Protective effects of type I and type II interferons toward Rous sarcoma virus-induced tumors in chickens

Growth of tumors induced by Rous sarcoma virus (RSV) is controlled by allel es at the major histocompatibility complex locus in chickens, indicating th at immunological host defense mechanisms play a major role. We show here th at the resistance phenotype of CB regressor chickens can be partially rever ted by treating the animals with a monoclonal antibody that neutralizes the major serotype of chicken type 1 interferon, ChIFN-alpha. Injection of rec ombinant ChIFN-alpha into susceptible CC progressor chickens resulted in a dose-dependent inhibition of RSV-induced tumor development. This treatment was not effective, however, in CC chickens challenged with a DNA construct expressing the v-src oncogene, suggesting that the beneficial effect of typ e 1 interferon in this system resulted from its intrinsic antiviral activit y and probably not from indirect immunmodulatory effects. By contrast, reco mbinant chicken interferon-gamma strongly inhibited tumor growth when given to CC chickens that were challenged with the v-src oncogene, indicating th at the two cytokines target different steps of tumor development. (C) 1999 Academic Press.