Transgene-induced cardiotoxicity in high-dose AAV gene transfer

Gene delivery technologies based on adeno-associated virus (AAV) vectors have yielded promising results for the treatment of monogenic diseases. Preclinical studies and clinical trials have highlighted that infusing high AAV vector doses can induce cytotoxicity, resulting in the death of the patient in a few cases. In the wake of signs of cardiac symptoms in several human patients after gene transfer, we investigated the effects on the heart of systemic administration of high doses of AAV vectors expressing three different transgenes, corresponding to Duchenne muscular dystrophy, γ-sarcoglycanopathy, and fukutin-related protein deficiency. In all these cases, we observed the possibility of cardiotoxicity with high-dose injections that we related to transgene expression. Consequently, strategies reducing or preventing expression in the heart prevented the appearance of such cardiotoxicity and were also confirmed to be safe in non-human primates. Dissection of the mechanisms at stake revealed activation of stress cascades, leading to cardiomyocyte death due to protein overload or abnormal homeostasis of location or function of the specific protein. Our data highlighted a particular sensitivity of the heart to transgene expression, suggesting the importance of finely regulating the expression of transgenes in this vital organ in any gene therapy approach.