BackgroundRecent studies demonstrated that the triple combination CFTR modulator therapy elexacaftor/tezacaftor/ivacaftor (ETI) improves lung function and reduces pulmonary exacerbations in CF patients with at least oneF508delallele. However, effects of ETI on downstream consequences of CFTR dysfunction,i.e.abnormal viscoelastic properties of airway mucus, chronic airway infection and inflammation have not been studied. The aim of this study was, therefore, to determine the longitudinal effects of ETI on airway mucus rheology, microbiome and inflammation in CF patients with one or twoF508delalleles aged 12 years and older throughout the first 12 months of therapy.MethodsIn this prospective observational study, we assessed sputum rheology, the microbiome, inflammation markers and proteome before and 1, 3 and 12 months after initiation of ETI.ResultsIn total, 79 patients with CF and at least oneF508delallele and 10 healthy controls were enrolled in this study. ETI improved the elastic modulus and viscous modulus of CF sputum at 3 and 12 months after initiation (allp<0.01). Further, ETI decreased the relative abundance ofPseudomonas aeruginosain CF sputum at 3 months and increased the microbiome α-diversity at all timepoints.ETI also reduced IL-8 at 3 months (p<0.05) and free NE activity at all timepoints (allp<0.001), and shifted the CF sputum proteome towards healthy.ConclusionsOur data demonstrate that restoration of CFTR function by ETI improves sputum viscoelastic properties, chronic airway infection and inflammation in CF patients with at least oneF508delallele over the first 12 months of therapy, however, without reaching levels close to healthy.

Background: Airway mucus provides important protective functions in health and abnormal viscoelasticity is a hallmark of muco-obstructive lung diseases such as cystic fibrosis (CF). However, previous studies of sputum macrorheology from healthy individuals and patients with CF using different experimental protocols yielded in part discrepant results and data on a systematic assessment across measurement settings and conditions remain limited.Objectives: The aim of this study was to develop an optimized and reliable protocol for standardized macrorheological measurements of airway mucus model systems and native human sputum from healthy individuals and patients with muco-obstructive lung disease.Methods: Oscillatory rheological shear measurements were performed using bovine submaxillary mucin (BSM) at different concentrations (2% and 10% solids) and sputum samples from healthy controls (n = 10) and patients with CF (n = 10). Viscoelastic properties were determined by amplitude and frequency sweeps at 25°C and 37°C with or without solvent trap using a cone-plate geometry.Results: Under saturated atmosphere, we did not observe any temperature-dependent differences in 2% and 10% BSM macrorheology, whereas in the absence of evaporation control 10% BSM demonstrated a significantly higher viscoelasticity at 37°C. Similarly, during the measurements without evaporation control at 37°C we observed a substantial increase in the storage modulus G′ and the loss modulus G″ of the highly viscoelastic CF sputum but not in the healthy sputum.Conclusion: Our data show systematically higher viscoelasticity of CF compared to healthy sputum at 25°C and 37°C. For measurements at the higher temperature using a solvent trap to prevent evaporation is essential for macrorheological analysis of mucus model systems and native human sputum. Another interesting finding is that the viscoelastic properties are not much sensitive to the applied experimental deformation and yield robust results despite their delicate consistency. The optimized protocol resulting from this work will facilitate standardized quantitative assessment of abnormalities in viscoelastic properties of airway mucus and response to muco-active therapies in patients with CF and other muco-obstructive lung diseases.