Wellstone Center Projects

Project 1: “The implications of Dystrophin-specific T Cells for DMD Gene Correction”

Proof-of-principle studies in mouse and dog models of Duchenne muscular dystrophy (DMD) have established that gene replacement therapy is a promising treatment strategy.  Attempts to apply the tenets learned from pre-clinical to clinical protocols did not predict dystrophin-specific T cells targeting novel epitopes on muscle fibers downstream of the mutation.  In one case these were expressed on revertant fibers, a finding contrary to the axiom that forecasts a tolerizing role for these fibers. Another treatment paradigm, gentamicin-induced mutation suppression, proved equally confounding because dystrophin-specific T cells were isolated from the blood and muscle following treatment.  These observations require further study to achieve success in gene correction strategies for DMD.   We can achieve high levels of muscle fiber transduction through vascular delivery of transgene to specific leg muscles in the rhesus macaque.  This sets the stage for clinical efficacy.

Project 1 will evaluate (DMD) patients’ immune response as it relates to dystrophin-specific T cells through blood and muscle biopsy before and after glucocorticoid therapy. This will be followed by a clinical trial using gene transfer.

The specific aims of Project 1 are:

1. Characterize properties of dystrophin-specific T cells that influence the pathogenesis and treatment of DMD.
2. Define changes in dystrophin-specific T cell immunity after initiation of glucocorticoid therapy.
3. Perform a vascular delivery clinical gene transfer trial using AAV8.MCK.micro-dystrophin in subjects based on predictive factors permissive of prolonged gene expression.

Project 2: “Strategies to Overcome immunity in Gene Therapy of DMD”

Initial human clinical trials of gene therapy for DMD have revealed immune response that may prevent efficient, sustained expression of therapeutic dystrophin.  Project 2 will define, in a non-human primate model, the impact of humoral and cellular immunity on transgene expression.  A primary goal is to define strategies to evade inhibitory or destructive immune responses that are directly relevant to human gene replacement in DMD.

In Project 2 we propose to use AAV-immune rhesus macaques to:

1. Enhance transgene delivery to muscle of AVV-immune individuals by transient depletion of serum neutralizing antibodies to the vector capsid, and determine if this provokes a memory capsid-specific T cell response that destroys transduced myocytes.
2. Define the role of CD4+ and/or CD8+ T cells against a foreign transgene product in clearance or rAAV-transduced myocytes.
3. Determine if transient blockade of T cells activation and expansion facilitates persistent expression of a non-self transgene.