Editing Bluetongue disease (section)

==Microbiology==
Bluetongue is caused by the [[pathogen]]ic [[virus (biology)|vector-borne RNA virus]], [[Bluetongue virus]] (BTV),<ref name = roy/> of the genus ''[[Orbivirus]]'' within the ''[[Sedoreoviridae]]'' family.<ref name=specieslist /> The virus particle consists of 10 strands of double-stranded RNA surrounded by two protein shells. Unlike other [[arboviruses]], BTV lacks a [[lipid]] envelope. The virus exhibits icosahedral symmetry, with a diameter of approximately 80–90&nbsp;nm.<ref name="Saminathan_2020" /><ref name="Roy2008">{{cite journal | vauthors = Roy P | title = Functional mapping of bluetongue virus proteins and their interactions with host proteins during virus replication | journal = Cell Biochemistry and Biophysics | volume = 50 | issue = 3 | pages = 143–157 | year = 2008 | pmid = 18299997 | doi = 10.1007/s12013-008-9009-4 | s2cid = 984334 }}</ref>  The structure of the 70&nbsp;nm core was determined in 1998 and was at the time the largest atomic structure to be solved.<ref name="Rossmann1999">{{cite journal | vauthors = Rossmann MG, Tao Y | title = Courageous science: structural studies of bluetongue virus core | journal = Structure | volume = 7 | issue = 3 | pages = R43–R46 | date = March 1999 | pmid = 10368304 | doi = 10.1016/s0969-2126(99)80031-8 | doi-access = free }}</ref>

The 10 viral genome segments have been found to encode 7 structural (VP1–VP7) and 5 non-structural (NS1, NS2, NS3/NS3A, NS4 and NS5) proteins.<ref name="Saminathan_2020" /> There are currently more than 28 known serotypes of BTV.<ref name="Saminathan_2020" /><ref name="Rodríguez-Martín_2021" /><ref name="John_2022" /><ref name="Yang_2021" /> The sequence of genome Seg-2 and its translated protein VP2, as well as that of Seg-6 and its translated protein VP5, exhibit variations that determine the serotypes.<ref name="Saminathan_2020" />

The two outer capsid proteins, VP2 and VP5, mediate attachment and penetration of BTV into the target cell. VP2 and VP5 are the primary antigenic targets for antibody targeting by the host immune system.  The virus makes initial contact with the cell with VP2, triggering [[receptor-mediated endocytosis]] of the virus.  The low pH within the [[endosome]] then triggers BTV's membrane penetration protein VP5 to undergo a conformational change that disrupts the endosomal membrane.<ref name="Roy2008"/>  Uncoating yields a transcriptionally active 470S core particle which is composed of two major proteins VP7 and VP3, and the three minor proteins VP1, VP4 and VP6 in addition to the dsRNA genome. There is no evidence that any trace of the outer capsid remains associated with these cores, as has been described for reovirus. The cores may be further uncoated to form 390S subcore particles that lack VP7, also in contrast to reovirus. Subviral particles are probably akin to cores derived ''in vitro'' from virions by physical or proteolytic treatments that remove the outer capsid and causes activation of the BTV transcriptase. In addition to the seven structural proteins, three non-structural (NS) proteins, NS1, NS2, NS3 (and a related NS3A) are synthesised in BTV-infected cells. Of these, NS3/NS3A is involved in the egress of the progeny virus. The two remaining non-structural proteins, NS1 and NS2, are produced at high levels in the cytoplasm and are believed to be involved in virus replication, assembly and morphogenesis.<ref name=roy>{{cite book |chapter-url=http://www.horizonpress.com/avir| vauthors = Roy P |year=2008|chapter=Molecular Dissection of Bluetongue Virus|title=Animal Viruses: Molecular Biology|publisher=Caister Academic Press|pages=305–54| isbn =978-1-904455-22-6}}</ref>