Assessment of bioactivity of a recombinant chicken interferon-gamma expressed using a baculovirus expression system

The full-length coding sequence of chicken interferon-γ (ChIFN-γ) was cloned into a baculovirus nonfusion vector, pFastBacDual, and expressed in Sf21 insect cells. Recombinant ChIFN-γ (rChIFN-γ) protein was found to be expressed both intracellularly as well as in the culture supernatants. The affinity-purified rChIFN-γ contained 14, 17, and 28 kDa proteins, possibly representing both glycosylated and nonglycosylated protein forms of ChIFN-γ. The bioactivity of rChIFN-γ was confirmed in vitro by production of nitric oxide in a chicken macrophage cell line (HD11) and antiviral activity against vesicular stomatitis virus in primary chicken embryonic fibroblast cells. Further, HD11 cells stimulated with rChIFN-γ showed significant upregulation of inducible nitric oxide synthases, IFN-γ, interleukin-1β, interleukin-12p35, signal transducers and activators of transcription 1, class II, major histocompatibility complex, transactivator, and major histocompatibility complex II-β chain (BL-B) transcripts. In conclusion, the present study provides information on the ability of functionally active rChIFN-γ expressed in a baculovirus system in inducing significant transcriptional upregulation of various immune system-related genes, including those that encode cytokines, antigen-presenting molecules, and transcription factors involved in the major histocompatibility complex and IFN-signaling pathway.