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00.003.0.01.003. Lassa virus

Cite this publication as: ICTVdB Management (2006). 00.003.0.01.003. Lassa virus. In: ICTVdB - The Universal Virus Database, version 4. Büchen-Osmond, C. (Ed), Columbia University, New York, USA

Cite this site as: ICTVdB - The Universal Virus Database, version 4. http://www.ncbi.nlm.nih.gov/ICTVdb/ICTVdB/

Table of Contents

Biocontainment Level

Distribution of this virus falls under quarantine restrictions. It is recommended to handle this virus at the biocontainment level BSL-4.

Classification

This is a description of a vertebrate virus at the species level.

ICTVdB Virus Code: 00.003.0.01.003. Virus accession number: 03001003. Former virus code: 03.0.1.1.003; accession number: 03011003.
NCBI Taxonomy Identifier Taxon ID: 11620.

Name, Synonyms and Lineage

ICTV approved acronym: LASV. Virus is an ICTV approved species of the genus 00.003.0.01. Arenavirus in the family 00.003. Arenaviridae.

Virion Properties

Morphology

Virions consist of an envelope and a nucleocapsid. Virus capsid is enveloped. Virions are spherical to pleomorphic measuring (50-)110-130(-300) nm in diameter. The envelope surrounds probably two nucleocapsids; has surface projections. Surface projections are distinctive club-shaped peplomers that are spaced widely apart and covering evenly the surface. Surface projections are composed of one type of protein. Surface projections are 10 nm long. Host ribosomes are seen inside the envelope (in varying numbers). Nucleocapsid is elongated and exhibits helical symmetry. Virions consist of two nucleocapsids. The nucleocapsid is filamentous and forming a closed circle; has a "string of beads" appearance with a varying length with a length of 1000-1300 nm (L segment, 450-640 nm (S segment) and a width of 3-4 nm. Nucleocapsid contains a polymerase complex and a nucleoprotein complex. Nucleocapsids are isolated nucleocapsids, free of contaminating host ribosomes organized in closed circles and display a linear array of nucleosomal subunits.
























Electron micrograph of courtesy of FA Murphy.

Nucleic Acid

The Mr of the genome constitutes 2% of the virion by weight. The genome is segmented and consists of two segments of linear, negative-sense to ambisense, single-stranded RNA. The genome is transcriptional inactive. Minor species of non-genomic nucleic acid are also found in virions. The encapsidated nucleic acid is mainly of genomic origin, but virions may also contain subgenomic RNA and nucleic acid of host origin including three host rRNA and three subgenomic mRNA that are derived from genomic S RNA (for the precursor of protein N and the precursor of protein GPC), or L RNA (for the Z protein). RNA segments are not homologous. The complete genome is about 5000-7400 nucleotides long. Sequence can be accessed from EBI-EMBL and GenBank. The RNA-L is fully or partially sequenced. Complete sequence is 7400 nucleotides long (depending on isolate). RNA-S is fully sequenced and complete sequence is about 3400 nucleotides long. The genome has a virus coded terminal protein; which is circular, but not covalently closed. Nucleotide sequences at the 3'–terminus are largely complementary to similar regions on the 5' end. The 5'–end of the genome does not have cap. The 3'–terminus has conserved nucleotide sequences; in all segments and species of same genus; sequence has 19–30 nucleotides in length; in S RNA. The intergenic region has S a hairpin configuration (potential). The multipartite genome is encapsidated, each segment in a separate nucleocapsid, and the nucleocapsids are surrounded by one envelope. Each virion contains often segments of the genome in non-equimolar proportions (due to frequent packaging of S RNA strands).

GenBank records for nucleotide sequence(s); complete genome sequences.

Proteins

Proteins constitute about 70% of the particle weight.

The viral genome encodes structural proteins and non-structural proteins. Virions consist of 5 structural proteins located in the ribonucleoprotein complex.

Structural Proteins: Envelope protein GPC has a molecular mass of 75000–76000 Da. Envelope protein is formed by tetramers forming the viral spikes (GP-1 and GP-2). During post-translational processing envelope protein has been cleaved from the precursor protein into GP-1 (G1) and GP-2 (G2) and modifications occur that include glycosylation. Envelope protein G1 has a molecular mass of 44000 Da, it is interacting with viral receptors which possess virus neutralization activity. During post-translational processing envelope proteins are glycosylated. Envelope protein G2 has a molecular mass of 34000–44000 Da, is involved in membrane fusion for viral entry which is acid dependent (pH 4.5–5.5). During post-translational processing envelope proteins are glycosylated. Nucleocapsid protein N has a molecular mass of 63000–72000 Da, it is binding to the genomic RNA and forming a ribonucleoprotein complex. Nucleocapsid protein Z has a molecular mass of 10000–14000 Da, it is a putative zinc binding protein and forming an internal structural component.

Non-Structural Proteins: 3–4 non-structural proteins are found. The virus codes for enzymes and genome associated polypeptides; an RNA-dependent RNA polymerase. In addition to the polymerase, the virus codes for enzymes such as transcriptase, replicase, proteinase (poly(U) and poly(A) polymerases); 1 internal protein(s). Non-structural protein L protein, an RNA dependent RNA polymerase.

Lipids

Lipids are are located in the envelope. Virions are composed of 20% lipids by weight. The composition of viral lipids and host cell membranes are similar. The lipids are of host origin are derived from plasma membranes.

Carbohydrates

Carbohydrates are found in virions; constitute 8% of virion dry weight; are present as glycoproteins; are complex glycans.




















Arenavirus genome map.

Genome Organization and Replication

Virions attach to undefined receptors to enter host cells via the endosomal route.

The process of intracellular uncoating of virions occurs in the cytoplasm and the viral nucleic acid is delivered to the cell cytoplasm, the site of mRNA transcription.

Transcription: The viral genome is transcribed by a viral RNA-dependent RNA polymerase into 2 mRNAs (N and L mRNA). The transcribed mRNAs are subgenomic in a viral-complementary sense.

Biological Properties

Natural Host

Virus infects during its life cycle a variety of vertebrate hosts. Virus has an enzootic cycle and is transmitted from rodents to humans, or rodents to other vertebrates. Domain Viral hosts belong to the Domain Eucarya.

Domain Eucarya Kingdom Animalia.

Kingdom Animalia Phylum Chordata.

Phylum Vertebrata Subphylum Vertebrata.

Class Mammalia.

Class Mammalia Order Rodentia and Primates;
Family Hominidae; virus infects Homo sapiens (human); Suborder Sciurognathi; Family Muridae; Subfamily Murinae; virus infects Genus Mastomys.

Geographical Distribution

The virus occurs in Namibia.

Ecology, Epidemiology and Control

A fact sheet on this virus is available from the Centers for Disease Control and Prevention (CDC), National Center for Infectious Diseases (NCID).

References

References

The following generic references are cited in the most recent ICTV Report.

References

PubMed References.



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DELTA - DEscription Language for TAxonomy developed by Dr Mike Dallwitz, Toni Paine and Eric Zurcher, CSIRO Entomology, Canberra, Australia. ICTVdB - The Universal Virus Database, developed for the International Committee on Taxonomy of Viruses by Dr Cornelia Büchen-Osmond is written in DELTA. The virus descriptions in ICTVdB are coded by, or using data from experts in the field of virology or members ICTV. The character list is the underlying code. All virus descriptions are based on the character list and natural language translations are automatically generated and formatted for display on the Web from the descriptions in DELTA-format. The description has been generated automatically from DELTA files. DELTA - DEscription Language for TAxonomy developed by Dr Mike Dallwitz, Toni Paine and Eric Zurcher, CSIRO Entomology, Canberra, Australia.

ICTVdB - The Universal Virus Database, developed for the International Committee on Taxonomy of Viruses (ICTV) by Dr Cornelia Büchen-Osmond, is written in DELTA. The virus descriptions in ICTVdB are coded by ICTV members and experts, or by the ICTVdB Management using data provided by the experts, the literature or the latest ICTV Report. The character list is the underlying code. All virus descriptions are based on the character list and natural language translations from the encoded descriptions are automatically generated and formatted for display on the Web.

Developer of the DELTA software: M. J. Dallwitz, T. Paine and E. Zurcher

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Last updated on 25 April 2006 by Cornelia Büchen-Osmond
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