Purpose
In our previous work we induced and prevented LHON in mice by sequential injections of two AAV’s, one containing wild-type ND4 and the other mutant human ND4. Development of neutralizing antibodies prevented separation of the double injections by more than a few days, thus we were unable to determine whether wild-type ND4 could improve vision after it was lost. Transgenic mutant ND4 mice have visual loss that begins at 3 months and progresses to blindness 8-11 months after birth. Using transgenic mutant ND4 mice we evaluated whether visual loss can be reversed by intraocular injection of AAV expressing wild-type human ND4.
Methods
Transgenic mice (n=44) expressing the mutant human NADH ubiquinone oxidoreductase subunit 4 (muthND4) were separated into two groups. The wild-type human ND4 gene with a FLAG epitope tag, under control of the mitochondrial HSP promoter (sc-HSP-ND4FLAG), was packaged with mito-targeted AAV2 (COX8). To intervene quickly after the onset of visual loss, both eyes of mice with low PERG amplitudes were injected with mitochondrially targeted scAAV containing the wild-type (WT) human ND4. Littermates with better vision (higher PERG amplitudes) were injected with sterile PBS.
Results
To intervene quickly after the onset of visual loss, both eyes of mice with low PERG amplitudes were injected with mitochondrially targeted scAAV containing WT human ND4. Littermates with better vision (higher PERG amplitudes) were injected with sterile PBS. One month later, the amplitudes of wild-type ND4 rescued mice improved compared to their baseline values (p=4.6E-5) (Fig. 1A) and those of littermates injected with PBS (p=0.0005), in whom amplitudes dropped significantly compared to their baseline (p=0.001) (Fig. 1B).
Conclusions
Visual loss induced by the mutant ND4 in its early stages appears to be rescued by gene therapy with the wild-type allele suggesting hope for acutely blinded LHON patients.