Collaborative Project #9: Novel Macrophage and Regulatory T Cell Interactions that Promote the Pathogenesis of Duchenne Muscular Dystrophy
Collaborating Investigator: Armando Villalta, PhD
Affiliation: Assistant Professor, Physiology & Biophysics; University of California, Irvine
Funding Source: NIH
Grant Number: 2R01NS120060
Project Period: 09/30/20-08/31/25
Significance
Duchenne muscular dystrophy (DMD) is caused by loss-of-function mutations in the dystrophin gene that lead to widespread muscle degeneration, and the disease is therefore frequently treated via dystrophin gene replacement therapy using recombinant adeno-associated virus (rAAV)-microdystrophin. Unfortunately, many patients develop immune responses to either rAAV or the dystrophin protein itself, creating an urgent need to counteract immune rejection of this life-saving and potentially curative DMD treatment. The Villalta Lab seeks to determine whether rAAV and dystrophin immunity limit the efficacy and long-term stability of rAAV microdystrophin gene therapy and to develop novel immunotherapeutic approaches that will overcome these limitations. The presence of pre-existing or induced vector-specific immunity raises concerns that the host immune system may potentially serve as a barrier to treatment, impeding the efficacy of rAAV microdystrophin gene therapy and preventing repeat dosing. Thus, developing strategies to study and mitigate rAAV-specific immunity will be paramount in the effort to improve dystrophin restoration and allow continual dosing of gene therapy. The objective of this CP is to determine whether muscle-specific delivery of molecular interventions that induce potent expansion of regulatory T cells (Tregs) will lead to durable suppression of rAAV immunity to improve the efficacy of rAAV-microdystrophin gene therapy and enable repeat dosing.
Approach
Aim 1: Determine whether Tregs suppress rAAV- and dystrophin-specific T cells. Preliminary mouse studies revealed that Treg depletion led to a pathogenic increase in effector and/or memory-like T in the context of DMD. We will use similar depletion approaches to determine whether Tregs suppress AAV- and dystrophin-specific T cells, which would motivate the use of the Treg-potentiating molecule F5111 IC to overcome autoimmune attack.
Aim 2: Use a ligand-assisted, muscle-specific delivery of F5111 IC to suppress antigen-specific T cells and permit repeat dosing. We will fuse F5111 IC to an antibody fragment that targets dystroglycan-alpha to achieve muscle-specific delivery of our engineered therapeutic. The Treg-expanding activity of the muscle-targeted fusion program will be characterized in vitro and in vivo, informing further development of disease-specific ICs.
Push-Pull relationship
Push: The NCBIB will design an IL-2 IC fused to an anti-dystrophin antibody that will be provided to the Villalta Lab. The Villalta Lab will characterize the in vivo biodistribution of our engineered fusion protein and quantify dystrophin-specific Treg induction in response to fusion protein treatment. The Villalta Lab will then assess the performance of our engineered fusion protein in animal models of DMD.
Pull: The Villalta Lab will provide feedback to NCBIB on the performance of the fusion proteins in DMD models. These data will be used by the NCBIB to further engineer the IC, specifically by tuning the affinity of the anti-dystrophin antibody, as well as tuning the intramolecular affinity between IL-2 and the anti-IL-2 antibody within the IC.