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Gene therapy is a powerful approach to promote spinal cord regeneration. For a clinical application it is important to restrict therapeutic gene expression to the appropriate time window to limit unwanted side effects. The doxycycline (dox)-inducible system is a widely used regulatable gene expression platform, however, this system depends on a bacterial-derived immunogenic transactivator. The foreign origin of this transactivator prevents reliable regulation of therapeutic gene expression and currently limits clinical translation. The glycine-alanine repeat (GAR) of Epstein-Barr virus nuclear antigen-1 protein inhibits its presentation to cytotoxic T cells, allowing virus-infected cells to evade the host immune system. We developed a chimeric transactivator (GARrtTA) and show that GARrtTA has an immune-evading advantage over "classical" rtTA in vivo. Direct comparison of lentiviral vectors expressing rtTA and GARrtTA in the rat spinal cord shows that the GARrtTA system is inducible for 6 doxycycline-cycles over a 47 week period, whereas with the rtTA-based system luciferase reporter expression declines during the 3rd cycle and is no longer re-inducible, indicating that GARrtTA provides an immune-advantage over rtTA. Immunohistochemistry revealed that GARrtTA expressing cells in the spinal cord appear healthier and survive better than rtTA expressing cells. Characterization of the immune response shows that expression of GARrtTA, in contrast to rtTA, does not recruit cytotoxic T-cells to the transduced spinal cord. This study demonstrates that fusion of the GAR domain to rtTA results in a functional doxycycline-inducible transactivator with a clear immune-advantage over the classical rtTA in vivo., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

UBB(+1), a mutant form of ubiquitin, is both a substrate and an inhibitor of the proteasome which accumulates in the neuropathological hallmarks of Huntington disease (HD). In vitro, expression of UBB(+1) and mutant huntingtin synergistically increase aggregate formation and polyglutamine induced cell death. We generated a UBB(+1) transgenic mouse line expressing UBB(+1) within the neurons of the striatum. In these mice lentiviral driven expression of expanded huntingtin constructs in the striatum results in a significant increase in neuronal inclusion formation. Although UBB(+1) transgenic mice show neither a decreased lifespan nor apparent neuronal loss, they appear to be more vulnerable to toxic insults like expanded polyglutamine proteins due to a modest proteasome inhibition. These findings underscore the relevance of an efficient ubiquitin-proteasome system in HD., (Copyright 2009 Elsevier Inc. All rights reserved.)