Murine gammaherpesvirus MHV68 See Murid herpesvirus

Murine hepatitis virus (MHV) A species in the genus Coronavirus. Serologically related to Rat coronavirus and sialo-dacryoadenitis virus of rats. Often a silent infection of laboratory mice which may be activated by passage of other viruses such as leukemia virus, or by cortisone, urethane or enterotoxin from Gramnegative bacteria, or by thymectomy. Injection of virus into mice infected with the parasite Eperythrozoon coccoides usually produces fatal hepatitis but in its absence there is often no disease. Neurotropic strains infect cotton rats and hamsters when given i.c. All strains are antigenically similar but vary in patho-genicity, and have been numbered 1-4. Type 1 was the original isolate. Type 2 was activated on mouse leukemia passage in Princeton mice and produced hepatitis in the absence of E. coccoides. Type 3 is also pathogenic for weanling mice in the absence of E. coccoides, and causes ascites in older mice. Type 4 causes encephalomyelitis with demyeli-nation and some focal liver necrosis in mice. Virus is present in excreta and is highly infectious. Transplacental transmission has not been demonstrated. Genome is positive, single-stranded RNA, 30kb in length, with a 5'-cap and 3' poly A tract.

Synonyms: murine coronavirus; mouse hepatitis virus.

Murine poliovirus

Cavanagh D et al (1994) Arch Virol 135, 227 Wege H et al (1982) Curr Top Microbiol Immun 99, 165

murine herpesvirus Synonym for murid herpesvirus 7.

murine K virus Synonym for Murine pneu-motropic virus (Kilham polyomavirus).

Murine leukemia virus (MLV) A species in the genus Gammaretrovirus. There are many strains and all mice probably carry one or more viruses. The first strain was isolated from AKR mice by Gross. Strains can be grouped by their envelope antigens or the antigens they induce on the surface of infected cells. They vary in the type of leukemia that they induce, but this also depends on the strain and age of the host animal. The Gross, Moloney and Kaplan strains injected into newborn mice cause thymus-dependent lymphocytic leukemia after a latent period of 3-4 months. The mechanism of leukemogenesis involves activation of cellular proto-oncogenes after proviral insertion. Abelson and Friend strains injected into adult mice cause splenomegaly and erythroblastic leukemia in a few weeks, as they carry oncogenes in the genome (v-abl, which encodes a tyrosine-specific protein kinase and gp52, which encodes a viral glyco-protein). Sarcoma-inducing strains which carry a transduced cellular oncogene can transform cells in culture but are defective for virus replication, requiring a helper leukemogenic virus to provide information for the viral coat proteins. Laboratory strains and exogenous viruses are transmitted mainly via the milk, but in nature the endogenous virus probably passes to the young via the egg or sperm. There are three subspecies:

(1) Ecotropic murine type C viruses, the laboratory strains of exogenous leukemia- and sarcoma-inducing virus. Members of this subspecies show reciprocal viral interference.

(2) Xenotropic murine type C viruses.

(3) Amphotropic murine type C viruses. Synonyms: mouse type C oncovirus; Moloney virus.

Hung Fan (1994) In The Retroviridae, vol. 3, edited by JA Levy. New York: Plenum Press, p. 313

Stockert E et al (1979) J Exp Med 149, 200

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