Sensitivities of neurotropic arboviruses to human interferon

The sensitivities of selected neurotropic arboviruses (St. Louis encephalitis, Western equine encephaltis, and La Crosse viruses) to human interferon and polyriboinosinic-polyribocytidylic acid (poly I-poly C) were determined in primary human fetal glial cell cultures. The sensitivities were measured by an end point (inhibition of virus yield). All of the viruses were sensitive to human interferon and poly I-poly C; St. Louis encephalitis and Western equine encephalitis viruses were inhibited at concentrations of interferon actually measured in the brains of persons who died from these infections. For St. Louis encephalitis and Western equine encephalitis viruses, viral replication and induction of interferon varied among cell cultures derived from individual fetuses. The present experiments may provide an approach toward understanding the problem of different host susceptibilities to neurotropic arbovirus infections.