Use of replication-competent retroviral vectors in an immunocompetent intracranial glioma model.
OBJECTIVE
The authors had previously reported on a replication-competent retrovirus (RCR) that has been demonstrated to be stable, capable of effective transduction, and able to prolong survival in an intracranial tumor model in nude mice. The purpose of this study was further investigation of this gene therapy option.


METHODS
The transduction efficiency of RCR in RG2, an immunocompetent intracranial tumor model, was tested in Fischer 344 rats. The immune response to the RCR vector was expressed by the quantification of CD4, CD8, and CD11/b in tumors. The pharmaceutical efficacy of the suicide gene CD in converting prodrug 5-fluorocytosine (5-FC) to 5-fluorouracil (5-FU) was measured using fluorine-19 nuclear magnetic resonance (19F-NMR) spectroscopy. Animal survival data were plotted on Kaplan-Meier survival curves. Finally, the biodistribution of RCR was determined using quantitative real-time polymerase chain reaction (RT-PCR) for the detection of retroviral env gene. There was no evidence of viral transduction in normal brain cells. Neither severe inflammation nor immunoreaction occurred after intracranial injection of RCR-green fluorescent protein compared with phosphate-buffered saline (PBS). The 19F-NMR spectroscopy studies demonstrated that RCR-CD was able to convert 5-FC to 5-FU effectively in vitro. The infection of RG2 brain tumors with RCR-CD and their subsequent treatment with 5-FC significantly prolonged survival compared with that in animals with RG2 transduced tumors treated with PBS. In contrast to the nude mouse model, evidence of virus dissemination to the systemic organs after intracranial injection was not detected using RT-PCR.


CONCLUSIONS
The RCR-mediated suicide gene therapy described in this paper effectively transduced malignant gliomas in an immunocompetent in vivo rodent model, prolonging survival, without evidence of severe intracranial inflammation, and without local transduction of normal brain cells or systemic organs.
Wang
Weijun
W
Department of Neurosurgery, Keck School of Medicine, University of Southern California, Los Angeles, California 90033, USA.
Tai
Chien-Kuo
CK
Kershaw
Allan D
AD
Solly
Sounkary K
SK
Klatzmann
David
D
Kasahara
Noriyuki
N
Chen
Thomas C
TC
D000818:Animals; D001932:Brain Neoplasms / Q000235:genetics / Q000378:metabolism / Q000628:therapy*; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000235:genetics; D004279:DNA, Viral / Q000032:analysis / Q000235:genetics; D004195:Disease Models, Animal; D004660:Encephalitis / Q000503:physiopathology / Q000517:prevention & control; D005437:Flucytosine / Q000378:metabolism; D041722:Genes, Transgenic, Suicide / Q000235:genetics*; D015316:Genetic Therapy / Q000379:methods* / Q000639:trends; D005822:Genetic Vectors / Q000235:genetics / Q000627:therapeutic use*; D005910:Glioma / Q000235:genetics / Q000378:metabolism / Q000628:therapy*; D006801:Humans; D016867:Immunocompromised Host / Q000235:genetics; D008297:Male; D050130:Oncolytic Virotherapy / Q000379:methods* / Q000639:trends; D051381:Rats; D011916:Rats, Inbred F344; D012190:Retroviridae / Q000235:genetics*; D015996:Survival Rate; D014161:Transduction, Genetic / Q000379:methods / Q000639:trends; D016896:Treatment Outcome; D014779:Virus Replication / Q000235:genetics
D004279:DNA, Viral; D005437:Flucytosine