Infection with HRV-C during acute asthma in adults is associated with increased sputum neutrophils and self-reported severity of symptoms

Introduction: Human rhinovirus C (HRV-C) causes increased asthma exacerbation severity compared to species A and B in children. The role of HRV-C in acute asthma in adults remains unclear. Aim: To determine whether HRV-C induces an excessive inflammatory response and increased severity of symptoms in acute asthma. Methods: Adult asthmatics were prospectively recruited on presentation to hospital with exacerbation. Samples were collected within 24 hours of admission. HRV 59 non-coding region were sequenced for HRV typing. Analyses were adjusted for age, gender, smoking, ICS use and bacterial infection. Results: Patients (n=47) were 16-45 years and 70% were females. HRV was detected in 43% (n=16) with 10 HRV-A and 6 HRV-C. Sputum total cell count was elevated in patients with HRV-C (1.83 x 10 9 cells/L, 95% CI 0.53-6.37, p=0.036) compared to all other patients (0.40 x 10 9 , 95% CI 0.24-0.64), driven mainly by increased neutrophils (1.05 x 10 9 cells/L, 95% CI 0.13-8.76, p=0.026 vs. 0.15 x 10 9 , 95% CI 0.08-0.28). Mean % neutrophils were 73.7 with HRV-C vs. 51.1 in the others (p=0.046). Levels of eosinophils were not different between the groups. No change was observed in patients with HRV-A. Patient reported exacerbation severity was higher with HRV-C (8.67 95% CI 7.64-9.70, p=0.046 vs. 6.01, 95% CI 5.05-7.15). When cases of bacterial infection were excluded, the conclusions remain the same. Conclusion: HRV-C, but not HRV-A, seems to amplify the inflammatory response of the lower airways during an asthma exacerbation, promoting neutrophil recruitment and aggravating symptoms. Larger studies are needed to confirm this and elucidate the underlying pathways.