Comparison of biological activities of natural and recombinant chicken interferon-gamma

In recent years, chicken interferon-gamma (ChlFN-gamma) has been identified and cloned from a chicken T cell line. In this study, recombinant ChIFN-ga mma produced in the baculovirus and prokaryotic (Escherichia coli) expressi on systems were characterized and their activity was compared to that of na turally ChIFN-gamma produced by mitogen-activated splenic T cells. The bacu lovirus-derived ChIFN-gamma protein (Bac-ChIFN-gamma) proved to have physio chemical properties and biological activities similar to those of natural C hIFN-gamma. Indeed, Bac-ChIFN-gamma was able to inhibit the replication of cytolytic viruses in chicken embryo fibroblasts and to activate macrophages , as was determined by nitric oxide production. Levels ranging between 100 and 300 mu g/ml of BacChIFN-gamma could be obtained in the supernatants of infected insect cells. On the other hand, yields of the E, coli produced Ch IFN-gamma rarely exceeded 100 mu g/ml after purification steps and although it was also able to activate the HD11 macrophage cell line in a specific m anner, no anti-viral activity could be demonstrated. Therefore, the baculov irus expression system is an appropriate system for the high-level expressi on of biologically active ChIFN-gamma and will allow further studies of the immunomodulatory and therapeutic effects of this cytokine in vivo. (C) 199 9 Elsevier Science B.V. All rights reserved.