Abstract
Arenaviridae is a family for ambisense RNA viruses with genomes of about 10.5 kb that infect mammals, snakes, and fish. The arenavirid genome consists of two or three single-stranded RNA segments and encodes a nucleoprotein (NP), a glycoprotein (GP) and a large (L) protein containing RNA-directed RNA polymerase (RdRP) domains; some arenavirids encode a zinc-binding protein (Z). This is a summary of the International Committee on Taxonomy of Viruses (ICTV) report on the family Arenaviridae, which is available at www.ictv.global/report/arenaviridae.
Keywords: Arenaviridae, arenavirus, ICTV Report, mammarenavirus, reptarenavirus, taxonomy
Virion
Arenavirids produce virions that are spherical or pleomorphic in shape and 40–200 nm in diameter, with dense lipid envelopes (Table 1 and Fig. 1). The virion surface layer is covered with club-shaped projections that have distinctive stalk and head regions. These projections consist of trimeric spike structures of two virus-encoded membrane glycoprotein (GP) subunits (GP1 and GP2) and, in the case of some arenavirids, a stable signal peptide (SSP). Isolated ribonucleoprotein (RNP) complexes are organized into ‘beads-on-a-string’-like structures [1, 2].
Table 1.
Characteristics of members of the family Arenaviridae
|
Example |
lymphocytic choriomeningitis virus (S: AY847350; L: AY847351), species Mammarenavirus choriomeningitidis, genus Mammarenavirus |
|---|---|
|
Genome |
Two or three single-stranded, usually ambisense, RNA molecules (segments): small (S), medium (M), and large (L) |
|
Replication |
Ribonucleoprotein complexes containing anti-genomic RNA serve as templates for synthesis of genomic RNA |
|
Translation |
From capped and non-polyadenylated mRNAs. The 5′ cap structure is obtained via cap-snatching from cellular mRNAs |
|
Host range |
Fish (antennaviruses), mammals (mammarenaviruses), reptiles (hartmaniviruses and reptarenaviruses), and potentially also ticks |
|
Taxonomy |
Realm Riboviria, kingdom Orthornavirae, phylum Negarnaviricota, class Ellioviricetes, order Bunyavirales; >4 genera and >59 species |
Fig. 1.
(a) Electron micrograph of lymphocytic choriomeningitis virus budding from an infected cell. (b) Illustration of a particle in (a) showing the spherical and enveloped particle (grey) that is spiked with glycoproteins (GP, gold) around a layer of zinc-binding proteins (Z, brown). The small (S) and large (L) ribonucleoprotein (RNP) complexes inside the particle consist of nucleoprotein (NP; blue) and large (L; green) protein.
Genome
Arenavirid genomes consist of two or three single-stranded, typically ambisense, RNA segments (small [S], medium [M], and large [L]). Some of these RNAs encode two proteins in non-overlapping open reading frames of opposite polarities that are separated by non-coding intergenic regions (IGRs) (Fig. 2). The S RNA encodes a nucleoprotein (NP) in the virus genome-complementary strand and, in many cases, a virus glycoprotein precursor (GPC) in the virus genome-sense strand. The L RNA segment encodes a large (L) protein in the virus genome-complementary strand and, in some cases, a zinc-binding protein (Z) in the virus genome-sense sequence [1–3].
Fig. 2.
Mammarenavirus genome. The ends of both segments are complementary at their termini, likely promoting the formation of panhandle RNP complexes within the virion. GP, glycoprotein gene; L, large protein gene; NP, nucleoprotein gene; Z, zinc-binding protein gene.
Replication
Arenavirions attach to cell-surface receptors or attachment factors and enter via the endosomal route. Some viruses engage intracellular receptors in endosomes. pH-dependent fusion with late endosomes releases the virion RNP complex into the cytoplasm. The virus RNP directs both RNA genome replication and gene transcription. During replication, L protein reads through the IGR transcription–termination signal and generates uncapped antigenomic and genomic RNAs. Transcription of mRNAs encoding GPC and Z occurs only after the first round of virus replication, during which S and L antigenomes are produced. Arenavirid mRNAs lack 3′-terminal poly(A) tracts but have several non-templated 5′ bases, consistent with the use of a cap-snatching mechanism to initiate transcription. Virion budding occurs from the cellular plasma membrane, thereby providing the virion envelope [1, 2].
Taxonomy
Current taxonomy: ictv.global/taxonomy. The family Arenaviridae is included in the negarnaviricot order Bunyavirales. Arenavirids are most closely related to mypovirids, nairovirids, phenuivirids and wupedevirids. Arenavirids differ from most other bunyavirals by having segmented genomes with ambisense organization. The family includes several genera and >59 species. Some arenavirids can cause severe diseases in humans (e.g. Lassa fever) [4]. Other arenavirids cause disease in captive snakes [3, 5].
Resources
Full ICTV Report on the family Arenaviridae: www.ictv.global/report/arenaviridae.
Funding information
Production of this summary, the online chapter, and associated resources was supported by the Microbiology Society. This work was supported in part through the Laulima Government Solutions, LLC, prime contract with the U.S. National Institute of Allergy and Infectious Diseases (NIAID) under Contract No. HHSN272201800013C. J.H.K. performed this work as an employee of Tunnell Government Services (TGS), a subcontractor of Laulima Government Solutions, LLC, under Contract No. HHSN272201800013C. The content of this publication should not be interpreted as necessarily representing the official policies, either expressed or implied, of the U.S. Department of Health and Human Services or of the institutions and companies affiliated with the authors.
Acknowledgements
We thank Stuart G. Siddell, Elliot J. Lefkowitz, Sead Sabanadzovic, Peter Simmonds, F. Murilo Zerbini, Evelien Adriaenssens, Mart Krupovic, Jens H. Kuhn, Luisa Rubino, Arvind Varsani (ICTV Report Editors) and Donald B. Smith (Managing Editor, ICTV Report). We also thank Anya Crane and Jiro Wada (Integrated Research Facility at Fort Detrick), for critically editing the text and preparing figures.
Conflicts of interest
The authors declare that there are no conflicts of interest.
Footnotes
Abbreviations: GP, glycoprotein; GPC, glycoprotein precursor; IGRs, intergenic regions; L, large; M, medium; NP, nucleoprotein; RNP, ribonucleoprotein; S, small; SSP, stable signal peptide; Z, zinc-binding protein.
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