title: Caspase inhibition with XIAP as an adjunct to AAV vector gene-replacement therapy: improving efficacy and prolonging the treatment window.
abstract: OBJECTIVE
  AAV-mediated gene therapy in the rd10 mouse, with retinal degeneration caused by mutation in the rod cyclic guanosine monophosphate phosphodiesterase β-subunit (PDEβ) gene, produces significant, but transient, rescue of photoreceptor structure and function. This study evaluates the ability of AAV-mediated delivery of X-linked inhibitor of apoptosis (XIAP) to enhance and prolong the efficacy of PDEβ gene-replacement therapy.
  
  
  METHODS
  Rd10 mice were bred and housed in darkness. Two groups of animals were generated: Group 1 received sub-retinal AAV5-XIAP or AAV5-GFP at postnatal age (P) 4 or 21 days; Group 2 received sub-retinal AAV5-XIAP plus AAV5- PDEβ, AAV5-GFP plus AAV5- PDEβ, or AAV- PDEβ alone at age P4 or P21. Animals were maintained for an additional 4 weeks in darkness before being moved to a cyclic-light environment. A subset of animals from Group 1 received a second sub-retinal injection of AAV8-733-PDEβ two weeks after being moved to the light. Histology, immunohistochemistry, Western blots, and electroretinograms were performed at different times after moving to the light.
  
  
  RESULTS
  Injection of AAV5-XIAP alone at P4 and 21 resulted in significant slowing of light-induced retinal degeneration, as measured by outer nuclear thickness and cell counts, but did not result in improved outer segment structure and rhodopsin localization. In contrast, co-injection of AAV5-XIAP and AAV5-PDEβ resulted in increased levels of rescue and decreased rates of retinal degeneration compared to treatment with AAV5-PDEβ alone. Mice treated with AAV5-XIAP at P4, but not P21, remained responsive to subsequent rescue by AAV8-733-PDEβ when injected two weeks after moving to a light-cycling environment.
  
  
  CONCLUSIONS
  Adjunctive treatment with the anti-apoptotic gene XIAP confers additive protective effect to gene-replacement therapy with AAV5-PDEβ in the rd10 mouse. In addition, AAV5-XIAP, when given early, can increase the age at which gene-replacement therapy remains effective, thus effectively prolonging the window of opportunity for therapeutic intervention.
authors.affiliation: Department of Ophthalmology and Visual Sciences, University of Michigan Medical School, Ann Arbor, Michigan, United States of America.
authors.forename: Jingyu
authors.initials: J
authors.lastname: Yao
authors.forename: Lin
authors.initials: L
authors.lastname: Jia
authors.forename: Naheed
authors.initials: N
authors.lastname: Khan
authors.forename: Qiong-Duan
authors.initials: QD
authors.lastname: Zheng
authors.forename: Ashley
authors.initials: A
authors.lastname: Moncrief
authors.forename: William W
authors.initials: WW
authors.lastname: Hauswirth
authors.forename: Debra A
authors.initials: DA
authors.lastname: Thompson
authors.forename: David N
authors.initials: DN
authors.lastname: Zacks
mesh_terms: D000818:Animals; D061945:Caspase Inhibitors; D054707:Cyclic Nucleotide Phosphodiesterases, Type 6 / Q000096:biosynthesis / Q000235:genetics*; D000229:Dependovirus / Q000235:genetics; D004195:Disease Models, Animal; D004596:Electroretinography; D015316:Genetic Therapy / Q000379:methods*; D005822:Genetic Vectors; D008027:Light / Q000009:adverse effects; D051379:Mice; D008810:Mice, Inbred C57BL; D020419:Photoreceptor Cells, Vertebrate / Q000378:metabolism; D012162:Retinal Degeneration / Q000235:genetics / Q000628:therapy*; D051636:X-Linked Inhibitor of Apoptosis Protein / Q000627:therapeutic use
chemical_list: D061945:Caspase Inhibitors; D051636:X-Linked Inhibitor of Apoptosis Protein; D054707:Cyclic Nucleotide Phosphodiesterases, Type 6; C517438:Pde6b protein, mouse