Expression and purification of human interferon gamma using a plant viral vector

A plant viral vector engineered from an in vivo infectious clone of zucchini yellow mosaic virus (ZYMV) was used to express the human interferon-gamma (INF-γ) in planta. The INF-γ gene was in frame inserted between the P1 and HC-Pro ORFs of the ZYMV vector. The infectious activity of the vector was approved by rubbing the plasmid on Chenopodium quinoa and observing local lesions. Individual lesions were mechanically transferred to the systemic host plant zucchini squash at the stage of cotyledonary leaf. The stability of INF-γ expression was assessed by successive passages of recombinant viruses from infected plant and throughout the period of 35 days after inoculating in a single plant. Then, the leaf tissues of inoculated plant were analyzed for the presence of transgene by RT-PCR and western blot analysis. The recombimamt protein was purified using affinity chromatography method. The results showed approximately 1–1.2 mg INFγ per 100 g tissues were purified from leaves two weeks post inoculation. Also, the vector was remarkably stable in squash after six serial passages and 35 days. The procedure provides a convenient and fast method for production of large quantities of pure INF-γ in planta. The system also has a potential for production of other proteins of interest in cucurbits to use as immunogen to produce antiserum or use for other purposes.