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

项目摘要/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人住院死亡，其中大多数死亡发生在小于 三个月大。再次感染是常见的，那些发展为严重毛细支气管炎的人面临进一步的风险 患上哮喘等慢性肺部疾病的风险。过去通过以下途径预防婴儿RSV感染的努力 接种福尔马林灭活病毒是灾难性的，导致80%的接种者住院 在社区获得性RSV感染之后。这阻碍了近50年来RSV疫苗的开发 好几年了。我们和其他研究人员使用新生(即7日龄)RSV感染的小鼠模型来 在人类婴儿身上模拟这种疾病。最近，我们发现I型干扰素(干扰素-I)的反应是 在新生小鼠中缺乏，这与在人类婴儿中的发现一致。就像反复感染一样 由于适应性免疫不足，我们评估了抗体反应，并证明， 由于缺乏干扰素-I，新生小鼠和婴儿不能产生RSV特异性IgA。我们确定了一个 免疫球蛋白A的产生需要干扰素α 老鼠。这一点尤其重要，因为RSV特异性的IgA反应与保护显著相关 与成人不同，婴儿和新生小鼠在感染后不会产生这种反应。 干扰素α诱导新生小鼠产生呼吸道合胞病毒特异性免疫球蛋白A并减轻呼吸道合胞病毒病 严肃性。重要的是，表达IL10但不表达IgA的新生儿B调节淋巴细胞(NBregs)已经 在RSV感染的婴儿和新生小鼠中观察到的时间框架与降低的干扰素-I水平一致。 综上所述，这些发现指导了我们的假设，即未能产生保护性的IgA反应 呼吸道粘膜是呼吸道合胞病毒严重程度的原因。我们将使用以下工具来探索这一假设的有效性 来自人类婴儿RSV感染队列和与年龄相关的小鼠模型的独特样本集 明确的目标。目的1将证明婴儿不能诱导呼吸道合胞病毒特异性免疫球蛋白A。 对RSV感染的反应是疾病严重性增加的原因。目标2将确定是否未能 诱导BAFF/APRIL抑制婴儿对RSV的IgA应答。目标3将确立 NBregs抑制婴儿中RSV特异性IgA的产生。I型干扰素的年龄依赖性调节 调节呼吸道合胞病毒感染后呼吸道黏膜保护性IgA反应的发展 小说。我们将在B细胞亚群上采用创新的方法，包括单细胞RNASeq(ScRNASeq) RSV感染的婴儿样本和RSV感染的新生小鼠样本中的空间转录 描述Breg的表型、转录程序和局部功能。来自这些研究的数据 将对严重RSV疾病的理解产生积极的范式转换影响，并产生新的 推进儿科疫苗设计的免疫学指标。

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.