Scalable Technology to Produce Pharmaceutical Grade Plasmid DNA for Gene Therapy

The use of gene therapy is a promising process for the prevention, treatment and cure of diseases such as cancer and acquired inmudeficiency syndrome (AIDS); increasing a considerable interest during the last decade (Prather et al., 2003). This process requires considerable amounts of plasmid DNA (pDNA) that should be homogeneous with respect to structural form and DNA sequence (O Kennedy et al., 2003). It was shown that naked DNA injected into muscle tissue is expressed in vivo; also the introduction of immunogenic sequences can result in animal vaccination against the encoded peptide (Vogel & Sarver 1995). In general, DNA-based vaccines are considered very safe due, in part, to the lack of genetic integration, and to the absence of specific immune response to the plasmid itself (Robinson, 2000), making its property very attractive. This approach was successfully tested for vaccination against several viral infections such as: West Nile virus vaccine licensed in 2005 by the USDA; in horses; is currently in phase II trial in humans; and the H5N1 influenza DNA vaccine currently undergoing phase I clinical trials (Phue, 2008). When the concept of a DNA vaccine first popped onto the scene in the early 1990s, it seemed too simple, too easy and too bizarre to be true. Regardless the considerable scientific effort over the past few years, no gene-therapy product has yet reached the market, at the moment. Only several clinical trials have been carried out and thousands of people have received (pDNA) without serious adverse effects (Prazeres et al., 1999). By virtue of the developments made recently in biotechnology and molecular medicine, the speculation of 20 years ago that gene technology would become a powerful tool to cure disease directly, has become reality (Schleef, 1999) and the market of one of these products would exceed US$45 billion. The trend toward testing DNA vaccines as part of combination trials can be seen in both the large vaccine producers like Merck, Aventis Pasteur and Wyeth as well as in smaller research companies (Powell, 2004). Although the processes of production for many genetherapy vectors have been developed in pharmaceutical companies, the information of large-scale pDNA production is scarce and usually not available to the scientific community (Xu et al., 2005).