This study aims to investigate the role of IL-5 in suppressing anti-viral immune responses in bronchial epithelial cells (BECs) and in peripheral blood mononuclear cells (PBMCs) from 5 people with asthma.

IL-5 has been shown to be present in higher levels in those with asthma, more so during viral infection. The investigators know from existing evidence that having increased levels of interferon (IFN) reduces asthma exacerbations and viral load. The investigators suspect that IL-5 reduces the immune response during viral infection in bronchial epithelial cells (BECs) and peripheral blood mononuclear cells (PBMCs) by reducing levels of IFN. The aim is to investigate if increased IL-5 in stable eosinophilic asthma and asthma exacerbations suppresses anti-viral immunity in bronchial epithelial cells and in peripheral blood mononuclear cells directly via IL-5 receptor signalling, suppressing rhinovirus induction of IFNs. The investigators also will evaluate if anti-IL-5 therapies suppress IL-5 concentrations in stable and exacerbated asthma in vivo and whether suppression of IL-5 in vivo restores deficient anti-viral immunity in BECs and PBMCs, thereby protecting against asthma exacerbations.

Must be eligible for the study 'Mechanisms of Adverse Effects of Long-Acting Beta-Agonists in Asthma' (MAELABA) (19SM5101).

Those with mild asthma on as required salbutamol only.