Nasal IL-15 Levels Are Similar Between Asthmatics and Controls During Asthma Exacerbations and Viral Upper Respiratory Infections

Eighty percent of children with asthma exacerbations will have an associated viral infection. Asthmatics with low IL-15 levels have been shown to have higher symptoms during experimental rhinovirus challenge. We evaluated nasal filter paper from children during asthma exacerbations and compared them to the acute symptoms experienced by the children to find correlations. Further, we correlated IL-15 levels with acute symptoms in the asthma group. We recruited 83 patients (exacerbating asthma, n = 58; controls, n= 25) ages 4-18 years with upper respiratory infection symptoms from the Emergency Department. Baseline Pediatric Respiratory Symptoms (PRS) Scores were recorded. Nasopharyngeal swabs were used to detect the presence of respiratory viruses by viral genome sequencing. Nasal filter paper was used to collect nasal mucosal lining fluid, and, after elution, inflammatory mediators were analyzed using bead-array immunoassays. IL-15 levels were found to be higher in all patients with viral infections than those without (Median= 5.50pg/mL and 2.88pg/mL, respectively; p<0.05). IL-15 levels were similar between subjects with viral-induced asthma exacerbations and controls with viral-induced cold symptoms (p=NS). In the asthma subjects, there was some positive correlation between IL-15 levels and acute symptoms by PRS (R2=0.08, p<0.05). Despite previous reports of IL-15 deficiency in asthmatics, we confirm similar IL-15 responses in exacerbating asthmatics and controls. Furthermore, in a cross-sectional study, we found that asthmatics with higher IL-15 levels have more acute respiratory symptoms.