Abstract
Purpose :
rAAV2/2-ND4 gene therapy was developed to treat vision loss via allotopic expression of human wt-ND4 protein in mitochondria of retinal ganglion cells of LHON patients carrying the G11778 ND4 point mutation in mtDNA. Given that LHON is a sequential bilateral disease, patients will need to receive rAAV2/2-ND4 in both eyes. As AAV can trigger host immune response, we quantified anti-AAV2/2 neutralizing antibodies (NAbs) in serum and aqueous humor following sequential bilateral intravitreal (IVT) injections of rAAV2/2-ND4 to Cynomolgus monkeys.
Methods :
Male monkeys received IVT injection of vehicle (n=3 / time point) or rAAV2/2-ND4 (4.3×1010 vg/eye; 90mL; n=6 / timepoint) in the right eye at Day 1, and in the left eye either at Day 15 or at Month 3 (i.e. Day 92). After the second eye injection, animals were observed for 3 months. Anti-AAV2/2 NAbs were quantified in serum and aqueous humor samples by luciferase cell-based assay.
Results :
Anti-AAV2 NAbs were quantified in serum of animals after treatment with a 15-day delay between eyes, starting between Days 15 and 28. NAbs persisted up to Month 3.5 with titers up to 1:1,323. For animals whose eyes were treated 3 months apart, serum NAbs generally increased at Month 3-3.5, leading to a maximum titer up to 1:1,265 at Month 3.5-4. Serum NAbs then decreased until Month 6, without reaching baseline levels.
In animals treated 15 days apart, no NAbs were found in the aqueous humor of either eye. In animals treated 3 months apart, NAbs were quantified in aqueous humor of initially treated right eyes from Day 28 to Month 3.5 in 2 of 4 animals, and at Month 3.5 in the other 2 animals. Only 1 animal had aqueous NAbs in the left eye at Month 3.5, i.e. when NAbs peaked in its right eye. No clinical or histopathological ocular findings were associated with this NAb increase in eyes. There was no correlation between NAb titers in serum and in aqueous humor.
Conclusions :
An anti-AAV2 NAb response was induced in serum in all rAAV2/2-ND4 treated animals, regardless of the delay between eye injections. NAbs were also quantified in aqueous humor, but only when eye injections were 3 months apart, without inducing observable ocular manifestations. These results raise the possibility that, for sequential eye administration of LHON patients, a 2-week delay between eye treatments may afford mitigation of the ocular immune response.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.