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Mol Ther Methods Clin Dev. 2018 Aug 4;10:257-267. doi: 10.1016/j.omtm.2018.07.011. eCollection 2018 Sep 21.

An Observational Study from Long-Term AAV Re-administration in Two Hemophilia Dogs.

Author information

1
Gene Therapy Center, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
2
Division of Pharmacoengineering and Molecular Pharmaceutics, Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
3
Department of Pathology and Laboratory Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
4
Department of Pediatrics, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
5
Department of Biochemistry, University of Alabama at Birmingham, Birmingham, AL, USA.
6
Department of Pharmacology, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.

Abstract

Adeno-associated virus (AAV) vectors have been successfully applied in hemophilia clinical trials. However, this approach is limited to patients without AAV-neutralizing antibodies (NAbs). In this study, we explored the feasibility of AAV re-administration in hemophilia A dogs treated initially 8 years ago with AAV8.canine FVIII. After the re-administration in two NAb-negative dogs with AAV8 vectors carrying human factor VIII (hFVIII), along with the proteasome inhibitor bortezomib, we observed a phenotypic improvement in both dogs that persisted in one dog. Phenotypic improvement disappeared at 59 days after re-administration in the other dog, and specific cytotoxic T lymphocytes (CTLs) to the capsid were detected at day 17, but not to hFVIII. hFVIII inhibitors were observed at day 59 and gradually increased. Mechanistic studies demonstrated an increase in pro-inflammatory cytokines, a decrease in immunomodulatory cytokines, as well as lower Tregs after re-administration. These results suggest that hFVIII inhibitor development may contribute to the therapeutic failure via immune response activation. Interestingly, it takes about 30-50 days for AAV NAb titers to decrease by half. Collectively, this study suggests that re-administration of the same AAV serotype after long-term follow-up is feasible and that the study of AAV NAb kinetics will provide important information for predicating the efficacy of re-administration.

KEYWORDS:

AAV; NAbs; hFVIII; hFVIII inhibitor; hemophilia; human factor VIII; neutralizing antibodies; re-administration

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