Defining Molecular Phenotypes of Exacerbation Prone Asthmatics

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Viral exacerbations of asthma are responsible for 1.8 million emergency room visits and 0.4 million hospitalizations in the US each year, constituting a major public health problem and economic burden. Human rhinoviruses (HRVs) are the dominant instigators of asthma exacerbations in children and adults, but the mechanisms by which these viruses cause exacerbations are poorly understood. This application seeks to use new approaches to identify pediatric patients who are likely to progress to exacerbation with HRV infection, and develop new agents to prevent exacerbations. In these studies we will compare 100 exacerbation-prone asthmatic children with several control cohorts and follow them longitudinally. For each subject we will sample their “environmental exposure cloud” using personal exposure monitors (Project 1). We will determine how the exposure cloud influences exacerbations and identify the constituents that produce exacerbations with the highest frequency. Subjects will have their nasal epithelium sampled for determining their transcriptomic profiles (Project 2). Nasal epithelial cells will also be grown in air-liquid interface cultures and the transcriptome will be analyzed after IL-13, tobacco smoke and HRV challenge. In parallel, we will examine the epigenetic landscape of the CD4+ T cells from each subject and determine how molecular programming regulates the immune activity contributing to exacerbation-prone asthma (Project 3). We will also probe for crosstalk between epithelial cells and CD4+ T cells by testing if the epithelial cells produce factors that alter the epigenetics of the lymphocytes. The analyses of epithelial cells and CD4+T cells will be examined in the context of environmental exposures and clinical outcomes. In project 4 we will examine the activity of pulmonary surfactant protein A (SP-A) and the surfactant lipids, palmitoyl-oleoyl-phosphatidylglycerol (POPG) and phosphatidylinositol (PI) as inhibitors of HRV infections using patient epithelial cells in culture. The effects of surfactant components and HRV upon the epithelial transcriptome will be investigated to identify mechanisms by which inhibitors affect host cell transcription patterns. We will also determine if the inhibitors regulate the production of epithelial factors that modulate CD4+ T cell pro-asthmatic activity. Experiments with PI and its structural analogs, and HRV, will be conducted in mice to test their in vivo anti-viral activity. Additional mouse studies will use a house dust mite immunogen and HRV1B infection as a model for asthma exacerbations. The efficacy of phospholipids as suppressors of asthma exacerbations will be critically tested using the mouse model. From these studies we expect to identify important environmental promoters of asthma exacerbation that work in combination with HRV. We also expect to identify epithelial transcriptomic signatures and CD4+ T cell transcriptomic signatures and epigenetic landmarks that will be highly predictive of asthma exacerbations. Our studies with surfactant constituents will provide us with information about the utility of these molecules as preventives and therapeutics for HRV induced asthma exacerbations.