mM formic acid elution step, as described elsewhere (2,49). Total IgG Abs were affinity-captured from plasma or sera using a Protein G AssayMAP Cartridge Rack on the Bravo (Agilent Technologies, Santa Clara, CA) or Protein G Sepharose 4 Fast Flow beads (GE Healthcare, Uppsala, Sweden) in a 96-well filter plate (Millipore Multiscreen, Amsterdam, Netherlands), respectively, as described elsewhere (2,30,52).…”

“…Eluates from both anti-S and total IgG affinity-purification were dried by vacuum centrifugation and subjected to tryptic cleavage followed by LC-MS analysis as described previously (2,30).…”

“…Recent work from Farkash et al and Chakraborty et al did not pick up this transient response due to sampling of two and fourweeks after the first dose, respectively(26,41). This afucosylated response was similar, but less pronounced than observed in natural SARS-CoV-2 infections(2,30). The transient afucosylated IgG1 glycosylation pattern after vaccination suggests that a co-stimulus may be missing to induce memory B cells and long-lived IgG + PCs producing stable anti-S IgG1…”

Afucosylation of HLA-specific IgG1 as a potential predictor of antibody pathogenicity in kidney transplantation

“…Antibody effector functions are highly affected by the composition of the N-glycan present at the conserved N-glycosylation site in the Fc region (60,61,(87)(88)(89). Hitherto, it has been repeatedly shown that disease-specific antibodies can exhibit skewed glycosylation profiles, that in turn associate with disease prognosis and outcome (73,(90)(91)(92)(93). Historically, one of the key limitations of glyco-profiling such antibodies is their low serum prevalence and high sample requirement.…”