Cell-mediated immune response to respiratory syncytial virus infection: relationship to the development of reactive airway disease.

The possibility that cell-mediated immunity might play a role in the pathogenesis of infection with respiratory syncytial virus was evaluated in a study of 39 infants. Infection with RSV was confirmed by identification of virus in nasopharyngeal secretions using immunofluorescence, and by tissue culture infectivity. CMI, as determined by a whole blood lymphocyte transformation technique, was evaluated in samples taken 0 to 10 and 20 to 60 days after the onset of illness. Patients diagnosed as having RSV-induced bronchiolitis or recurrence of asthma had evidence of significantly (P less than 0.01) higher degree of CMI in the 0 to 10-day period than patients with RSV pneumonia or upper respiratory illness. Higher CMI activity in the 20 to 60-day period was also seen in patients with more severe illness, with moderate-to-severe degree of hypoxia. A positive correlation was observed between the degree of LTF activity in samples taken 20 to 60 days after the onset of illness ard subsequent episodes of wheezing. Eleven patients had one or more episodes of wheezing in the first six months after RSV infection. LTF activity in samples taken during the 20 to 60-day period from these patients was significantly higher (P less than 0.02) than LTF activity in corresponding samples from six patients who were free of wheezing in the six months after RSV infection. The results suggest that alterations of RSV-specific cell-mediated immune mechanisms may result in an increased tendency toward airway reactivity on primary and subsequent exposure to RSV and possibly to other agents.