Sputum Proteomics reveals unique signatures linked to key outcomes in cystic fibrosis trials

Abstract

Rationale: Lung function (FEV1) and quality of life (QoL) are key outcomes in most interventional clinical trials conducted in people living with cystic fibrosis. However, no robust pre-clinical surrogates for FEV1 and QoL exist. The precise physiological mechanisms leading to treatment-related improvements in these outcomes are incompletely understood. In this post-hoc analysis we explored the relationship between changes in the sputum proteome and these outcomes with the aim of identifying translational biomarkers. Methods: Paired sputum samples collected during the AZTEC-CF study (NCT02894684) pre and post 14 days of antibiotic treatment for an acute pulmonary exacerbation were included. Samples were analysed using in vitro Mesoscale Discovery (MSD) assays and by nano LC-MS/MS. Peptide identification and quantification was performed and the log-fold change for individual proteins and relationships between protein change and changes in FEV1 and QoL were evaluated. Results: Distinct patterns were found between proteins that correlated with FEV1 and those that correlated with QoL improvements. FEV1 improvement was characterised by increases in bacterially-derived proteins accompanied by decreases in proteins relating to neutrophil degranulation. Conversely, changes in QoL were associated with increases in antiprotease and antioxidant proteins. MSD analysis revealed changes in some neutrophil-associated markers significantly correlated with FEV1 improvements, but no markers significantly correlated with QoL improvements. Conclusions: These results suggest changes in two key CF clinical trial outcomes (FEV1 and QoL) may be underpinned by different physiological mechanisms. Understanding these divergent mechanisms is vital to fortify optimal clinical trial design in CF and panels of biomarkers may be needed to improve translational confidence.