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Brian C Gilger, Laura Conatser, Jacklyn H Salmon, Richard Davis, Matthew Hirsch; AAV vector-mediated HLA-G expression to prevent corneal transplant rejection. Invest. Ophthalmol. Vis. Sci. 2018;59(9):3317.
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© ARVO (1962-2015); The Authors (2016-present)
Rejection rates following corneal transplantation (CT) remain high. Current treatments are limited in efficacy and elicit undesirable effects. We aim to develop an effective therapy to reduce corneal graft rejection using an adeno-associated virus (AAV) gene therapy designed to exploit the natural immune tolerance mechanism of human leukocyte antigen G (HLA-G).
Self-complementary AAV (scAAV) cassettes containing codon optimized HLA-G1 (transmembrane) or HLA-G5 (soluble) isoforms were validated in human cell culture with no indication of toxicity. Prior to CT, corneal donor buttons were incubated in a solution containing scAAV8G9-GFP (control) or scAAV8G9-HLA-G1/G5 for 1 hour. Rabbit or transplant grade human cornea were used as donor tissue. Central full-thickness CT was performed in one eye of normal New Zealand White rabbits. Ocular inflammation, corneal vascularization, corneal thickness, and rejection index (RI) were monitored after surgery. Once rejected, the rabbits were euthanized and eyes collected. Corneal sections were stained for GFP or HLA-G abundance. Serum collected before and after CT was analyzed for capsid neutralizing antibodies. Also, liver, brain, kidney, heart, gluteal muscle, and draining lymph nodes were harvested for assessment of vector biodistribution.
In allotransplantation (rabbit donor to rabbit host), corneal vascularization and corneal graft edema were observed in GFP treated rabbit corneas by 10 days after surgery (RI > 6). HLA-G1/G5 treated rabbit CT remained clear with no corneal vascularization over 84 days. In xenotransplantation (human donor to rabbit host), HLA-G therapy significantly delayed rejection from 17.75+/-3.0 days after surgery (GFP) to 29.0+/-4.6 days (HLA-G) (p=0.015). Cornea sections showed high levels of HLA-G or GFP immunostaining throughout the stroma. Vector biodistribution was limited to the eye.
The data demonstrate ex vivo incubation of corneal grafts with scAAV8G9-HLA-G1/G5 prevented rejection of allograph CT and more importantly, delayed rejection in xenotransplantation. Validation is needed in other relevant models, but to prevent human to human, or animal to human CT rejection would be directly applicable to millions of patients worldwide with vision loss each year. Beyond the eye, successful execution of these studies would set precedence for use of ex vivo AAV-HLA-G in theoretically any tissue transplantation.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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