Intranasal recombinant interferon-alpha 2b (rIFN-alpha 2b) protects against natural colds due to rhinoviruses, but apparently not against those caused by viruses. Because rIFN-beta serine17 (rIFN-beta ser) appears less active than rIFN-alpha 2b in preventing natural rhinovirus colds, we compared the two IFNs in two in vitro assays against selected respiratory viruses. In a yield reduction assay, both IFNs had comparable activity against rhinovirus types 39 and 1A and coronavirus 229E, which were inhibited by 90% or more at IFN concentrations of 10(-11) to 10(-10) gram of protein/ml (approximately 2-20 IU/ml). Similar activities were observed with rIFN-beta ser against rhinoviruses isolated from clinical specimens. At concentrations of 10(-9) gram protein/ml, both IFNs inhibited the growth of influenza A and parainfluenza viruses, but not of adenovirus or respiratory syncytial virus in the cell culture systems tested. Thus, the different clinical protection conferred by rIFN-alpha 2b and rIFN-beta ser in studies of natural rhinovirus colds are not accounted for by differences in their in vitro activity against these viruses, and other explanations must be found.
Comparative susceptibility of respiratory viruses to recombinant interferons-alpha 2b and -beta.