[Frontiers in Bioscience S4, 133-141, January 1, 2012]

Development of safe and effective nonviral gene therapy by eliminating CpG motifs from plasmid DNA vector

Yuki Takahashi1, Makiya Nishikawa1, Yoshinobu Takakura1

1Department of Biopharmaceutics and Drug Metabolism, Graduate School of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Kyoto, 606-8501, Japan

TABLE OF CONTENTS

1. Abstract
2. Introduction
3. Biological role of CpG motifs in the body
3.1. Response to CpG dinucleotides in mammals
3.2. CpG motifs in epigenetic regulation of gene expression
4. CpG motifs in plasmid DNA vector
4.1. Inflammatory response to plasmid DNA
4.1.1. Inflammatory response to plasmid DNA
4.1.2. Inflammatory response to plasmid DNA delivered by carrier
4.1.3. TLR9-independent recognition and inflammatory response to plasmid DNA
4.2. Effect of CpG motifs in plasmid DNA on transgene expression from the DNA
4.2.1. Relationship between the transgene expression profile from plasmid DNA and the number of CpG motifs
4.2.2. Factors that link CpG motifs with transgene expression
5. Conclusions
6. Acknowledgement
7. References

1. ABSTRACT

Nonviral gene therapy is expected to become a regular treatment for a variety of difficult-to-treat diseases, such as cancer and virus infection. Plasmid DNA, which is used in most nonviral gene delivery systems, usually contains, unmethylated cytosine-guanine dinucleotides, so called CpG motifs. CpG motifs are recognized by immune cells as a danger signal, leading to an inflammatory response. Such inflammatory responses could affect the safety and effectiveness of nonviral gene therapy. Therefore, reducing the number of CpG motifs in plasmid DNA has been used to increase the potency of plasmid DNA-based gene therapy. Previous studies have demonstrated that CpG reduction can extend the time period of transgene expression from plasmid DNA after in vivo gene transfer. In this review, the biological functions of the CpG motif are briefly summarized. Then, safety issues of nonviral gene therapy are discussed from the viewpoint of the inflammatory response to the CpG motif in plasmid DNA, and the effects of the CpG motif in plasmid DNA on the transgene expression profile of nonviral gene transfer are reviewed.