DataSheet_1_Complement Alternative and Mannose-Binding Lectin Pathway Activation Is Associated With COVID-19 Mortality.docx

BackgroundThe SARS-CoV-2 infection triggers excessive immune response resulting in increased levels of pro-inflammatory cytokines, endothelial injury, and intravascular coagulopathy. The complement system (CS) activation participates to this hyperinflammatory response. However, it is still unclear which activation pathways (classical, alternative, or lectin pathway) pilots the effector mechanisms that contribute to critical illness. To better understand the immune correlates of disease severity, we performed an analysis of CS activation pathways and components in samples collected from COVID-19 patients hospitalized in Grenoble Alpes University Hospital between 1 and 30 April 2020 and of their relationship with the clinical outcomes.
MethodsWe conducted a retrospective, single-center study cohort in 74 hospitalized patients with RT-PCR-proven COVID-19. The functional activities of classical, alternative, and mannose-binding lectin (MBL) pathways and the antigenic levels of the individual components C1q, C4, C3, C5, Factor B, and MBL were measured in patients’ samples during hospital admission. Hierarchical clustering with the Ward method was performed in order to identify clusters of patients with similar characteristics of complement markers. Age was included in the model. Then, the clusters were compared with the patient clinical features: rate of intensive care unit (ICU) admission, corticoid treatment, oxygen requirement, and mortality.
ResultsFour clusters were identified according to complement parameters. Among them, two clusters revealed remarkable profiles: in one cluster (n = 15), patients exhibited activation of alternative and lectin pathways and low antigenic levels of MBL, C4, C3, Factor B, and C5 compared to all the other clusters; this cluster had the higher proportion of patients who died (27%) and required oxygen support (80%) or ICU care (53%). In contrast, the second cluster (n = 19) presented inflammatory profile with high classical pathway activity and antigenic levels of complement components; a low proportion of patients required ICU care (26%) and no patient died in this group.
ConclusionThese findings argue in favor of prominent activation of the alternative and MBL complement pathways in severe COVID-19, but the spectrum of complement involvement seems to be heterogeneous requiring larger studies.

背景：严重急性呼吸综合征冠状病毒2型（SARS-CoV-2）感染可触发过度免疫应答，导致促炎细胞因子水平升高、内皮损伤及血管内凝血病。补体系统（Complement System, CS）的激活参与了此次过度炎症反应，但目前尚不清楚究竟是哪些激活通路（经典途径、旁路途径或凝集素途径）介导了促成重症疾病的效应机制。为更好地明确疾病严重程度的免疫相关影响因素，我们对2020年4月1日至30日期间，在格勒诺布尔阿尔卑斯大学医院住院的新冠病毒感染（COVID-19）患者的样本开展了补体系统激活通路及组分的分析，并探究其与临床结局的关联。
方法：本研究为单中心回顾性队列研究，纳入74名经实时荧光定量聚合酶链反应（RT-PCR）确诊为新冠病毒感染的住院患者。于患者入院时采集其样本，检测经典途径、旁路途径及甘露糖结合凝集素（MBL）通路的功能活性，以及补体各组分C1q、C4、C3、C5、B因子（Factor B）及MBL的抗原水平。采用沃德（Ward）法进行系统聚类分析，以识别具有相似补体标志物特征的患者亚组，分析模型纳入年龄因素。随后将各亚组与患者临床特征进行对比，包括重症监护病房（ICU）收治率、糖皮质激素治疗情况、氧疗需求及病死率。
结果：基于补体参数共识别出4个患者亚组，其中2个亚组具有显著特征：其一（n=15）的患者表现为旁路途径与凝集素途径激活，且与其余所有亚组相比，其MBL、C4、C3、B因子及C5的抗原水平更低；该亚组的患者病死率（27%）、氧疗需求率（80%）及重症监护病房收治率（53%）均更高。与之相反，第二个亚组（n=19）呈现炎症特征，表现为经典通路活性及补体组分抗原水平均较高；该亚组重症监护病房收治率较低（26%），且无患者死亡。
结论：本研究结果支持重症新冠病毒感染患者的补体系统以旁路途径及MBL通路的显著激活为核心特征，但补体系统的参与模式存在异质性，需开展更大规模的研究进一步验证。