Difference between revisions of "Adenoviridae - Overview"

Latest revision as of 15:39, 5 July 2012

Introduction

Adenoviridae are a group of double-stranded DNA viruses with an icosahedral nucleocapsid. Many Adenoviridae have been isolated from mammals and birds, but only a small number of these cause significant veterinary disease. The family consists of four genera: Mastadenovirus, Aviadenovirus, Atadenovirus and Siadenovirus. The Mastadenoviruses include Canine Adenovirus 1 (CAV-1) and Canine Adenovirus 2 (CAV-2), which cause Infectious Canine Hepatitis and respiratory disease respectively. Equine Adenovirus A (also known as Equine Adenovirus 1) is also a Mastadenovirus and causes respiratory signs in horses.

Aviadenoviruses are viruses of poultry and other birds. The genus contains inclusion body hepatitis, quail bronchitis and other avian viruses not associated with a particular disease. The Atadenovirus and Siadenovirus genera contain viruses that until recently were unassigned. These include egg drop syndrome virus and adenoviral splenomegaly of chickens as Atadenoviruses, and turkey haemorrhagic enteritis as a Siadenovirus.

Classification

The family Adenoviridae contains four genera:-

atadenovirus: bovine adenovirus type D, duck adenovirus A, ovine adenovirus D
aviadenovirus: fowl adenoviruses A to E, goose adenovirus, turkey adenovirus
mastadenovirus: the mammalian adenoviruses - bovine types A, B, C; canine type A; equine types A and B; ovine types A and B; porcine types A, B, C.
siadenovirus: turkey adenoviruses type A, including the virus of marble spleen disease.

Viral Characteristics

The genetic information of Adenoviridae is conveyed by a single, linear molecule of double-stranded DNA which encodes around 30 proteins. Under the influence of both host and virus-encoded factors, the DNA replicates and is transcribed within the host nucleus, where virion assembly also occurs. Basophilic and/or acidophilic inclusions may therefore be seen in the nucleus of an adenovirus-infected cell.

The virus genome is contained within a non-enveloped icosahedral nucleocapsid, which comprises capsomeres (called hexons) and twelve vertex capsomeres (called pentons). A fibre antigen protrudes from each of the twelve pentons, and this attaches to host cell receptors as well as being a type-specific haemagglutinin. This fibre antigen is a feature specific to the Adenoviridae. The hexon of mammalian adenoviruses contains a cross-reacting group antigen.

Replication

Adenoviruses enter the host cell by means of interaction of the receptor, coxsackievirus adenovirus receptor (CAR), with a domain on the fibre protein called the knob domain. Some reports suggest that MHC molecules and sialic acid residues may also function as adenovirus receptors. This initial interaction is followed by a secondary interaction where a motif in the penton protein interacts with αv integrin, stimulating endocytosis of the adenovirus via clathrin-coated pits. Once inside the cell the endosome acidifies, causing the capsid components of the adenovirus to dissociate and releasing the virion into the cytoplasm. The virus is then transported by the microtubule network to the nuclear pore complex, where the adenovirus particle disassembles and DNA enters the nucleus. Viral DNA associates with histone proteins, and replication begins.

The virus replication process is divided to the early and late phases, which are separated by DNA replication. Genes transcribed in the early phase are are responsible for producing non-structural, regulatory proteins. These regulatory proteins control the expression of host proteins necessary for DNA synthesis, activate other virus genes and help prevent death of the infected cell by host immune defences. Once the early genes prepared virus proteins, replication machinery and replication substrates, the adenovirus genome is able to replicate. A protein covalently bound to the 5’ end of the adenovirus genome acts as a primer, and the viral DNA polymerase then uses a strand displacement mechanism for replication. The late phase of the adenovirus life cycle produces structural proteins in which to pack the new genetic material. The virus can then be release from the cell by lysis.

Transmission

Adenoviruses are stable to chemical and physical agents and adverse pH conditions, allowing for prolonged survival outside of the body. Aerosol transmission in respiratory droplets is the primary route of spread, but faeco-oral transmission is also possible.

Adenoviridae - Overview Learning Resources
Literature Search Search for recent publications via CAB Abstract (CABI log in required)	Adenoviridae publications

References

Carter, GR and Wise, DJ (2005) A Concise Review of Veterinary Virology, International Veterinary Information Service.
Fenner, F J et al (1993). Veterinary Virology (Second Edition). Academic Press, Inc.
Wu and Nemerow, G R (2004) Virus yoga: the role of flexibility in virus host cell recognition. Trends in Microbiology, 12(4), 162–168.
Meier and Greber, U F (2004) Adenovirus endocytosis. The Journal of Gene Medicine, 6, S152–S163.

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+{{OpenPagesTop}}
 ==Introduction==
-Adenoviridae are a group of double-stranded DNA viruses with an icosahedral nucleocapsid. Many Adenoviridae have been isolated from mammals and birds, but only a small number of these cause significant veterinary disease. The family consists of four genera: Mastadenovirus, Aviadenovirus, Atadenovirus and Siadenovirus. The Mastadenoviruses include Canine Adenovirus 1 (CAV-1) and Canine Adenovirus 2 (CAV-2), which cause [[Infectious Canine Hepatitis]] and respiratory disease respectively. Equine Adenovirus A (also known as Equine Adenovirus 1) is also a Mastadenovirus and causes respiratory signs in horses.
+Adenoviridae are a group of double-stranded DNA viruses with an icosahedral nucleocapsid. Many Adenoviridae have been isolated from mammals and birds, but only a small number of these cause significant veterinary disease. The family consists of four genera: Mastadenovirus, Aviadenovirus, Atadenovirus and Siadenovirus. The Mastadenoviruses include [[Canine Adenovirus 1]] (CAV-1) and [[Canine Adenovirus 2]] (CAV-2), which cause [[Infectious Canine Hepatitis]] and respiratory disease respectively. [[Equine Adenovirus]] A (also known as Equine Adenovirus 1) is also a Mastadenovirus and causes respiratory signs in horses.
 Aviadenoviruses are viruses of poultry and other birds. The genus contains inclusion body hepatitis, quail bronchitis and other avian viruses not associated with a particular disease. The Atadenovirus and Siadenovirus genera contain viruses that until recently were unassigned. These include egg drop syndrome virus and adenoviral splenomegaly of chickens as Atadenoviruses, and turkey haemorrhagic enteritis as a Siadenovirus.
+==Classification==
+The family Adenoviridae contains four genera:-
+# atadenovirus: [[Bovine Adenovirus|bovine adenovirus]] type D, duck adenovirus A, ovine adenovirus D
+# aviadenovirus: [[Avian Adenoviruses|fowl adenoviruses A to E, goose adenovirus, turkey adenovirus]]
+# mastadenovirus: the mammalian adenoviruses - [[Bovine Adenovirus|bovine]] types A, B, C; [[Canine Adenovirus 1|canine]] type A; [[Equine Adenovirus|equine]] types A and B; ovine types A and B; [[Porcine Adenovirus|porcine]] types A, B, C.
+# siadenovirus: turkey adenoviruses type A, including the virus of marble spleen disease.
 ==Viral Characteristics==
 The genetic information of Adenoviridae is conveyed by a single, linear molecule of double-stranded DNA which encodes around 30 proteins. Under the influence of both host and virus-encoded factors, the DNA replicates and is transcribed within the host nucleus, where virion assembly also occurs. Basophilic and/or acidophilic inclusions may therefore be seen in the nucleus of an adenovirus-infected cell.
-The virus genome is contained within a non-enveloped icosohedral nucleocapsid, which comprises capsomeres (called hexons) and twelve vertex capsomeres  (called pentons). A fibre antigen protrudes from each of the twelve pentons, and this attaches to host cell receptors as well as being a type-specific haemagglutinin.  This fibre antigen is a feature specific to the Adenoviridae. The hexon of mammalian adenoviruses contains a cross-reacting group antigen.
+The virus genome is contained within a non-enveloped icosahedral nucleocapsid, which comprises capsomeres (called hexons) and twelve vertex capsomeres  (called pentons). A fibre antigen protrudes from each of the twelve pentons, and this attaches to host cell receptors as well as being a type-specific haemagglutinin. This fibre antigen is a feature specific to the Adenoviridae. The hexon of mammalian adenoviruses contains a cross-reacting group antigen.
-==Transmission==
+==Replication==
-Adenoviruses are stable to chemical and physical agents and adverse pH conditions, allowing for prolonged survival outside of the body. Aerosol transmission in respiratory droplets is the primary route of spread, but faeco-oral transmission is also possible.
-==Replication==
+Adenoviruses enter the host cell by means of interaction of the receptor, coxsackievirus adenovirus receptor (CAR), with a domain on the fibre protein called the knob domain. Some reports suggest that MHC molecules and sialic acid residues may also function as adenovirus receptors. This initial interaction is followed by a secondary interaction where a motif in the penton protein interacts with αv integrin, stimulating endocytosis of the adenovirus via clathrin-coated pits. Once inside the cell the endosome acidifies, causing the capsid components of the adenovirus to dissociate and releasing the virion into the cytoplasm. The virus is then transported by the microtubule network to the nuclear pore complex, where the adenovirus particle disassembles and DNA enters the nucleus. Viral DNA associates with histone proteins, and replication begins.
-Adenoviruses possess a linear dsDNA genome and are able to replicate in the nucleus of mammalian cells using the host’s replication machinery.
+The virus replication process is divided to the early and late phases, which are separated by DNA replication. Genes transcribed in the early phase are are responsible for producing non-structural, regulatory proteins. These regulatory proteins control the expression of host proteins necessary for DNA synthesis, activate other virus genes and help prevent death of the infected cell by host immune defences. Once the early genes prepared virus proteins, replication machinery and replication substrates, the adenovirus genome is able to replicate. A protein covalently bound to the 5’ end of the adenovirus genome acts as a primer, and the viral DNA polymerase then uses a strand displacement mechanism for replication. The late phase of the adenovirus life cycle produces structural proteins in which to pack the new genetic material. The virus can then be release from the cell by lysis.
-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.[2]
+==Transmission==
-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 nucleus via the nuclear pore.[3] After this the DNA associates with histone molecules. Thus viral gene expression can occur and new virus particles can be generated.
+Adenoviruses are stable to chemical and physical agents and adverse pH conditions, allowing for prolonged survival outside of the body. Aerosol transmission in respiratory droplets is the primary route of spread, but faeco-oral transmission is also possible.
-The adenovirus 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 alternatively spliced to generate monocistronic mRNAs compatible with the host’s ribosome, allowing for the products to be translated.
+{{Learning
+|literature search = [http://www.cabdirect.org/search.html?rowId=1&options1=AND&q1=Adenoviridae&occuring1=title&rowId=2&options2=AND&q2=&occuring2=freetext&rowId=3&options3=AND&q3=&occuring3=freetext&x=28&y=8&publishedstart=yyyy&publishedend=yyyy&calendarInput=yyyy-mm-dd&la=any&it=any&show=all Adenoviridae publications]
+}}
-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).
+==References==
-Some adenoviruses under specialized conditions can transform cells using their early gene products. E1a (binds 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.
+#Carter, GR and Wise, DJ (2005) '''A Concise Review of Veterinary Virology''', ''International Veterinary Information Service''.
+#Fenner, F J et al (1993). '''Veterinary Virology (Second Edition).''' ''Academic Press, Inc''.
+#Wu and Nemerow, G R (2004) Virus yoga: the role of flexibility in virus host cell recognition. ''Trends in Microbiology'', '''12(4)''', 162–168.
+#Meier and Greber, U F (2004) Adenovirus endocytosis. ''The Journal of Gene Medicine'', '''6''', S152–S163.
-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 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.
+{{review}}
-==References==
+{{OpenPages}}
-[[Category:Adenoviridae]][[Category:To Do - Lizzie]]
+[[Category:Adenoviridae]]  [[Category:Expert Review]]