cardioviruses

Cardioviruses are a genus of small, non-enveloped, positive-sense RNA viruses in the family Picornaviridae. The genus includes several species, with Theiler's murine encephalomyelitis virus (TMEV) and Encephalomyocarditis virus (EMCV) being the best known. They infect a variety of mammals, though their natural reservoirs differ; TMEV is primarily a rodent pathogen, while EMCV has a broader host range and can infect livestock and occasionally humans.

Genome and structure: They have a nonsegmented, positive-sense RNA genome of about 7.2 to 9.0 kb, arranged to encode a single polyprotein that is cleaved into structural proteins VP1–VP4 and nonstructural proteins 2A–3D. The genome contains a 5' nontranslated region with an internal ribosome entry site (IRES) and is 3' polyadenylated. The virion is non-enveloped, icosahedral, about 28–30 nm in diameter.

Replication and pathogenesis: Virus entry is via receptor-mediated endocytosis; replication occurs in the cytoplasm. EMCV infection in animals commonly causes myocarditis, while TMEV infection can produce acute disease and, in susceptible mouse strains, chronic demyelinating disease of the central nervous system, a model widely used in research on multiple sclerosis. In humans, cardioviruses are rarely pathogenic but can be associated with mild febrile illness or myocarditis in rare cases.

Diagnosis and control: Laboratory diagnosis uses RT-PCR, serology, or virus isolation. There are no widely used human vaccines; control relies on hygiene, animal husbandry, and biosecurity to prevent infections in animals.

Research use: TMEV and EMCV are established models in viral immunology, neurology, and cardiology, contributing to understanding of viral pathogenesis and host responses.