High serum granulocyte-colony stimulating factor characterises neutrophilic COPD exacerbations associated with dysbiosis.

introductionCOPD exacerbations are heterogeneous and can be triggered by bacterial, viral, or noninfectious insults. Exacerbations are also heterogeneous in neutrophilic or eosinophilic inflammatory responses. A noninvasive peripheral biomarker of COPD exacerbations characterised by bacterial/neutrophilic inflammation is lacking. Granulocyte-colony stimulating factor (G-CSF) is a key cytokine elevated during bacterial infection and mediates survival, proliferation, differentiation and function of neutrophils.

objectiveWe hypothesised that high peripheral G-CSF would be indicative of COPD exacerbations with a neutrophilic and bacterial phenotype associated with microbial dysbiosis.

methodsSerum G-CSF was measured during hospitalised exacerbation (day 0 or D0) and after 30 days of recovery (Day30 or D30) in 37 subjects. In a second cohort, serum and sputum cytokines were measured in 59 COPD patients during stable disease, at exacerbation, and at 2-weeks and 6-weeks following exacerbation.

resultsSerum G-CSF was increased during exacerbation in a subset of patients. These exacerbations were enriched for bacterial but not viral or type-2 biologies. The median serum G-CSF level was 1.6-fold higher in bacterial exacerbation compared to nonbacterial exacerbation (22 pg·mL

conclusionsHigh serum G-CSF enriches for COPD exacerbations characterised by neutrophilic inflammation with underlying bacterial dysbiosis.