Table 3.

Advantages and Disadvantages of Viral Vectors for Gene Therapy

Vector	Advantages	Disadvantages
Enveloped
HSV/r	Broad cell tropism, high tropism for neurons latency in neurons, very stable	Expression of viral genes
		Highly toxic
		Transient transgene expression in cells other than neurons
HSV/a	Broad cell tropism, high tropism for neurons latency in neurons, very stable	No expression of viral genes
	Large transgene capacity	Lower toxicity
Retrovirus	Persistent transgene expression	Infects dividing cells only
		Integration into host genome
		Risk of insertion mutagenesis
Lentivirus	Broad cell tropism	Integration into host genome
	Infection of dividing and non dividing cells	Risk of insertion mutagenesis
	Persistent transgene expression	Risk of seroconversion
Non-enveloped
Rad	Broad cell tropism, infection of dividing and non dividing cells	Expression of viral proteins
	High titer stocks, good yields	Inflammatory and immune responses
		Transient expression
		RCA potential contamination
HD-Ad	Broad cell tropism, infection of dividing and non dividing cells	Difficulty in large scale production
	Non expression of viral proteins	Helper virus and RCA potential contamination
	Lower inflammatory and cellular immune response
	Longer term transgene expression
AAV	Broad cell tropism	Small insertion capacity
	Infection of dividing and non dividing cells	Integration into host genome
	Non expression of viral proteins
	Discrete immune response