Host determinants of human metapneumovirus immunity and pathogenesis

描述（由申请方提供）：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重复感染，在老年患者和具有基础医学状况的个体中引起严重疾病。对hMPV免疫和发病机制了解甚少，并且没有获得许可的疫苗或治疗剂。现有的有限信息表明，hMPV与其他副粘病毒（包括呼吸道合胞病毒）之间存在根本差异。因此，拟议研究的中心目标是阐明对hMPV的免疫机制，并确定宿主免疫应答对疾病的贡献。我们提出了三个互补的具体目标，阐明hMPV免疫和发病机制。在具体目标1中，将定义抗体在保护和疾病中的作用。将用hMPV感染B细胞缺陷型小鼠，并在继发感染后评估病毒生长和肺病理学。被动血清转移实验将确定是否需要抗体进行保护。将使用NK细胞缺陷型小鼠确定抗体依赖性细胞毒性在免疫和疾病中的作用。在特异性目的2中，将测定hMPV融合（F）蛋白介导预防再感染的能力。小鼠将用F蛋白免疫并用编码不同F蛋白的工程化病毒攻击。将评价免疫和攻毒小鼠的呼吸道疾病和异常免疫应答。这些实验将检验hMPV F蛋白疫苗与增强的疾病无关以及hMPV F蛋白能够诱导广泛的保护性免疫的假设。在具体目标3中，将定义T细胞对hMPV免疫和发病机制的贡献。将用hMPV感染初始T细胞缺陷型小鼠，并评估病毒复制和肺病理学。T细胞缺陷小鼠将接种hMPV，允许清除感染，并再次激发以确定T细胞对保护免受继发性感染和肺病理学的贡献。CTL表位疫苗接种和克隆的MHC I类限制性表位特异性CD8+ T细胞系的过继转移将用于确定病毒特异性CD8+ T细胞是否有助于病理学。本申请中提出的实验结果将揭示宿主免疫可导致感染消退和免疫发病机制的机制。这些发现将推进hMPV免疫病理学的知识，指导hMPV治疗和疫苗的开发，并对其他呼吸道病毒具有广泛的适用性。

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.