SARS-CoV-2 infection and MHC class I function in bats

项目摘要 新冠肺炎是由高传染性冠状病毒引起的一种危险的流行性疾病 SARS-CoV-2，由蝙蝠经人畜共患传播而产生。CD8阳性T细胞有助于 通过杀死受感染的细胞来消除病毒，防止病毒在受感染的个体中扩张，以及 限制他人受到感染的机会。CD8阳性T细胞通过以下途径杀死病毒感染细胞 识别表面主要组织相容性复合体I类(MHC-I)分子 与从病毒蛋白中提取的多肽有关。像许多病毒一样，SARS-CoV-2 编码影响MHC-I-肽复合体表面表达的特定蛋白质，结果 抵抗T细胞介导的杀伤。我们假设，由于SARS-CoV-2病毒转移 从蝙蝠到人类，它的MHC-I抑制特性在蝙蝠身上进化。我们进一步假设 这是因为对病毒的进化压力是通过面部的自然选择来调节的 对于长期暴露在蝙蝠免疫系统中，抑制MHC-I功能将更加有效 在蝙蝠身上比在人类身上。对这些假说的研究受到缺乏适当假设的限制。 试剂。这项建议试图通过在小鼠身上开发抗体来补救这种情况 在酵母中识别BAT MHC-I蛋白及其等价物的兔和纳米体 更多的人类基因产物促进基因的产生和表面表达 含有结合抗原肽的MHC-I分子，即TAP1和TAP2，Tapasin， 钙网蛋白和硫醇氧化还原酶ERp57(PDIA3)。当我们生产这些试剂时，我们将 利用它们来表征蝙蝠体内MHC-I限制性抗原的处理过程，并确定如何 SARS-CoV-2感染对其有影响。我们已经鉴定出四种SARS-CoV-2蛋白 单独导致MHC-I在人类中下调，我们建议这些蛋白质 联合作用导致感染的MHC-I表面表达减少 细胞。我们的目标是确定这些基因产物以及潜在的其他基因产物是否会影响 蝙蝠细胞中同样的过程以及它们做得有多好。理解MHC-I的功能和适应性 蝙蝠的免疫力将帮助我们揭示为什么它们是冠状病毒的强大宿主。 确定蝙蝠如何在这种病毒的感染下存活下来，可能会建议进行有针对性的治疗 提高人类抵抗它们的能力并增强我们的控制能力的方法 并击败未来的冠状病毒大流行。

Project Summary COVID-19 is a dangerous pandemic disease caused by the highly infectious coronavirus SARS-CoV-2, which arose by zoonotic transfer from bats. CD8-positive T cells contribute to viral elimination by killing infected cells, preventing viral expansion in an infected individual and limiting the exposure of others to infection. CD8-positive T cells kill virally infected cells by recognizing Major Histocompatibility Complex class I (MHC-I) molecules on their surface that are associated with peptides derived from viral proteins. Like many viruses, SARS-CoV-2 encodes specific proteins that affect surface expression of MHC-I-peptide complexes, resulting in resistance to T cell-mediated killing. We hypothesize that, since SARS-CoV-2 transferred from bats to humans, its MHC-I inhibitory properties evolved in bats. We further hypothesize that, because evolutionary pressure on the virus was mediated by natural selection in the face of chronic exposure to the bat immune system, inhibition of MHC-I function will be more efficient in bats than in humans. Investigating these hypotheses is limited by the lack of appropriate reagents. This proposal seeks to remedy the situation by developing antibodies in mice and rabbits and nanobodies in yeast that identify bat MHC-I proteins as well as the bat equivalents of the additional human gene products that facilitate the generation and surface expression of MHC-I molecules containing bound antigenic peptides, namely TAP1 and TAP2, tapasin, calreticulin and the thiol oxidoreductase ERp57 (PDIA3). As we produce these reagents we will use them to characterize MHC-I-restricted antigen processing in bats and determine how SARS-CoV-2 infection affects it. We have identified four SARS-CoV-2 proteins that independently cause MHC-I down-regulation in humans, and we suggest that these proteins acting in combination are responsible for the reduction in MHC-I surface expression in infected cells. Our goal is to determine whether these gene products, and potentially others, affect the same process in bat cells and how well they do it. Understanding MHC-I function and adaptive immunity in bats will help us to uncover why they are a such potent reservoir for coronaviruses. Determining how bats survive infection by such viruses may suggest targeted therapeutic approaches to improve the ability of humans to resist them and enhance our ability to control and defeat future coronavirus pandemics.