LOW-LEVEL EXPRESSION OF A MUTANT COXSACKIEVIRAL CDNA INDUCES A MYOCYTOPATHIC EFFECT IN CULTURE - AN APPROACH TO THE STUDY OF ENTEROVIRAL PERSISTENCE IN CARDIAC MYOCYTES

Background-Enteroviral ribonucleic acids have been identified in heart muscle of a subset of patients with myocarditis and dilated cardiomyo pathy as well as in a mouse model of persistent coxsackievirus B3 (CVB 3) infection, suggesting that persistent viral infection along with ac tivation of an immune response may contribute to the pathogenesis of o ngoing cardiac disease and dilated cardiomyopathy in certain patients. It is still not known whether persistence of the viral genome contrib utes to the pathogenesis of dilated cardiomyopathy. Methods and Result s-To determine whether low-level enteroviral gene expression similar t o that observed with viral persistence can induce myocytopathic effect s without formation of infectious virus progeny, the full-length infec tious cDNA copy of CVB3 was mutated at the VP0 maturation cleavage sit e. This prevented formation of infectious virus progeny. In myocytes t ransfected with this mutated cDNA copy of the viral genome, both posit ive- and negative-strand viral RNAs were detected, demonstrating that there was replication of the viral genome by the RNA-dependent RNA pol ymerase, The level of viral protein expression was found to be below l imits of detection by conventional methods of protein detection, thus resembling restricted virus replication, Nonetheless, the CVB3 mutant was found to induce a cytopathic effect in transfected myocytes, which was demonstrated by inhibition of cotransfected MLC-2v luciferase rep orter activity and an increase in release of lactate dehydrogenase fro m transfected cells. Conclusions-This study demonstrates that restrict ed replication of enteroviral genomes in myocytes in a pattern similar to that observed in hearts with persistent viral infection can induce myocytopathic effects without generation of infectious virus progeny.