Our recent clinical trial using adeno-associated viral vectors (AAV) to deliver Mini-Dystrophin to the muscle of patients with Duchenne muscular dystrophy (DMD) was met with an unexpected result;after treatment, a Dystrophin-specific T-cell response was found in two patients, which was related to revertant fiber development prior to therapy. These Dystrophin-specific T cells have the potential to eradicate all genetically modified muscle resulting in an ineffective therapy, as well as presenting a general concern for gene therapy communities in general. Currently, no strategy exists to avoid transgene-specific CTLs, whether they are pre-existing or therapy- induced, and systemic long-term immunosuppression is considered a non-viable option. However, particular viruses found in nature have evolved a potential solution to this dilemma by synthesizing small peptides that inhibit antigen presentation only in transduced cells. In preliminary experiments, we demonstrate that the cellular synthesis of these viral inhibitory peptides (termed VIPRs) prevents the surface presentation of a well-defined antigen, thus protecting transduced cells from the host's immune response. In the current proposal, we will use a canine DMD model (GRMD) to evaluate the evasion ability of VIPRs from Dystrophin- specific CTL-mediated elimination of AAV transduced muscles. First, we will test whether the utilization of VIPRs can block the induction of a Dystrophin-specific CTL response after AAV muscle injection (Aim 1). Next, we will study whether the application of VIPRs will help AAV transduced muscle fibers escape pre-existing Dystrophin-specific CTL-mediated elimination (Aim 2). To decrease the vector cassette size for efficient virion package and/or to enhance the evasion ability of VIPRs, we will optimize the VIPR domains and test the immune evasion capacity of mutant variants (Aim 3). By delivering VIPRs and mini-dystrophin in the same vector, this approach ensures that antigen presentation will be attenuated only in AAV- transduced cells without systemic side effects on the immune system (as would be the case using immunosuppressive drugs or by the application of regulatory T-cells). Collectively, this proposal outlines a promising strategy to overcome our clinical DMD observations and concerns for gene therapy studies in general, by creating an AAV vector capable of avoiding the host's immune response to a foreign protein.
In this proposal we will study the immune-mediated clearance of genetically modified cells in dystrophic muscle. Then, we will rely on an approach taken from human viruses to evade the host's immune response which can kill gene therapy treated cells. This evasion technique will be employed during therapeutic treatment using a viral gene therapy vector in large animal models of Duchenne muscular dystrophy (DMD). Positive outcomes from these studies will justify moving this strategy forward into a clinical trial to treat patients wit DMD.
|Hirsch, Matthew L; Wolf, Sonya J; Samulski, R J (2016) Delivering Transgenic DNA Exceeding the Carrying Capacity of AAV Vectors. Methods Mol Biol 1382:21-39|
|Vance, Melisa; Llanga, Telmo; Bennett, Will et al. (2016) AAV Gene Therapy for MPS1-associated Corneal Blindness. Sci Rep 6:22131|
|Xiao, Ping-Jie; Mitchell, Angela M; Huang, Lu et al. (2016) Disruption of Microtubules Post-Virus Entry Enhances Adeno-Associated Virus Vector Transduction. Hum Gene Ther 27:309-24|
|Li, Chengwen; Wu, Shuqing; Albright, Blake et al. (2016) Development of Patient-specific AAV Vectors After Neutralizing Antibody Selection for Enhanced Muscle Gene Transfer. Mol Ther 24:53-65|
|Nicolson, Sarah C; Li, Chengwen; Hirsch, Matthew L et al. (2016) Identification and Validation of Small Molecules That Enhance Recombinant Adeno-associated Virus Transduction following High-Throughput Screens. J Virol 90:7019-31|
|Hirsch, M L (2015) Adeno-associated virus inverted terminal repeats stimulate gene editing. Gene Ther 22:190-5|
|Goodrich, L R; Grieger, J C; Phillips, J N et al. (2015) scAAVIL-1ra dosing trial in a large animal model and validation of long-term expression with repeat administration for osteoarthritis therapy. Gene Ther 22:536-45|
|Hastie, Eric; Samulski, R Jude (2015) Recombinant adeno-associated virus vectors in the treatment of rare diseases. Expert Opin Orphan Drugs 3:675-689|
|Lentz, Thomas B; Samulski, R Jude (2015) Insight into the mechanism of inhibition of adeno-associated virus by the Mre11/Rad50/Nbs1 complex. J Virol 89:181-94|
|Wang, M; Crosby, A; Hastie, E et al. (2015) Prediction of adeno-associated virus neutralizing antibody activity for clinical application. Gene Ther 22:984-92|
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