Lymphocystis disease virus 2 LCDV2 A

tentative species in the genus Lymphocystivirus, varying in size from 130 to 300nm. Lymphocystis is a common, chronic, but rarely fatal disease affecting fish of several of the higher orders. The infection is found worldwide in numerous species of fish, both marine and freshwater. Tumor-like masses appear on the skin and fins, persist for long periods, but ultimately regress. They are caused by massive increases (100000-fold) in the size of infected cells, which contain large cytoplasmic inclusions. Outbreaks in the wild occur mainly in the summer. Parasites may help to spread the disease, but the large lymphocystis cells burst in water and may release infective virus. Transmission is possible by applying infectious lesion material to abraded skin, but may be difficult between species. The bluegill, Lepomia macrochirus, is a useful experimental subject. Synonym: dab lymphocystis disease virus.

Weissenberg R (1965) Ann NY Acad Sci 126, 362

lymphocyte A spherical, non-phagocytic leukocyte white blood cell with a large nucleus which is involved in the specific immune response. Divided by ontogeny and function into B lymphocytes (humoral immunity) and T lymphocytes (cell-mediated immunity). Found in blood, lymph and lymphoid tissues. When activated by antigen the cells enlarge and proliferate and are called 'lymphoblasts'.

Lymphocytic choriomeningitis virus

(LCMV) The type species of the genus Arenavirus. In sections virions are pleo-morphic, 110-130nm in diameter, consisting of a bilayered envelope with thin projections and an interior containing electron-dense granules appearing at the time of budding from the cell surface. Nucleic acid single-stranded RNA separable into two segments: L, 7.2kb and S,

3.4kb in length. The 3' terminal sequences are similar (19-30nt) between the two RNA segments. Coding sequences are ambisense. The L segment encodes the L protein (2210 amino acids) in negative sense and two small proteins X (95 amino acids) and Z (90 amino acids) in positive sense. The S segment encodes the NP protein (558 amino acids) in negative sense and the GP protein (498 amino acids) in positive sense. In addition, virions encapsidate variable amounts of full-length complementary RNAs and subgenomic mRNAs as well as cellular RNAs such as ribosomal RNAs. The virus replicates on the CAM but no lesions are produced. Also replicates in chick, mouse, cattle and monkey cell cultures, but CPE may only be seen on adaptation. In mouse cell cultures a persistent, non-cytolytic infection is established. Replication is inhibited by actinomycin D because host cell mRNAs are required as primers for RNA transcription. Probably an inapparent infection in naturally infected house mice, but has been isolated from humans, monkeys, dogs, field mice of Apodemus sp, hamsters and guinea pigs. When a colony of laboratory mice becomes infected, disease appears in young mice infected in utero but the infection soon becomes latent. In guinea pigs there is a generalized disease, often fatal, with patchy pneumonia. In humans infection may be inapparent or an influenza-like fever but lymphocytic choriomeningitis of varying severity may occur. Mice infected i.c. develop tremors and have tonic convulsions in which they may die.

Buchmeier MJ and Zajuc AJ (1999) In Persistent Viral Infections, edited by R Ahmed and ISY Chen. New York: John Wiley, p. 575 Salvato MS (editor) (1993) The Arenaviridae. New York: Plenum Press Welsh RM (1999) In Encyclopedia of Virology, Second edition, edited by A Granoff and RG Webster. London: Academic Press, p. 915

lymphoid leukemia viruses A name used for mouse leukemia viruses, usually of low leukemogenic potency, which may be separated from Friend or Rauscher leukemia viruses. They cause immunodepression and may also act as a helper virus.

Lyssavirus lymphokines Heterogeneous group of cytokines secreted by T lymphocytes which function as regulators of the immune response. Examples are inter-leukin 2 and interferon y.

lymphoproliferative assays Lymphocyte proliferation in response to an antigenic stimulus can be used to measure the recall response to the antigen and provides an in vitro correlate of the delayed-type hypersensitivity response. Only persons exposed to a given virus by natural infection or vaccination will show a lymphoproliferative response to it when their lymphocytes are tested in the presence of antigen-presenting cells in culture.

Mawle AC (1996) In Virology Methods Manual, edited by BWJ Mahy and HO Kangro. London: Academic Press, p. 147

lymphoproliferative disease (LD) A progressive disease caused by EBV (HHV4) infection in immunocompromised individuals such as transplant recipients and those infected with HIV. In most cases the proliferating cells are of B-cell origin, but about 12% are of T-cell origin. If untreated, the disease can evolve into immunoblastic lymphoma or multiple myeloma.

Nalesnik M (1998) Springer Semin Immunopathol 20, 325

lymphoproliferative disease of turkeys virus An unassigned species in the family Retroviridae. Present in the blood of turkeys with lymphoproliferative disease, an acute infection occurring only in turkeys. No other natural host is known, but chickens can be infected experimentally. There is splenomegaly, hepatomegaly and infiltration of other organs and nerves with pleomorphic mononuclear cells. The disease is of economic importance as in birds aged 10-12 weeks the mortality may exceed 20%. Can be transmitted by injecting the cell-free serum of diseased birds into young birds, but has not been isolated in vitro. Cross-nucleic acid hybridization tests and sequence analysis distinguish LPDV from avian sarcoma-leukemia viruses or avian reticuloendotheliosis viruses.

Chajut A et al (1992) Gene 122, 349

Davison I and Borenstein B (1999) Acta Virol

43, 136

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