Integrase-deficient lentivirus: opportunities and challenges for human gene therapy.

Lentiviruses are powerful tools for gene delivery and have been widely used for the dissection of gene functions in both replicating and quiescent cells. Recently, lentiviruses have also been used for delivering target sequences in gene therapy. Although the lentiviral system provides sustained exogenous gene expression, serious concerns have been raised due to its unfavorable insertion-mediated mutagenesis effect, thereby resulting in the silencing or activation of some unexpected genes.