Increased T-helper Cell 2 Response in Infants With Respiratory Syncytial Virus Bronchiolitis Hospitalized Outside Epidemic Peak.

ABSTRACT

AIM: To test the hypothesis that the balance of type-1/type-2 immune response differs between infants hospitalized with respiratory syncytial virus (RSV) bronchiolitis during the peak months and those during the nonpeak months. METHODS: We prospectively enrolled 90 unrelated full-term previously healthy infants hospitalized during the first year of life for RSV sole bronchiolitis over 2 epidemics (November 2016 to April 2017 and October 2017 to April 2018). We stratified infants as follows hospitalized during the peak months (n 71) and during the nonpeak months (n 19). The frequencies of CD4+ producing interferon (IFN)-γ and interleukin (IL)-4 and of CD8+ producing IFN-γ T cells were measured by flow cytometry from infant peripheral whole blood. The T-helper cell (Th2) polarization index was calculated as the ratio between CD4+ T cells producing IL-4 and CD4+ T cells producing IFN-γ. RESULTS: Infants hospitalized during nonpeak months were significantly less frequently breast-fed, had a higher eosinophils count, a significantly higher percentage of CD4+ T cells producing IL-4 and higher Th2 polarization index than infants hospitalized during the peak months. CONCLUSIONS: We elucidated the presence of different endotypes in infants with RSV sole bronchiolitis. Previously healthy full-term infants hospitalized during the nonpeak months seem to be more likely those with a possible predisposition to atopy.