Adult asthma exacerbation and respiratory syncytial virus specific IgE detection in sputa

Abstract

Background: Acute exacerbation in asthmatics has been believed to be closely associated with respiratory viral infections. Considering the possibility of viral antigen sensitization, several studies had tried to detect respiratory syncytial virus (RSV) virus specific IgE from mice models and asthmatics. However, such approaches have not yet been fully established. Materials & Methods: We investigated the respiratory viral detection rate, species, seasonal variation, and sequential dynamics with total 132 induced sputa samples, collected for two years, from lower airway of Korean adult asthmatics (n=60) and controls (n=10) with acutely exacerbated respiratory symptoms. Multiplex reverse trascriptase-polychain reaction (mPCR) for 12 respiratory viral species (adenovirus, rhino A virus, coronavirus OC43 and 229E/NL63, metapneumovirus, influenza A and B virus, parainfluenza viruses 1, 2, 3, and respiratory syncytial virus (RSV) A and B) were performed with those specimens. Then, we selected total 50 sputa samples and, with those specimens, detected specific IgE (in sputa supernatant) to crude RSV whole antigens and its recombinant attachment G protein core fragment (Gcf) by ImmunoCAP system (CAP), and measured Interferon-γ, IL-5, and IL13 by ELISA. Results: Among 132 induced sputum samples, total 15 respiratory viral detections in mPCR were observed in asthma patients and COPD controls (n= 13, and 2, respectively). RSV was the most frequently detected species among these (53%, 8/15). One multiple and two sequential detections were observed in three asthmatics. Among asthmatics, CAP specific IgE to Gcf (Gcf-sIgE) and IL-5 in sputa supernatant were higher in the subjects with RSV detection by mPCR (p<0.05, respectively). RSV-sIgE, Interferon-γ and IL-13 were detected in several subjects but failed to show statistical differences between the groups. In ROC analyses with the CAP measured asthmatics, the best coordinate cutoff of Gcf-sIgE, predicting RSV detection by mPCR, was 0.285 kU/L (AUC 0.73, 95% CI 0.47-0.82; SE 81.3%, SP 65.4%, PPV 59.1%, NPV 85.0%). Conclusions: In this study, RSV was the most frequently detected viral species among the sputa from the exacerbated adult asthmatics. We applied the conventional CAP immunoassay to detecting the specific IgE antibodies to crude RSV whole antigens and its Gcf, using the sputum samples. Gcf-sIgE and IL-5 elevation in the sputa from the adult asthmatics with ever detections of RSV by mPCR, suggests that RSV protein sensitization and Th2 pathway may have roles on RSV associated asthma exacerbations in adults.