Picornavirus 460071 222613860 2008-06-30T07:31:26Z Les boys 7373191 Reverted 1 edit by [[Special:Contributions/116.33.73.35|116.33.73.35]]; Test edits. ([[WP:TW|TW]]) {{Taxobox | name = Picornavirus | virus_group = iv | familia = ''Picornaviridae'' | subdivision_ranks = Genera | subdivision = ''[[Enterovirus]]''<br> ''[[Rhinovirus]]''<br> ''[[Hepatovirus]]''<br> ''[[Cardiovirus]]''<br> ''[[Aphthovirus]]''<br> ''[[Parechovirus]]''<br> ''[[Erbovirus]]''<br> ''[[Kobuvirus]]''<br> ''[[Teschovirus]]'' }} A '''Picornavirus''' is a [[virus]] belonging to the [[family (biology)|family]] ''Picornaviridae''. Picornaviruses are non-enveloped, [[positive-stranded]] RNA viruses with an [[icosahedral]] [[capsid]]. The [[genome]] [[RNA]] is unusual because it has a [[protein]] on the 5' end that is used as a [[primer (molecular biology)|primer]] for [[Transcription (genetics)|transcription]] by [[RNA polymerase]]. The name is derived from [[pico]] meaning small, and RNA referring to the [[ribonucleic acid]] genome, so "picornavirus" literally means ''small [[RNA virus]]''. Picornaviruses are separated into nine distinct genera and include many important pathogens of humans and animals.<ref name=MettenleiterSobrino>{{cite book | author = Mettenleiter TC and Sobrino F (editors). | title = Animal Viruses: Molecular Biology | publisher = Caister Academic Press | year = 2008 | url=http://www.horizonpress.com/avir | id = [http://www.horizonpress.com/avir ISBN 978-1-904455-22-6 ]}}</ref> The diseases they cause are varied, ranging from acute "common-cold"-like illnesses, to poliomyelitis, to chronic infections in livestock. Two main categories are [[enteroviruses]] and [[rhinovirus]]es. ==Classification== Picornaviruses are classed under [[Baltimore's viral classification system]] as group IV viruses as they contain a single stranded, positive sense RNA [[genome]] of between 7.2 and 9.0 kb in length. Like most positive sense RNA genomes, the genetic material alone is infectious; although substantially less [[virulent]] than if contained within the viral particle, the RNA can have increased infectivity when transfected into cells. The genome itself is the same sense as mammalian mRNA, being read 5’ to 3’. Unlike [[mammalian]] [[mRNA]] Picornaviruses do not have a 5’ CAP but a virally encoded protein known as [[VPg]], however like mammalian mRNA the genome does have a poly A tail at the 3’ end. There is an un-translated region (UTR) at both ends of the Picornavirus genome. The 5’ UTR is longer, being around 600-1200 BP in length, compared to that of the 3’ UTR, which is around 50-100bp. It is thought that the 5’ UTR is important in translation and the 3’ in negative strand synthesis; however the 5’ end may also have a role to play in virulence of the virus. The rest of the genome encodes structural proteins at the 5’ end and non-structural proteins at the 3’ end in a single polyprotein. Experimental data from single step growth-curve-like experiments have allowed scientists to look at the replication of the picornaviruses in great detail. The whole of replication occurs within the host cell cytoplasm and infection can even happen in cells that do not contain a [[cell nucleus|nucleus]] (known as enucleated cells) and those treated with [[actinomycin D]] (this antibiotic would inhibit viral replication if this occurred in the nucleus.) ==Structure of the Picornaviruses== The [[capsid]] is an arrangement of 60 protomers in a tightly packed [[Icosahedral]] structure. Each protometer consists of 4 [[polypeptide]]s known as VP (viral protein)1, 2, 3 and 4. All of these VP polypeptides originate from one protomer known as VP0 that is [[cleaved]] to give the different capsid components. The [[Icosahedral]] is said to have a triangulation number of 3, this means that in the [[icosahedral]] structure each of the 60 triangles that make up the capsid are split into 3 little triangles with a subunit on the corner. Depending on the type and degree of dehydration the viral particle is around 27-30nm in diameter. The viral genome is around 2500nm in length so we can therefore conclude that it must be tightly packaged within the capsid along with substances such as [[sodium]] ions in order to cancel out the negative charges on the RNA caused by the [[phosphate]] groups. ==Picornavirus replication== The viral particle binds to cell surface receptors. This causes a conformational change in the viral capsid proteins, and [[myristic acids]] are released. These acids form a pore in the cell membrane through which RNA is injected[http://pathmicro.med.sc.edu/virol/polio.htm]. Once inside the cell, the RNA un-coats and the (+) strand RNA genome is replicated through a double-stranded RNA intermediate that is formed using viral RDRP (RNA-Dependent RNA polymerase). Translation by host cell ribosomes is not initiated by a 5' G cap as usual, but rather is initiated by an IRES (Internal Ribosome Entry Site). The viral lifecycle is very rapid with the whole process of replication being completed on average within 8 hours. However as little as 30 minutes after initial infection, cell protein synthesis declines to almost zero output – essentially the macromolecular synthesis of cell proteins is “shut off”. Over the next 1-2 hours there is a loss of margination of [[chromatin]] and [[wiktionary:Homogeneity|homogeneity]] in the nucleus, before the viral proteins start to be synthesized and a vacuole appears in the cytoplasm close to the nucleus that gradually starts to spread as the time after infection reaches around 3 hours. After this time the cell plasma membrane becomes permeable, at 4-6 hours the virus particles assemble, and can sometimes be seen in the cytoplasm. At around 8 hours the cell is effectively dead and lyses to release the viral particles. ==History== In 1897, [[foot-and-mouth disease]] virus (FMDV), the first animal virus, was discovered. FMDV is the prototypic member of the ''[[Aphthovirus]]'' genus in the ''[[Picornaviridae]]'' family. <ref name=sobrino1>{{cite book |chapterurl=http://www.horizonpress.com/avir|author=Martinez-Salas et al|year=2008|chapter=Foot-and-Mouth Disease Virus|title=Animal Viruses: Molecular Biology|publisher=Caister Academic Press|id=[http://www.horizonpress.com/avir ISBN 978-1-904455-22-6]}}</ref>The [[plaque]] assay was developed using poliovirus. Both RNA dependent RNA polymerase and polyprotein synthesis were discovered by studying poliovirus infected cells. ==Types of Picornavirus== Picornaviruses are separated into nine distinct genera. Contained within the picornovirus family are many organisms of importance as [[vertebrate]] and human pathogens, shown in the table below. {| border="1" cellpadding="4" |+ '''''Picornavirus Genera, Species and Serotypes''''' |- valign="bottom" | width="20%" | '''''[[Genus]]''''' | width="30%" | '''''[[Species]]''''' (* signifies [[type species]]) | width="50%" | '''''[[Serovar|Serotypes]]''''' |- | rowspan="9" | ''[[Enterovirus]]'' | ''[[Bovine enterovirus]]'' | two types: bovine enterovirus (BEV) 1 and BEV-2 |- valign="TOP" | ''Human enterovirus A'' | 21 types including some [[coxsackie A virus]]es and enteroviruses |- valign="TOP" | ''Human enterovirus B'' | 57 types including enteroviruses, [[coxsackie B]] viruses, [[echovirus]]es, and [[swine vesicular disease virus]] |- valign="TOP" | ''Human enterovirus C'' | 14 types including some [[coxsackie A virus]]es and enteroviruses |- valign="TOP" | ''Human enterovirus D'' | three types: EV-68, EV-70, EV-94 |- valign="TOP" | ''[[Poliovirus]]'' * | three types: poliovirus (PV) 1, PV-2 and PV-3 |- valign="TOP" | ''[[Porcine enterovirus]] A'' | one type: porcine enterovirus (PEV) 8 |- valign="TOP" | ''Porcine enterovirus B'' | two types: PEV-9 and PEV-10 |- valign="TOP" | ''[[Simian enterovirus]] A'' | one type: simian enterovirus (SEV) A1 |- | rowspan="2" | ''[[Rhinovirus]]'' | ''Human rhinovirus A'' * | 74 serotypes |- valign="TOP" | ''Human rhinovirus B'' | 25 serotypes |- | rowspan="2" | ''[[Hepatovirus]]'' | ''[[Hepatitis A]] virus'' * | one serotype: Hepatitis A virus (HAV) |- valign="TOP" | [[Avian encephalomyelitis-like virus]]es | one type: avian encephalomyelitis virus (AEV) |- | rowspan="2" | ''[[Cardiovirus]]'' | valign="TOP" | ''[[Encephalomyocarditis virus]]'' * | one serotype: encephalomyocarditis virus (EMCV). Note: [[Columbia SK virus]], [[Maus Elberfeld virus]] and [[Mengovirus]] are strains of EMCV. |- valign="TOP" | ''[[Theilovirus]]'' | five types: [[Theiler's murine encephalomyellitis virus]] (TMEV), [[Vilyuisk human encephalomyelitis virus]] (VHEV), Theiler-like virus (TLV) of rats, Saffold virus (SAFV) 1 and SAFV-2 |- | rowspan="2" | ''[[Aphthovirus]]'' | ''[[Foot-and-mouth disease]] virus''<ref name=sobrino1>{{cite book |chapterurl=http://www.horizonpress.com/avir|author=Martinez-Salas et al|year=2008|chapter=Foot-and-Mouth Disease Virus|title=Animal Viruses: Molecular Biology|publisher=Caister Academic Press|id=[http://www.horizonpress.com/avir ISBN 978-1-904455-22-6]}}</ref> * | seven serotypes: O, A, C, Southern African Territories (SAT) 1, SAT 2, SAT 3 and Asia 1 |- valign="TOP" | ''[[Equine rhinitis]] A virus'' | single serotype: equine rhinitis A virus (ERAV) |- | rowspan="2" | ''[[Parechovirus]]'' | ''Human parechovirus'' * | six types: Human parechovirus (HPeV) 1, HPeV-2, HPeV-3, HPeV-4, HPeV-5, HPeV-6 |- valign="TOP" | ''[[Ljungan virus]]'' | Possibly three types have been described |- valign="TOP" | ''[[Erbovirus]]'' | ''Equine rhinitis B virus'' * | Three types: equine rhinitis B virus (ERBV) 1, ERBV-2, ERBV-3 |- | rowspan="2" | ''[[Kobuvirus]]'' | ''[[Aichi virus]]'' * | single serotype: Aichi virus (AiV) |- valign="TOP" | ''[[Bovine kobuvirus]]'' | Single serotype: bovine kobuvirus (BKV) |- valign="TOP" | ''[[Teschovirus]]'' | ''[[Porcine teschovirus]]'' * | 11 serotypes: porcine teschovirus (PTV) 1 to PTV-11 |- | colspan="3" | '''''Sources''''' * {{cite web | url = http://www.nlm.nih.gov/cgi/mesh/2007/MB_cgi?term=Picornaviridae | title = Picornaviridae | accessdate = 2007-09-03 | publisher = [[National Library of Medicine]] | work = [[Medical Subject Headings]] (MeSH)}} * {{cite web | url = http://www.picornaviridae.com/ | title = Picornavirus | accessdate = 2007-09-03 | publisher = [[Institute for Animal Health]]}} * {{Cite web | year = 2006 | title = ICTVdB - The Universal Virus Database, version 4 | editor = Büchen-Osmond, C. | publisher = Columbia University, New York, USA | url = http://www.ncbi.nlm.nih.gov/ICTVdb/ICTVdB/}} * {{Citation | publication-date=[[2005-02-08]] | contribution=Porcine Enteroviral Encephalomyelitis | contribution-url=http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/102100.htm | editor-last = Kahn | editor-first=Cynthia M. | editor2-last=Line | editor2-first=Scott | title=The Merck Veterinary Manual | edition=9th | publisher=[[Merck & Co.|Merck]] | id=ISBN 0911910506}} |} Enteroviruses infect the [[enteric]] tract as it is visible from its name. On the other hand, rhinoviruses infect primarily the [[nose]] and the [[throat]]. Enteroviruses replicate at 37°C, whereas Rhinoviruses grow better at 33°C, as this is the lower temperature of the nose. Enteroviruses are stable under acid conditions and thus they are able to survive exposure to [[gastric acid]]. In contrast, Rhinoviruses are acid-labile and that is the reason why Rhinoviruses are restricted to the nose and throat. ==See also== * [[Dicistroviridae]] * [[VPg]] * [[Animal virology|Animal viruses]] ==References== {{reflist}} ==External links== * [http://www.mcb.uct.ac.za/cann/335/Picornaviruses.html Picornaviruses] - description, replication, disease * [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=12058 Picornaviruses in NCBI Taxonomy browser] * [http://www.picornaviridae.com/ ''Picornaviridae'' classification] by the International Committee on Taxonomy of Viruses * [http://www.horizonpress.com/gateway/animal-viruses.html Animal viruses] [[Category:Viruses]] [[Category:Picornaviruses| ]] [[de:Picornaviridae]] [[es:Picornaviridae]] [[fr:Picornaviridae]] [[it:Picornaviridae]] [[nl:Picornavirus]] [[ja:ピコルナウイルス科]] [[pl:Pikornawirusy]] [[pt:Picornavirus]] [[zh:微小核糖核酸病毒科]]