Gene therapy for inborn errors of liver metabolism: progress towards clinical applications

Table 1 Overview of gene therapy vectors.

	Genetic material	Packaging capacity	Vector genome forms	Advantages	Disadvantages
Retrovirus	RNA	8 kb	Integrated	- High efficiency integration	- Transduction only in dividing cells
				- No viral immune response	- Insertional carcinogenesis
				- Long-term expression
Lentivirus	RNA	8 kb	Integrated	- Non-dividing cells	- Integration into active genes
				- Long-term expression	- Risk of replication competent HIV
Adenovirus	dsDNA	Up to 35 kb (HDAd)	Episomal	- Non-dividing cells	- Acute toxicity
				- Large cloning capacity
				- High transduction levels
				- Long-term expression (HDAd)
Adeno-associated vectors	ssDNA	5–9 kb	Episomal (> 90%)	- Non-dividing cells	- Limited cloning capacity
			Integrated (< 10%)	- Long-term expression	- CTL-mediated immune reaction
Naked plasmid DNA	dsDNA	Unlimited	Episomal	- Non dividing cells	- Low efficiency of transduction
				- No inflammatory response	- Efficient and clinically relevant delivery method still to be developed
				- Large cloning capacity
				- Long-term expression
				- Ease preparation

dsDNA = double stranded DNA; ssDNA = single stranded DNA; HDAd = helper-dependent adenoviral vector; CTL = cytotoxic T lymphocyte.

ISSN: 1824-7288