Xīlǎng virus (XILV) is the only classified striavirus. Like thamnoviruses, but unlike cuevaviruses, dianloviruses, ebolaviruses, and marburgviruses, striaviruses appear to infect fish (Shi et al., 2018). Notably, striavirus genomes contain nine gene overlaps, encode at least three proteins without obvious homologs in other filovirus genera, and do not encode ribonucleoprotein (RNP) complex-associated protein (VP24).
Physicochemical and physical properties
Virions are assumed to contain one or several copies of linear negative-sense single‑stranded RNA genomes that are encapsidated independently.
Striaviruses likely express at least 10 proteins, of which six (nucleoprotein [NP], polymerase cofactor [VP35], transcriptional activator [VP30], the matrix protein [VP40], glycoprotein [GP1,2], and large protein [L]) are homologs of proteins expressed by cuevaviruses, dianloviruses, ebolaviruses, and marburgviruses and four (NP, VP35, GP1,2, and L) are homologs of proteins expressed by thamnoviruses (Hume and Mühlberger 2019). The second most abundant structural protein in virions is assumed to be NP, which encapsidates the striavirus genome. The least abundant protein is assumed to be L, which mediates striavirus genome replication and transcription (Shi et al., 2018, Hume and Mühlberger 2019).
Genome organization and replication
The striavirus genome has the gene order 3′-NP-VP35-VP40-U1-GP-U2-VP30-U3-U4-L-5′, with U denoting genes expressing proteins of unknown function (Figure 1.Striavirus). The undetermined extragenic sequences at the extreme 3′-end (leader) and 5′-end (trailer) of the genome are assumed to be conserved and partially complementary. Genes are flanked by unique conserved transcriptional initiation and termination (polyadenylation) sites. All striavirus genes overlap.
Figure 1.Striavirus. Schematic representation of the striavirus genome organization. Genome is drawn to scale. Courtesy of Jiro Wada, NIH/NIAID/DCR/IRF-Frederick, Fort Detrick, MD, USA.
The replication strategy of striaviruses remains to be studied.
Striaviruses were discovered in 2011 by high-throughput sequencing of samples taken from striated frogfish (Antennarius striatus (G. Shaw, 1794)) captured by fishing trawlers in the East China Sea (Shi et al., 2018).
Derivation of names
Striavirus: from Antennarius striatus, the fish species to which the presumed host of XILV, striated frogfish, has been assigned (Shi et al., 2018).
Species demarcation criteria
The genus currently includes only a single species.
|Species||Virus name||Isolate||Accession number||RefSeq number||Available sequence||Virus Abbrev.|
|Xilang striavirus||Xīlǎng virus; Wēnlǐng frogfish filovirus||Xīlǎng virus/A.striatus-wt/CHN/2018/XYHYS28627||MG599980||Complete coding genome||XILV|