Gene therapy retroviral genome

Fig. 22.2. Schematic for retroviral gene therapy. Retroviral particles containing RNA that encodes the gene of interest are prepared and added to the recipient cells. The retroviral vector is internalized and then releases its genetic material into the cytoplasm. Reverse transcriptase uses the viral template to produce a DNA copy of the desired gene and this gene can then be integrated into the recipient cell s genome. The integrated gene then serves as a template for transcription into mRNA and translation into protein.

Some 24 per cent of all gene therapy clinical trials undertaken to date have employed retroviral vectors as gene delivery systems. Retroviruses are enveloped viruses. Their genome consists of ssRNA of approximately 5-8 kb. Upon entry into sensitive cells, the viral RNA is reverse transcribed and eventually yields double-stranded DNA. This subsequently integrates into the host cell genome (Box 14.1). The basic retroviral genome contains a minimum of three structural genes ... 

Fig. 6.4. Retroviral vectors. A. Structure of the provirus or the DNA copy of the retroviral genome. B and C. Prototype retroviral vectors approved for use in gene therapy protocols. ADA, adenosine deaminase LTR, long-terminal repeat RTase, reverse transcriptase.

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