Persistent transgene product in retina, optic nerve and brain after intraocular injection of rAAV

Abstract

Recombinant adeno-associated virus (rAAV) is a promising vector for retinal application as it transduces photoreceptors and retinal pigment epithelium cells efficiently and in a stable fashion. Because rAAV also transduces retinal ganglion cells, we reasoned that ocular application of rAAV might result in delivery of transgenic protein to the CNS. Here we describe high levels of green fluorescent protein (GFP) persisting at least 6 months in optic nerves and brains of mice and dogs after intravitreal delivery of rAAV-GFP. There was no clinical or histological evidence of inflammatory response although a mild humoral Th-2 response to viral capsid proteins was detected. These findings have important implications with respect to therapeutic applications of rAAV.

Immune response following intraocular delivery of recombinant viral vectors

“…AAV serotype 2 (AAV2) has been used successfully and efficiently through subretinal injection to transduce photoreceptors and RPE in a number of gene therapy paradigms. [12][13][14][15][16][17][18][19][20][21][22][23][24][25] This virus also targets ganglion cells efficiently if it is injected intravitreally 26,27 (Figure 1). AAV2 has not been found, as yet, to target structures in the anterior chamber of the eye.…”

“…After intraocular delivery of AAV, there is suppression of DTH, but an induction of IgG1 and IgG2b (Th2-type) antibodies. 26,27,49 This appears at least in part because of the fact that AAV does not transduce APCs. 48 This virus can, however, induce a strong antibody response directed at both viral antigens and the transgene.…”

“…48 This virus can, however, induce a strong antibody response directed at both viral antigens and the transgene. [25][26][27] Antibodies are detected in intraocular fluid (anterior chamber fluid and vitreous) as well as in serum. Nevertheless, the immune response following intraocular injection of AAV is similar to that described in ACAID (ie, a predominant Th2 like response).…”

Recombinant AAV-mediated gene transfer to the retina: gene therapy perspectives

“…[17][18][19] Intravitreal injection of rAAV-2 leads to efficient ganglion cell transduction. [20][21][22][23] We and others have studied rAAV chimeric serotypes in which the vector is flanked by AAV-2 ITRs, but encapsidated in an AAV-1, -2, -3, -4 or -5 shell generating rAAV-2/1,-2/2, -2/3, -2/4 and -2/5, respectively. In the mouse, subretinal injection of rAAV-2/1egfp shows early onset of EGFP expression (3-4 days) with transgene expression restricted to the RPE.…”

“…26 Regarding intravitreal injection, it has been demonstrated that following delivery of rAAV-2/2gfp, high levels of GFP protein persist for at least 6 months in the optic nerves and brains of mice and dogs. 20 In addition, injection of rAAV-2/2lacZ in the vitreous cavity of guinea pigs leads to b-galactosidase expression in fibers, glial cells and blood vessels of the optic nerve. 22 More recently, it was shown that GUSB activity can be detected in the brain after intravitreal injection of rAAV-2/2gusb in mucopolysaccharidosis VII mice, suggesting that the protein, not the vector, spreads within the brain by both neuronal transport and diffusion.…”