Roles of human surfactant collectin variants in the susceptibility of COVID-19

在不到两年的时间里，已有超过480万人死于2019冠状病毒病（COVID-19）。 COVID-19是由严重急性呼吸道综合征冠状病毒2（SARS-CoV-2）引起的传染病。 SARS-CoV-2感染后的发病率和死亡率主要是由于炎性细胞的大量涌入。 细胞和细胞因子进入肺部，导致急性肺损伤（ALI）和急性呼吸窘迫综合征 （ARDS）。个体在感染SARS-CoV-2后表现出不同程度的疾病严重程度。人类 表面活性剂蛋白A和D（hSP-A和hSP-D）是C型凝集素（表面活性剂凝集素）的两个成员， 模式识别蛋白，它们在免疫系统中作为一线宿主防御和先天免疫起着关键作用。 肺和其他器官的粘膜表面。我们的初步数据和最近的体外研究表明， hSP-A和hSP-D能与SARS-CoV-2 Spike蛋白结合，抑制病毒在肺内侵入和复制 上皮细胞有趣的是，hSP-A和hSP-D的基因是高度多态性的， 在一般人群中已经鉴定了它们中的每一个的等位基因。然而，HSP的机制作用- A和hSP-D基因变异体在COVID-19发病机制中的作用尚不清楚。长期目标是确定 hSP-A和hSP-D基因变异在SARS-CoV-2诱导的ALI/ARDS易感性和严重程度中的作用 并开发用于治疗COVID-19的新型变体特异性治疗药物。这项建议旨在 确定表面活性剂集合和刺突蛋白的分子相互作用，并定义 hSP-A和hSP-D遗传变异导致个体对COVID-19的易感性。我们的核心假设是， hSP-A和hSP-D基因变异对SARS-CoV-2诱导的SARS易感性和严重性的影响 通过抑制SARS-CoV-2感染性和调节粘膜天然免疫和病理生理学来治疗ALI/ARDS。 最近，我们建立了一种新的双重人源化转基因小鼠模型， 表达人血管紧张素转换酶-2（SARS-CoV-2同源受体）和hSP-A或hSP-D基因 变量。这种双hTG模型为我们研究先天性免疫应答提供了有力的工具， hSP-A和hSP-D变体在SARS-CoV-2感染后的机制作用。我们提出两个具体目标 目的1：研究hSP-A和hSP-D基因变异体与SARS-CoV-2刺突蛋白的相互作用 蛋白质和对肺上皮细胞中病毒进入和复制的抑制作用。目标2：定义差异 hSP-A基因变异体在抑制病毒感染和调节SARS-CoV-2诱导的ALI中的作用 在双hTG小鼠模型中调节TLR/NF-kB/IFN信号传导。这项建议得到我们的大力支持。 初步数据和适用于COVID-19研究的可用新型双hTG模型。我们预计 成功完成拟议的研究将建立一种新的COVID-19小鼠模型，并具有更好的 了解hSP-A和hSP-D在COVID-19发病机制中的先天免疫作用， 开发新型免疫调节疗法和个性化药物。

More than 4.8 million people have died due to coronavirus disease 2019 (COVID-19) in less than two years. COVID-19 is an infectious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Morbidity and mortality following SARS-CoV-2 infection are predominantly due to a robust influx of inflammatory cells and cytokines into the lungs resulting in acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). Individuals exhibited different degree of disease severity after SARS-CoV-2 infection. Human Surfactant proteins A and D (hSP-A and hSP-D), two members of C-type lectin (surfactant collectin), are pattern recognition proteins, and they play a critical role as a first-line host defense and innate immunity in the mucosal surfaces of the lung and other organs. Our preliminary data and recent in vitro studies demonstrated that hSP-A and hSP-D can bind to SARS-CoV-2 Spike protein and inhibit viral entry and replication in lung epithelial cells. Interestingly, the genes of hSP-A and hSP-D are highly polymorphic, and several genetic variants (alleles) for each of them have been identified in the general population. However, the mechanistic roles of hSP- A and hSP-D genetic variants in the pathogenesis of COVID-19 are unknow. The long-term goal is to determine the roles of hSP-A and hSP-D genetic variants in susceptibility and severity to SARS-CoV-2-induced ALI/ARDS and to develop novel variant-specific therapeutic drug for the treatment of COVID-19. This proposal aims to determine molecular interaction of surfactant collection and Spike protein, and define the mechanistic roles of hSP-A and hSP-D genetic variants causing individual susceptibilities to COVID-19. Our central hypothesis is that hSP-A and hSP-D genetic variants differentially influence susceptibility and severity to SARS-CoV-2-induced ALI/ARDS by inhibiting SARS-CoV-2 infectivity and modulating mucosal innate immunity and pathophysiology. Recently, we have generated a new double-humanized transgenic (double-hTG) mouse model, which express human angiotensin-converting enzyme-2 (SARS-CoV-2 cognate receptor) and hSP-A or hSP-D genetic variant. This double-hTG model provides us with a powerful tool to study the innate immune response and mechanistic roles of hSP-A and hSP-D variants following SARS-CoV-2 infection. We propose two specific aims to test our hypothesis: Aim 1: Study the interactions of hSP-A or hSP-D genetic variants with SARS-CoV-2 spike protein and the inhibitory effect on viral entry and replication in lung epithelial cells. Aim 2: Define the differential roles of hSP-A genetic variants in inhibiting viral infectivity and modulating SARS-CoV-2-induced ALI through regulating TLRs/NF-kB/IFN signaling in a double-hTG mouse model. The proposal is strongly supported by our preliminary data and available novel double-hTG model suitable for COVID-19 study. We expect that the successful completion of the proposed studies will establish a novel COVID-19 murine model, and have a better understanding of the innate immune roles of hSP-A and hSP-D in COVID-19 pathogenesis that is crucial to develop novel immunomodulatory therapies and personalized medicine.