Arenaviruses

Group V: (-)sense RNA Viruses
Family	Genus	Type Species	Hosts
Arenaviridae	Arenavirus	Lymphocytic choriomeningitis virus	Vertebrates

Morphology:

Pleiomorphic, enveloped particles, 50-300nm diameter. The enveloped virus particles are roughly spherical and have an average diameter of 90-140nm. Viewed in cross-section, they show grainy particles which are ribosomes acquired from host cells. This characteristic that gave them their name, derived from the Latin "arena," meaning"sandy."

Nucleocapsid: helical, 2 proteins - nucleocapsid ('N'), RNA polymerase ('L').

Envelope: 2 glycoprotein spikes, GP1 & GP2.

Genome:

Linear, s/s RNA. Two segments, both with an ambisense organization.

L (~5.7kb) - encodes L and Z proteins
S (~2.8kb); 5' part is (+)sense and encodes G protein; 3' part (-)sense, encodes N protein

Replication is similar to that of ambisense Bunyaviruses (Phleboviruses/Tospoviruses):

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Replication:

Receptors: Receptor use by pathogenic arenaviruses. Virology. 2006 Jun 20.

There are two rounds of transcription (one before, one after the formation of a 'reverse-sense' RNA intermediate) to cope with the ambisense coding strategy:

Phlebovirus replication

Pathogenesis:

A relatively 'new' family which first came to prominence with the identification of a 'new' disease in Nigeria in 1969 (Lassa fever). It is estimated that there may be up to 300,000 infections and 5,000 deaths from Lassa fever in West Africa each year. A number of arenaviruses cause disease in humans worldwide:

Virus:	Disease:
Lymphocytic choriomeningitis virus	Lymphocytic choriomeningitis
Lassa virus	Lassa fever
Junin virus	Argentine hemorrhagic fever
Machupo virus	Bolivian hemorrhagic fever
Guanarito virus	Venezuelan hemorrhagic fever
Sabia	Brazilan haemorrhagic fever

Host Range: These are rodent viruses (e.g. Lassa fever - Mastomys genus) & do not require arthropods for spread, do not infect insect cells. Hence, human infections are zoonotic (transmitted from animal to humans).

Pathogenesis: In natural (rodent) hosts, produce chronic (life-long) infections. Also capable of establishing a persistent infection in cell lines - a model for this type of infection, e.g:

LCMV: Lymphocytic choriomeningitis virus, a murine virus which has been studied in detail as a model for chronic virus infection. In mice, virus does not cause much cell damage. Pathogenesis is believed to result from CTL response to virus-infected cells. Rarely infects man, causing a mild disease (occasionally severe with haemorrhaging).

LCMV

In humans, congenital LCMV infection can cause birth defects.

Lassa Fever: Natural host is small Nigerian rodent, Mastomys natalensis - transfer to man occurs via droppings (not Arthropods). Human infections (rare) are highly infectious, produce severe, systemic febrile disease with high mortality. This contrast with the rodent infection where there is apparently no pathology (virus is adapted to host). Mastomys natalensis and Lassa Fever. Emerging Infectious Diseases, 12, 2006.

Arenaviruses

Morphology:

Genome:

Replication:

Pathogenesis:

Some Arenaviruses are important in that they are emerging viruses.