Redirecting lentiviral vectors by insertion of integrin-tageting peptides into envelope proteins.

BACKGROUND Targeting gene therapy vectors that can home in on desired cell and tissue types in vivo comprise the ultimate gene delivery system. We have previously developed targeting lentiviral vectors by pseudotyping vectors with modified Sindbis virus envelope proteins. The envelope protein contains the Fc-binding region of protein A (ZZ domain), so the virus can be conjugated with antibodies. The conjugated antibody mediates specific transduction of the cells and tissues expressing the target antigens, both in vitro and in vivo. However, more stable conjugation of targeting molecules would be optimal for use in immunocompetent animals, as well as in humans. METHODS We inserted integrin-targeting peptides into two sites of the targeting envelope proteins and determined whether the peptides serve as receptor-binding regions of the envelope proteins and redirect the pseudotyped viruses. RESULTS The integrin-targeting peptides can mediate binding to cells via the interaction with integrins on target cells and transduction. Peptides with a higher binding affinity increase titers of pseudotyped virus. We found two regions on the envelope protein that can accommodate insertion and serve as receptor-binding regions. Combining the peptides in two distinct regions increased the titers of the virus. CONCLUSIONS Successful incorporation of targeting molecules into the envelope protein will broaden the application of targeting vectors for a wide variety of experimental and clinical settings.