Lymphocytic choriomeningitis virus

Lymphocytic choriomeningitis virus
Negative stain electron micrograph of an arenavirus from a mouse that tested positive for LCM
Virus classification
Group:	Group V ((−)ssRNA)
Family:	Arenaviridae
Genus:	Mammarenavirus
Species:	Lymphocytic choriomeningitis virus

Lymphocytic choriomeningitis
Classification and external resources
Specialty	infectious disease
ICD-10	A87.2
ICD-9-CM	049.0
DiseasesDB	30803
eMedicine	med/1350
MeSH	D008216
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Lymphocytic choriomeningitis (LCM) is a rodent-borne viral infectious disease that presents as aseptic meningitis, encephalitis or meningoencephalitis. Its causative agent is the lymphocytic choriomeningitis virus (LCMV), a member of the family Arenaviridae. The name was coined by Charles Armstrong in 1934.

The Gale Encyclopedia of Medicine defines lymphocytic choriomeningitis (LCM) as "a viral infection of the membranes surrounding the brain and spinal cord and of the cerebrospinal fluid." The name is based on the tendency of an individual to have abnormally high levels of lymphocytes during infection. Choriomeningitis is "cerebral meningitis in which there is marked cellular infiltration of the meninges, often with a lymphocytic infiltration of the choroid plexuses."

There are several strains of LCM virus, among which the most widely used are LCMV Armstrong and LCMV Clone 13. Armstrong is the original virus strain which was isolated from the brain by Charles Armstrong in 1934. It triggers a vigorous cytotoxic T lymphocytes(CTL) response and thus, it is cleared rapidly by the host. This is referred to as acute (Armstrong) LCMV infection. On the other hand, Clone 13 is a variant of the Armstrong viral strain, isolated from the spleen and is consequently tropic for visceral organs. It was first isolated from mice which sustained a persistent LCMV infection from birth. This variant potentiates a less vigorous CTL response in the immune system, and thus can ultimately persist in the host organism indefinitely. The latter is referred to as chronic (Clone 13) LCMV infection.

LCMV is a spherical enveloped virus with a diameter between 60 and 300 nm. The helical nucleocapsid contains an RNA genome consisting of two negative single-stranded RNA segments. The negative RNA strand, complementary to the necessary mRNA strand, indicates that it must first be transcribed into a positive mRNA strand before it can be translated into the required proteins. The L strand is ambisense RNA, encoding multiple proteins in opposite directions, separated by an intergenic region. It is approximately 7.2 kb in size and encodes a high-molecular-mass protein (L; 200 kDa) and an 11 kDa small polypeptide Z with unknown function and a ring finger motif. The viral RNA-dependent RNA polymerase is encoded by the L protein which contains conserved characteristic motifs throughout all the RNA-dependent, RNA-polymerases. The S strand is ambisense and approximately 3.4 kb in size. It encodes the two main structural proteins: nucleo-protein (63 kDa) and glycoprotein C (75kDa). The latter undergoes posttranslational cleavage and results in the synthesis of two mature virion glycoproteins, GP-1 (40 to 46 kDa) and GP-2 (35 kDa). The spikes present on the virion envelope are dictated by tetramer formation of GP-1 and GP-2.

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