Cytokine response after severe respiratory syncytial virus bronchiolitis in early life

Background: Immune response after viral infection usually involves T(H)1-mediated response; however, severe respiratory syncytial virus (RSV) infection appears to be associated with the development of asthma, a T(H)2-predominant phenotype. Objective: To understand the early and subsequent immunologic response to a serious RSV infection in children over time. Methods: A total of 206 previously healthy infants hospitalized with severe RSV bronchiolitis were enrolled in a prospective cohort called the RSV Bronchiolitis in Early Life study. Peripheral blood T cells were obtained immediately after RSV infection and at 2, 4, and 6 years of age, stimulated with phorbol 12-myristate 13-acetate and ionomycin, and analyzed for IL-2, IL-4, IL-13, and IFN-gamma by flow cytometry and real-time PCR. Results: Of the children, 48% (n = 97) developed asthma (physician-diagnosed), and 48% (n = 97) had eczema by age 6 years; 32% (n = 48 of 150) developed allergic sensitization by 3 years of age. Children with asthma had lower IL-13 expression at 6 years of age than those without (P = .001). IFN-gamma, IL-2, and IL-4 levels did not differ by asthma or eczema status during follow-up (all P > .05). Allergic sensitization was not associated with differences in cytokine levels during follow-up (all P > .05). Conclusion: Severe RSV infection early in life is associated with a high incidence of asthma and eczema. Contrary to expectations, subsequent immunologic development in those who developed asthma, eczema, or allergic sensitization was not associated with a T(H)2 phenotype in the peripheral blood.