Table I.

Summary of viral vectors used in gene therapy.

Viral vector	Structure	Advantages	Disadvantages
Adenovirus	Double-stranded DNA	DNA incorporated into host cell nucleus Infects dividing and quiescent cells Transient gene expression Lower risk of genotoxicity Large DNA inserts	Transient gene expression Immunogenic Insertional mutagenesis
Adeno-associated virus (AAV)	Single-stranded DNA	Infects dividing and quiescent cells Long-term gene expression Non-cytotoxic Non-immunogenic	Small DNA inserts
Retrovirus	Single-stranded RNA	DNA incorporated into host cell genome Long-term stable gene expression	Insertional mutagenesis Oncogene activation
Lentivirus	Single-stranded RNA	DNA incorporated into host cell genome Long-term stable gene expression Infects dividing and quiescent cells Replication incompetent No insertion into oncogene