Gyrovirus | |
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Virus classification ![]() | |
(unranked): | Virus |
Family: | Anelloviridae |
Genus: | Gyrovirus |
Gyrovirus is a genus of viruses, in the family Anelloviridae . Until 2011, chicken anemia virus was the only Gyrovirus identified, but since then gyroviruses have also been identified in humans. Diseases associated with this genus include: chicken infectious anemia, which is associated with depletion of cortical thymocytes and erythroblastoid cells. [1] [2]
The genus contains the following species: [2]
Gyroviruses have an average size of 19 to 27 nanometers. They are nonenveloped and have an icosahedral capsid with T=1 symmetry. The unique, single protein, trumpet-shaped capsomeres of Gyrovirus are arranged into 12 pentomers yielding a capsid 60 units in size. The genome is circular, non-segmented, and 2290–2320 nucleotides long. [2] [3] [4]
Genus | Structure | Symmetry | Capsid | Genomic arrangement | Genomic segmentation |
---|---|---|---|---|---|
Gyrovirus | Icosahedral | T=1 | Non-enveloped | Circular | Monopartite |
The Gyrovirus genome consists of negative sense, single-stranded, circular, DNA. The genome is relatively small at 2,300 nucleotides. and contains three overlapping open reading frames that code for only three known proteins. [5]
The Gyrovirus genome codes for a single polysistronic mRNA that subsequently codes for three proteins, VP1, VP2, and VP3. VP1 is the 51kd capsid protein; in addition to its structural function, it also contains motifs for rolling circle replication in the C-terminal region. VP2 is a 23kd nonstructural protein with phosphatase activity. Virions with mutations in SP2 are still replication competent; however, their cytopathic effects were highly attenuated. [6] VP3, also called apoptin, is a 13kd protein that has been shown to independently induce apoptosis in chicken cells. Apoptin is also being researched for its ability to induce apoptosis in human tumor cells. [7] [8]
Viral replication is nuclear. Entry into the host cell is achieved by penetration into the host cell. [1] Upon entering the host cell, the virus converts from single stranded to double stranded, circular DNA using host cell machinery. The circular dsDNA is then used as a template for transcription and for replication via a rolling circle mechanism similar to phiX174. [9] DNA-templated transcription, with some alternative splicing mechanism is the method of transcription. The virus exits the host cell by nuclear egress, and nuclear pore export. Birds serve as the natural host. Transmission routes are fecal-oral, parental, egg transmission, and respiratory. [1]
Genus | Host details | Tissue tropism | Entry details | Release details | Replication site | Assembly site | Transmission |
---|---|---|---|---|---|---|---|
Gyrovirus | Birds | Chicken: Thymocytes, erythrobalstoid cells; Egg: embryonal tissues and eggshell membrane | Cell receptor endocytosis | Budding | Nucleus | Nucleus | Horizontal: oral-fecal; vertical: bird to egg |
Chicken anemia virus (CAV) was, until 2011, the only member of genus Gyrovirus identified. [10] It causes disease worldwide in areas where chickens are produced. CAV causes severe anemia, hemorrhaging, and depletion of lymphoid tissue through the destruction of bone marrow erythroblastoid cells. [5] The disease affects mainly young chicks not protected by maternal antibodies. Age resistance to disease begins at about one week, but can be overcome however by coinfection with immunosuppressive diseases, such as bursal disease virus, Marek’s disease, and others. [11]
A second virus in this genus—Avian gyrovirus 2—has been described. [12] The viral genome shares ~40% of its sequence with Chicken anemia virus (CAV). The genome is 2383 nucleotides long and has three partially overlapping open reading frames encoding the proteins VP1, VP2 and VP3. These proteins share 38.8%, 40.3%, and 32.2% amino acid identities between their homologs in the CAV.
Two species have been described from humans—human gyrovirus and human gyrovirus 3. [13] [14] [15] Human gyrovirus 1 appears to be the same virus as avian gyrovirus 2. A fourth gyrovirus—gyrovirus 4 (GyV4)—has been isolated from human stool and chicken meat. [16]
The rhinovirus is a positive-sense, single-stranded RNA virus belonging to the genus Enterovirus in the family Picornaviridae. Rhinovirus is the most common viral infectious agent in humans and is the predominant cause of the common cold.
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Aphthovirus is a viral genus of the family Picornaviridae. Aphthoviruses infect split-hooved animals, and include the causative agent of foot-and-mouth disease, Foot-and-mouth disease virus (FMDV). There are seven FMDV serotypes: A, O, C, SAT 1, SAT 2, SAT 3 and Asia 1, and four non-FMDV serotypes belonging to three additional species Bovine rhinitis A virus (BRAV), Bovine rhinitis B virus (BRBV) and Equine rhinitis A virus (ERAV).
Dependoparvovirus is a genus in the subfamily Parvovirinae of the virus family Parvoviridae; they are Group II viruses according to the Baltimore classification. Some dependoparvoviruses are also known as adeno-associated viruses because they cannot replicate productively in their host cell without the cell being coinfected by a helper virus such as an adenovirus, a herpesvirus, or a vaccinia virus.
Enterovirus E is a picornavirus of the genus Enterovirus. The virus may also be referred to as enteric cytopathic bovine orphan virus (ECBO). It is endemic in cattle populations worldwide, and although normally fairly nonpathogenic, it can cause reproductive, respiratory, or enteric disease – particularly when the animal is concurrently infected with another pathogen.
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Murine polyomavirus is an unenveloped double-stranded DNA virus of the polyomavirus family. The first member of the family discovered, it was originally identified by accident in the 1950s. A component of mouse leukemia extract capable of causing tumors, particularly in the parotid gland, in newborn mice was reported by Ludwik Gross in 1953 and identified as a virus by Sarah Stewart and Bernice Eddy at the National Cancer Institute, after whom it was once called "SE polyoma". Stewart and Eddy would go on to study related polyomaviruses such as SV40 that infect primates, including humans. These discoveries were widely reported at the time and formed the early stages of understanding of oncoviruses.
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Minor capsid protein VP2 and minor capsid protein VP3 are viral proteins that are components of the polyomavirus capsid. Polyomavirus capsids are composed of three proteins; the major component is major capsid protein VP1, which self-assembles into pentamers that in turn self-assemble into enclosed icosahedral structures. The minor components are VP2 and VP3, which bind in the interior of the capsid.
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