Associação dos níveis de interferon com a gravidade da infecção por influenza em pacientes pediátricos

Abstract

Background/Aim: According to experimental data, interferon type I has a key role in innate immune response against influenza infection. Studies on humans are still scarce and the characterization of interferon response in children may help to identify patients at risk. Our aim is to compare respiratory levels of interferon-α and influenza disease severity in pediatric patients. Methods: Children aged less than five years of age with influenza-like illness seeking pediatric care within the first 72 hours of disease onset were prospectively included. Clinical and demographic data and respiratory secretions through nasal wash were obtained. Influenza infection was confirmed with Reverse-Transcription Polymerase Chain Reaction and respiratory levels of interferon-α were measured by ELISA. Enrolled individuals were followed until the end of disease. Patients whose influenza infection was excluded were used as control group. Results: Twenty four patients with confirmed influenza infection were included, five of them requiring hospitalization. Subtypes A(H3N2) and B were confirmed in ten and fourteen patients, respectively. Seventy-six patients without influenza, 39 of them hospitalized, were included as controls. Age younger than 6 months was significantly more frequent in individuals from both hospitalized groups compared to outpatients (59% vs 23.2%, p<0.01). All other clinical and demographical data were similar among groups. Median levels of interferon-α were significantly higher in outpatients with influenza than both inpatients with influenza and patient without influenza, hospitalized or not (p<0.001). Median in pg/ml (interquartile amplitude) were 263.2 (58.3-634), 0 (0-49), 0 (0-2.6) and 0 (0-19.4) in four groups above, respectively. Conclusion: Lower levels of interferon-α in patients with more severe influenza reinforce experimental evidence about its protective role in influenza infection severity.