Improved Gene Delivery and In Vivo Imaging

目前，由于缺乏一种非侵入性和临床有用的手段来监测载体的持久性、生物分布和转基因在体内的表达，基因治疗受到了限制。当前项目的目标是测试旨在改善局部腺病毒介导基因治疗后基因表达空间分布的策略，以便整个器官在尽可能少的病毒（以限制毒性）的情况下接受足够临床疗效的病毒剂量。一种基于碘化钠同调子（NIS）的新报告基因将被表征其监测治疗性基因表达的能力，并与正在开发的其他催化活性测量进行对比。有三个具体的目标

Gene therapy is currently limited by the lack of a non-invasive and clinically useful means to monitor vector persistence and biodistribution and transgene expression in vivo. The goal of the current project is to test strategies devised to improve the spatial distribution of gene expression following the local administration of adenovirus-mediated gene therapy so that the entire organ receives a viral dose sufficient for clinical efficacy with as little virus as possible (to limit toxicity). A new reporter gene based on the sodium iodide symporter (NIS) will be characterized with regard to its ability to monitor therapeutic gene expression and contrasted with other measurements of catalytic activity under development. There are three specific aims of the proposed studies. 1. Compare the distribution of NIS reporter gene expression to that of CD/HSV-1 TK therapeutic gene expression. If it can be shown that NIS activity is a surrogate marker of therapeutic gene expression, NIS imaging could eliminate the biopsy currently used to assess transgene expression and allow for dynamic and whole body monitoring of transgene expression. 2. Evaluate new vector formulations and injections conditions designed to optimize placement of the adenovirus within the prostate to obtain maximal organ coverage. This work will provide the scientific basis for a clinical trial described in Project 3. 3. Contrast the prodrug-labeled approach of monitoring transgene expression to the NIS approach. This aim tests the hypothesis that the bystander effect can be measured and exceeds the area of gene expression. Bystander effect will be measured using autoradiography of bound radiolabeled prodrugs ([3H]-ganciclovir-MP, [14C]-5-FdUMP) and compared to iodide localization following transduction of NIS. Finally the measurements will be extended to non-invasive techniques using [19F]-MR chemical shift imaging of 5-FU and 123(I)uptake using SPECT imaging of NIS activity. A large animal model is needed for the proposed studies. We plan to use the prostates of large, mongrel dogs. The studies described represent "proof of principle" and will generate significant new knowledge that will benefit the gene therapy and medical communities.