Abstract
Summary An interferon prepared from the allantoic fluid of chick embryos infected with WS influenza A was found to inhibit plaque formation of EEE virus linearly in a semi-logarithmic plot between dilutions of 3:200 and 1:20. Higher concentrations of interferon, however, did not inhibit plaque formation in the predicated manner. This interferon also inhibited synthesis of cell-associated viral RNA in chick cultures infected with EEE virus. However, such inhibition was found to be consistently less than the inhibition of infectious virus replication. It is suggested that interferon does not act merely by inhibtion of viral RNA but that it interferes either directly or indirectly with the synthesis of other viral components or with the reactions underlying the assembly of these components.