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A summary of this ICTV online (10th) report chapter has been published as an ICTV Virus Taxonomy Profile article in the Journal of General Virology, and should be cited when referencing this online chapter as follows:
Dietzgen, R.G., Ghedin, E., Jiāng, D., Kuhn, J.H., Song, T., Vasilakis, N., Wang, D., and ICTV Report Consortium. 2017, ICTV Virus Taxonomy Profile: Nyamiviridae, Journal of General Virology, (In Press).
The Nyamiviridae is a family of viruses in the order Mononegavirales with unsegmented, negative-sense RNA genomes of approximately 11–12 kb that produce enveloped, spherical virions (Kuhn et al., 2013). The Nyamiviridae includes the genera Nyavirus, Peropuvirus, and Socyvirus that form monophyletic clades on phylogenetic analysis of the RNA polymerase. Nyamiviruses have a similar genome organization, including the number and locations of genes identified by homology with those of other mononegaviruses. Viruses of the genus Nyavirus are tick-borne and some of them also infect birds (Takahashi et al., 1982). Other nyamiviruses that were isolated from parasitoid wasps have been classified into the genus Peropuvirus (Wang et al., 2017), while members of the Socyvirus genus infect plant parasitic nematodes (Bekal et al., 2011).
Table 1.Nyamiviridae. Characteristics of the family Nyamiviridae.
Nyamanini virus (FJ554526), species Nyamanini nyavirus, genus Nyavirus
Enveloped, spherical particles, approximately 100–130 nm in diameter
Negative-sense, single-stranded, unsegmented RNA of 11.3-12.2 kb
Nuclear: the RNA-dependent RNA polymerase engages with ribonucleoprotein at the genome 3’ end
Individual putatively polyadenylated mRNAs are translated in the cytoplasm
Invertebrates; ticks, parasitoid wasps, nematodes; land- and seabirds
The genera Nyavirus, Peropuvirus, and Socyvirus include 5 species
Virions are enveloped and spherical with a diameter of 100–130 nm (Figure 1.Nyamiviridae).
Figure 1.Nyamiviridae. Transmission electron micrograph of Vero E6 cells infected with Sierra Nevada virus. High magnification of virions (V) budding from the cell surface. M indicates mitochondria. Bar = 1 μm. Contributed by Dr Vsevolod Popov, Department of Pathology, Center for Biodefense and Emerging Infectious Diseases, University of Texas Medical Branch, Galveston, TX, USA.
Unsegmented, negative-sense, single-stranded RNA, 11–12 kb.
Nyamiviruses encode 5 or 6 structural proteins. Among them are the nucleocapsid protein (N), glycoprotein (G) and RNA-dependent RNA polymerase (L) that are identified based on sequence similarity and structural properties shared with mononegavirus homologues. Functions of the other encoded proteins are largely unknown, but may be those of matrix and polymerase cofactor proteins.
Nyamivirus negative-sense, single-stranded RNA genomes range from 11.3–12.2 kb (Figure 2.Nyamiviridae). All known nyamiviruses have unsegmented genomes with 5 or 6 open reading frames (ORFs) that encode the structural proteins. Knowledge about nyamivirus replication is limited. Nyamanini virus (genus Nyavirus) replicates in the nucleus of infected cells.
Figure 2.Nyamiviridae. Genome organization of viruses in the family Nyamiviridae: Nyamanini virus, Midway virus, Sierra Nevada virus, soybean cyst nematode virus 1, and Pteromalus puparum negative-strand RNA virus 1. Boxes indicate the position and length of each ORF (numbered consecutively I-VI or I-V), with boxes that are in the same horizontal position indicating ORFs that are in the same reading frame. Putative nucleocapsid protein (N), phosphoprotein (P), glycoprotein (G) and RNA-dependent RNA polymerase (L) ORFs are indicated. Genome sizes (bases) are indicated.
An antigenic relationship between Nyamanini virus and Midway virus (genus Nyavirus) was demonstrated by complement fixation tests.
Viruses of the genus Nyavirus are tick-borne and some of them also infect birds, while members of the Socyvirus genus infect plant parasitic nematodes, and members of the genus Peropuvirus infect parasitoid wasps.
Due to the small number of genus members, no firm genus demarcation criteria have been established beyond phylogeny and the hosts the viruses infect. The genome sequence of Pteromalus puparum negative-strand RNA virus 1 (PpNSRV-1; genus Peropuvirus) is only 13.8% identical to that of soybean cyst nematode virus 1 (SbCNV-1; genus Socyvirus), and 10.9–12.3 % identical to that of viruses in the genus Nyavirus, which is lower than the 17% identity between members of the genera Nyavirus and Socyvirus. Given the extent of divergence of viruses in the Peropuvirus genus from viruses in the rest of the family, this genus may, in the future, need to be moved out of the family Nyamiviridae.
Nyamiviridae: acronym of the first three letters of “Nyamanini Pan” (place of isolation of Nyamanini virus in South Africa) and the first two letters of “Midway Atoll” (place of isolation of Midway virus in the USA), and the suffix -viridae (ending denoting a virus family) → Neo-Lat. n. fem. pl. Nyamiviridae – the family of nyamiviruses.
Viruses assigned to each genus appear to form monophyletic clades but bootstrap support in the phylogenetic analyses of L polymerase amino acid sequences is weak (Figure 3.Nyamiviridae). Nyamiviruses have a similar genome organization, including the number and locations of genes identified by homology with those of other mononegaviruses (Figure 2.Nyamiviridae).
Figure 3.Nyamiviridae. Phylogenetic tree of mononegavirus L polymerase protein sequences highlighting Nyamiviridae and its genera. Amino acid sequences were aligned using MUSCLE and then filtered by Gblocks to identify and select conserved regions. The resulting alignment was imported into RAxML-HPC to generate a maximum likelihood phylogenetic tree, using the GTR substitution model, a gamma distribution of rates across sites, and 1,000 bootstrap replicates. The tree was plotted using the ggtree package in R. The colors indicate the different mononegavirus families and nyamivirus genera. The tips of the tree show virus names and GenBank accession numbers.
Some biological properties of nyamiviruses appear to be similar to those of filoviruses (mononegavirus family Filoviridae) and bornaviruses (mononegavirus family Bornaviridae).
Members of the unassigned mononegavirus genus Crustavirus (including Wēnzhōu crab virus 1) may need to be included in the family Nyamiviridae.
Běihǎi rhabdo-like virus 3
Běihǎi rhabdo-like virus 4
Běihǎi rhabdo-like virus 5
Wēnzhōu tapeworm virus 1
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