Enterovirus Persistence in Cardiac Cells of Patients Suffering From Idiopathic Dilated Cardiomyopathy is Linked to 5' Terminal Genomic RNA-Deleted Viral Populations With Viral-Encoded Proteinase Activities.

BACKGROUND: Group B enteroviruses are common causes of acute myocarditis which can be a precursor of chronic myocarditis and dilated cardiomyopathy (DCM), leading causes of heart transplantation. To date, the specific viral functions involved in the development of DCM remain unclear.

METHODS: Total RNA from cardiac tissue of patients suffering from DCM was extracted, and sequences corresponding to the 5' termini of enterovirus RNAs were identified. Following NexGen RNA sequencing, viral cDNA clones mimicking the enterovirus RNA sequences found in patient tissues were generated in vitro, and their replication and impact on host cell functions were assessed on primary human cardiac cells in culture.

RESULTS: Major enterovirus B populations characterized by 5' terminal genomic RNA deletions ranging from 17 to 50 nucleotides were identified either alone or associated with low proportions of intact 5' genomic termini. In situ hybridization and immuno-histological assays detected these persistent genomes in clusters of cardiomyocytes. Transfection of viral RNA into primary human cardiomyocytes demonstrated that deleted forms of genomic RNAs displayed early replication activities in the absence of detectable viral plaque formation, whereas mixed deleted and complete forms generated particles capable of inducing cytopathic effects at levels distinct from those observed with full-length forms alone. Moreover, deleted or full-length and mixed forms of viral RNA were capable of directing translation and production of proteolytically active viral 2Apro in human cardiomyocytes.

CONCLUSIONS: We demonstrate that persistent viral forms are composed of B-type enteroviruses harboring a 5' terminal deletion in their genomic RNAs and that these viruses alone or associated with full-length populations of helper RNAs could impair cardiomyocyte functions by the proteolytic activity of viral 2Apro in unexplained DCM cases. These results provide a better understanding of the molecular mechanisms that underlie the persistence of EV forms in human cardiac tissues and should stimulate the development of new therapeutic strategies based on specific inhibitors of the CV-B 2Apro activity for acute and chronic cardiac infections.