Nodaviridae


Nodaviridae is a family of viruses. Vertebrates and invertebrates serve as natural hosts. There are currently nine species in this family, divided among 2 genera. Diseases associated with this family include: viral encephalopathy and retinopathy in fishes.

Virology

The virus is not enveloped and has an icosahedral capsid ranging from 29 to 35 nm in diameter. The capsid is constructed of 32 capsomers.
The genome is linear, positive sense, bipartite single stranded RNA consisting of 4500 nucleotides with a 5’ terminal methylated cap and a non-polyadenylated 3’ terminal.
RNA1, which is ~3.1 kilobases in length, encodes a protein that has multiple functional domains: a mitochondrial targeting domain, a transmembrane domain, an RNA-dependent RNA polymerase domain, a self-interaction domain and an RNA capping domain. In addition, RNA1 encodes a subgenomic RNA3 that encodes protein B2, an RNA silencing inhibitor.
RNA2 encodes protein α, a viral capsid protein precursor, which is auto-cleaved into two mature proteins, a 38 kDa β protein and a 5 kDa γ protein, at a conserved Asn/Ala site during virus assembly.
GenusStructureSymmetryCapsidGenomic arrangementGenomic segmentation
BetanodavirusIcosahedralT=3Non-envelopedLinearSegmented
AlphanodavirusIcosahedralT=3Non-envelopedLinearSegmented

Life cycle

Viral replication is cytoplasmic. Entry into the host cell is achieved by penetration into the host cell. Replication follows the positive stranded RNA virus replication model. Positive stranded RNA virus transcription, using the internal initiation model of subgenomic RNA transcription is the method of transcription. Vertebrates and invertebrates serve as the natural host. Transmission routes are contact and contamination.
GenusHost detailsTissue tropismEntry detailsRelease detailsReplication siteAssembly siteTransmission
BetanodavirusFish-UnknownLysisCytoplasmCytoplasmPassive diffusion, direct contact
AlphanodavirusInsects, mammals, fishes-UnknownLysisCytoplasmCytoplasmUnknown

Taxonomy

The members of the genus Alphanodavirus were originally isolated from insects while those of the genus Betanodavirus were isolated from fish. A small number of nodoviruses seem to lie outside either of these clades.
While NoV remains the type species of Alphanodavirus, Flock house virus is the best studied of the nodaviruses.

History

The name of the family is derived from the Japanese village of Nodamura, Iwate Prefecture where Nodamura virus was first isolated from Culex tritaeniorhynchus mosquitoes.