Elucidating Mechanisms of Mucosal Immune Protection Against Respiratory Syncytial Virus in Infants

项目总结/摘要： 呼吸道合胞病毒（RSV）是婴儿下呼吸道病毒感染的头号原因 每年造成约60，000例住院死亡，其中大多数死亡发生在婴儿中， 三个月大再感染是常见的，那些发展为严重细支气管炎的人有进一步的风险 患上慢性肺部疾病如哮喘的风险。过去通过以下措施预防婴儿RSV感染的努力 用福尔马林灭活的病毒接种疫苗是灾难性的，导致80%的接种者住院 社区获得性RSV感染后。这阻碍了近50年的RSV疫苗开发 年我们和其他研究人员使用了新生儿（即，<7日龄）RSV感染小鼠模型， 在人类婴儿身上模仿这种疾病最近，我们已经表明，I型干扰素（IFN-I）的反应， 在新生小鼠中缺乏，这与人类婴儿中的发现一致。由于反复感染 表明适应性免疫力不足，我们评估了抗体应答并证明， 与IFN-I缺乏一致，新生小鼠和婴儿不能产生RSV特异性伊加。我们确定了一个 通过证明伊加的产生需要IFNα， 小鼠这一点尤其重要，因为RSV特异性伊加应答与保护作用显著相关， 并且与成年人相反，婴儿和新生小鼠在感染后不能产生这种反应。 新生小鼠给予IFNα诱导RSV特异性伊加产生并减少RSV疾病 严重性。重要的是，表达IL 10而非伊加的新生儿B调节性淋巴细胞（nBCLs）已被证实是一种免疫调节因子。 在RSV感染的婴儿和新生小鼠中观察到与IFN-I水平降低一致的时间范围。 总之，这些发现指导了我们的假设，即不能在小鼠中产生保护性伊加反应， 呼吸道粘膜是RSV严重性的原因。我们将探讨这一假设的有效性使用 来自人类婴儿RSV感染队列和年龄相关小鼠模型的独特样品集， 具体目标。目的1将证明婴儿不能诱导粘膜RSV特异性伊加， 对RSV感染的应答导致疾病严重程度的提高。目标2将决定是否未能 诱导BAFF/APRIL阻碍了婴儿中对RSV的伊加应答的发展。目标3将规定， NBSP抑制婴儿中RSV特异性伊加的产生。I型干扰素的年龄依赖性调节 调节RSV感染后呼吸道粘膜中保护性伊加应答的发展， 小说我们将采用创新的方法，包括B细胞亚群的单细胞RNAseq（scRNASeq）， 来自RSV感染婴儿的样品和来自RSV感染新生小鼠的样品中的空间转录组学， 表征布雷格表型、转录程序和局部功能。数据来源于这些研究 将对严重RSV疾病的理解产生积极的范式转变影响， 免疫学目标，以推进儿科疫苗设计。

PROJECT SUMMARY/ABSTRACT: Respiratory syncytial virus (RSV) is the number one cause of lower respiratory tract viral infection in infants and is responsible for ~60,000 in-hospital deaths annually, with most deaths occurring in infants less than three months of age. Reinfections are common, and those who develop severe bronchiolitis are at further risk of developing chronic lung diseases such as asthma. Past efforts to prevent RSV infection in infants through vaccination with formalin-inactivated virus were disastrous resulting in 80% of vaccinees being hospitalized following community-acquired RSV infection. This has hampered RSV vaccine development for nearly 50 years. We, and other researchers, have used neonatal (i.e., <7d of age) mouse models of RSV infection to mimic the disease in human infants. Recently, we have shown that type I interferon (IFN-I) responses are deficient in neonatal mice, which is consistent with findings in human infants. As repeated infections are indicative of insufficient adaptive immunity, we assessed antibody responses and demonstrated that, congruent with deficiencies in IFN-I, neonatal mice and infants fail to produce RSV-specific IgA. We identified a mechanistic relationship between these components by demonstrating that IgA production requires IFNα in mice. This is especially important, because RSV-specific IgA responses correlate significantly with protection from disease and, in contrast to adults, infants and neonatal mice fail to mount such responses upon infection. IFNα administration in neonatal mice induced RSV-specific IgA production and decreased RSV disease severity. Importantly, neonatal B regulatory lymphocytes (nBregs) expressing IL10, but not IgA, have been observed in RSV-infected infants and neonatal mice in a time-frame consistent with decreased IFN-I levels. Together, these findings guide our hypothesis that failure to develop protective IgA responses in the respiratory mucosa is responsible for RSV severity. We will explore the validity of this hypothesis using unique sample sets from human infant RSV infection cohorts and age-relevant mouse models with three specific aims. Aim 1 will demonstrate that the inability of infants to induce mucosal RSV-specific IgA in response to RSV infection is responsible for enhanced disease severity. Aim 2 will determine whether failure to induce BAFF/APRIL hinders the development of IgA responses to RSV in infants. Aim 3 will establish that nBregs suppress RSV-specific IgA production in infants. The idea that age-dependent regulation of type I IFN regulates the development of protective IgA responses in the respiratory mucosa following RSV infection is novel. We will employ innovative methodologies including single-cell RNAseq (scRNASeq) on B-cell subsets in samples from RSV-infected infants and spatial transcriptomics in samples from RSV-infected neonatal mice to characterize Breg phenotypes, transcriptional programs, and local functions. Data derived from these studies will have a positive paradigm-shifting impact on the understanding of severe RSV disease and yield novel immunological targets to advance pediatric vaccine design.