title: Establishing the Lysine-rich Protein CEST Reporter Gene as a CEST MR Imaging Detector for Oncolytic Virotherapy.
abstract: OBJECTIVE
  To (a) evaluate whether the lysine-rich protein (LRP) magnetic resonance (MR) imaging reporter gene can be engineered into G47Δ, a herpes simplex-derived oncolytic virus that is currently being tested in clinical trials, without disrupting its therapeutic effectiveness and (b) establish the ability of chemical exchange saturation transfer (CEST) MR imaging to demonstrate G47Δ-LRP.
  
  
  METHODS
  The institutional subcommittee for research animal care approved all in vivo procedures. Oncolytic herpes simplex virus G47Δ, which carried the LRP gene, was constructed and tested for its capacity to replicate in cancer cells and express LRP in vitro. The LRP gene was detected through CEST imaging of lysates derived from cells infected with G47Δ-LRP or the control G47Δ-empty virus. G47Δ-LRP was then tested for its therapeutic effectiveness and detection with CEST MR imaging in vivo. Images of rat gliomas were acquired before and 8-10 hours after injection of G47Δ-LRP (n = 7) or G47Δ-empty virus (n = 6). Group comparisons were analyzed with a paired t test.
  
  
  RESULTS
  No significant differences were observed in viral replication or therapeutic effectiveness between G47Δ-LRP and G47Δ-empty virus. An increase in CEST image contrast was observed in cell lysates (mean ± standard deviation, 0.52% ± 0.06; P = .01) and in tumors (1.1% ± 0.3, P = .02) after infection with G47Δ-LRP but not G47Δ-empty viruses. No histopathologic differences were observed between tumors infected with G47Δ-LRP and G47Δ-empty virus.
  
  
  CONCLUSIONS
  This study has demonstrated the ability of CEST MR imaging to show G47Δ-LRP at acute stages of viral infection. The introduction of the LRP transgene had no effect on the viral replication or therapeutic effectiveness. This can aid in development of the LRP gene as a reporter for the real-time detection of viral spread. Online supplemental material is available for this article.
authors: From the Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology (C.T.F.), and Brain Tumor Research Center, Department of Neurosurgery (J.S.B., A.K., G.F.), Massachusetts General Hospital and Harvard Medical School, 185 Cambridge St, Simches CRPZN-3800, Boston, MA 02114; F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Md (G.L., M.T.M., A.A.G.), The Russell H. Morgan Department of Radiology and Radiological Science (G.L., M.T.M., A.A.G.), The Johns Hopkins University, Baltimore, Md; Department of Neurosurgery, Josephine Nefkens Institute, Erasmus MC, Rotterdam, the Netherlands (A.K., M.L.M.L.); and Cellular Imaging Section and Vascular Biology Program, Institute for Cell Engineering, The Johns Hopkins University School of Medicine, Baltimore, Md (A.A.G.).
authors: Christian T
authors: CT
authors: Farrar
authors: Jason S
authors: JS
authors: Buhrman
authors: Guanshu
authors: G
authors: Liu
authors: Anne
authors: A
authors: Kleijn
authors: Martine L M
authors: ML
authors: Lamfers
authors: Michael T
authors: MT
authors: McMahon
authors: Assaf A
authors: AA
authors: Gilad
authors: Giulia
authors: G
authors: Fulci
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D017930:Genes, Reporter; D008239:Lysine; D008279:Magnetic Resonance Imaging; D008297:Male; D050130:Oncolytic Virotherapy / Q000379:methods*; D051381:Rats; D011916:Rats, Inbred F344; D018139:Simplexvirus
chemical_list: D008239:Lysine