Introduction/classification

Mouse hepatitis virus (MHV) is a member of the Coronaviridae family in the order Nidovirales. Coronaviruses are classified into one of three antigenic groups, with MHV classified as a member of group 2 [1]. Members of the Coronaviridae family infect a wide range of species including humans, cows, pigs, chickens, dogs, cats, bats, and mice. In addition to causing clinically relevant disease in humans ranging from mild upper respiratory infection (e.g., HCoV [human coronavirus]-OC43 and HCoV-229E responsible for a large fraction of common colds) to severe acute respiratory syndrome (SARS) [2, 3], coronavirus infections in cows, chickens, and pigs exact a significant annual economic toll on the livestock industry.

MHV is a natural pathogen of mice that generally is restricted to replication within the gastrointestinal tract [4, 5]. However, there exist several laboratory strains of MHV that have adapted to replicate efficiently in the central nervous system (CNS) of mice and other rodents. Depending on the strain of MHV, virulence and pathology ranges from mild encephalitis with subsequent clearance of the virus and the development of demyelination to rapidly fatal encephalitis. Thus, the neurotropic strains of MHV have proved to be useful systems in which to study processes of virus- and immune-mediated demyelination, virus clearance and/or persistence in the CNS, and mechanisms of virus evasion from the immune system.

Neurotropism and neuroinvasiveness have also has been described for two other members of the Coronaviridae family, HCoV-OC43 and SARS-coronavirus (CoV) (Table 4.1).