Immunoadsorption enables successful rAAV5-mediated repeated hepatic gene delivery in nonhuman primates

Abstract

Key Points• IA procedure decrease anti-AAV5 NABs to levels compatible with a successful AAV5 vector readministration.• Patients positive for anti-AAV antibodies could benefit from AAVbased gene therapy after IA treatment.Adeno-associated virus (AAV)-based liver gene therapy has been shown to be clinically successful. However, the presence of circulating neutralizing antibodies (NABs) against AAV vector capsids remains a major challenge as it may prevent successful transduction of the target cells. Therefore, there is a need to develop strategies that would enable AAV-mediated gene delivery to patients with preexisting anti-AAV NABs. In the current study, the feasibility of using an immunoadsorption (IA) procedure for repeated, liver-targeted gene delivery in nonhuman primates was explored. The animals were administered IV with recombinant AAV5 (rAAV5) carrying the reporter gene human secreted embryonic alkaline phosphatase (hSEAP). Seven weeks after the first rAAV treatment, all of the animals were readministered with rAAV5 carrying the therapeutic hemophilia B gene human factor IX (hFIX). Half of the animals administered with rAAV5-hSEAP underwent IA prior to the second rAAV5 exposure.The transduction efficacies of rAAV5-hSEAP and rAAV5-hFIX were assessed by measuring the levels of hSEAP and hFIX proteins. Although no hFIX was detected after rAAV5-hFIX readministration without prior IA, all animals submitted to IA showed therapeutic levels of hFIX expression, and a threshold of anti-AAV5 NAB levels compatible with successful readministration was demonstrated. In summary, our data demonstrate that the use of a clinically applicable IA procedure enables successful readministration of an rAAV5-based gene transfer in a clinically relevant animal model. Finally, the analysis of anti-AAV NAB levels in human subjects submitted to IA confirmed the safety and efficacy of the procedure to reduce anti-AAV NABs. Furthermore, clinical translation was assessed using an immunoglobulin G assay as surrogate.

Capsid-specific removal of circulating antibodies to adeno-associated virus vectors

“…1b). As previously published 25,27 , the Plasmapheresis animal displayed the highest VGCN in all tissues, closely followed by the Naïve animal. Conversely, as expected, the Control animal had the lowest VGCN in most tissues except for spleen ( Fig.…”

“…1:1000) pre-treatment antibodies. In the preclinical setting, non-specific plasma absorption of circulating IgG has also been explored as a strategy to remove anti-AAV antibodies [24][25][26][27] .…”

Blockade of the costimulatory CD28‐B7 family signal axis enables repeated application of AAV8 gene vectors

“…Accordingly, preexisting AAV antibody levels would not be reduced by using CTLA4‐IgG. Other technologies such as immune adsorption columns could be used to remove preexisting AAV8 antibodies . However, CTLA‐4 IgG could play an important role in suppressing preexisting memory T‐cell responses that are considered to kill transduced hepatocytes …”

Successful Transduction with AAV Vectors after Selective Depletion of Anti-AAV Antibodies by Immunoadsorption

“…It has recently been reported that AAV5 has an unusual immune profile. [16][17][18] For instance, a recent publication suggests that non-human primates with NAb titers of an average of >5,000 show only a 2.9-fold reduction in transduction compared to animals that are negative for NAbs. 18 Unfortunately, a detailed description of the NAb assay is not provided by Ferreira and colleagues.…”

“…[16][17][18] For instance, a recent publication suggests that non-human primates with NAb titers of an average of >5,000 show only a 2.9-fold reduction in transduction compared to animals that are negative for NAbs. 18 Unfortunately, a detailed description of the NAb assay is not provided by Ferreira and colleagues. 18 However, a thorough investigation of the literature cited in Salas et al 18 (and of relevant articles that have been cited in articles referenced in their publication 16,17 ) suggests that in their NAb assay, the number of vg-containing particles per mL serum is $3.8 Â 10 5 .…”