Objective:

Background:

LN is an AAV2-based gene therapy for LHON patients carrying the m.11778G>A MT-ND4 mutation. All LN gene therapy trials have demonstrated a bilateral effect after unilateral intravitreal injection.

Design/Methods:

Two patients with MT-ND4-LHON received an intravitreal injection of LN in one eye and a sham injection in the other within 6 months after bilateral vision loss. Post-mortem histopathological and molecular (ddPCR) analyses were performed on laser-captured retinal and optic nerve samples.

Results:

Within 2 months of gene therapy, both participants developed intraocular inflammation in the treated eye; both events resolved within months. Patient 1 died of acute alcohol toxicity and patient 2 of cardiac arrest. Patient 1 had severe optic atrophy and loss of retinal ganglion cells (RGCs), while patient 2 was a milder case of LHON, with consistent preservation of RGCs and optic nerve axons, with only the temporal fibers lost. In patient 1, an angiocentric lymphocytic chronic inflammation was noted in the optic nerve head and temporal retina. No persistent inflammation was seen in patient 2. AAV2-ND4 distribution in the treated eye was asymmetric in both patients, more prevalent in temporal RGCs. A much lower level of AAV2-ND4 was detected in the retina of the untreated eye in both cases. MtDNA copy number was upregulated in both eyes of patient 2, possibly reflecting better preservation of RGCs and axons.

Conclusions:

This is the first postmortem study of human eyes injected unilaterally with AAV2-based gene therapy. Gene transfection of RGCs was successful in both eyes despite unilateral administration. AAV2-ND4 transfer seems to be facilitated by axonal preservation, to be confirmed and further characterized by additional analyses of the eyes, nerves, optic chiasm and optic tracts from patient 2.