A chimeric anti-vascularization immunomodulator prevents high-risk corneal transplantation rejection via ex vivo gene therapy.

Corneal blindness affects more than 5 million individuals, with over 180,000 corneal transplantations (CTs) performed annually. In high-risk CTs, almost all grafts are rejected within 10 years. Here, we investigated adeno-associated virus (AAV) ex vivo gene therapy to establish immune tolerance in the corneal allograft to prevent high-risk CT rejection. Our previous work has demonstrated that HLA-G contributes to ocular immune privilege by inhibiting both immune cells and neovascularization; however, homodimerization is a rate-limiting step for optimal HLA-G function. Therefore, a chimeric protein called single-chain immunomodulator (scIM), was engineered to mimic the native activity of the secreted HLA-G dimer complex and eliminate the need for homodimerization. In a murine corneal burn model, AAV8-scIM significantly reduced corneal vascularization and fibrosis. Next, ex vivo AAV8-scIM gene delivery to corneal allografts was evaluated in a high-risk CT rejection rabbit model. All scIM-treated corneas were well tolerated and transparent after 42 days, while 83% of vehicle-treated corneas were rejected. Histologically, AAV-scIM-treated corneas were devoid of immune cell infiltration and vascularization, with minimal fibrosis at the host-graft interface. The data collectively demonstrate that scIM gene therapy prevents corneal neovascularization, reduces trauma-induced corneal fibrosis, and prevents allogeneic CT rejection in a high-risk large animal model.