PROJECT SUMMARY/ABSTRACT Prematurity affects one in nine live births in the US and is a well-described risk factor for more severe and recurrent respiratory infection during infancy and development of asthma. While it is clear that gestational age at birth and age at infection influence severity of respiratory infection, host immunologic response, and risk of long-term impact on lung development and function, our understanding of the mechanism driving these associations remains poorly understand. Limited human infant autopsy studies have revealed aberrations in the development and function of the airway epithelium, which serves as the first line barrier of defense against inhaled pathogens. Models of newborn airway epithelium to study why premature babies are at higher risk of infection and long-term ramifications, such as asthma, are lacking. We have developed a method of isolating airway basal cells from respiratory secretions of newborns born prematurely and at term. These cells can be expanded long-term and retain the ability to differentiate into pseudo-stratified airway epithelium making them a powerful system to model pre-term and full-term airways. In preliminary experiments, cilia differentiated from basal cells isolated from premature newborns are longer, beat slower, are less dense, and have decreased linear mucociliary flow compared to full-term infant controls. We also found that developmental and immunity related gene expression pathways are differentially expressed in pre-term basal cells. Using our innovative method of isolating and growing epithelial cells derived from patient-specific basal cells we will study how prematurity alters airway epithelium function. We will define the airway basal cell defect due to prematurity by phenotyping pre- and full-term basal cells. Basal cells lines from pre- and full-term infants will be differentiated in air-liquid interface culture and their differentiation potential, epithelial and cilliary function will be comprehensively evaluated. We will also study how prematurity impacts the inflammatory response of differentiated basal cells following RSV infection. Finally, gene co-expression networks and chromatin accessibility will be used to identify the molecular signature associated with the basal cell prematurity defect related to differentiation and RSV-infection response. The successful execution of these aims will establish patient-specific derived airway basal cells as a practical and biologically relevant model system. In addition, our results will provide a better understanding of the molecular mechanisms linking prematurity and early life RSV infection with longer-term morbidities such as asthma, which are important for improving prevention and treatment strategies.