PROJECT SUMMARY Wildfire smoke increasingly contributes to ambient air pollution and more specifically PM2.5 and has been associated with increased respiratory virus morbidity and mortality. We have previously shown that exposure of human volunteers to woodsmoke (WS) significantly modifies acute antiviral host defense responses to influenza. Similarly, we have preliminary evidence indicating that simulation of wildfire smoke affects viral infections in human nasal epithelial cells (HNECs) in vitro. Since concurrent exposures to wildfires and respiratory viruses will likely increase worldwide due to climate change, understanding the clinical manifestation, cellular mechanisms, and chemical components causing modified antiviral defense presents an important research gap critical to public health. We have already demonstrated that computational modeling approaches can establish the presence of harmful chemicals in different wildfire smoke conditions as drivers of toxicity. Integrating these translational research and computational analysis models, the central hypothesis of this proposal is that wildfire smoke affects multiple steps of antiviral defense pathways in the respiratory mucosa and that chemical signatures within the complex pollutant mixtures can be associated as drivers of biological responses. Specific Aim 1 will use in vitro exposure and infection of HNECs to determine the mechanisms of wildfire smoke-induced changes in antiviral defense function and identify the chemical signatures mediating these responses. HNECs will be exposed to a variety of different emission mixtures simulating different wildfire scenarios. Changes in viral infection and multi-omic assessment of immune and inflammatory responses will be assessed. Using computational modeling, chemical and molecular signatures driving the responses in HNECs in vitro will be determined. Specific Aim 2 will determine the effects of WS exposures and influenza infection on nasal immunity in humans in vivo, using inoculation with the live attenuated influenza virus (LAIV) vaccine as a model to elicit antiviral defense responses in the respiratory mucosa. Volunteers will be randomized for exposures to WS/Filtered Air followed by inoculation with LAIV/Placebo. Using multi-omic platforms, samples will be analyzed for immune biomarkers, as well as markers of viral replication and sinonasal symptoms, followed by computational analysis associating biomarkers with infection outcomes. This application aims to comprehensively assess the impact of wildfires on respiratory mucosal antiviral defenses by examining viral entry and replication, antibody production, as well as mucosal metabolomics, transcriptomics, and proteomics mediating cellular defenses. The parallel investigations of in vitro (SA1) and clinical (SA2) outcomes will yield both immediate translational impact and in-depth mechanistic insights into the effects of wildfires on respiratory antiviral defenses. Ultimately, this applicatio...