Increased lymphoid MxA expression in acute asthma exacerbation in children

Background: Although the association between acute asthma exacerbation and viral infection has been well documented, virus identification rates vary. It has recently been reported that the expression of MxA protein in lymphoc ytes, inducible by type I interferons, can serve as a sensitive marker for viral infection in the host. The objective was to determine the contributio n of viral infection to precipitation of asthma attacks in children. Methods: We studied 186 asthmatic children, aged 0-12 years, over a 1-year period to evaluate MxA protein levels in peripheral blood lymphocytes by us ing a flow cytometric analysis in whole blood. Results: Of all the subjects, 80 (47%) exhibited significantly elevated lev els of MxA expression in lymphocytes, presumably indicating the states of v iral infection. The association of viral infections with acute asthma exace rbation seemed to be marked in younger children: enhanced MxA expression wa s seen in 73.3% of infants (aged 0-1 year), 49.5% of toddlers (aged 2-5 yea rs), and 26% of schoolchildren (aged 6-12 years). Seasonal changes in the f requency of viral infection associated with deterioration were also observe d. Conclusions: Flow cytometric assay of MxA protein expression in whole blood appears to be an easy and useful method to evaluate viral infections in ac ute asthma exacerbation.