title: Tyrosine-mutant AAV8 delivery of human MERTK provides long-term retinal preservation in RCS rats.
abstract: OBJECTIVE
  The absence of Mertk in RCS rats results in defective RPE phagocytosis, accumulation of outer segment (OS) debris in the subretinal space, and subsequent death of photoreceptors. Previous research utilizing Mertk gene replacement therapy in RCS rats provided proof of concept for treatment of this form of recessive retinitis pigmentosa (RP); however, the beneficial effects on retinal function were transient. In the present study, we evaluated whether delivery of a MERTK transgene using a tyrosine-mutant AAV8 capsid could lead to more robust and longer-term therapeutic outcomes than previously reported.
  
  
  METHODS
  An AAV8 Y733F vector expressing a human MERTK cDNA driven by a RPE-selective promoter was administrated subretinally at postnatal day 2. Functional and morphological analyses were performed at 4 months and 8 months post-treatment. Retinal vasculature and Müller cell activation were analyzed by quantifying acellular capillaries and glial fibrillary acidic protein immunostaining, respectively.
  
  
  RESULTS
  Electroretinographic responses from treated eyes were more than one-third of wild-type levels and OS were well preserved in the injection area even at 8 months. Rescue of RPE phagocytosis, prevention of retinal vasculature degeneration, and inhibition of Müller cell activation were demonstrated in the treated eyes for at least 8 months.
  
  
  CONCLUSIONS
  This research describes a longer and much more robust functional and morphological rescue than previous studies. We also demonstrate for the first time that an AAV8 mutant capsid serotype vector has a substantial therapeutic potential for RPE-specific gene delivery. These results suggest that tyrosine-mutant AAV8 vectors hold promise for the treatment of individuals with MERTK-associated RP.
authors.affiliation: Department of Ophthalmology, College of Medicine, University of Florida, 1600 SW Archer Road, Gainesville, FL 32610, USA. wdeng@ufl.edu
authors.forename: Wen-Tao
authors.initials: WT
authors.lastname: Deng
authors.forename: Astra
authors.initials: A
authors.lastname: Dinculescu
authors.forename: Qiuhong
authors.initials: Q
authors.lastname: Li
authors.forename: Sanford L
authors.initials: SL
authors.lastname: Boye
authors.forename: Jie
authors.initials: J
authors.lastname: Li
authors.forename: Marina S
authors.initials: MS
authors.lastname: Gorbatyuk
authors.forename: Jijing
authors.initials: J
authors.lastname: Pang
authors.forename: Vince A
authors.initials: VA
authors.lastname: Chiodo
authors.forename: Michael T
authors.initials: MT
authors.lastname: Matthes
authors.forename: Douglas
authors.initials: D
authors.lastname: Yasumura
authors.forename: Li
authors.initials: L
authors.lastname: Liu
authors.forename: Fowzan S
authors.initials: FS
authors.lastname: Alkuraya
authors.forename: Kang
authors.initials: K
authors.lastname: Zhang
authors.forename: Douglas
authors.initials: D
authors.lastname: Vollrath
authors.forename: Matthew M
authors.initials: MM
authors.lastname: LaVail
authors.forename: William W
authors.initials: WW
authors.lastname: Hauswirth
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D015153:Blotting, Western; D004195:Disease Models, Animal; D004596:Electroretinography; D005500:Follow-Up Studies; D015316:Genetic Therapy / Q000379:methods*; D005822:Genetic Vectors; D006801:Humans; D007150:Immunohistochemistry; D007267:Injections; D046529:Microscopy, Electron, Transmission; D009154:Mutation; D010957:Plasmids; D011518:Proto-Oncogene Proteins / Q000008:administration & dosage* / Q000627:therapeutic use; D012313:RNA / Q000235:genetics; D051381:Rats; D011922:Rats, Mutant Strains; D020794:Receptor Protein-Tyrosine Kinases / Q000008:administration & dosage* / Q000627:therapeutic use; D012160:Retina; D055213:Retinal Pigment Epithelium / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D012174:Retinitis Pigmentosa / Q000235:genetics / Q000378:metabolism / Q000628:therapy*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors; D041623:Tomography, Optical Coherence; D019076:Transgenes; D014443:Tyrosine / Q000235:genetics; D000076202:c-Mer Tyrosine Kinase
chemical_list: D011518:Proto-Oncogene Proteins; D014443:Tyrosine; D012313:RNA; C097072:MERTK protein, human; D020794:Receptor Protein-Tyrosine Kinases; D000076202:c-Mer Tyrosine Kinase