Abstract
Amnoonviridae is a family of negative-sense RNA viruses with genomes totalling about 10.3 kb. These viruses have been found in fish. The amnoonvirid genome consists of 10 segments, each with at least 1 open reading frame (ORF). The RNA1–3 ORFs encode the three subunits of the viral polymerase. The RNA4 ORF encodes a nucleoprotein. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the family Amnoonviridae, which is available at ictv.global/report/amnoonviridae.
Keywords: ICTV Report, taxonomy, Amnoonviridae, tilapinevirus, tilapia lake virus
Virion
Amnoonvirids produce sphercial, slightly pleomorphic (likely enveloped) particles 55–100 nm in diameter [1, 2] (Table 1).
Table 1.
Characteristics of members of the family Amnoonviridae
|
Example |
tilapia lake virus (KU751814–KU751823), species Tilapinevirus tilapiae, genus Tilapinevirus |
|---|---|
|
Virion |
Enveloped, spherical; 55–100 nm |
|
Genome |
About 10.3 kb of decasegmented negative-sense RNA |
|
Replication |
Unknown |
|
Translation |
Unknown |
|
Host range |
Actinopterygiid fish |
|
Taxonomy |
Realm Riboviria, kingdom Orthornavirae, phylum Negarnaviricota, class Insthoviricetes, order Articulavirales; the family includes the genus Tilapinevirus and the species Tilapinevirus tilapiae |
Genome
The amnoonvirid genome comprises 10 segments of linear negative-sense RNA with a total length of of about 10.3 kb (tilapia lake virus – RNA1 :1641 nt; RNA2 : 1471 nt; RNA3 :1371 nt; RNA4 : 1250 nt; RNA5 :1099 nt; RNA6 : 1044 nt; RNA7 : 777 nt; RNA8 :657 nt; RNA9 : 548 nt; and RNA10 : 465 nt) (Fig. 1). All 10 segments have conserved, complementary sequences at their 5′- and 3′-ends. The RNA1 ORF encodes a protein with an RNA-directed RNA polymerase (RdRP) domain homologous to the PB1 of influenza C virus (Orthomyxoviridae: Gammainfluenzavirus) [3–5]. The RNA2 and RNA3 ORFs encode the PB2 and PA polymerase subunit homologues of orthomyxovirids [6]. The RNA4 ORF encodes a nucleoprotein [7].
Fig. 1.
Genome organisation of tilapia lake virus. ORFs are coloured according to the predicted protein function (NP, nucleoprotein gene; PA, polymerase subunit 3 gene; PB1, polymerase subunit 1 gene encoding an RdRP domain; PB2, polymerase subunit 2 gene). Genes of unknown function are coloured grey.
Replication
Cell entry occurs via dynamin-mediated endocytosis in a cholesterol-dependent, cytoskeleton-dependent manner that is independent of clathrin and pH [8].
Pathogenicity
Tilapia lake virus is highly virulent in tilapia, with systemic infection involving most organs. Infection results in lethargy, ocular disease (such as cataracts, endophthalmitis or exophthalmos), skin erosions and haemorrhages, and severe anaemia, leading to death in >80 % of cases [1].
Taxonomy
Current taxonomy: ictv.global/taxonomy. The family Amnoonviridae includes the genus Tilapinevirus for one species of viruses that infect fish. Viruses in the family Amnoonviridae are most closely related to articulaviral orthomyxovirids [4] (Fig. 2).
Fig. 2.
Phylogenetic relationships of the RdRP core domain of viruses in the phylum Negarnaviricota. For full details see Amnoonviridae ICTV Report.
Resources
Full ICTV Report on the family Amnoonviridae: ictv.global/report/amnoonviridae.
Funding information
Production of this Profile, the ICTV Report, 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 US 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 US 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, Luisa Rubino, Arvind Varsani (ICTV Report Editors), and Donald B. Smith (Managing Editor, ICTV Report). We thank Anya Crane (Integrated Research Facility at Fort Detrick, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Fort Detrick, Frederick, MD, USA) for critically editing the manuscript.
Conflicts of interest
The authors declare that there are no conflicts of interest.
Footnotes
Abbreviations: NP, nucleoprotein; RdRP, RNA-directed RNA polymerase.
References
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