Detection of IgA and IgG but not IgE antibody to respiratory syncytial virus in nasal washes and sera from infants with wheezing.

BACKGROUND AND OBJECTIVE: The capacity of respiratory syncytial virus (RSV) to stimulate an IgE antibody response and enhance the development of atopy and asthma remains controversial. Nasal washes and sera from 40 infants (20 with wheezing, 9 with rhinitis, and 11 without respiratory tract symptoms) were obtained to measure IgE, IgA, and IgG antibody to the immunodominant, F and G, virion proteins from RSV. STUDY DESIGN: Children (aged 6 weeks to 2 years) were enrolled in the emergency department during the mid-winter months and seen at follow-up when they were asymptomatic. All nasal washes were tested for RSV antigen. Determinations of antibody isotypes (IgE, IgA, and IgG) to RSV antigens were done in nasal washes and sera by using an enzyme-linked immunosorbent assay. In a subset of nasal washes, IgE to RSV was also evaluated by using a monoclonal anti-F(c)E antibody-based assay. RESULTS: Fifteen patients with wheezing, two with rhinitis, and one control subject tested positive for RSV antigen at enrollment. Thirteen patients with wheezing were <6 months old, and most (77%) were experiencing their first attack. Among the children with positive test results for RSV antigen, an increase in both nasal wash and serum IgA antibody to RSV-F(a) and G(a) was observed at the follow-up visit. However, there was no evidence for an IgE antibody response to either antigen. CONCLUSION: Both IgA and IgG antibodies to the immunodominant RSV-F(a) and G(a) antigens were readily detected in the nasal washes and sera from patients in this study. We were unable to demonstrate specific IgE antibody to these antigens and conclude that the production of IgE as a manifestation of a T(H)2 lymphocyte response to RSV is unlikely.

Eosinophil cationic protein in serum and nasal washes from wheezing infants and children.

OBJECTIVE: To compare eosinophil counts and concentrations of eosinophil cationic protein (ECP) in serum and nasal wash fluid from wheezing infants and children with those from age-matched children without respiratory tract symptoms. DESIGN: A case-control study of 71 children treated for wheezing and 59 control subjects in the University of Virginia Pediatric Emergency Department. The patients ranged from 2 months to 16 years of age. Eosinophil numbers and ECP concentrations were assessed in serum and nasal washes. Total serum IgE was measured and the radioallergosorbent test was used to measure IgE antibody to common inhalant allergens. RESULTS: Among children less than the age of 2 years, markedly elevated levels of ECP (> 200 ng/ml) were measured in nasal washes from 9 (41%) of 22 wheezing patients and 1 (6%) of 17 control subjects (p < 0.03). None of these children had a positive radioallergosorbent test result for IgE antibody to common aeroallergens or a nasal smear containing 10% eosinophils. Few of the wheezing children under 2 years of age had either increased concentrations of total IgE or ECP in their serum or an elevated total blood eosinophil count. After the age of 2 years, the percentage of patients with nasal ECP levels greater than 200 ng/ml was also significantly higher in wheezing children than in control subjects (p < 0.001), and a positive correlation was observed between ECP concentrations in their nasal washes and other eosinophil responses (total blood eosinophil counts, serum ECP levels, and nasal eosinophil counts). CONCLUSION: Increased concentrations of ECP were detected in nasal washes from wheezing infants and children, indicating that eosinophils may contribute to the pathogenesis of airway inflammation in some children who wheeze early in life.