Severe Asthma Exacerbations and Mepolizumab Treatment

Longitudinal, observational study to evaluate the infective etiology and the inflammatory profile of asthma exacerbations in severe asthmatic patients treated (as part of routine medical care) with the humanized monoclonal antibody against interleukin-5 Mepolizumab. The participants receive Mepolizumab as part of routine medical care (see inclusion criteria). The study will assess the effect of the intervention (Mepolizumab) on airway microbial compositions and on airway/systemic inflammation at exacerbation and at stable state. The patients will be evaluated at baseline (the day of Mepolizumab initiation, before Mepolizumab administration - V0), at 1 month after Mepolizumab initiation (treatment visit - V1), at exacerbation (exacerbation visit - V2) and at 3 months after the exacerbation event (convalescence visit - V3) up to 12-month study period (Table 1). To perform the convalescence visit, a 3-month extension of the study period will be applied if the exacerbation occurs from month 9 to month 12 from the initiation of Mepolizumab. Recurrent exacerbation events will be evaluated separately when a paired-3-month convalescence visit can be performed within the study period. The patients will contact the center/researchers in case of worsening of the respiratory symptoms to schedule the exacerbation visit. The visit will be performed within 7 days from the beginning of the deterioration of the symptoms. At each visit, the following procedures will be performed in all the patients: 1) Clinical/pharmacological assessment (including assessment of asthma control; and measurements of central and peripheral fractional exhaled nitric oxide); 2) lung function tests (including lung volumes evaluation and small airway functional assessment by impulse oscillometry - IOS); 3) blood and sputum differential inflammatory cell counts; 4) sputum samples for microbiological assays (conventional sputum cultures and Multiplex Real Time PCR for virus and bacterial detection); 5) blood and sputum samples for cytokine profiling. In a representative subgroup of patients (n=30) breath condensate, blood and sputum samples will be performed for: 1) airway microbiome (16S ribosomal RNA Sequencing) evaluation; 2) blood innate immune responses; 3) transcriptomics and proteomics of sputum inflammatory cells; 4) breathomics. The study has been submitted for approval to the ethics committee, and informed written consent will be obtained from each enrolled subject.