Abstract 3810: Antiviral RNA Interference Mediated by a Recombinant Cardiotropic AAV9 Vector Improves Cardiac Function in Coxsackievirus B3 Cardiomyopathy

Abstract

RNA interference (RNAi) has potential to be a novel therapeutic strategy in diverse areas of medicine. We report here on targeted RNAi for the treatment of a viral cardiomyopathy which is a major cause of sudden cardiac death or terminal heart failure in children and young adults. RNAi therapy employs small regulatory RNAs to achieve its effect but in vivo use of synthetic small interfering RNAs is limited by instability in plasma and low transfer into target cells. We instead evaluated an RNAi strategy using short hairpin RNA (shRdRp) directed at the RNA polymerase (RdRP) of Coxsackievirus B3 (CoxB3) in HeLa cells, primary rat cardiomyocytes (PNCMs), and CoxB3-infected mice in vivo. A conventional AAV2 vector expressing shRdRp protected HeLa against virus-induced death, but this vector type was unable to transduce PNCMs. In contrast, an analogous pseudotyped AAV2.6 vector was protective also in PNCMs and reduced virus replication by >3 log10 steps. Finally, we evaluated intravenous treatment of mice with an AAV2.9-shRdRp vector since AAV9 carries the most cardiotropic AAV capsid currently known for in vivo use. Mice with CoxB3 cardiomyopathy had disturbed left ventricular (LV) function with impaired parameters of contractility (dP/dtmax 3006±287 vs. 7482±487 mmHg/s, p<0.01) and diastolic relaxation (dP/dtmin -2224±195 vs. -6456±356 mmHg/s, p<0.01 and Tau 16.2±1.1 vs. 10.7±0.6 ms, p<0.01) as compared to control mice. AAV2.9-shRdRp treatment significantly attenuated the cardiac dysfunction compared to control vector-treated mice on day 10 after CoxB3 infection: dP/dtmax 3865±354 vs. 3006±287 mmHg/s (p<0.05) and dP/dtmin -3245±231 vs. −2224±195, mmHg/s (p<0.05), and Tau 11.9±0.5 vs. 16.2±1.1 ms (p<0.01). The data show, for the first time, that intravenously injected AAV9 has the potential to target RNAi to the heart and suggest AAV9-shRNA vectors as a novel therapeutic approach for cardiac disorders.