T4 The respiratory mycobiome is perturbed during viral infection in COPD and drives type 2 immunopathology and exacerbation severity

<h3>Introduction</h3> The existence of resident fungal communities (‘mycobiome’) within the lungs has only recently been discovered, and their role in health and disease remains unknown. Mycobiota are altered in chronic obstructive pulmonary disease (COPD), but the consequences of these perturbations have not been characterised. Given that fungi can promote type 2 inflammation and mucus hypersecretion, features of COPD that are augmented during exacerbations, we hypothesised that the mycobiome could be a key determinant of exacerbation pathogenesis. <h3>Methods</h3> We quantified total sputum fungal burden by qPCR at baseline and during infection in separate cohorts of experimentally induced and naturally occurring viral exacerbations of COPD. Fungal burden was correlated with measures of immunopathology and clinical exacerbation severity. Subsequently, we modelled fungal dysbiosis in mice through administration of low dose <i>Aspergillus Fumigatus</i> (a major constituent of the COPD airway mycobiome) prior to infection with rhinovirus A1 to investigate effects upon pulmonary immune responses. <h3>Results</h3> Individuals with COPD across the two studies (n=52) had increased sputum fungal burden compared to healthy control subjects (n=19) at stable state (figure 1A). Experimental rhinovirus infection led to increased sputum fungal loads from baseline in COPD subjects but not healthy controls with significant differences between these groups at day 9 and 12 post-infection (figure 1B). Similarly, sputum fungal burden increased during virus-associated naturally occurring exacerbations (figure 1C). During experimental challenge, sputum fungal loads positively correlated with viral loads, type 2 inflammatory responses including eotaxin 1/3, IL-4, IL-5 and Muc5ac (figure 1D) and clinical exacerbation severity (lower respiratory tract symptom scores) (figure 1D). In mice, administration of low dose <i>Aspergillus</i> to model airway fungal dysbiosis enhanced rhinovirus replication at 24 hours post-infection. <i>Aspergillus</i> administration also elevated recruitment of lung neutrophils, eosinophils and induction of IL-13 and Muc5ac proteins by rhinovirus (all P&lt;0.05). <h3>Conclusion</h3> The airway mycobiome is altered in COPD and further perturbed by respiratory viral infections. Mycobiota may be an important driver of type 2 immunopathology and severity during virus-induced COPD exacerbations. Our ongoing profiling of fungal community composition within these studies will shed further light on the key mycobiota that may be amenable to future therapeutic targeting.