Multi-center evaluation of the threat of established and emerging respiratory viral infections in pediatric transplant recipients

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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.