Targeting macrophages to reduce the combined injury effects of radiation and virus exposure

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PROJECT SUMMARY/ABSTRACT: Pneumonitis and fibrosis occur after oncologic lung radiotherapy (RT) or TBI conditioning for BMT. The sustained production of inflammatory cytokines, dysregulated macrophage activation and perpetual ROS generation are considered molecular mediators of these events. SARS-CoV-2- confirmed patients experience lower respiratory tract illness, dyspnea and peripheral fibrosis, along with production of proinflammatory cytokines from recruited immune cells; events that indicate the lungs are susceptible to SARS-CoV-2 infection, with old age and comorbidities also identified as predisposing conditions. Therefore, both high-dose RT and viral infection promote proinflammatory microenvironments in the lung, the recruitment of macrophage populations and cytokine signaling; suggesting a commonality to mechanisms of pulmonary fibrosis that involve a ‘cytokine storm’. In support of this, we reported preliminary data that lung- targeted RT, alone or combined with TBI, increased mortality and fibrosis from influenza virus A (HKx31 (H3N2)) and exacerbated infection risks in radiation-sensitive organs. Since both local microenvironmental alterations and innate immune cell recruitment were implicated, we now hypothesize that lung radiation produces long- term changes in the lung microenvironment that affect immune responses to respiratory viral pathogens. We will investigate the immediate (<24h) mechanistic interactions responsible for long-term lung injury (>26 wks) caused by combined exposures to focal lung RT followed by virus, and vice versa, using 3D precision cut lung slices and mouse models. The overall goal is to develop molecular-based protective/mitigating strategies. Aim 1.1: To investigate how prior lung irradiation of C57BL/6 and C3H mice, and dose-dependent radiation- induced lung injury, affects sensitivity and susceptibility to virus infection using Influenza and murine corona viral strains to model SARS-CoV-2 infection. Also, to investigate how persistent or latent lung injury from the first insult impacts the sensitivity to the second insult by varying the time interval between the two insults. Aim 1.2: To investigate how viral infection and the viral-induced ‘cytokine storm’ alters lung radiosensitivity, and the temporal progression through radiation-induced pneumonitis and fibrosis. Aged mice will also be used to determine how age- and weight-related co-morbidity factors exacerbate the risk for combined pulmonary injury. Aim 1.3: Use human 3D lung slice cultures to investigate how viral infection alters mechanisms of RT-induced DNA DSB repair, and the impact on cell lethality. Aim 2: To determine if mitigating inflammation and/or oxidative stress in the lungs with antioxidants AEOL-10150 and NaI, or preventing the aberrant recruitment and activation of infiltrating macrophages at sites of pulmonary injury by targeting the CD200 receptor, will mitigate risks for combined radiation and viral exposures. These studies will be significant because they model the relationship between radiation damage and viral infectivity in the lung, and offer the potential for molecular-targeted mitigation for RT and combined viral injury.