The effect of an interferon inducer on influenza virus.

The double-stranded complex of polyriboinosinic acid and polyribocytidilic acid (poly I.poly C) was shown to inhibit effectively the infection of human cells with 4 common human respiratory pathogens-influenza A2, rhinovirus 13, respiratory syncytial and parainfluenza-1 viruses. This protection was observed with levels of poly I.poly C which did not induce the release of detectable amounts of interferon. Mice could be protected from pulmonary influenza A2 infections by intranasal instillation of poly I.poly C before challenge with virus. Administration of poly I.poly C directly to the respiratory tract was found superior to systemic administration in the case of the pulmonary infection studied.