Impact of Community Respiratory Viral Infections in Urban Children With Asthma

Abstract

To prospectively evaluate the influence of viral infection on respiratory symptoms, lung function, and nasal cytokines in children with asthma living in an urban environment.The study included 53 children with asthma living in Detroit, Michigan.Subjects were recruited with a screening questionnaire distributed through a community-based research partnership. Subjects participated in 4 2-week surveillance assessments, corresponding with fall, winter, spring, and summer seasons over the course of 1 year. During each 2-week surveillance period, spirometry, fraction of exhaled nitric oxide, symptom reports, and nasal lavage samples were obtained on 3 separate occasions. Respiratory symptoms were measured by using a previously published respiratory symptom score. “Sick periods” were defined when symptom scores were >2, and an additional assessment with previously stated measurements was completed over the 1-week sick period. Subjects were contacted weekly via telephone to monitor for illnesses and initiate sick period assessments. Nasal lavage samples were analyzed for the following: presence of respiratory viral nucleic acid, rhinovirus typing and viral copy numbers, and messenger RNA and protein expression analysis of select biomarkers previously shown to be elevated in rhinovirus infection.The investigators enrolled 53 subjects, who were predominantly African American, elementary school–aged, and had high prevalence of home smoke exposure. Approximately 75% of subjects had mild intermittent or mild persistent asthma. Six hundred fifty-eight nasal aspirates were obtained. Of the samples, 22.9% of surveillance samples and 33.7% of respiratory illness samples were virus positive, with rhinovirus accounting for 48.9% of infections. Comparing the presence of respiratory virus with high- and low-symptom illnesses, children with severe colds (symptom scores >5) had signs of airway inflammation on spirometry with a statistically significant decrease of ∼10% of predicted forced expiratory flow at 25% to 75% of pulmonary volume as well as higher biomarker elevations in both nasal messenger RNA of CXCL-10 and protein expression of CXCL8, CXCL10, CCL-2, and CCL-4 when compared with virus-negative asymptomatic conditions. Mild virus-positive colds (symptoms scores 1–4) and asymptomatic infections showed normal airway function by spirometry and fewer biomarker elevations. Viral-negative coldlike illnesses had increased nitric oxide with otherwise normal spirometry.Urban children with asthma have reduced forced expiratory flow at 25% to 75% of pulmonary volume and higher elevations of nasal biomarkers during high-symptom respiratory infections compared with low-symptom infections or symptomatic virus-negative illnesses.Researchers in this study prospectively evaluate the effect of viral infections on respiratory symptoms and lung function in urban children with asthma. High-symptom colds were associated with decreases in small airway function compared with lower-symptom illnesses. Interestingly, the nasal biomarkers elevated during symptomatic viral infections were related to neutrophil recruitment and not eosinophil or allergic response. Also, many upper respiratory tract illnesses in the study were virus negative, suggesting other triggers for symptoms.