ABSTRAm. In order to determine whether IgE production occurs predominantly at mucosal or systemic sites, we studied the production of respiratory syncytial virus (RSV)-specific antibody in serum and nasopharyngeal secretions (NPS) from 41 patients with RSV infection using an enzyme-linked immunosorbent assay. RSV-IgE was found in higher titer in samples of N P S than in simultaneously obtained serum specimens at all phases of illness. Despite the excess dilution incurred in the collection process, RSVIgE was frequently detected in N P S specimens while it was undetectable in serum. In 20 selected subjects, ratios of RSV antibody in NPS:serum were 2.00 for RSV-IgE, 2.42 for RSV-IgA, and 0.01 for RSV-IgG. Also the geometric mean value of ratios of RSV-1gE:RSV-IgG was 1.74 in N P S and 0.05 in serum, while the geometric mean value of ratios of RSV-1gA:RSV-IgG were 1.85 in N P S and 0.09 in serum. These data suggest that IgE production occurs predominantly at mucosal surfaces. Although the importance of IgE as a mediator of hypersensitivity diseases has been well established, the site of production of this immunoglobulin isotype remains controversial. Investigations of IgE production in the respiratory tract have demonstrated increased ratios of total IgE to albumin in respiratory secre- Vol. 19, No. 5, 1985 Printed in U.S. A. tions in comparison to serum (I) as well as indirect evidence that grass pollen-specific IgE antibody in nasal secretions is produced locally (2). The study of IgE responses to an infectious agent would allow for an evaluation of the kinetics of IgE production at both systemic and mucosal sites following a single exposure to the antigen. Any potential modulating effects on antibody responses from repeated exposure to an antigen such as grass pollen would therefore be avoided.RSV is a common cause of respiratory illness in young infants, and severe forms of illness appear to be mediated, at least in part, by the production of RSV-specific IgE antibody. We undertook the current study of the antibody response in serum and NPS to RSV infection in order to determine whether IgE antibody responses to an infectious agent occur primarily at mucosal or systemic immunocompetent tissue sites. The data suggest that, while RSV infection stimulates a strong antibody response at both sites, IgE antibody to the virus is formed in much greater quantities in the respiratory tract.
MATERIALS AND METHODSPatient population and sample collection. The study population consisted of 4 1 infants less than 1 yr of age either hospitalized due to RSV infection or followed as part of an ongoing study of respiratory illnesses in childhood. At the time of recruitment into the study, the objectives and risks of the study were explained and a signed statement of informed consent was obtained. Patients were classified as having either URI alone, pneumonia, or bronchiolitis on the basis of clinical and radiographic criteria described in previous publications from this laboratory (3). According to these criteria, nine patie...
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