Gene transfer of integration defective anti-HSV-1 meganuclease to human corneas ex vivo.

Corneal graft rejection is a major problem in chronic herpetic keratitis (HK) patients with latent infection. A new class of antiviral agents targeting latent and active forms of herpes simplex virus type 1 (HSV-1) is importantly required. Meganucleases are sequence-specific homing endonucleases capable of inducing DNA double-strand breaks. A proof-of-concept experiment has shown that tailor-made meganucleases are efficient against HSV-1 in vitro. To take this work a step forward, we hypothesized that the pre-treatment of human corneas in eye banks using meganuclease-encoding vectors will allow HK patients to receive a medicated cornea to resist the recurrence of the infection and the common graft rejection problem. However, this strategy requires efficient gene delivery to human corneal endothelium. Using recombinant adeno-associated virus, serotype 2/1 (rAAV2/1), efficient gene delivery of a reporter gene was demonstrated in human corneas ex vivo. The optimum viral dose was 3.7 × 10(11) VG with an exposure time of 1 day, followed by 6 days incubation in de-swelling medium. In addition, 12 days incubation can result in transgene expression in excess of 70%. Using similar transduction conditions, meganuclease transgene expression was detected in 39.4% of the endothelial cells after 2 weeks in culture. Reduction of the total viral load in the media and the endothelial cells of corneas infected with HSV-1 was shown. Collectively, this work provides information about the optimum conditions to deliver genetic material to the cornea, and demonstrates for the first time the expression of meganuclease in human corneas ex vivo and its antiviral activity. In conclusion, we demonstrate that the treatment of human corneas in eye banks before transplantation is a new approach to address the unmet clinical needs in corneal diseases.

The I-CreI meganuclease and its engineered derivatives: applications from cell modification to gene therapy.

Meganucleases (MNs) are highly specific enzymes that can induce homologous recombination in different types of cells, including mammalian cells. Consequently, these enzymes are used as scaffolds for the development of custom gene-targeting tools for gene therapy or cell-line development. Over the past 15 years, the high resolution X-ray structures of several MNs from the LAGLIDADG family have improved our understanding of their protein-DNA interaction and mechanism of DNA cleavage. By developing and utilizing high-throughput screening methods to test a large number of variant-target combinations, we have been able to re-engineer scores of I-CreI derivatives into custom enzymes that target a specific DNA sequence of interest. Such customized MNs, along with wild-type ones, have allowed for exploring a large range of biotechnological applications, including protein-expression cell-line development, genetically modified plants and animals and therapeutic applications such as targeted gene therapy as well as a novel class of antivirals.