Project Summary/Abstract
Viral vectors enjoy widespread use for gene transfer to multiple cell types and organ systems in both research
studies and, increasingly, in therapeutic strategies. For studies of the CNS, the ability of the viral vector to
effectively and selectively infect the desired cell types within the CNS plays a critical role in the subsequent
interpretation of study outcomes. However, most viral vectors are somewhat promiscuous in their cell type
specificity. Although a particular vector pseudotype may primarily infect one type of cell, the additional “off-
target” infection of other cell types may introduce unwanted variance to the study outcomes. In some recent
studies, the intended infection of astrocytes also resulted in the unwanted infection of neurons, undermining
the studies’ conclusions. Thus, there is a need to improve the current state of cell-type tropism to one of cell-
type selectivity to specifically and exclusively target the desired cell type and eliminate off-target effects. A
similar unmet need is the lack of a tool to selectively target a previously infected cell for a subsequent “follow-
up” gene delivery. In this Exploratory/Developmental R21 mechanism project, we propose to build upon the
popular expression of the avian TVA receptor used to enable EnvA-pseudotyped rabies virus delivery of a
fluorescent reporter gene for transsynaptic labeling in the CNS. Our aims are in the context of our interest to
perform direct in vivo cellular reprogramming of glial progenitor cells into neurons. In aim 1, we will use our
current retroviral approach to infect proliferating glial progenitor cells in the adult brain to express the avian
TVA receptor. We will then be able to selectively target the TVA-expressing glial progenitor cells for gene
transfer using EnvA-pseudotyped lentivirus. In aim 2, we will directly target the glial progenitor cells by
pseudotyping lentivirus to exclusively bind to a cell-specific membrane receptor. This will facilitate the
demonstration of targeted infection of glial progenitor cells through selective and exclusive gene transfer.
Including TVA in the cell specific receptor-pseudotyped lentivirus construct will permit subsequent selective
targeting by EnvA-pseudotyped lentivirus for delivery of subsequent reprogramming factors or other gene
transfer.
