Lack of induction by rhinoviruses of systemic type I interferon productionor enhanced MxA protein expression during the common cold

To study whether MxA protein expression is systemically upregulated during rhinovirus infection, blood specimens were collected from 40 patients with common cold and MxA expression in mononuclear cells analyzed by flow cytome try, None of the patients with a confirmed rhinovirus infection (n =15) or with an infection of unknown etiology (n = 20) had elevated expression of t he MxA protein (median fluorescence intensity, 549 and 582, respectively) w hen compared to healthy controls (n = 11, median 590). Patients with influe nza infections had significantly elevated values (n = 5, median 750), and i nterferon could be detected only in serum samples from influenza patients. In conclusion, expression of MxA in blood lymphocytes and an apparently sys temic type I interferon response is not induced during rhinovirus infection or during most other cases of common cold in young adult patients.