Recombinant DNA-produced human interferon-alpha 2 inhibited the replication of influenza A and B viruses in primary rhesus monkey kidney cells (RMK). Human interferon-alpha 2 interacted additively or synergistically with rimantadine hydrochloride or ribavirin in reducing the yield of clinical isolates of either H3N2 or H1N1 subtype influenza A viruses. The combination of human interferon-alpha 2 and ribavirin also inhibited the replication of an influenza B virus to a greater extent than either single agent. In addition to drug concentration, the virus inoculum and duration of culture were important variables in determining the degree of inhibition. Single drugs or combinations did not significantly inhibit the growth of uninfected RMK cells, which indicated that the observed interactions with respect to antiviral activity were not due to cell cytotoxicity.

Volume 25, no. 1, p. 56, column 1, line 34: ... rimantadine had greater plaque inhibitory activity.. ." should read "... amantadine had greater plaque inhibitory activity.