Multi-center Evaluation of the Threat of Established and Emerging Respiratory Viral Infections in Pediatric Transplant Recipients

呼吸道病毒感染（RVI）改变了世界。RVI是传染病发病的主要原因， 接受造血细胞移植（HCT）和实体器官移植（SOT）的儿童死亡率。 通过定性PCR筛查的RVI诊断是敏感的，但不幸的是不能区分疾病和 存在病毒核酸或预测从上呼吸道进展至更严重下呼吸道的风险 疾病（LRTD）。在COVID-19时代，许多中心现在使用移植前RVI筛查，但其影响 在无症状宿主中的检测率未知。整合定量病毒载量、病毒测序和/或 宿主免疫（T细胞和抗体）反应可以提供新的预测工具， RVI和LRTD的进展。我们的目标是建立一个全面的RVI诊断和疾病 进展预测模型在接受移植的儿童。我们提出了一个前瞻性的多中心 对2000例儿童移植受者进行的流行病学研究，采用巢式病例对照免疫学和病毒学 子研究。这将是在HCT和SOT接受者的任何年龄组中进行的最大规模的RVI研究。我们将利用 儿科移植ID网络（PIDTRAN），一个由21个全国性站点组成的联盟，也是唯一一个 致力于儿科移植感染性疾病。我们将在2020年获得移植前的血液和鼻腔样本。 所有2000名移植参与者在登记时以及移植后+100天的血液。在目标1中，我们 使用定性PCR确定病毒核酸检测阳性的流行率，然后进行定量 对阳性标本进行PCR（qPCR）和病毒测序（宏基因组学）。我们假设， 呼吸道病毒核酸或某些病毒基因型将鉴定处于RVI或疾病进展风险中的患者。 在目标2中，我们将开发和验证一种免疫分类器，以预测RVI和进展为LRTD的风险 在一项针对三种主要儿科病毒（RSV、副流感病毒3型和人类）的巢式子研究中， 偏肺病毒我们将描述移植前的体液和细胞免疫反应， 与移植前免疫学和移植后+100天相比，发生这些RVI的患者 未感染的匹配对照的免疫应答。结合宿主反应和病毒学数据 (qPCR和病毒宏基因组学）也将在进展或未进展为LRTD的RVI病例之间进行比较 来鉴定生物标记物。我们假设特异性定性或定量抗体应答的患者 和/或特异性T细胞库将具有上级的临床结果。表征全面的 移植前的病毒和宿主反应，我们将学会预测谁有RVI和LRTD的风险， 干预与延迟移植，以及PCR阳性指示潜在疾病时。这些结果将 使我们能够为儿童的个性化临床管理制定新的循证儿科指南， 这也为未来在这些高危患者人群中进行的抗病毒和疫苗研究提供了信息。

Respiratory viral infections (RVI) have changed the world. RVI are a leading cause of infectious morbidity and mortality in children undergoing hematopoietic cell transplantation (HCT) and solid organ transplantation (SOT). RVI diagnosis by qualitative PCR screening is sensitive, but unfortunately does not distinguish disease from presence of viral nucleic acid or predict risk for progression from upper to the more severe lower respiratory tract disease (LRTD). In the COVID-19 era, many centers now use pre-transplant RVI screening, but the implications of detection in an asymptomatic host are unknown. Integrating quantitative viral load, viral sequencing, and/or host immune (T cell and antibody) responses could provide novel predictive tools to stratify the risk of developing an RVI and the progression to LRTD. Our objective is to establish a comprehensive RVI diagnostic and disease progression predictive model in children undergoing transplantation. We propose a prospective multi-center epidemiologic study of 2000 pediatric transplant recipients, with a nested case-control immunologic and virologic substudy. This will be the largest study on RVI in any age group of HCT and SOT recipients. We will leverage the Pediatric Transplant ID Network (PIDTRAN), a consortium of 21 nationwide sites and the only group dedicated to pediatric transplant infectious diseases. We will obtain pre-transplant blood and nasal samples in all 2000 transplant participants at enrollment and also blood at day +100 post-transplant. In Aim 1, we will determine the prevalence of viral nucleic assay positivity using qualitative PCR and then perform quantitative PCR (qPCR) and viral sequencing (metagenomics) on positive specimens. We hypothesize that the quantity of respiratory viral nucleic acid or certain viral genotypes will identify patients at risk for RVI or disease progression. In Aim 2, we will develop and validate an immunological classifier to predict risk of RVI and progression to LRTD in a nested substudy focused on three major pediatric viruses: RSV, parainfluenza virus 3, and human metapneumovirus. We will characterize pre-transplant humoral and cellular immune responses in the subset of patients who develop those RVIs compared with pre-transplant immunologic and day +100 post-transplant immune responses from uninfected matched controls. The combination of host response and virologic data (qPCR and viral metagenomics) will also be compared between RVI cases who do or do not progress to LRTD to identify biomarkers. We hypothesize that patients with specific qualitative or quantitative antibody responses and/or specific T cell repertoires to RVI will have superior clinical outcomes. Characterizing a comprehensive viral and host response pre-transplant, we will learn to predict who is at risk of RVI and LRTD and needs early intervention vs. delay of transplant, and when PCR positivity is indicative of potential disease. These results will allow us to generate novel evidence-based pediatric guidelines for personalized clinical management of children undergoing transplant, and also inform future antiviral and vaccine studies in these high-risk patient populations.