Sputum alarmin levels delineate distinct T2 cytokine pathways and patient subgroups in asthma

Abstract

ABSTRACTRationaleAsthma is a chronic airway disease driven by multiple immunologic pathways that determine the clinical response to therapy. Current diagnostic methods are incapable of discriminating subtypes of asthma and guiding targeted treatment. We hypothesized that sputum cytokine profiles could help to identify immunologically-defined disease subtypes and individualize therapy in patients with severe asthma.ObjectivesDefine asthma subtypes associated with sputum alarmin and cytokine levels.MethodsCross-sectional analysis of clinical features and sputum from 200 asthmatic patients was performed. 10 cytokines belonging to alarmin, T2, and non-T2 pathways were measured. Pearson correlation was used to identify cytokine modules. Latent class analysis was used to cluster patients by cytokine expression.Measurements and Main ResultsThree modules of highly correlated cytokines were identified including a non-T2 module, the IL-1βmod (IL-1β, IL-6, GCSF), and two distinct T2 modules: TSLPmod (TSLP, IL-4, IL-5, IL-9) and IL-33mod (IL-33, IL-13, IL-21). The TSLPmod was associated with asthma severity, airway obstruction, eosinophilia, and elevated FeNO. Patient clustering revealed three subgroups; two different subgroups showed expression of T2 modules.ConclusionsAnalysis of sputum cytokines revealed three discrete signaling modules in patients with asthma. Unexpectedly, the inclusion of alarmins led to separation of canonical T2 cytokines into two unique modules; IL-5 grouped with TSLP, while IL-13 grouped with IL-33. In addition, patient clustering revealed two distinct endotypes associated with T2 immune signaling. These findings indicate a new layer of immunologic heterogeneity within the T2 paradigm, and suggest that sputum cytokine profiling may hold diagnostic utility for patients with asthma.