Lack of Immunotoxicity After Regional Intravenous (RI) Delivery of rAAV to Nonhuman Primate Skeletal Muscle

Abstract

In the absence of an immune response from the host, intramuscular (IM) injection of recombinant adeno-associated virus (rAAV) results in the permanent expression of the transgene from mouse to primate models. However, recent gene transfer studies into animal models and humans indicate that the risk of transgene and/or capsid-specific immune responses occurs and depends on multiple factors. Among these factors, the route of delivery is important, although poorly addressed in large animal models. Here, we compare the IM and the drug-free regional intravenous (RI) deliveries of rAAV in nonhuman primate (NHP) skeletal muscle monitoring the host immune response toward the transgene. We show that IM is consistently associated with immunotoxicity and the destruction of the genetically modified myofibers, whereas RI allows the stable expression of the transgene. This has important implications for the design of clinical trials for gene transfer in skeletal muscle.

Peripheral transvenular delivery of adeno-associated viral vectors to skeletal muscle as a novel therapy for hemophilia B

“…In this study, expression levels of transgene were stable for at least 34 months and 4-to 8-fold higher after intravascular (via ATVRX) versus intramuscular delivery of vector. 38 A subsequent study from the same group used the LEA29Y transgene delivered intramuscularly or intravascularly to prevent responses to the transactivator protein rtTA-M2, 39 showing better results when the vector encoding LEA29Y was administered via ATVRX. Several other reports show successful muscle transduction with viral and nonviral vectors using intravascular routes with or without pressure delivery.…”

Human Treg responses allow sustained recombinant adeno-associated virus–mediated transgene expression

“…AAT deficiency remains a very high target for full replacement, and many questions remain, as higher doses and immune suppression are contemplated for future trials. However, given the scalability of rAAV vector production (34), the availability of clinically tolerable limb infusion methods (22,23,35,36), and the relatively modest levels of immune suppression that may have a salient effect (6), it would seem that trials designed to achieve therapeutic levels of serum AAT should be feasible.…”

Progress with Recombinant Adeno-Associated Virus Vectors for Gene Therapy of Alpha-1 Antitrypsin Deficiency

“…One way that has been shown to effectively target the entire limb is to employ a regional limb delivery method, whereby the vector is delivered into the vasculature of a limb that has been isolated from the systemic circulation using a tourniquet. [30][31][32][33][34][35][36][37][38] These methods have long been used in human patients to treat limb neoplasia and proofof-concept gene therapy delivery studies have been performed in patients with muscular dystrophy. 31,33 There is also evidence that limb infusion delivery has a lower level of immune stimulation compared with intramuscular delivery, which may increase transgene expression.…”

“…31,33 There is also evidence that limb infusion delivery has a lower level of immune stimulation compared with intramuscular delivery, which may increase transgene expression. 38 Other methods to decrease the immune response could be employed, including systemic immunosuppression, either in response to clinical evidence of inflammation (rise in serum creatine kinase, indicating myocyte damage) or prophylactically for a short period of time beginning at or before vector delivery to prevent an immune response from being initiated. Another strategy to decrease the immune response might be to select or create a capsid type with lower preexisting immunity or immune profile in humans.…”