Article

Safety of AAV Factor IX Peripheral Transvenular Gene Delivery to Muscle in Hemophilia B Dogs

Division of Hematology and Center for Cellular and Molecular Therapeutics, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania 19104, USA.
Molecular Therapy (Impact Factor: 6.43). 07/2010; 18(7):1318-29. DOI: 10.1038/mt.2010.73
Source: PubMed

ABSTRACT Muscle represents an attractive target tissue for adeno-associated virus (AAV) vector-mediated gene transfer for hemophilia B (HB). Experience with direct intramuscular (i.m.) administration of AAV vectors in humans showed that the approach is safe but fails to achieve therapeutic efficacy. Here, we present a careful evaluation of the safety profile (vector, transgene, and administration procedure) of peripheral transvenular administration of AAV-canine factor IX (cFIX) vectors to the muscle of HB dogs. Vector administration resulted in sustained therapeutic levels of cFIX expression. Although all animals developed a robust antibody response to the AAV capsid, no T-cell responses to the capsid antigen were detected by interferon (IFN)-gamma enzyme-linked immunosorbent spot (ELISpot). Interleukin (IL)-10 ELISpot screening of lymphocytes showed reactivity to cFIX-derived peptides, and restimulation of T cells in vitro in the presence of the identified cFIX epitopes resulted in the expansion of CD4(+)FoxP3(+)IL-10(+) T-cells. Vector administration was not associated with systemic inflammation, and vector spread to nontarget tissues was minimal. At the local level, limited levels of cell infiltrates were detected when the vector was administered intravascularly. In summary, this study in a large animal model of HB demonstrates that therapeutic levels of gene transfer can be safely achieved using a novel route of intravascular gene transfer to muscle.

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    • "Staining for FoxP3 revealed the presence of FoxP3+ /CD4+ T cells in muscle tissue after injection of alipogene tiparvovec. Previous work involving intravascular delivery of the canine FIX transgene by AAV2/2 in the muscle in a dog model for hemophilia B (Arruda et al., 2005; Haurigot et al., 2010) showed that stable transgene expression was associated with the presence of Tregs. Our findings support the theory proposed by Mays and Wilson (2011) that in case AAV vector administration does not initiate sufficient innate immune activation, a mechanism of passive tolerance may result through ignorance, anergy, or deletion. "
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    • "Transient immunosuppression with cyclophosphamide prevented anti-cFIX antibody formation and resulted in sustained transgene expression via either an intramuscular or intravascular delivery route (Herzog et al., 2001; Arruda et al., 2005, 2010). In another study by Haurigot et al. (2010), 6 weeks of immunosuppression with cyclophosphamide did not prevent the development of anti-AAV antibody and T cell infiltrates in muscle, and the T cells were transgene specific. "
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