Neonatal Oxygen and Susceptibility to Respiratory Viral Infections

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ABSTRACT Bronchopulmonary dysplasia (BPD) is a chronic lung disease seen in premature infants requiring oxygen supplementation and ventilation. Although the use of exogenous surfactant and mild ventilation strategies has reduced mortality, infants who leave the hospital continue to exhibit reduced lung function even as adolescents. They are also more likely to develop asthma, be sensitive to second hand cigarette smoke, and be re-hospitalized when infected with respiratory viruses. Since these findings suggest BPD never fully repairs, there is an urgent need to understand how oxygen supplementation permanently disrupts lung development and how these changes enhance susceptibility to respiratory insults. To address this need, we developed a mouse model to understand how short-term oxygen exposure disrupts lung development and alters the response to influenza A virus infection, a common respiratory virus often encountered by age 2 in humans. Like children born prematurely, adult mice exposed to high oxygen (hyperoxia) as newborns had altered lung compliance that was attributed to increased alveolar simplification and disrupted epithelial cell differentiation. When infected with influenza A virus, these mice showed persistent inflammation, altered T cell responses, fibrosis, and increased mortality compared to infected mice that had been exposed to room air at birth. Because viral clearance was also delayed, we hypothesize that high oxygen supplementation to the developing lung increases susceptibility to infection by disrupting the host's ability to effectively clear respiratory viruses. Preliminary studies have identified three possible mechanisms by which changes in respiratory epithelial development could affect innate and adaptive immune responses to viral infection. While investigating these mechanisms in mice, viral clearance and ability to mobilize an appropriate immune response will be investigated in children born prematurely that received high oxygen supplementation. By integrating research findings in mice and humans, we hope to ultimately identify novel therapeutic opportunities for improving the health of children born prematurely.