Cumulative Mutations in the Genome of Echovirus 6During Establishment of a Chronic Infection in Precursors of Glial Cells

Abstract

Although Enteroviruses are mainly described as responsible for acute diseases, their role in severe chronic pathology has been also established. Echovirus 6-like sequences have been detected by PCR analysis in central nervous system specimens from patients presenting with Amyotrophic Lateral Sclerosis. These findings suggested a persistent infection with viruses that underwent, genetic changes precluding viral particle release. To support this hypothesis, we developed a model system of Echovirus 6 chronic infection in precursors of glial cells. The nucleotide sequences of the 5'non-translated region (5'NTR), 2A and 3C regions of the virus developing persistent genome were analysed during establishment of the chronic phenotype. This study revealed that at day 160 of chronic infection, several mutations were observed: one mutation at nucleotide 108 upstream the domain II of the internal ribosome entry site (IRES) structure, one mutation at nucleotide 30 in the cloverleaf, and two mutations in the 2A region (translated in His48 to Tyr, and Ile 123 to Met). No mutations were detected in the 3C region. The impact of these mutations on viral replication have been analysed in a rabbit reticulocyte lysate (RRL) translation assay supplemented with HeLa cell lysate, and by plaque assay. Viruses with these mutations displayed a phenotype with a significant reduction of replication, while in vitro translation was not affected by the nucleotide 108 mutation. This model allowed the description of molecular changes observed in the genome of Echovirus 6 during the establishment of a chronic infection phenotype, and may be helpful for the understanding of the mechanisms leading Enteroviruses to develop chronic infections in man.

Virus-Host Coevolution in a Persistently Coxsackievirus B3-Infected Cardiomyocyte Cell Line

“…A broad range of cytolytic viruses, including enteroviruses, establish persistent types of infections both in vivo and in vitro (4,5,8,15,28,33). In most cases, this is induced by selection of virus mutants that are less cytopathic (2,20,53). Other mechanisms comprise coevolution of both cells and viruses (1,6,50).…”

The Roles of Picornavirus Untranslated Regions in Infection and Innate Immunity

“…A murine model revealed that sequences within the 5′-UTR SL II of CVB3 are determinants of cardiovirulence and contribute to CVB3-induced heart disease ( Dunn et al, 2000 , 2003 ). Furthermore, Beaulieux et al (2005) developed a model system of echovirus 6 chronic infection and revealed two mutations in the 5′-UTR 6 months after the start of the infection: a single mutation at nt 30 in the cloverleaf and a mutation at 108 nts upstream of domain II of IRES. It is thought that these 5′-UTR mutations may help establish a persistent disease state, although the exact mechanism needs to be elucidated.…”

Prolonged Viral RNA Detection in the Central Nervous System of One-Week-Old Swiss Albino Mice following Coxsackievirus B4 and Echovirus 9 Infection

“…Our results regarding the prolonged detection of enteroviral RNA in CNS of experimentally infected mice are in agreement with those of Feuer et al [5] who demonstrated that CV-B3 can persist in the CNS of infected BALB/c newborn mice up to 90 days p.i., despite the lack of infectious virus. As far as the issue of a persistent infection with echovirus, a model of E-6 chronic infection in precursors of glial cells has been described [21]. However, to the best of our knowledge, a persistent infection of CNS with E-9 has not been reported previously.…”