Table_1_Evaluation of Mannose Binding Lectin Gene Variants in Pediatric Influenza Virus-Related Critical Illness.DOCX

Background: Mannose-binding lectin (MBL) is an innate immune protein with strong biologic plausibility for protecting against influenza virus-related sepsis and bacterial co-infection. In an autopsy cohort of 105 influenza-infected young people, carriage of the deleterious MBL gene MBL2_Gly54Asp(“B”) mutation was identified in 5 of 8 individuals that died from influenza-methicillin-resistant Staphylococcus aureus (MRSA) co-infection. We evaluated MBL2 variants known to influence MBL levels with pediatric influenza-related critical illness susceptibility and/or severity including with bacterial co-infections.
Methods: We enrolled children and adolescents with laboratory-confirmed influenza infection across 38 pediatric intensive care units from November 2008 to June 2016. We sequenced MBL2 “low-producer” variants rs11003125(“H/L”), rs7096206(“Y/X”), rs1800450Gly54Asp(“B”), rs1800451Gly57Glu(“C”), rs5030737Arg52Cys(“D”) in patients and biologic parents. We measured serum levels and compared complement activity in low-producing homozygotes (“B/B,” “C/C”) to HYA/HYA controls. We used a population control of 1,142 healthy children and also analyzed family trios (PBAT/HBAT) to evaluate disease susceptibility, and nested case-control analyses to evaluate severity.
Results: We genotyped 420 patients with confirmed influenza-related sepsis: 159 (38%) had acute lung injury (ALI), 165 (39%) septic shock, and 30 (7%) died. Although bacterial co-infection was diagnosed in 133 patients (32%), only MRSA co-infection (n = 33, 8% overall) was associated with death (p < 0.0001), present in 11 of 30 children that died (37%). MBL2 variants predicted serum levels and complement activation as expected. We found no association between influenza-related critical illness susceptibility and MBL2 variants using family trios (633 biologic parents) or compared to population controls. MBL2 variants were not associated with admission illness severity, septic shock, ALI, or bacterial co-infection diagnosis. Carriage of low-MBL producing MBL2 variants was not a risk factor for mortality, but children that died did have higher carriage of one or more B alleles (OR 2.3; p = 0.007), including 7 of 11 with influenza MRSA-related death (vs. 2 of 22 survivors: OR 14.5, p = 0.0002).
Conclusions:MBL2 variants that decrease MBL levels were not associated with susceptibility to pediatric influenza-related critical illness or with multiple measures of critical illness severity. We confirmed a prior report of higher B allele carriage in a relatively small number of young individuals with influenza-MRSA associated death.

背景：甘露糖结合凝集素（Mannose-binding lectin, MBL）是一种先天免疫蛋白，在抵御流感病毒相关脓毒症及细菌合并感染方面具有充分的生物学合理性。在105名流感感染青年的尸检队列中，8例死于流感合并耐甲氧西林金黄色葡萄球菌（methicillin-resistant Staphylococcus aureus, MRSA）感染的个体中，有5例携带有害MBL基因MBL2_Gly54Asp(“B”)突变。本研究评估了已知可影响MBL水平的MBL2基因变异与儿童流感相关性重症易感性和/或严重程度的关联，其中涵盖细菌合并感染场景。
方法：本研究于2008年11月至2016年6月期间，在38家儿科重症监护病房招募经实验室确认感染流感的儿童及青少年。对受试者及其亲生父母的MBL2“低表达”变异位点rs11003125(“H/L”)、rs7096206(“Y/X”)、rs1800450Gly54Asp(“B”)、rs1800451Gly57Glu(“C”)、rs5030737Arg52Cys(“D”)进行测序。检测受试者血清MBL水平，并比较低表达纯合子(“B/B”、“C/C”)与HYA/HYA对照者的补体活性。本研究以1142名健康儿童作为人群对照，同时通过家系三联体分析（PBAT/HBAT）评估疾病易感性，并采用嵌套病例对照分析评估疾病严重程度。
结果：本研究共对420例确诊流感相关性脓毒症患者进行基因分型：其中159例（38%）发生急性肺损伤（ALI），165例（39%）出现感染性休克，30例（7%）死亡。尽管133例患者（32%）被诊断为细菌合并感染，但仅MRSA合并感染（共33例，占总研究对象的8%）与死亡风险显著相关（p < 0.0001），30例死亡患儿中11例（37%）存在该合并感染。MBL2基因变异可如预期般预测血清MBL水平及补体激活状态。通过家系三联体分析（纳入633名亲生父母）或与人群对照比较，均未发现流感相关性重症易感性与MBL2基因变异存在关联。MBL2基因变异与入院时疾病严重程度、感染性休克、急性肺损伤或细菌合并感染诊断均无显著关联。低表达MBL的MBL2基因变异并非死亡的危险因素，但死亡患儿携带至少1个B等位基因的比例更高（比值比OR=2.3；p=0.007），其中11例因流感合并MRSA感染死亡的患儿中有7例携带该等位基因（vs. 22名存活者中仅2例携带，OR=14.5，p=0.0002）。
结论：降低MBL水平的MBL2基因变异与儿童流感相关性重症易感性及多项重症严重程度评估指标均无关联。本研究验证了此前一项针对少量青年流感合并MRSA感染死亡病例的报道，即此类人群中B等位基因携带率更高。