Humoral immune response to subretinal AAV8 in non-human primates

Abstract

Purpose : Knowledge of the humoral immune response to single subretinal administration of clinical grade recombinant adeno-associated virus (rAAV) in non-human primates is a key factor for the development of safe and efficient clinical trial protocols for retinal gene therapy. This study investigated longitudinal changes of anti-drug-antibody (ADA) titres in non-human primates (NHPs, Macacca fascicularis) between before and after single administration of rAAV8-pseudotyped virus.

Methods : 18 NHPs received subretinal injections in three cohorts (high dose: 1x10¹² vector genomes [vg], low dose: 1x10¹¹ vg, or vehicle only) and concomitant immunosuppressive therapy equivalent to a clinical trial scenario. Four additional animals received intravitreal injections to mimic via falsa application. Baseline samples were compared to those taken 1, 2 and 3 days and 1, 4 and 13 weeks after application of the vector. A sandwich-ELISA was developed and used to quantify ADAs directed against the rAAV8 capsid

Results : ADA titres in all animals of the high dose group stayed constant over the 13-week observation period. Variability was greater in the low dose and the intravitreal control cohort. Mean titres pre- and 4 weeks post-treatment were 50.82 ± 35.67 (mean ± sd) and 47.70 ± 30.24 in all animals receiving vector. The mean titres of low and high dose group did not vary from the ones of the control group, which had received only saline injections.

Conclusions : This study provides data relevant for clinical retinal gene therapy trials, where rAAV8 might be used for subretinal delivery of therapeutic transgenes. When mimicking the clinical scenario with clinical grade vector, surgery and concomitant immunosuppression, no induction of anti-drug-antibodies occurred in non-human primates.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.