Recent successes of viral vector-based gene replacement therapy in human clinical trials underscore the therapeutic potential of gene therapy. In contrast to conventional medication, therapeutic viral vectors are given as a single dose and their levels cannot be adjusted to meet the therapeutic needs of an individual patient. Thus, one cannot overestimate the importance of animal model-based preclinical studies as a means to characterize the efficacy and safety of gene therapy regimens. Most preclinical trials are based on a rodent model comprising a large number of animals of the same strain, and a large animal model involving a smaller number of animals. Importantly, the effects of the genetic background of mouse strains employed in preclinical studies on the safety and efficacy of viral vectors has not been characterized. Similarly the effects of the patient’s genetic background on the outcome of gene therapy regimens cannot be evaluated. Consequently, several gene therapy clinical trials have resulted in major adverse effects, which could not be observed in relevant earlier preclinical studies. The overall goal of the proposed studies is to characterize the effects of the host genetic background on the efficacy and safety of lentiviral vector-based gene replacement therapy. Our experimental approach is premised on 40 Collaborative Cross (CC) mouse strains, which were derived by multiple crossing of 12 known founder strains. The genetic backgrounds of these mouse strains are well defined, will be utilized to study the effects of the host genetic background on the overall efficacy and safety of lentiviral vector gene delivery, and to identify putative genetic loci affecting these processes. This research proposal comprises three specific aims: in Aim 1, we will focus on characterizing the effects of the host genetic background on the ability of lentiviral vectors to deliver and maintain long term hepatic transgene expression, as well as lentiviral vector efficiency and pattern of integration. Intra-strain crossing will be employed to identify putative gene loci involved in these processes. The optimal mouse strains for lentiviral vector-based hepatic gene delivery (demonstrating highest long-term transgene expression) will be identified. In Aim 2, we will employ CC mouse embryo fibroblasts (MEF’s) to study the effects of the host genetic background on the early steps of, as well as overall lentiviral vector transduction. Gene loci involved in these processes will be identified. The ability of the MEF-based model to predict in vivo transduction efficiency will be determined. In Aim 3, we will characterize the effects of the host genetic background on: the ability of lentiviral vectors to maintain therapeutic levels of factor IX in vivo, the immune responses to factor IX and vector-transduced hepatocytes, and on the development of thrombotic pathologies in the presence of high levels exogenous factor IX.
|Effective start/end date||9/2/15 → 6/30/19|
- NIH National Heart, Lung, and Blood Institute (NHLBI)