IMPROVED GENE-TRANSFER INTO HUMAN-LYMPHOCYTES USING RETROVIRUSES WITHTHE GIBBON APE LEUKEMIA-VIRUS ENVELOPE

Gene-modified lymphocytes have a potential role in the therapy of canc er, infectious diseases, and genetic disorders of the immune system. C urrent gene therapy protocols involving gene transfer into lymphocytes utilize retroviruses with amphotropic envelope proteins. However, tra nsduction efficiencies in lymphocytes using these viruses are relative ly low. A potential strategy to improve gene transfer efficiency is th e utilization of alternative retroviral envelopes that target unique r eceptors on the cell surface. One such alternative retroviral envelope , the gibbon ape leukemia virus (GALV) envelope, targets a distinct su rface receptor (GLVR-1) that is 60% homologous but not cross-reactive to the amphotropic receptor (GLVR-2/RAM-1), Understanding the relation ship between receptor expression and transduction efficiency is import ant for designing new strategies to improve gene transfer. Therefore, me compared GLVR-1 and GLVR-2 mRNA levels in lymphocytes and found tha t GLVR-1 was expressed 8- to 19-fold higher than GLVR-2. We then analy zed whether this enhanced expression of GLVR-1 correlated with increas ed infectivity of lymphocytes by retroviral vectors that utilize the G ALV envelope compared to those that use the amphotropic envelope. We e valuated retroviral vectors packaged with either PA317 or PG13, which express the amphotropic and GALV envelopes, respectively. Lymphocyte t ransduction with PG13-packaged vectors was 4- to 18-fold higher than t hat with PA317-packaged vectors. These findings suggest that receptor expression level is an important factor in retroviral-target interacti ons and that gene transfer into human T lymphocytes should be performe d with retroviruses that use the GALV envelope as opposed to retroviru ses that use the amphotropic envelope.