Aspergillus fumigatus and the human response to infection - the role of the bronchial epithelium Gemma Elizabeth Hayes, The University of Manchester, Doctor of Philosophy, January 2017 Background: A. fumigatus is an important human pathogen with disease manifestations being entirely dependent on the underlying state of the host immune system. Inhalation of A. fumigatus conidia forms the major route of infection and the bronchial epithelium forms the primary barrier to initial infection. However a paucity of data exists surrounding epithelial response in the presence of A. fumigatus, although recent evidence suggests it is more than a passive bystander. The contribution of genetic mutations and subtle immune deficiency to the pathogenesis of the most common forms of aspergillosis, severe asthma with fungal sensitisation (SAFS), allergic bronchopulmonary aspergillosis (ABPA) and chronic pulmonary aspergillosis (CPA) are also poorly defined. Aim: This thesis explores these areas using a variety of techniques to address three key hypotheses: 1.The bronchial epithelium mounts an inflammatory response to the presence of inhaled conidia over the first 12 hours of infection. 2.The tyrosine kinase Fer, mutated in some individuals with asthma, is involved in the response of the healthy bronchial epithelium to A. fumigatus 3.Patients with CPA with deficiencies in the IL12-IFN gamma axis display a specific disease phenotype and benefit from replacement IFN gamma Results: A combination of RNASeq analysis, computer modelling, flow cytometry and ELISA suggest that the bronchial epithelium mounts a permissive, perhaps phagocytic, transcriptional response; raising the possibility of the development of unchecked latent reservoirs of bronchial infection within the bronchial epithelium in early infection. There is no evidence of a transcriptional or secretory inflammatory epithelial response. Transcriptional and translational evaluation of Fer, using qRT-PCR and Western Blot, demonstrates the presence of Fer in multiple cell types, including bronchial and alveolar lung cell lines, and reduced expression in the presence of serum. No changes in the quantity or phosphorylation state of Fer were demonstrated over the first 12 hours of infection, or in the face of escalating conidial dose. Preliminary data also suggests that Fer may be secreted into the extracellular environment. Retrospective cohort analysis of 41 patients treated with IFN gamma demonstrates that replacement therapy is tolerated and may be a useful adjunctive therapy in patients with deficiencies in the IL12-IFN gamma axis. However no specific patient phenotype most associated with response could be identified, and multiple areas for future research were highlighted. Conclusion: This is the first description of the transcriptional response of the bronchial epithelium to A. fumigatus over 12 hours and the first significant exploration of Fer within the respiratory epithelium. In terms of therapy the demonstration of possible benefit from IFN gamma therapy paves the way for further studies and highlights the need for greater research into assessment of the underlying disease phenotype in CPA. Overall important areas for further research have been highlighted and effective assays developed to facilitate this.