PROJECT SUMMARY / ABSTRACT Lung transplantation (LT) recipients suffer from life-threatening pulmonary infections that can trigger acute rejection and death. Although vaccination is the most effective way for preventing infections, vaccine efficacy is limited in immunocompromised solid organ transplant recipients. Two recent JAMA studies suggest that most transplant recipients fail to mount antibody responses to SARS-CoV-2 mRNA vaccines; anti-metabolite immunosuppressants further dampened this response. To facilitate more effective vaccination strategies, there is an urgent unmet need to understand vaccine responses in immunosuppressed LT recipients. Adopting a system vaccinology approach, this grant characterizes complex vaccine-elicited immune responses to address the problem of deficient vaccine immunogenicity in LT recipients. As the COVID-19 pandemic heightens focus on the vulnerability of LT recipients, the creation of a vaccine-oriented biobank to facilitate system biology analyses can strengthen the newly-formed NIH LT Consortium. In this proposal, we unite physicians/scientists from Stanford, Inova-Fairfax, and Houston Methodist to build a vaccination-oriented biorepository as the focus of a clinical center (CC). Responding to the RFA to explore center-specific hypotheses, our CC seeks an answer to the pressing question: ‘how do LT recipients respond to vaccinations?’ The grant hypothesis is that a vaccination-oriented biorepository will facilitate the holistic analysis of influenza vaccine-induced immune responses in LT recipients from geographically distant regions and that the use of an anti-metabolite immunosuppressant predicts reduced protective innate and adaptive responses in these patients. In Aim 1, biospecimens from patients immunized by vaccines against COVID-19, varicella-zoster, pneumococcus, and influenza will be prospectively collected and banked to generate the biorepository. To address hypothesis-driven questions achievable with a modest budget, Aim 2 uses system vaccinology tools to evaluate the influenza vaccines, the most common vaccinations administered to LT patients. Aim 2a characterizes humoral and innate immunity, Aim 2b focuses on cellular immunity, and Aim 2c builds a vaccine response network with bioinformatics tools. Aim 2 will also assess whether the use of an anti-metabolite as immunosuppression reduces influenza vaccine immunogenicity. The rationale for focusing on influenza over COVID-19 is that most patients will be vaccinated against the latter when this project begins. However, our CC is well-equipped to test other types of vaccinations when future initiatives are available. In addition to fostering interactions and shared resources within the LT Consortium, the main purpose of the Stanford CC is to improve vaccine designs, adjuvants, and administration protocols in at-risk LT patients through an improved understanding of immune responses. Information gleaned here can inform and improve vaccination eff...