Molecular Cloning and Expression of Human Gamma Interferon (IFN-Y) Full cDNA in Chinese Hamster Ovary (CHO) Cells

IFN-g is mostly secreted by activated CD4+, CD8+ T cells and NKcells. This cytokine has immunomodulatory, anti-cancer and anti-microbial effects and is important for prophylaxis, diagnosis and treatment of chronic infections and cancers. The purpose of this study was to clone the full cDNA of human IFN-g and express it on CHO cell line. Lymphocytes from a healthy individual were isolated and activated by phytohaemagglutinin (PHA) in vitro. After 4 hours, total RNA extracted and first cDNA strand was synthesized. cDNA was amplified with primers containing EcoRI and NotI sites. The amplified fragment and the PcDNA3.1 vector were cut by EcoRI and NotI and ligated. The construct (pcDNA3.1-IFN-γ) was transferred into E.coli (strain: DH5α) using CaCl2 method and selected by plating on a medium containing ampicillin. The construct sequence was confirmed by PCR and sequence analysis. Construct expression was achieved by performing a calcium phosphate-mediated transfection into CHO cells and followed by selection of stable drug (G418) resistant clones by limiting dilution assay (LDA). The IFN-γ production by transected CHO cells was measured using ELISA technique.Results and Out of 33 grown transformed bacterial colonies, only6 had the entire sequences of the insert and one of them was used for the transfectionexperiment. Out of 768 wells, 5 clones produced more than 100 ng/ml/106cells of IFN-γ. Among the 5 clones, one with the maximum production of INF-g (143 ng/ml/106cells) was selected and used for propagation.