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00.061.1.06.008. Visna/maedi virus

Cite this publication as: ICTVdB Management (2006). 00.061.1.06.008. Visna/maedi 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/

Isolate Description

Location: Iceland.

Host of Isolate and Habitat Details
Source of isolate: Karakul rams.

Reference to Isolation Report
recent report on disease by Cecil Fox (promed@usa.healthnet.org, 24 Mar).

Events surrounding the introduction of Karakul rams into Iceland in 1932.

The rams were imported (after a quarantine period) in an effort to produce pelts for commerce by breeding with Icelandic sheep (that had arrived on the island in about 1000AD). After several years sheep on the recipient farms began to behave strangely and began dying of respiratory distress. About ten percent of these sheep became demented and wasted. These two symptoms were first thought separate and two names were assigned, maedi (=dyspnea, pronounced my-thee) for the interstitial pneumonitis and visna (=wasting) for the dementia.

Through brilliant work by Bjorn Sigurdsson and his colleagues, the first lentivirus was isolated, characterized, and a series of unsuccessful vaccines were produced. After Sigurdsson's untimely death control efforts were continued also without success and a final solution was achieved in the 1960s by eradicating the sheep population entirely and restocking. Despite the fact that maedi virus is an excellent modell for that other lentivirus, HIV, little use has been made of this animal model.

Classification

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

ICTVdB Virus Code: 00.061.1.06.008. Virus accession number: 61106008. Obsolete virus code: 00.061.0.06.008.; 61.0.6.4.002; superceded accession number: 61006008; 61064002.
NCBI Taxon Identifier NCBI Taxonomy ID: 11741.

Name, Synonyms and Lineage

ICTV approved acronym: VISNA. Virus is an ICTV approved species of the genus 00.061.1.06. Lentivirus; subfamily 00.061.1. Orthoretrovirinae in the family 00.061. Retroviridae.

Morphology

Virions consist of an envelope, a nucleocapsid, a nucleoid, and a matrix protein. Virus capsid is enveloped. Virions are spherical to pleomorphic. Virions measure 80-100 nm in diameter. Surface projections are densely dispersed, small, inconspicuous spikes that cover evenly the surface. Surface projections are 8 nm long. The nucleoid is concentric. The core is rod-shaped, or is truncated cone-shaped.

Physicochemical and Physical Properties

Virions have a buoyant density in sucrose of 1.13-1.18 g cm-3. Virions are sensitive to treatment with heat, detergents, and formaldehyde. The infectivity is not affected by irradiation.

Nucleic Acid

The Mr of the genome constitutes 2% of the virion by weight. The genome is dimeric; not segmented and contains a single molecule of linear. The genome is -RT. The genome is positive-sense, single-stranded RNA. The complete genome is of one monomer 9200 nucleotides long, is fully sequenced. Sequenced genome has the accession number(s)
[M60609]; [M60610]. The genome has terminally redundant sequences. The terminally redundant sequences have long terminal repeats (LTR) (of about 600 nt). The 5'-end of the genome has a methylated nucleotide cap; cap sequence type is of type 1 m7G5ppp5'GmpNp. The 3'-terminus has of each monomer a poly (A) tract. The 3'-terminus has a tRNA-like structure (and accepts lysin). Each virion contains two copies of the genome in a dimeric configuration; 2 copies per particle (held together by hydrogen bonds to form a dimer).

GenBank records for nucleotide sequences; complete genome sequences.

Proteins

Proteins constitute about 60% of the particle weight.

The viral genome encodes structural proteins and non-structural proteins. Virions consist of 5 structural protein(s) (major).

Non-Structural Proteins: usually 4 non-structural protein(s) are found. The virus codes for an RNA-dependent DNA polymerase.

Lipids

Lipids are present and located in the envelope. Virions are composed of 35% lipids by weight. The composition of viral lipids and host cell membranes are similar. The lipids are of host origin and are derived from plasma membranes.

Polyamines

Other compounds that have been detected in the virus particles are 3% carbohydrates.



















Genome map of a lentivirus by C. Büchen-Osmond and J. Whitehead.

Genome Organization and Replication

By itself, genomic nucleic acid is not infectious.

Translation: Replication involves a reverse transcription step.

Replication cycle Features: the genome has infectious viruses have 4 main genes coding for the virion proteins in the order: 5'-gag-pro-pol-env-3'. There are additional genes depending on the virus whose products are involved in regulation of synthesis and processing virus RNA and other replicative functions. The LRT is about 600nt long, of which the U3 region is 450, the R sequence 100 and the U5 region some 70 nt long.

Antigenicity

Although different antigenic determinants have different specificities, the antigenic determinants are in general type-specific and serogroup-specific. Antigenic determinants that possess type-specific reactivity are found on the envelopes. Antigenic determinants that possess type-specific reactivity are found on the glycoproteins. The type-specific antigenic determinants are involved in antibody mediated neutralization.

Cross-reactivity is found. Cross-reactivity between some species of the same serotype, but not with all (but not between members of different genera). Classification of members of this taxon is occasionally based on their antigenic properties.

Biological Properties

Natural Host

Virus infects during its life cycle a single type of vertebrate host.
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 Artiodactyla;
Family Bovidae: Subfamily Caprinae; virus infects Genus Capra ibex (goat).

References

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

PubMed References.

Data Sources and Contributions

A web site on the "Biosafety Considerations for Research with Lentiviral Vectors" can be found at National Institute of Health, the Office of Biotechnology Activities.

Images

Taxon images: • EM by Garry et al (1990) Science 250, 1127-1129. • diagram by James Whitehead and Cornelia Büchen-Osmond.



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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

ICTVdB and DELTA related References

Comments to ICTVdB Management
Last updated on 25 April 2006 by Cornelia Büchen-Osmond
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