Cytokine profiles in the respiratory tract during primary infection with human metapneumovirus, respiratory syncytial virus, or influenza virus in infants

Objectives. We characterized the T helper cytokine profiles in the respiratory tract of infants infected with influenza virus, human metapneumovirus, and respiratory syncytial virus to examine whether these agents elicit similar cytokine responses and whether T helper type 2 polarization is associated with wheezing and severe disease. Methods. A prospective study of infants who were seeking medical help for acute upper and/or lower respiratory tract infection symptoms for the first time and were found to be infected with influenza, human metapneumovirus, or respiratory syncytial virus was performed. Respiratory viruses were detected in nasal secretions with reverse transcriptase-polymerase chain reaction assays. The study was performed in emergency departments and outpatient clinics in Buenos Aires, Argentina. T cell cytokine responses were determined in nasal secretions with immunoassays and reverse transcriptase-polymerase chain reaction assays. Results. Influenza elicited higher levels of interferon-gamma, interleukin- 4, and interleukin-2 than did the other agents. Human metapneumovirus had the lowest interferon-gamma/ interleukin- 4 ratio (T helper type 2 bias). However, no association was found between T helper type 2 bias and overall wheezing or hospitalization rates. Conclusions. These findings show that viral respiratory infections in infants elicit different cytokine responses and that the pathogeneses of these agents should be studied individually.