Host immune responses after suprachoroidal delivery of AAV8 in nonhuman primate eyes

Abstract

The suprachoroid is a potential space located between the sclera and choroid of the eye which provides a novel route for ocular drug or viral vector delivery. Suprachoroidal injection of AAV8 using transscleral microneedles enables widespread transgene expression in eyes of nonhuman primates, but may cause intraocular inflammation. We characterized the host humoral and cellular immune responses after suprachoroidal delivery of AAV8 expressing green fluorescent protein (GFP) in rhesus macaques, and found that it can induce a mild chorioretinitis that resolves after systemic corticosteroid administration, with recovery of photoreceptor morphology but persistent immune cell infiltration after 3 months. Suprachoroidal AAV8 triggered B-cell and T-cell responses against GFP, but only mild antibody responses to the viral capsid as compared to intravitreal injections of the same vector and dose. Systemic biodistribution studies showed lower AAV8 levels in liver and spleen after suprachoroidal injection compared with intravitreal delivery. Our findings suggest that suprachoroidal AAV8 primarily triggers host immune responses to GFP, likely due to sustained transgene expression in scleral fibroblasts outside the blood-retinal barrier, but elicits less humoral immune reactivity to the viral capsid than intravitreal delivery due to lower egress into systemic circulation. Thus, suprachoroidal AAV delivery of human transgenes may have significant translational potential for retinal gene therapy.

Ocular Inflammation and Treatment Emergent Adverse Events in Retinal Gene Therapy

“…The loss in transgene expression was attributed to chorioretinal infiltration of inflammatory cells which was accompanied by greater humoral and cellular responses to the GFP transgene, whereas intravitreal injection of the same vector and dose produced minimal transgene expression but greater sequestration to the spleen and stronger antibody responses to the AAV8 capsid. 86 Interestingly, GFP expression after suprachoroidal vector delivery appears to persist in scleral fibroblasts at month 3. Together, these studies suggest that the greater trabecular outflow of viral vectors from the vitreous cavity to the bloodstream and spleen can trigger stronger host immune responses to the AAV capsid, compared with the slower uveoscleral outflow of virus from the suprachoroidal space.…”

Suprachoroidal Delivery of Small Molecules, Nanoparticles, Gene and Cell Therapies for Ocular Diseases

“…The potential of SC gene therapies using marker genes, such as green fluorescent proteins (GFP) and luciferase, has been studied preclinically [ 80 , 81 , 82 ]. Briefly, multiple animal studies have demonstrated proof of concept with GFP expression after SC injections of adeno-associated viral vector (AAV) and nonviral vectors expressing GFP [ 83 , 84 , 85 , 86 , 87 , 88 , 89 , 90 ]. In addition, the application of nanoparticle systems to deliver drugs or gene therapy into the SCS may further enhance therapeutic potential by optimizing for durability or particle spread [ 91 , 92 ].…”

Drug Delivery via the Suprachoroidal Space for the Treatment of Retinal Diseases

“…Yiu et al and Chung et al [ 93 , 95 ] reported a lower systemic humoral immune response with SC AAV8, compared to IVT AAV8; however, intraocular inflammation was more evident with AAV8 delivered to the SCS, compared to the subretinal space. Furthermore, there was a decreased transgene expression after 2 and 3 months that was hypothesized to be due to cellular damage and phagocytic activity related to the increased local inflammation.…”