Retinal cell type expression specificity of HIV-1-derived gene transfer vectors upon subretinal injection in the adult rat: influence of pseudotyping and promoter

Background Gene therapy, and particularly gene restoration, is currently a great hope for non-curable hereditary retinal degeneration. Clinical applications require a gene transfer vector capable of accurately targeting particular cell types in the retina. To develop such a vector, we compared the expression of a reporter gene after subretinal injections of lentiviral constructs of various pseudotypes and with the transgene expression driven by various promoters. Methods Lentiviral vectors expressing the green fluorescent protein (GFP) under the transcriptional control of cytomegalovirus (CMV), mouse phosphoglycerate kinase (PGK), human elongation factor 1-alpha (EF1 alpha), or human rhodopsin (RHO) promoters were pseudotyped by vesicular stomatitis virus (VSV) or Mokola virus envelope proteins. These constructs were injected into the subretinal space of adult rdy rats. GFP expression was analyzed in vivo 1 and 4 weeks after injection by fundus examination. The precise location of transgene expression was then determined by immunohistochemistry and in situ hybridization. Results Constructs of both vesicular stomatitis virus and Mokola pseudotypes with ubiquitous promoters led to a strong expression of GFP in vivo. Histological studies confirmed the production of GFP in the retinal pigment epithelium (RPE) in most cases. However, only the combination of the VSV pseudotype with the RHO promoter led to GFP production in photoreceptors, and did so in a sporadic manner. Conclusions Mokola-pseudotyped lentiviral vectors are effective for specific gene transfer to the RPE. Neither VSV- nor Mokola-pseudotyped lentiviral vectors are adequate for efficient gene transfer to photoreceptors of adult rats. Copyright (c) 2005 John Wiley & Sons, Ltd.