Abstract
Noninvasive and repetitive monitoring of a virus in target tissues and/or specific organs of the body is highly desirable for the development of safe and efficient cancer virotherapeutics. We have previously shown that the oncolytic vaccinia virus GLV-1h68 can target and eradicate human tumors in mice and that its therapeutic effects can be monitored by using optical imaging. Here, we report on the development of a derivative of GLV-1h68, a novel recombinant vaccinia virus (VACV) GLV-1h99, which was constructed to carry the human norepinephrine transporter gene (hNET) under the VACV synthetic early promoter placed at the F14.5L locus for deep-tissue imaging. The hNET protein was expressed at high levels on the membranes of cells infected with this virus. Expression of the hNET protein did not negatively affect virus replication, cytolytic activity in cell culture, or in vivo virotherpeutic efficacy. GLV-1h99-mediated expression of the hNET protein in infected cells resulted in specific uptake of the radiotracer [131I]-meta-iodobenzylguanidine (MIBG). In mice, GLV-1h99-infected tumors were readily imaged by [124I]-MIBG positron emission tomography. To our knowledge, GLV-1h99 is the first oncolytic virus expressing the hNET protein that can efficiently eliminate tumors and simultaneously allow deep-tissue imaging of infected tumors.
Highlights
Oncolytic viral therapy exploits the lifecycle of viruses to infect, replicate within, and lyse cancer cells
The construct of GLV-1h99 used in this study was derived from GLV-1h68 by replacing the Renilla luciferase-green fluorescent protein (GFP) (RUCGFP) expression cassette at the F14.5L locus with the human norepinephrine transporter gene (hNET) expression cassette by homologous recombination in infected cells
Lack of GFP expression was confirmed by fluorescence microscopy, and expression of β-galactosidase and β-glucuronidase was demonstrated by X-gal and X-GLcA staining, respectively (Supplementary Figure 1 online)
Summary
Oncolytic viral therapy exploits the lifecycle of viruses to infect, replicate within, and lyse cancer cells. Many virus types, including adenoviruses [1], herpes simplex viruses [2], Newcastle disease virus [3], myxoma virus [4], vaccinia virus (VACV) [5], and vesicular stomatitis virus [6], are being investigated as potential agents for oncolytic virotherapy of cancer in humans. It is of general interest to try to develop imaging techniques that enable tracking of therapeutic gene delivery in gene-therapy protocols. A deep-tissue imaging technique in tracking virusinfected cells in the body may allow real-time, ongoing assessment of therapy and obviate the need for multiple and repeated tissue biopsies. The tracking of viral delivery could give clinicians the ability to correlate efficacy and therapy, as well as to monitor virus toxicity
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