Mouse Hepatitis Virus

This chapter attempts to provide an overview of the important aspects of mouse hepatitis virus (MHV) experimental biology while emphasizing the virus as a naturally occurring mouse pathogen. Even this is complicated, as it is impossible to generalize with this virus, due to marked differences in the biologic behavior of the myriad virus strains, plus the marked effects of a large number of host factors. It is now known that the MHV group is represented by numerous variants that are constantly mutating, and that these viruses can be biologically separated into respiratory (polytropic) MHVs and enterotropic MHVs, with distinctly different patterns of tissue tropism. This dichotomy is emphasized for discussion, but biology is never absolute. Many of the early MHV isolations are made as a result of contamination of biological materials that correlated with their polytropic biologic behavior. Their stated tropisms frequently were the result of the investigators' research interests and many have therefore been subjected to selective passage that favors a particular tissue tropism. All MHV isolates are related genetically and antigenically, but isolates can be differentiated by genetic sequencing, cross-serum neutralization, or with monoclonal antibodies. Genetic and antigenic relationships are not predictive of biologic behavior.