Evaluation of nasal levels of interferon and clinical severity of influenza in children

Abstract

BackgroundExperimental data show that type I interferon has a key role in innate immune response against influenza infection. ObjectiveWe compared nasal levels of interferon-α2 and β among inpatients and outpatients with influenza. Study designChildren younger than 5 years of age with influenza-like illness seeking care at the emergency department within the first 72 h of disease onset were prospectively included. Clinical and demographic data and secretions through nasal wash were obtained. Influenza infection was assessed through reverse-transcription polymerase chain reaction and nasal levels of interferon-α2 and β were measured by enzyme-linked immunosorbent assay. All patients followed until the end of the disease. ResultsOne hundred patients were included, of which 24 had confirmed influenza infection, and 5 of them were hospitalized. Subtypes A (H3N2) and B were confirmed in 10 and 14 patients, respectively. Seventy-six patients without influenza, including 48% of outpatients, were recruited as controls. All hospitalized patients were significantly younger regardless of influenza status (age <6 months in 59% vs. 23.2%, p < 0.001). All other data were similar among the groups. Comparing median levels of interferon-α2 among children with influenza, levels were significantly higher in outpatients than in hospitalized patients and were 263.2 pg/mL (25–75 interquartile range: 58.3–634) and detectable in only one patient (90 pg/mL), respectively. The levels of interferon-α2 in controls and those of interferon-β in all groups were not detected. ConclusionsHigher levels of interferon-α2 in patients with less severe influenza reinforce experimental evidence about the protective role of interferon-α2 against influenza infection.