BACKGROUND: Elevated concentrations of eosinophil cationic protein (ECP)have been found in acute viral wheezing during infancy. Furthermore, RSV infection has been suggestedto stimulate type-2 cytokine responses. The aim of this study was to test whether serum ECP and solubleCD23 levels, which are markers of eosinophil and IgE responses, respectively, are elevated in infantshospitalized for acute respiratory syncytial virus (RSV) bronchiolitis. MATERIAL/METHODS: Fifty-fiveinfants aged 1-12 months (median: 4.2 months) consecutively hospitalized for acute bronchiolitis weredivided into two groups: RSV-positive (n=26) and RSV-negative patients (n=29). Serum ECP (s-ECP), solubleCD23 (sCD23), and total IgE were measured in all patients and in 23 asymptomatic infants (controls).RESULTS: Lower s-ECP levels were detected in the RSV-positive group (5.4+/-4.3 ng/dl) compared with controls(9.38+/-5.95 ng/dl, p=0.02), but they did not differ significantly from the values of RSV-negative patients(7.8+/-5.7 ng/dl). There was a trend to higher s-ECP values in patients with a positive family historyof atopy and/or a history of atopic dermatitis in the RSV-positive group (p=0.06). No differences insCD23 and total IgE levels among the groups were detected. No correlation between total IgE and sCD23values was observed. CONCLUSIONS: There is no evidence from our data to suggest that either RSV-positiveor RSV-negative acute bronchiolitis is associated with significant eosinophil-mediated degranulation.There is no evidence from the sCD23 data to support the hypothesis that IgE antibody responses are prominentduring the acute illness.

Keywords: Bronchiolitis, Viral - virology, Eosinophil Cationic Protein - blood, Receptors, IgE - blood, Respiratory Syncytial Virus Infections - virology