Adenoviridae 455651 220700836 2008-06-21T03:56:29Z DOI bot 6652755 Citation maintenance. Initiated by [[User:Fconaway|Fconaway]]. You can [[WP:DOI|use this bot]] yourself! Please [[User:DOI_bot/bugs|report any bugs]]. {{Taxobox | color=violet | name = Adenoviruses | image = Adenovirus 4.jpg | image_caption = Transmission electron micrograph of two adenovirus particles | virus_group = i | familia = '''''Adenoviridae''''' | subdivision_ranks = Genera | subdivision = ''[[Aviadenovirus]]''<br /> ''[[Atadenovirus]]''<br /> ''[[Mastadenovirus]]''<br /> ''[[Siadenovirus]]'' }} '''Adenoviruses''' are medium-sized (90–100 [[nanometer|nm]]), [[nonenveloped]] (naked) [[icosahedral]] viruses composed of a nucleocapsid and a double-stranded linear [[DNA]] genome. There are over 52 different [[serotype]]s in humans, which are responsible for 5–10% of upper respiratory infections in children, and many infections in adults as well. [[Virus]]es of the [[family (biology)|family]] ''Adenoviridae'' infect various species of animals, including humans. Adenoviruses were first isolated in human [[adenoid]]s (tonsils), from which the name is derived, and are classified as group I under the [[Baltimore classification]] scheme. Adenoviruses represent the largest nonenveloped viruses, because they are the maximum size able to be transported through the endosome (i.e. envelope fusion is not necessary). The virion also has a unique "spike" or [[fiber]] associated with each penton base of the [[capsid]] (see picture below) that aids in attachment to the host cell via the coxsackie-adenovirus receptor on the surface of the [[Host (biology)|host]] [[cell (biology)|cell]]. There are 51 immunologically distinct human adenovirus serotypes (6 species: ''Human adenovirus A'' through ''F'') that can cause human infections ranging from [[respiratory disease]] (mainly species HAdV-B and C), and conjunctivitis (HAdV-B and D), to gastroenteritis (HAdV-F serotypes 40 and 41). Adenoviruses are unusually stable to [[chemical]] or physical agents and adverse [[pH]] conditions, allowing for prolonged survival outside of the body and water. Adenoviruses are primarily spread via respiratory droplets, however they can also be spread by [[fecal]] routes as well. Most infections with adenovirus result in infections of the upper respiratory tract. Adenovirus infections often show up as [[conjunctivitis]], [[tonsilitis]] (which may look exactly like [[strep throat]] and cannot be distinguished from strep except by throat culture), an [[Otitis media|ear infection]], or [[croup]]. Adenoviruses can also cause [[gastroenteritis]] (stomach flu). A combination of conjunctivitis and tonsilitis is particularly common with adenovirus infections. Some children (especially small ones) can develop adenovirus [[bronchiolitis]] or [[pneumonia]], both of which can be severe. In babies, adenoviruses can also cause coughing fits that look almost exactly like [[whooping cough]]. Adenoviruses can also cause [[viral meningitis]] or [[encephalitis]]. Rarely, adenovirus can cause [[cystitis]] (inflammation of the urinary bladder—a form of [[urinary tract infection]]—with blood in the urine). Most people recover from adenovirus infections by themselves, but people with [[immunodeficiency]] sometimes die of adenovirus infections, and—rarely—even previously healthy people can die of these infections.<ref>{{cite news | url = http://www.cnn.com/2007/HEALTH/conditions/12/19/killer.cold/index.html | title = A killer cold? Even the healthy may be vulnerable | work = [[CNN]] | author = Amy Burkholder | date = [[2007-12-19]] | accessdate = 2007-12-19 }}</ref> Adenoviruses are often transmitted by coughed-out droplets, but can also be transmitted by contact with an infected person, or by virus particles left on objects such as towels and faucet handles. Some people with adenovirus gastroenteritis may shed the virus in their stools for months after getting over the symptoms. The virus can be passed from one person to another through some sexual practices, and through water in swimming pools that do not have enough chlorine in them. As with many other illnesses, good handwashing is one way to lessen the spread of adenoviruses from one person to another. Heat and [[bleach]] will kill adenoviruses on objects. ==Treatment and prevention== As with almost all viruses, there are no antibiotics that help with an adenoviral infection, so treatment is largely directed at the symptoms (such as acetaminophen for fever). A doctor may give antibiotic eyedrops for conjunctivitis, since it takes a while to test to see if the eye infection is bacterial or viral and to help prevent secondary bacterial infections. In the past, US military recruits were vaccinated against two serotypes of adenotypes, with a corresponding decrease in illnesses caused by those serotypes. The vaccine is no longer manufactured, and there are currently no vaccines available to protect against the adenovirus. Good hygiene, including handwashing, is still the best way to avoid picking up the adenovirus from an infected person. ==Genome== [[Image:Adenoviruses-genome.jpg|thumb|250 px|Schematic diagram of the linear adenovirus genome, showing Early genes (E) and Late genes (L).]] The adenovirus genome is linear, non-segmented double stranded (ds) DNA which is around 30–38 [[base pair#Length measurements|Kbp]]. This allows the virus to theoretically carry 30 to 40 [[genes]]. Although this is significantly larger than other viruses in its Baltimore group it is still a very simple virus and is heavily reliant on the host cell for survival and replication. An interesting feature of this viral genome is that it has a terminal 55 [[Kilodalton|kDa]] protein associated with each of the 5' ends of the linear dsDNA, these are used as primers in viral replication and ensure that the ends of the virus' linear genome are adequately replicated. ==Replication== Adenoviruses possess a linear dsDNA [[genome]] and are able to [[self-replication|replicate]] in the [[cell nucleus|nucleus]] of [[mammal]]ian cells using the host’s replication machinery. [[Image:Adenovirus structure.png|thumb|250px|right|The structure of adenovirus. 1 = penton capsomeres 2 = hexon capsomeres, and 3= viral genome (linear dsDNA)]] Entry of adenoviruses into the host cell involves two sets of interactions between the virus and the host cell. Entry into the host cell is initiated by the knob domain of the fiber protein binding to the cell receptor. The two currently established receptors are: CD46 for the group B human adenovirus serotypes and the coxsackievirus adenovirus receptor (CAR) for all other serotypes. There are some reports suggesting MHC molecules and sialic acid residues functioning in this capacity as well. This is followed by a secondary interaction, where a specialized motif in the penton base protein interacts with an [[integrin]] molecule. It is the co-receptor interaction that stimulates internalization of the adenovirus. This co-receptor molecule is αv integrin. Binding to αv integrin results in [[endocytosis]] of the virus particle via clathrin-coated pits. Attachment to αv integrin stimulates cell signaling and thus induces actin polymerization resulting in entry of the virion into the host cell within an [[endosome]].<ref name=Wu>{{cite journal | author=Wu and Nemerow | title=Virus yoga: the role of flexibility in virus host cell recognition | journal=Trends Microbiol | year=2004 | pages=162–168 | volume=12 | issue= | pmid=15051066 | format= | doi=10.1016/j.tim.2004.02.005 }}</ref> Once the virus has successfully gained entry into the host cell the endosome acidifies, which alters virus topology by causing capsid components to disassociate. These changes as well as the toxic nature of the pentons results in the release of the virion into the cytoplasm. With the help of cellular [[microtubules]] the virus is transported to the nuclear pore complex whereby the adenovirus particle disassembles. Viral DNA is subsequently released which can enter the [[Cell nucleus|nucleus]] via the [[nuclear pore]].<ref name=Meier>{{cite journal | author=Meier and Greber | title=Adenovirus endocytosis | journal=J Gene Med | year=2004 | pages=S152–S163 | volume=6 | issue= | pmid=14978758 | format= | doi=10.1002/jgm.553 }}</ref> After this the DNA associates with [[histone]] molecules. Thus viral gene expression can occur and new virus particles can be generated. The adenovirus [[Biological life cycle|life cycle]] is separated, by the [[DNA replication]] process, into two phases: an early and a late phase. In both phases a [[primary transcript]] is generated which is [[alternative splicing|alternatively spliced]] to generate [[monocistronic mRNA]]s compatible with the host’s [[ribosome]], allowing for the products to be [[translation (genetics)|translated]]. The early genes are responsible for expressing mainly non-structural, regulatory [[proteins]]. The goal of these proteins is threefold: to alter the expression of host proteins that are necessary for DNA [[synthesis]]; to activate other virus genes (such as the virus-encoded [[DNA polymerase]]); and to avoid premature death of the infected cell by the host-immune defenses (blockage of [[apoptosis]], blockage of [[interferon]] activity, and blockage of [[MHC class I]] translocation and expression). Some adenoviruses under specialized conditions can transform cells using their early gene products. E1a (binds [[Retinoblastoma protein|Retinoblastoma tumor suppressor protein]]) has been found to immortalize primary cells ''in vitro'' allowing E1b (binds [[p53]] tumor suppressor) to assist and stably transform the cells. Nevertheless, they are reliant upon each other to successfully transform the host cell and form [[tumors]]. DNA replication separates the early and late phases. Once the early genes have liberated adequate virus proteins, replication machinery and replication substrates, replication of the adenovirus genome can occur. A terminal protein that is covalently bound to the 5’ end of the adenovirus genome acts as a [[primer (molecular biology)|primer]] for replication. The viral DNA polymerase then uses a strand displacement mechanism, as opposed to the conventional [[Okazaki fragments]] used in mammalian DNA replication, to replicate the genome. The late phase of the adenovirus life cycle is focused on producing sufficient quantities of structural protein to pack all the genetic material produced by DNA replication. Once the viral components have successfully been replicated the virus is assembled into its protein shells and released from the cell as a result of virally induced cell [[lysis]]. ==Genera== This family contains the following [[genus|genera]]: *Genus ''[[Aviadenovirus]]''; type species: ''[[Fowl adenovirus A]]'' *Genus ''[[Atadenovirus]]''; type species: ''[[Ovine adenovirus D]]'' *Genus ''[[Mastadenovirus]]''; type species: ''[[Human adenovirus C]]''; others include [[AD-36]] *Genus ''[[Siadenovirus]]''; type species: ''[[Frog adenovirus]]'' ==Adenoviruses in humans== * See [[Adenovirus infection]] * See [[Adenovirus serotype 14]] ==Adenoviruses in animals== Two types of [[Canidae|canine]] adenoviruses are well known, type 1 and 2. Type 1 causes [[infectious canine hepatitis]], a potentially fatal disease involving [[vasculitis]] and [[hepatitis]]. Type 1 infection also can cause respiratory and eye infections. ''Canine adenovirus 2'' (CAdV-2) is one of the potential causes of [[kennel cough]]. Core [[vaccine]]s for [[dog]]s include attenuated live CAdV-2, which produces immunity to CAdV-1 and CAdV-2. CAdV-1 was initially used in a vaccine for dogs, but [[cornea]]l [[edema]] was a common complication.<ref name=Fenner>{{cite book|author=Fenner, Frank J.; Gibbs, E. Paul J.; Murphy, Frederick A.; Rott, Rudolph; Studdert, Michael J.; White, David O.|title=Veterinary Virology (2nd ed.)|publisher=Academic Press, Inc|year=1993|id=ISBN 0-12-253056-X}}</ref> Adenoviruses are also known to cause respiratory infections in [[horse]]s, [[cattle]], [[pig]]s, [[sheep]], and [[goat]]s. ''Equine adenovirus 1'' can also cause fatal disease in immunocompromised [[Arabian horse|Arabian foal]]s, involving pneumonia and destruction of [[pancreas|pancreatic]] and [[salivary gland]] tissue.<ref name=Fenner>{{cite book|author=Fenner, Frank J.; Gibbs, E. Paul J.; Murphy, Frederick A.; Rott, Rudolph; Studdert, Michael J.; White, David O.|title=Veterinary Virology (2nd ed.)|publisher=Academic Press, Inc|year=1993|id=ISBN 0-12-253056-X}}</ref> ==See also== *[[Infectious canine hepatitis]] {{Viruses}} {{Common Cold}} ==References== {{reflist}} ==Sources== [http://www.cdc.gov/ncidod/dvrd/revb/respiratory/eadfeat.htm Centers for Disease Control and Prevention--National Center for Diseases--Division of Viral and Rickettsial Diseases], Respiratory and Enteric Viruses Branch ==External links== *[http://www.microbiologybytes.com/virology/Adenoviruses.html MicrobiologyBytes: Adenoviruses] *[http://gsbs.utmb.edu/microbook/ch067.htm Adenoviruses General Concepts] *[http://pathmicro.med.sc.edu/mhunt/dna1.htm DNA virus replication strategies] *[http://www.vmri.hu/~harrach/ADENOSEQ.HTM Sequenced adenoviruses] *[http://www.genetherapynet.com Gene Therapy Net - Adenoviral vectors used in gene therapy] [[Category:Viruses]] [[ca:Adenovirus]] [[da:Adenoviridae]] [[de:Adenoviridae]] [[et:Adenoviirused]] [[es:Adenoviridae]] [[fa:آدنوویروس]] [[fr:Adenoviridae]] [[gl:Adenovirus]] [[hr:Adenovirus]] [[it:Adenovirus]] [[nl:Adenovirussen]] [[ja:アデノウイルス]] [[no:Adenovirus]] [[pl:Adenowirusy]] [[pt:Adenovirus]] [[ru:Аденовирусы]] [[sl:Adenovirusi]] [[fi:Adenovirus]] [[sv:Adenovirus]] [[zh:腺病毒]]