Study of dendritic cell-specific lentivector vaccine system

UnrestrictedFunctional gene therapy could allow for the potential treatment of numerous diseases. Thus, there is an increasing need to develop an in vivo gene delivery system that could achieve efficient gene transfer, cell-specific targeting, and long-term stable expression. Among various delivery methods, viral vector is still the most efficient system for gene delivery. There have been many attempts to develop targeted viral vectors by altering or restricting the natural host range. In this report, we described a novel viral vector system where the viral surface was engineered to display the designed proteins which facilate the necessary binding and fusion function for viral vector entry and fuse. In chapter 2, an anti-CD20 antibody and a fusogenic protein derived from Sindbis virus glycoprotein were engineered and co-displayed on the surface of gamma-retroviral vectors. These engineered gamma-retroviral vectors conferred their binding specificity to cells expressing CD20 and achieved efficient transduction towards CD20-expressing cells both in vitro and in vivo. In chapter 3, similar concept was applied on HIV-1-based lentiviral vector system which can efficiently transduce a variety of non-dividing cells. The lentiviral surface was engineered to co-display an anti-CD3 antibody and the same fusogenic molecule derived from Sindbis virus glycoprotein. The displayed antibody was able to direct the lentivector to bind to CD3-expressing cells and induce internalization. Subsequently, the incorporated fusogen responded to the low pH environment by triggering fusion to transfer the genetic materials to target cells. A mouse model was devised to show that a subcutaneous injection of such an engineered lentivector could achieve preferred modification of xenografted target cells in vivo.; Further study on this mutant fusogenic molecule derived from Sindbis virus glycoprotein showed that it keeps not only the prime fusion ability but also the specific binding for dendritic cells, which play an important role in the host immune system. In chapter 4, we constructed a dendritic cell (DC)-specific lentivector by pseudotyping the vector with this engineered Sindbis virus glycoprotein and utilized it as a potential vaccine delivery vehicle. Meanwhile, we assessed the level of anti-tumor immunity conferred by this engineered lentivector encoding the melanoma antigen gp100 in a mouse model