Table 1.

Viral vectors commonly used in gene therapy studies.

Viral vector	Packaging capacity (kb)	Features
Adenovirus	≤ 7.5	Transient expression in most of the cells, immunogenic.
Adeno-associated virus (AAV)	≤ 4	Long-term expression in dividing and non-dividing cells.
Herpes Simplex virus	≥ 30	Long-term expression in most of the cells; low toxicity.
Alphaviruses	≤ 7.5	Transient gene expression in most of the cells including neurons and glial cells; low immunogenicity.
Retrovirus	8	Long-term expression in dividing cells; genome integration.
Lentivirus	8	Long-term expression in both dividing and non-dividing cells; genome integration.