Cache Valley virus
| Cache Valley Virus | |
|---|---|
| Virus classification | |
| Group: | Group V ((−)ssRNA) |
| Family: | Bunyaviridae |
| Genus: | Orthobunyavirus |
| Species: | Cache Valley Virus |
Cache Valley virus (CVV) is a member of the Bunyaviridae family, Orthobunyavirus genus, and Bunyamwera serogroup, which was first isolated in 1956 from Culiseta inornata mosquitos collected in Utah’s Cache Valley. CVV is an enveloped arbovirus, nominally 80–120 nm in diameter, whose genome is composed of three single-stranded, negative-sense RNA segments. The large segment of related bunyaviruses is approximately 6800 bases in length and encodes a probable viral polymerase. The middle CVV segment has a 4463-nucleotide sequence and the smallest segment encodes for the nucleocapsid, and a second non-structural protein. CVV has been known to cause outbreaks of spontaneous abortion and congenital malformations in ruminants such as sheep and cattle. CVV rarely infects humans, but when they are infected it has caused encephalitis and multiorgan failure.
The Cache Valley Virus genome is split into three parts. The three parts are called the small, medium, and large segments, based on the number of bases. The large segment encodes the L protein, which is the RNA dependent RNA polymerase. The small segment utilizes an open reading frame with alternative initiation sites to encode two proteins. Depending on the initiation site, it can either code for the protein that makes up the nucleocapsid, N, or a non-structural protein, NSs. The medium segment encodes 2 type 1 integral transmembrane glycoproteins, Gn and Gc, as well as a non-structural protein Nsm. The Gc and Gn proteins start as one precursor protein and are then cleaved cotranslationally. They are modified by N-linked glycosylation.
The attachment, entry, replication, and release of CVV specifically have not been studied. However, there is information of the replication cycle for the genus orthobunyavirus, which CVV is a part of. A heterodimer of integral transmembrane proteins Gn and Gc form spikes on the surface of the virus particle. They are involved in virus attachment and cell fusion. Once inside the cell, the viral membrane fuses with the endosomal membrane, and the virus genome is released. Transcription involves an RNA dependent RNA polymerase, and it occurs in the cytoplasm of the cell. Transcription of the tripartite genome is terminated by a strong hairpin loop sequence at the end of each segment. Once the virus has replicated enough, it is encapsidated. Assembly and budding of the newly synthesized virions occurs at the membranes of the Golgi apparatus.
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