Persistent Infections by Picornaviruses

Viral persistence is currently one of the main public health problems. It depends on specific virus and host factors and particularly on the capacity of the virus to escape the immune defense. Some picornaviruses establish persistent infections in their natural animal hosts, while others are suspected to be responsible for chronic human diseases. This chapter focuses on the aspects relating to virus persistence. Theiler's murine encephalomyelitis virus (TMEV) persistence appears to be required for immune-mediated demyelination. During the chronic phase, the number of infected cells is always low, there are only small amounts of capsid proteins in infected cells, and viral RNA replication seems to be blocked at the minus-strand RNA synthesis step. Encephalomyocarditis virus (EMCV), another cardiovirus, establishes persistent infections in human erythroleu-kemic K562 cells. B group coxsackieviruses (CVBs) induce different effects in different types of cultured human renal cells, and interestingly, CVB1, -3, -4, and -5 established persistent infections in glomerular mesangial cells, which failed to develop cytopathic effects (CPE). The authors have started to study the molecular mechanisms of poliovirus (PV) persistence in HEp-2c cells because this cell model can be used for both lytic and persistent PV strains, allowing the identification of viral determinants involved in persistence. Persistent picornavirus infections are valuable models for understanding complicated pathologies resulting from persistent viral infections.