Biologic activities of natural and synthetic type I interferons.

Because alpha-interferon (IFN-alpha) has a number of therapeutic applications in the treatment of various human cancers and diseases of viral origin, an understanding of how this family of proteins interacts with cells to induce their pleiotropic biologic activities is essential. Available data suggest that recombinant IFN-alphas from both natural and synthetic genes bind to a common cell surface receptor and induce antiviral activity in a variety of cell lines. IFN-alphas were found to differ significantly in their abilities to bind to cells; this difference varied with the types of IFN-alpha and cell type used. Consensus interferon (IFN-con1), a nonnaturally occurring synthetic IFN, and IFN-alpha2b competed about equally well for receptor binding sites on Daudi and CaKi cells and were followed by IFN-alpha8 in the ability to compete. Results of affinity cross-linking experiments indicated that all three IFN-alphas interacted similarly with the multichain IFN-alpha receptor. IFN-alpha7, however, competed poorly for binding sites on both cell lines. Each of the IFN-alphas tested displayed discrete biologic differences, which also varied with the assay system used. IFN-con1 and IFN-alpha2b displayed similar antiviral activities on CaKi cells using vesicular stomatitis virus; the viral activities of these IFNs were significantly greater than those of IFN-alpha7 or IFN-alpha8. Studies with murine transfectants demonstrated significant differences in the various IFNs to interact with the IFN-alpha receptor-1 chain of the type I IFN receptor. It is yet to be established, however, that these various in vitro distinctions result in differences in clinical benefit or toxicity between the various subtypes.