| Research Abstract |
Tissue- or cell-specific targeting of vectors is critical to the success of gene therapy. We describe a novel approach to viral-mediated gene therapy, where viral replication and associated cytotoxicity are limited to a specific cell-type by the regulated expression of an essential immediately viral gene product. This is illustrated with a herpes simples virus type 1 vector(G92A)whose growth is restricted to albumin-expressing cells. G92A was constructed by inserting an albumin enhancer/promoter-ICP4 transgene into the thymidine kinase gene of mutant herpes simples virus type 1 dl20, deleted for both copies of the ICP4 gene. This vector also contains the Escherichia coli lacZ gene under control of the thymidine kinase promoter, a viral early promoter, to permit easy detection of infected cells containing replicating vector. In the adult, albumin is expressed uniquely in the liver and in hepatocellular carcinoma and is transcriptionally regulated. G92A efficiently replicated in vitro in two human hepatoma cell lines expressing albumin, but not in three human nonhepatoma, albumin-non-expressing tumor cell lines, while all cell lines were equally susceptible to a tissue ono-specific HSV recombinant, hrR3.
We applied the same strategy for the construction of glioma-specific replication competent HSV using GFAP promoter and enhancer units. However, although we tried homologous recombination several times, we have not yet obtained the aimed HSV.
While, we also applied the recombinant HSV, hrR3 for vascular lesions such as re-stenosis after balloon angioplasty. Now we are constructing vascular smooth muscle cell-specific replication competent HSV. We also constructed replication-incompetent adenovirus vectors expressing bFGF for the purpose of neuronal protection and angiogenesis in vivo.
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