44 | Targeted delivery of mir-486 to skeletal muscle: efficacy, tropism, and integrin dependency of MYOAAV2A vs. AAV9

Chiara Ricciardi¹, S. Perni¹, V. Sorrentino^1|2 | ¹Department of Molecular and Developmental Medicine, University of Siena, Italy; ²Interdepartmental Program of Molecular Diagnosis and Pathogenetic Mechanisms of Rare Genetic Diseases, Azienda Ospedaliera Universitaria Senese, Italy.

Abstract

Adeno-Associated Viruses (AAVs) are emerging as a promising tool for gene therapy as a way to modulate gene expression in specific tissues. Of particular interest to us is the application of AAV-based approach for treating congenital myopathies. The use of AAV in the muscle is complicated by the abundance and large distribution of this tissue in the body, requiring high dosages of the gene-delivery vector with higher risks of side effects, mostly related to liver toxicity. To address this challenge, we designed and selected a strong expression cassette for miR-486, known to ameliorate myopathic symptoms, through in vitro screening, and loaded it in the recently developed myotropic AAV virus MyoAAV2A to enhance skeletal muscle transduction and targeting. This delivery system achieves a high transduction and expression of miR-486 in mouse striated muscle while de-targeting the liver and the lungs. The higher muscle trophism and efficiency of MYOAAV2A compared to its parental serotype AAV9 depend on the presence of the integrin recognition motif, RGD, in the hypervariable region VIII of the virus capsid, possibly making its infection efficiency dependent on the presence of RGD-binding integrins (particularly αVβ6) in the sarcolemma. Our current understanding of how αVβ6 expression varies with age, muscle type, and in non-muscle organs is still limited, yet this knowledge could be valuable for designing MYOAAV-based therapeutic strategies. Here, we analysed the correlation between the transduction efficiency of MyoAAV2A and αVβ6 expression across various muscles, organs and mouse ages, comparing it with AAV9 as an integrin-independent control serotype.