Table 1.

Comparison of various viral vectors

Feature	Retroviral vector	Lentiviral vector	Helper-dependent adenoviral vector	Adeno-associated viral vector
Cloning capacity	~7.5 kb	~ 7.5 kb (< 18 kb)*	~ 37 kb	~ 4.7 kb (~ 10 kb)**
Integration	Yes (random)	Yes (random)	Essentially non	Minimal (random)
Transduction	Dividing cells	Dividing cells and non-dividing cells	Dividing cells and non-dividing cells	Dividing cells and non-dividing cells
Transduction efficiency	Good	Good	Excellent	Excellent
Immune problems	Few	Few	Moderate	Few

^*The titer of the lentiviral vector is dramatically reduced (Kumar et al., 2001).

^**This cloning capacity can be achieved by an intermolecular joining method.