Longitudinal evaluation of hyper-reflective foci in the retina following subretinal delivery of adeno-associated virus in non-human primates

Abstract

Purpose: The purpose of this study was to evaluate whether clinical grade recombinant adeno-associated virus serotype 8 (rAAV8) leads to increased appearance of hyperreflective foci (HRF) in the retina of non-human primates (NHPs) following subretinal gene therapy injection. Methods: Different doses of rAAV8 vector (rAAV8. human phosphodiesterase 6A subunit (hPDE6A) at lowdose: 1×1011 vector genomes (vg), medium dose: 5×1011 vg, or high dose: 1×1012 vg)were injected subretinally intothe left eyes of NHPs in a formal toxicology study in preparation of a clinical trial. Right eyes received sham-injection. After 3 months of in vivo, follow-up retinal sections were obtained and analyzed. The number of HRF on spectral domain-optical coherence tomography (SD-OCT) volume scans were counted from both eyes at 30 and 90 days. Results: Animals fromthe high-dose group showedmore HRF than in the low(P=0.03) and medium (P = 0.01) dose groups at 90 days. There was a significant increase in the mean number of HRF in rAAV8-treated eyes compared with sham-treated eyes at 90 days (P=0.02). Sham-treated eyes demonstrated a nonsignificant reduction of HRF numbers over time. In contrast, a significant increase over timewas observed in the rAAV8-treated eyes of the high dose group (P = 0.001). The presence of infiltrating B- and T-cells and microglia activation were detected in rAAV8-treated eyes. Conclusions: Some HRF in the retina appear to be related to the surgical trauma of subretinal injection. Although HRF in sham-treated retina tends to becomeless frequent over time, they accumulate in the high-dose rAAV8-treated eyes. This may suggest a sustained immunogenicity when subretinal injections of higher doses of rAAV8 vectors are applied, but it has lower impact when using more clinically relevant doses (low and medium groups). Translational Relevance: An increase or persistence of HRFs following retinal gene therapy may indicate the need for immunomodulatory treatment.