Applications of lentivirus vectors include stable gene transfer for gene delivery in gene and cell therapy. This includes using RNA interference technology to block the expression of specific genes. Along with RNAi, lentivirus can be used to introduce a new gene into human or animal cells. These applications are possible because of lentivirus vector’s ability to stably transfer genes, long term expression, and the ability to specifically infect cells by pseudotyping.

Lentivirus vectors do have some limitations such as a (somewhat) limited size constraint. Lentivirus vectors can package large gene inserts with a sharp titer decline after 10kb total proviral size. Typically a gene cloned into a transfer vector produces the highest titer virus when the final size is equal to or smaller than the WT HIV-1 genome (9.7kb).