Family: Filoviridae
Genus: Oblavirus
Distinguishing features
Oberland virus (OBLV) is the only classified oblavirus. Like striaviruses and thamnoviruses, but unlike cuevaviruses, dianloviruses, orthoebolaviruses, orthomarburgviruses, and tapjoviruses, oblaviruses infect fish (Hierweger et al., 2021). Notably, oblavirus genomes encode at least two proteins without obvious homologs in other filovirid genera, and do not encode matrix protein (VP40) or ribonucleoprotein (RNP) complex-associated protein (VP24) (Hume and Mühlberger 2019, Hierweger et al., 2021).
Virion
Virions are unknown.
Nucleic acid
Virions are assumed to contain one or several copies of the linear negative-sense single stranded RNA genome that are encapsidated independently.
Proteins
Oblaviruses likely express at least seven proteins, of which five (nucleoprotein [NP], polymerase cofactor [VP35], glycoprotein [GP1,2], transcriptional activator [VP30], and large protein [L]) are likely homologs of proteins expressed by all other filovirids (Hume and Mühlberger 2019, Hierweger et al., 2021). After VP40, the second most abundant structural protein in virions is assumed to be NP, which encapsidates the oblavirus genome. The least abundant protein is assumed to be L, which mediates oblavirus genome replication and transcription.
Genome organization and replication
The oblavirus genome has the gene order 3′-U1-NP-VP35-U2-GP-VP30-L-5′ (Hierweger et al., 2021), with U denoting genes expressing proteins of unknown function (Figure 1.Oblavirus). 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 (Hume and Mühlberger 2019).
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| Figure 1.Oblavirus. Schematic representation of oblavirus genome organization, drawn to scale. GP, glycoprotein gene; L, large protein gene; NP, nucleoprotein gene; U1/2, genes encoding proteins of unknown function; VP30, transcriptional activator gene; VP35, polymerase co-factor gene. Wavy lines indicate incomplete genome ends. |
The replication strategy of oblaviruses remains to be studied.
Biology
Oblaviruses were discovered by high-throughput sequencing of samples taken from farmed diseased European perch (percid Perca fluviatilis Linnaeus, 1758) imported to Switzerland from Germany (Hierweger et al., 2021).
Species demarcation criteria
The genus currently includes only a single species.