Foot-and-mouth disease virus
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The foot-and-mouth disease virus ( English foot-and-mouth disease virus , abbreviated FMDV , in German also MKSV) is a highly contagious virus species from the Picornaviridae family , together with the equine rhinitis B virus, forms the genus aphthovirus and shows a high mutation rate. The FMDV is the causative agent of foot and mouth disease in cloven-hoofed animals , especially domestic cattle .
properties
morphology
The virus particles (virions) of the FMDV are 23 to 27 nm in diameter and have an unusually smooth surface for picornaviruses. The capsid, which is very thin-walled at 3.3 nm, is made up of capsomeres consisting of the four capsid proteins , of which the capsid proteins 1A, 1B and 1D form the surface and lie on the outside, whereas the protein 1C lines the inside of the capsid. The capsid proteins of the FMDV are among the smallest of the picornaviruses , with a size of 208 to 220 amino acids . At the corners of the capsid, where there is a five-pointed symmetry (pentamer), the 1C is also accessible from the outside. The capsid protein 1D has an outwardly directed domain 17 to 23 amino acids long, the so-called GH loop, with which the virus recognizes its target cell and infects the cell via membrane receptors of the integrin family. The GH loop carries the conserved integrin recognition motif RGD at its end and binds in particular to αVβ6 integrin.
The capsid protein 1A is mainly responsible for the serological properties of the FMDV, to which neutralizing antibodies also bind. There are two determinants in the GH loop of the 1D. In some isolates there is a lot of empty, i.e. H. RNA-free and therefore non-infectious capsids ( 75-S component ), which, however, have the same serological properties as the complete virions (140-S component). Presumably they play some role in distracting the immune system .
Genome
The genome of the FMDV is about 8450 nt in size and codes for a polyprotein of 2332 amino acids in length. The viral (+) ssRNA can be read directly as mRNA and is capable of replication without further intermediate steps. In front of the start codon of the single open reading frame (ORF) there is a non-coding region (5'-NCR) which, at approx. 1200 to 1500 nt, is almost twice as long as in other picornaviruses. The size explains itself u. a. from a 100–400 nt long poly- cytosine tract (poly-C) in the front third of the 5'-NCR , which forms several pseudo-nodes as a secondary structure, depending on the isolate . Three different genomic virus proteins (VPg) are covalently bound to the 5'-NCR .
As with all species of the genera aphthovirus and cardiovirus, the reading frame of the FMDV does not begin with the capsid proteins, but with a so-called leader protein (L-protein), which has a protease function. The translation of the ORF begins with the FMDV at two alternative start codons, whereby two L-proteins of different lengths are formed (Lab and Lb). As with all picornaviruses, translation is initiated by an IRES . The Lb protein is now able to cleave to activate a cellular protease which initiates the breakdown of a cellular protein (p220), which in turn is part of the cellular translation initiation complex eIF-4F. As a result, the translation used by the cellular mRNAs is prevented by means of a 5'-cap structure and the entire cellular protein synthesis is blocked; only the virus, which because of its IRES does not need the factor eIF-4F, can now synthesize its proteins. One speaks here of a so-called "virus-host shutoff" ( shutoff of the host cell by the virus). In addition to the Lb protein, the C3 protease of the FMDV is also able to inactivate cellular initiation factors.
Biological properties
Host spectrum
A natural infection with the FMDV has been described in numerous cloven-hoofed animals and other mammals, mainly in horned animals ( Bovidae with the important representatives buffalo , bison , antelopes , gazelles , cattle , sheep and goats ), but also in deer ( Cervidae ), umbilical pigs ( Tayassuidae ), pigs ( Suidae ), hedgehogs ( Erinaceidae ), camels ( Camelidae ), giraffes ( Giraffidae ), long-tailed mice ( Muridae ), elephants ( Elephantidae ), bears ( Ursidae ) and tapirs ( Tapiridae ). On the basis of genetic studies of the FMDV isolated from wild animals, its distribution through large animal migrations , especially in Africa, can be shown. The FMDV also allows conclusions to be drawn about the migration routes of the herds. Under experimental conditions, the FMDV can also be applied to dogs , cats , rabbits and rats . In research, the artificial infection of guinea pigs and newborn mice is important. The virus can be grown very well in cell lines from hamster kidney cells (BHK-21: baby hamster kidney cells ); This cell line is also used to produce the vaccine against FMDV types.
stability
Due to the capsid formation over only a few polar amino acid groups, the FMDV is very sensitive to acids and is already inactivated at pH values below 6.8 . The acidification that occurs during normal meat ripening (pH <6.0) and in milk products made from sour milk inactivates the virus just as completely as normal stomach acid . Transmission of the virus via the gastrointestinal tract is therefore excluded. The virus can, however, be spread in products that are not acidified (bone marrow, fat, bacon, blood and frozen meat). The virus is not inactivated by low temperatures and high saline concentrations. The FMDV is very stable over a long period of time in a dry environment. Particularly dried-on saliva allows the wind to spread over distances of more than 10 km if dry climatic conditions are present.
Subtypes and distribution
The FMDV is distributed worldwide except in New Zealand , Australia and North America . The virus is endemic in much of Asia and South America, as well as most African countries. In Europe , it only occurs in sporadic outbreaks due to legal intervention and prophylactic vaccinations. The FMDV has a high antigenetic variability and a large number of different serotypes, variants and strains have been isolated. These differ in their serological and immunological properties. The first two types - and thus the so-called plurality of the virus - were characterized by Vallée and Carré in 1922 and named O ( Département Oise ) and A ( Ardennes ) after the location of the isolate . A third type (C) was discovered in Germany in 1926 and in 1952 three other types were isolated in Africa ( “Southern African Territories” SAT). The last type described so far was isolated in Asia in 1954 (Asia1). All types except the FMDV-C tend towards variability and the formation of further subtypes which, in addition to a type antigen, also have another strain-specific antigen. While all types are distributed differently geographically, the type FMDV-O can be found in all FMDV areas.
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- Species foot-and-mouth disease virus (FMDV)
- Foot-and-mouth disease virus A (FMDV-A) type, 32 subtypes
- Foot-and-mouth disease virus Asia 1 (FMDV-Asia1), 3 subtypes
- Foot-and-mouth disease virus C (FMDV-C) type
- Foot-and-mouth disease virus O (FMDV-O) type, 11 subtypes
- Foot-and-mouth disease virus type SAT 1 (FMDV-SAT1), 7 subtypes
- Foot-and-mouth disease virus type SAT 2 (FMDV-SAT2), 3 subtypes
- Foot-and-mouth disease virus type SAT 3 (FMDV-SAT3), 4 subtypes
Individual evidence
- ↑ ICTV Master Species List 2018b v1 MSL # 34, March 2019
- ↑ a b c d ICTV: ICTV Taxonomy history: Enterovirus C , EC 51, Berlin, Germany, July 2019; Email ratification March 2020 (MSL # 35)
- ↑ Abhay Kotecha, Quan Wang, Xianchi Dong, Serban L. Ilca, Marina Ondiviela: Rules of engagement between αvβ6 integrin and foot-and-mouth disease virus . In: Nature Communications . tape 8 , no. 1 , August 2017, ISSN 2041-1723 , p. 15408 , doi : 10.1038 / ncomms15408 , PMID 28534487 , PMC 5457520 (free full text) - ( nature.com [accessed April 30, 2020]).
- ↑ ME Piccone, S. Sira, M. Zellner, MJ Grubman: Expression in Escherichia coli and purification of biologically active L proteinase of foot-and-mouth disease virus . Virus Res. (1995) 35 (3): pp. 263-275 PMID 7785315
- ↑ GJ Belsham, GM McInerney, N. Ross-Smith: Foot-and-mouth disease virus 3C protease induces cleavage of translation initiation factors eIF4A and eIF4G within infected cells. J Virology (2000) 74 (1): pp. 272-280 PMID 10590115
- ↑ KE Federer: Susceptibility of the agouti (Dasyprocta aguti) to foot-and-mouth disease virus . Zentralbl Veterinarmed B (1969) 16 (9): pp. 847-854 PMID 4320315
- ↑ GR Thomson 2001, see list of references
- ^ W. Vosloo, AD Bastos, A. Michel, GR Thomson: Tracing movement of African buffalo in southern Africa . Rev Sci Tech. (2001) 20 (2): pp. 630-639 PMID 11548532
- ^ H. Vallée and H. Carré: Sur límmunité anti-aphteuse . Revue générale de médecine vétérinaire (Toulouse) 1922: 31, pp. 313-317
- ^ H. Vallée and H. Carré: Sur la pluralite du virus aphteux . Comptes rendus hebdomadaires des séances de l'Académie des Sciences, Paris (1922) 174, pp. 1498-1500
- ^ O. Waldmann and K. Trautwein: Experimental investigations on the plurality of the foot and mouth disease virus . Berliner Tierärztliche Wochenschrift (1926) 42: pp. 569–571
- ↑ JB Brooksby: Vesicular stomatitis and foot-and-mouth disease: analysis of mixed infection in cattle. J Hyg, London (1952) 50 (3): pp. 394-404 PMID 12990797
- ↑ CJ Bradish, WM Henderson, JB Brooksby: Electrophoretic studies of ox serum. 2. The sera of cattle infected with the virus of foot-and-mouth disease . Biochem J. (1954) 56 (2): pp. 335-341 PMID 13140197
literature
- G. Stanway, F. Brown et al .: Genus Aphthovirus. In: CM Fauquet, MA Mayo et al .: Eighth Report of the International Committee on Taxonomy of Viruses. London, San Diego, 2005, pp. 768f.
- S. Mordow, D. Falke: Molecular Virology. Spektrum Akad. Verlag, Heidelberg, Berlin 1997.
- Heinrich Liebermann: Textbook of the veterinary virology. Stuttgart 1992.
- GR Thomson, RG Bengis, CC Brown: Picornavirus Infections. In: ES Williams and IK Baker (eds.): Infectious diseases of wild animals. Iowa State University Press, Ames, Iowa, 3rd Edition 2001, pp. 119-130.