695. Effect of Neonatal Hepatic Gene Therapy on Cardiovascular Disease, Hearing, and Visual Function in Mice with MPS I
Authors: Hiroshi Kobayashi, Denise Petersen, Denise Carbonaro, Dianne Skelton, Shundi Ge, Carolyn Luzko, Paula Cannon, Maya Otto Dussel, Michael Rosol, Rex Moats, Hiroyuki Shimada, Donald B. Kohn
Journal: Molecular Therapy (2004)

Mucopolysaccharidosis type I (MPS I) is lysosomal storage disorder caused by deficiency of the enzyme, alpha-L-iduronidase (IDUA). We investigated gene therapy for MPS I by using a recombinant lentiviral (HIV-based) vector (pSMPU-MCU3-huID-IRES-eGFP) that contains the normal human IDUA cDNA as well as the enhanced green fluorescence protein (eGFP) reporter gene. We have demonstrated significant levels of IDUA gene expression by this vector in cell lines. To evaluate the effect of age on systemic gene transfer using this vector, we performed a single intravenous injection at different-ages in the IDUA gene knock-out mouse (developed by HH Li and EF Neufeld), treated as neonates (0 or 1-day old) (via facial vein, group 1, n=7), or as young-adults (8-week old) (via tail vein, group 2, n=5), with untreated age-matched control groups. We used the same weight-adjusted dosage of vector (1.65×10e5TU/kg) in neonates and young-adults, and sacrificed them at the same age (20-week old) to investigate the pathological changes, IDUA activity, and vector biodistribution in liver, spleen, kidney, heart, and brain. In the newborn group, almost no lysosomal storage was seen in all 5 organs (there was a little variance in the kidney). In contrast, in the young-adult group there was moderate accumulation in liver and spleen, and high levels were seen in heart, kidney, and brain. The IDUA activity was significantly higher (p<0.05) in the newborn group than in the young-adult group in the spleen (15.2% of normal in newborn group vs. 2.8% in adolescent group), kidney (24.3% vs.4.7%), heart (22.24% vs. 0.3%), and brain (37.7% vs. 1.3%). The higher level of IDUA activity in the liver of mice treated as newborns did not reach statistical significance (27.2% vs. 20.1%). The vector DNA copy numbers determined by real-time PCR for the eGFP sequences in the newborn group were significantly higher only in the brain (0.672% vs. 0.008% genome equivalents/cell) but were relatively higher in the other organs of the newborn group than that of the young-adult group. Expression of the eGFP gene in the brain was mainly in the neurons by immunohistochemistry. In summary, significantly better phenotype correction and vector gene biodistribution were seen in the newborn group compared with the young-adult group, despite the longer time elapsed since gene therapy in the former (20 weeks vs. 12 weeks). We concluded that the systemic injection of lentiviral vector for MPS I at the neonatal stage is much more effective than at the young-adult stage. Possible reasons include the incompletely formed blood-brain barrier, more efficient integration of the vector into neonatal tissues or hematopoietic stem cell, avoidance of deleterious immune response in the neonatal period. For long-term follow-up, we are evaluating the craniofacial skeletal change by x-ray and CT and are dynamically tracking injected vector by using bioluminescence imaging. These studies should be important for the development of gene therapy as an effective treatment for MPS I.