Abstract 3265: Prevention of Dystrophin Cleavage by Protease 2A Protects Against Coxsackieviral Protease 2A Mediated Cardiomyopathy
It has been previously demonstrated that dystrophin is cleaved in the cardiac myocyte by the viral protease 2A following infection with Coxsackievirus B3 (CVB3). In addition, it has been shown that expression of the CVB3 protease 2A alone in the heart is sufficient to cause cardiomyopathy. However, it is less clear whether the viral protease 2A mediated cardiomyopathy can be prevented by inhibiting cleavage of dystrophin by protease 2A or whether other protease 2A-mediated effects are more important.
METHODS: To prove this, we generated through homologous recombination knock-in (KI) strategy, a mouse that had a point mutation in dystrophin that prevents cleavage by protease 2A (DysKI). DysKI mice were then bred with mice that expressed protease 2A in the myocardium in an inducible manner by combining a lox-P inducible protease 2A transgenic with an α-MHC-MerCreMer (MCM) transgenic (DysKI2A/MCM). These mice were compared with protease 2A and MCM double transgenic mice that expressed wild-type dystrophin (DysWT2A/MCM). To induce protease 2A expression the mice were treated with tamoxifen for 5 days (40mg/kg/day).
RESULTS: At 3– 4 weeks after tamoxifen administration there was significantly more Evans blue dye uptake in DysWT2A/MCM myocytes than in the DysKI2A/MCM mice where dystrophin cleavage was prevented (1.36±0.32 vs 0.45±0.07% of myocytes, p=0.012). In addition, there was more fibrosis in the DysWT2A/MCM mice than the DysKI2A/MCM mice (4.17±0.73 vs 1.64±0.24% of the area of myocardium, p=0.0006). Echocardiography demonstrated severe cardiac dysfunction and LV chamber dilation in DysWT2A/MCM mice. However, this was not observed in DysKI2A/MCM mice.. (LVEDD=4.0±0.2 vs 3.5±0.04, LVESD=3.5±0.31 vs 2.4±0.08, FS=12.6±4.24 vs 30.6±2.37, DysWT2A/MCM vs DysKI2A/MCM, respectively, p<0.01).
CONCLUSION: Prevention of dystrophin cleavage by protease 2A clearly inhibits protease 2A-mediated cardiomyopathy. This demonstrates that even though protease 2A can cleave other host cell proteins, cleavage of dystrophin is required for the full cardiomyopathy that is caused by protease 2A expression. This indicates that the inhibition of dystrophin cleavage by protease 2A could be a novel therapeutic strategy in the treatment of viral myocarditis.