Porcine encephalomyocarditis virus persists in pig myocardium and infects human myocardial cells

Recent advances toward using pig tissues in human transplantation have made it necessary to determine the risk of transmitting zoonotic viruses from pigs to humans or vice versa. We investigated the suitability of the porcine encephalomyocarditis virus (EMCV) model for such studies by determining its ability to persist in pigs, escape detection by routine serological methods, and infect human cells. Intraperitoneal inoculation of 5-week-old pigs with EMCV-30, a strain isolated from commercial pigs, resulted in acute cellular degeneration, infiltration of lymphocytes, and apoptosis in myocardium in 13 of 15 (86.7%) pigs during the acute phase of disease (3 to 21 days postinfection), followed by less-severe lymphocytic infiltration and apoptosis in 5 of 10 (50%) pigs during the chronic phase of the disease (day 45 to 90 postinfection). In the brain, lymphocytic infiltration, neuronal degeneration, and gliosis were observed in 26 to 33% of pigs in the acute phase of disease whereas perivascular cuffing was the predominant feature during chronic disease. EMCV antigens and RNA were demonstrated in the myocardium and brain during the chronic phase of disease. Analysis of 100 commercial pigs that were negative for EMCV antibodies identified two pig hearts positive for EMCV RNA. Porcine EMCV productively infected primary human cardiomyocytes as demonstrated by immunostaining using a monoclonal antibody specific for EMCV RNA polymerase, which is expressed only in productively infected cells, and by a one-step growth curve that showed production of 100 to 1,000 PFU of virus per cell within 6 h. The findings that porcine EMCV can persist in pig myocardium and can infect human myocardial cells make it an important infectious agent to screen for in pig-to-human cardiac transplants and a good model for xenozoonosis.