The essential role of immunoglobulin G (IgG) in immune system regulation and combatting infectious diseases cannot be fully recognized without an understanding of the changes in its N-glycans attached to the asparagine 297 of the fragment crystallizable (Fc) domain that occur under such circumstances. These glycans impact the antibody stability, half-life, secretion, immunogenicity, and effector functions. Therefore, in this study, we analyzed and compared the total IgG glycome—at the level of individual glycan structures and derived glycosylation traits (sialylation, galactosylation, fucosylation, and bisecting N-acetylglucosamine (GlcNAc))—of 64 patients with influenza, 77 patients with coronavirus disease 2019 (COVID-19), and 56 healthy controls. Our study revealed a significant decrease in IgG galactosylation, sialylation, and bisecting GlcNAc (where the latter shows the most significant decrease) in deceased COVID-19 patients, whereas IgG fucosylation was increased. On the other hand, IgG galactosylation remained stable in influenza patients and COVID-19 survivors. IgG glycosylation in influenza patients was more time-dependent: In the first seven days of the disease, sialylation increased and fucosylation and bisecting GlcNAc decreased; in the next 21 days, sialylation decreased and fucosylation increased (while bisecting GlcNAc remained stable). The similarity of IgG glycosylation changes in COVID-19 survivors and influenza patients may be the consequence of an adequate immune response to enveloped viruses, while the observed changes in deceased COVID-19 patients may indicate its deviation.

如果不了解在这种情况下发生在片段可结晶 (Fc) 结构域天冬酰胺 297 上的N-聚糖的变化，就无法充分认识免疫球蛋白 G (IgG) 在免疫系统调节和对抗传染病中的重要作用。这些聚糖影响抗体稳定性、半衰期、分泌、免疫原性和效应器功能。因此，在这项研究中，我们分析并比较了 64 名流感患者、77 名流感患者的总 IgG 糖组——在单个聚糖结构和衍生糖基化特征（唾液酸化、半乳糖基化、岩藻糖基化和平分N-乙酰氨基葡萄糖 (GlcNAc)）水平上。 2019 年冠状病毒病 (COVID-19) 患者和 56 名健康对照者。我们的研究显示，已故的 COVID-19 患者中 IgG 半乳糖基化、唾液酸化和平分 GlcNAc（后者显示出最显着的减少）显着减少，而 IgG 岩藻糖基化则增加。另一方面，流感患者和 COVID-19 幸存者中的 IgG 半乳糖基化保持稳定。流感患者的IgG糖基化更具时间依赖性：在疾病的前7天，唾液酸化增加，岩藻糖基化和平分GlcNAc减少；在接下来的 21 天内，唾液酸化减少，岩藻糖化增加（而平分 GlcNAc 保持稳定）。 COVID-19 幸存者和流感患者 IgG 糖基化变化的相似性可能是对包膜病毒产生充分免疫反应的结果，而在已故 COVID-19 患者中观察到的变化可能表明其偏差。