Mechanism of interferon action: human leukocyte and immune interferons regulate the expression of different genes and induce different antiviral states in human amnion U cells.

The inhibition of virus replication and the induction of protein phosphorylation were examined in human amnion U and human fibroblast GM2767A cells treated with highly purified cloned human leukocyte and immune interferons synthesized in Escherichia coli. Both leukocyte interferon (IFN-alpha A) and immune interferon (IFN-gamma) possessed antiviral activity as measured by the single cycle yield reduction of vesicular stomatitis virus (VSV) in the human U and GM2767A cell lines. By contrast, only IFN-gamma and not IFN-alpha A inhibited the single cycle replication of reovirus in U and GM2767A cells. IFN-alpha A, but not IFN-gamma, efficiently induced the double-stranded RNA-dependent phosphorylation of the ribosome-associated protein P1 and the alpha subunit of protein synthesis initiation factor eIF-2 in U cells. However, neither IFN-alpha A nor IFN-gamma induced the phosphorylation of P1 and eIF-2 alpha in GM2767A cells. The antiviral activities of IFN-alpha A and IFN-gamma were synergistic for the inhibition of VSV but not for the inhibition of reovirus or the induction of protein phosphorylation. These results suggest that human leukocyte and immune interferons differentially regulate the expression of certain genes and induce mechanistically distinct antiviral states in human cells.