ECP has been found significantly elevated in sputum from atopic subjects subjected to experimental rhinovirus infection [136] and in nasal secretions from atopic infants with respiratory RSV infection (table 1) [75] . Eosinophils and ECP are associated with RSV infection in children's lungs [137] and RSV can infect, and replicate in eosinophils [138] . Recombinant ECP expressed in a baculovirus system was used to evaluate whether ECP can inactivate the B subtype of RSV. ECP (0.5 μM; 9.5 μg/mL) incubated with the virus showed a 6-fold reduction of the infectivity of the virus to a human pulmonary epithelial cell line [139] . This antiviral activity was lower than that found with EPX/EDN (54-fold reduction) [140] , but the infectivity was increased by addition of RNase inhibitor (RI) to both proteins during incubation. Mixing the two proteins did not mediate any synergistic effects on antiviral activity. RNase A, however [up to 4 mM (76 mg/mL)], did not exert antiviral activity, suggesting that the RNase site but not activity is important for inhibition of infectivity.