Host determinants of human metapneumovirus immunity and pathogenesis

描述(申请人提供)：人偏肺病毒(HMPV)是最近发现的一种副粘病毒，是下呼吸道感染的主要原因。HMPV在儿童和成人中引起反复感染，在老年患者和有潜在疾病的个人中引起严重疾病。HMPV的免疫机制和发病机制尚不清楚，目前还没有获得许可的疫苗或治疗方法。现有的有限信息表明，hMPV与包括呼吸道合胞病毒在内的其他副粘病毒之间存在根本差异。因此，这项研究的中心目标是阐明对hMPV的免疫机制，并确定宿主免疫反应对疾病的贡献。我们提出了三个互补的特异性目标来阐明hMPV的免疫机制和致病机制。在具体目标1中，将确定抗体在保护和疾病中的作用。B细胞缺陷小鼠将感染hMPV，并在二次感染后评估病毒生长和肺部病理。被动血清转移实验将确定是否需要抗体来保护。抗体依赖的细胞毒性在免疫和疾病中的作用将通过NK细胞缺陷小鼠来确定。在特定目标2中，将确定hMPV融合(F)蛋白介导对再感染的保护作用的能力。小鼠将用F蛋白免疫，并用编码不同F蛋白的工程病毒攻击。将对免疫和挑战小鼠进行呼吸道疾病和异常免疫反应的评估。这些实验将检验hMPV F蛋白疫苗将不会与疾病增强相关的假设，以及hMPV F蛋白能够诱导广泛的保护性免疫。在具体目标3中，将明确T细胞在hMPV免疫和发病机制中的作用。幼稚T细胞缺陷小鼠将感染hMPV，并将评估病毒复制和肺部病理。T细胞缺陷小鼠将被接种hMPV，允许清除感染，并再次接受挑战，以确定T细胞对预防二次感染和肺部病理的贡献。CTL表位疫苗和克隆的MHC I类限制性表位特异性CD8T细胞的过继转移将被用于确定病毒特异性CD8T细胞是否参与了病理过程。在本申请中提出的实验结果将揭示宿主免疫可以导致感染的解决和免疫发病机制的机制。这些发现将促进对hMPV免疫病理学的了解，指导hMPV疗法和疫苗的发展，并对其他呼吸道病毒具有广泛的适用性。 公共卫生相关性：该项目的目标是确定宿主对人类偏肺炎病毒(HMPV)的免疫机制。HMPV是最近发现的一种副粘病毒，是全球儿童下呼吸道疾病的主要原因。从这些实验中获得的知识对于开发安全有效的HMPV疫苗和疗法至关重要。此外，这项工作的结果将增加我们对呼吸道病毒和免疫系统之间的相互作用如何有助于疾病和保护的理解。

DESCRIPTION (provided by applicant): Human metapneumovirus (hMPV) is a recently discovered paramyxovirus that is a major cause of lower respiratory tract infection. hMPV causes repeat infections in children and adults and severe disease in older patients and individuals with underlying medical conditions. Mechanisms of hMPV immunity and pathogenesis are poorly understood and there are no licensed vaccines or therapeutics. The limited information available indicates that there are fundamental differences between hMPV and other paramyxoviruses, including respiratory syncytial virus. Accordingly, the central objective of the proposed research is to elucidate mechanisms of immunity to hMPV and define the contribution of host immune responses to disease. We propose three complementary specific aims to elucidate mechanisms of hMPV immunity and pathogenesis. In Specific Aim 1, the role of antibody in protection and disease will be defined. B cell-deficient mice will be infected with hMPV and viral growth and lung pathology assessed following secondary infection. Passive serum transfer experiments will determine whether antibody is required for protection. The role of antibody- dependent cellular cytotoxicity in immunity and disease will be determined using NK cell-deficient mice. In Specific Aim 2, the capacity of hMPV fusion (F) protein to mediate protection against reinfection will be determined. Mice will be immunized with F protein and challenged with engineered viruses encoding divergent F proteins. Immunized and challenged mice will be evaluated for respiratory disease and aberrant immune responses. These experiments will test the hypotheses that hMPV F protein vaccines will not be associated with enhanced disease and that hMPV F protein is capable of inducing broadly protective immunity. In Specific Aim 3, the contribution of T cells to hMPV immunity and pathogenesis will be defined. Naive T cell-deficient mice will be infected with hMPV, and viral replication and lung pathology will be assessed. T-cell-deficient mice will be inoculated with hMPV, allowed to clear infection, and rechallenged to determine the contribution of T cells to protection against secondary infection and lung pathology. CTL epitope vaccination and adoptive transfer of cloned MHC class I-restricted epitope-specific CD8+ T cell lines will be used to determine whether virus-specific CD8+ T cells contribute to pathology. Results of the experiments proposed in this application will reveal mechanisms by which host immunity can lead to both resolution of infection and immunopathogenesis. These findings will advance knowledge of hMPV immunopathology, guide the development of hMPV therapeutics and vaccines, and have broad applicability to other respiratory viruses. PUBLIC HEALTH RELEVANCE: The goal of this project is to define mechanisms of host immunity to human metapneumovirus (hMPV). hMPV is a recently discovered paramyxovirus that is a leading cause of lower respiratory tract disease in children worldwide. The knowledge gained from these experiments will be essential to develop safe and effective vaccines and therapeutics for HMPV. Further, the results of this work will increase our understanding of how interactions between respiratory viruses and the immune system contribute to disease and protection.