Lymphocytic choriomeningitis virus (LCMV) is a highly significant zoonotic infection of laboratory personnel who work with transplantable rodent tumors (particularly in hamsters) and rodent cell lines (Biggar et al., 1976; Pike, 1979), and of owners of pet hamsters (Parker et al., 1976). The virus also has importance as an unwanted contaminant that can alter research results of in vitro and in vivo rodent test systems (see below) and for the experimental study of virus-host interactions (Lehmann-Grube et al., 1983).
Lymphocytic choriomeningitis virus (LCMV) has been recognized as an important zoonotic agent and indigenous rodent pathogen for about five decades (Hotchin, 1971b). Traditionally, mice have been considered the primary source of LCMV infection. However, since 1960 three epidemics of LCMV infection involving at least 236 human cases have occurred in the United States, and all have been associated with Syrian hamsters, either as laboratory animals bearing transplantable tumors or as pets (Gregg, 1975). Because of the unique host-parasite relationship of LCMV infection in mice, experimental infections in mice have been used extensively as models for the investigation of such diverse phenomena as virus-specific immunological tolerance, virus-induced T-cell-mediated immunopathology, virus-induced immune complex disease, in vivo viral interference, and activation of natural killer cells (Lehmann-Grube et al., 1983).
LCMV is an RNA virus, family Arenaviridae, genus Arenavirus. LCMV is the type species of the genus. Other members of this genus include Lassa virus and the Tacaribe Complex (Amapari, Junin, Latino, Machupo, Parana, Pichinde, Tacaribe, and Tamiami Viruses). The LCMV strains used most widely for experimental purposes are WE, E-350, and CA 1371 (LehmannGrube, 1982; Matthews, 1982).
LCMV and other members of the genus Arenavirus have unique ultrastructural characteristics. The virions are pleomorphic, have a diameter of 50-300 nm (mean, 110-130 nm), and consist of a membranous envelope with surface projections surrounding an interior containing granules (host ribosomes that measure 20-25 nm in diameter) instead of a defined core. Virus particles bud from plasma membranes of infected cells and can form large intracytoplasmic inclusions (Murphy and Whitfield, 1975; Rawls and Buchmeier, 1975; Rawls and Leung, 1979).