Epi-CHO, an episomal expression system for recombinant protein production in CHO cells

Authors

  • Rajkumar Kunaparaju,

    1. School of Biotechnology & Biomolecular Sciences, University of New South Wales, Sydney NSW, Australia
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  • Mimi Liao,

    1. School of Biotechnology & Biomolecular Sciences, University of New South Wales, Sydney NSW, Australia
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  • Noelle-Anne Sunstrom

    Corresponding author
    1. School of Biotechnology & Biomolecular Sciences, University of New South Wales, Sydney NSW, Australia
    2. ACYTE Biotech Pty Ltd., University of New South Wales, Sydney NSW, Australia; telephone: +612 9 385 3693; fax: +61 2 9313 6710
    • ACYTE Biotech Pty Ltd., University of New South Wales, Sydney NSW, Australia; telephone: +612 9 385 3693; fax: +61 2 9313 6710.

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Abstract

This study describes the development of a transient expression system for CHO cells based on autonomous replication and retention of transfected plasmid DNA. A transient expression system that allows extrachromosomal amplification of plasmids permits more plasmid copies to persist in the transfected cell throughout the production phase leading to a significant increase in transgene expression. The expression system, named Epi-CHO comprises (1) a CHO-K1 cell line stably transfected with the Polyomavirus (Py) large T (LT) antigen gene (PyLT) and (2) a DNA expression vector, pPyEBV encoding the Py origin (PyOri) for autonomous plasmid amplification and encoding Epstein-Barr Virus (EBV) nuclear antigen-1 (EBNA-1) and OriP for plasmid retention. The CHO-K1 cell line expressing PyLT, named CHO-T was adapted to suspension growth in serum-free media to facilitate large-scale transient transfection and recombinant gene expression. Enhanced green fluorescent protein (EGFP) and human growth hormone (hGH) were used as reporter proteins to demonstrate transgene expression and productivity. Transfection of suspension-growing CHO-T cells with the vector pPyEBV encoding hGH resulted in a final concentration of 75 mg L−1 of hGH in culture supernatants 11 days following transfection. © 2005 Wiley Periodicals, Inc.

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