Local interferon-gamma levels during respiratory syncytial virus lower respiratory tract infection are associated with disease severity

To investigate the role of cell-mediated immunity during respiratory syncyt ial virus (RSV) infection, interferon (IFN)-gamma and interleukin (IL)-10 l evels in nasopharyngeal secretions were measured in infants with lower resp iratory tract infection (LRTI) caused by RSV. A novel technique was used to measure in vivo cytokine levels in nasopharyngeal aspirates (NPAs). Cytoki ne levels in the NPAs of 17 mechanically ventilated infants and 43 nonventi lated hospitalized infants were compared. As expected, mechanically ventila ted infants were significantly younger than nonventilated infants (7 vs. 14 weeks). IFN-gamma levels were above the limit of detection in the NPAs of 3 (18%) mechanically ventilated infants and in the NPAs of 26 (60%) nonvent ilated infants. IL-10 levels in the NPAs of mechanically ventilated and non ventilated infants were comparable. It is hypothesized that maturation-rela ted mechanisms have a key role in the development of RSV LRTI that results in mechanical ventilation.