Enteroviral RNA replication in the myocardium of patients with left ventricular dysfunction and clinically suspected myocarditis

Background-Previous studies dealing with the detection of enteroviral RNA i n human endomyocardial biopsies have not differentiated between latent pers istence of the enteroviral genome and active viral replication. Enterovirus es that are considered important factors for the development of myocarditis have a single-strand RNA genome of positive polarity that is transcribed b y a virus-encoded RNA polymerase into a minus-strand mRNA during active vir al replication. The synthesis of multiple copies of minus-strand enterovira l RNA therefore occurs only at sites of active viral replication but not in tissues with mere persistence of the viral genome. Methods and Results-We investigated enteroviral RNA replication versus ente roviral RNA persistence in endomyocardial biopsies of 45 patients with left ventricular dysfunction and clinically suspected myocarditis. Using revers e transcriptase polymerase chain reaction in conjunction with Southern blot hybridization, we established a highly sensitive assay to specifically det ect plus-strand versus minus-strand enteroviral RNA in the biopsies. Plus-s trand enteroviral RNA was detected in endomyocardial biopsies of 18 (40%) o f 45 patients, whereas minus-strand RNA as an indication of active enterovi ral RNA replication was detected in only 10 (56%) of these 18 plus-strand-p ositive patients. Enteroviral RNA was not found in biopsies of the control group (n=26). Conclusions-These data demonstrate that a significant fraction of patients with left ventricular dysfunction and clinically suspected myocarditis had active enteroviral RNA replication in their myocardium (22%). Differentiati on between patients with active viral replication and latent viral persiste nce should be particularly important in future studies evaluating different therapeutic strategies. In addition, molecular genetic detection of entero viral genome and differentiation between replicating versus persistent viru ses is possible in a single endomyocardial biopsy.