Poxviridae
Encyclopedia
Poxviruses are virus
es that can, as a family, infect both vertebrate
and invertebrate
animals.
Four genera of poxviruses may infect humans: orthopox, parapox, yatapox, molluscipox.
Orthopox: smallpox
virus (variola), vaccinia
virus, cowpox
virus, monkeypox
virus;
Parapox: orf virus, pseudocowpox, bovine papular stomatitis virus;
Yatapox: tanapox
virus, yaba monkey tumor virus
;
Molluscipox: molluscum contagiosum virus
(MCV).
The most common are vaccinia (seen on Indian subcontinent) and molluscum contagiousum, but monkeypox infections are rising (seen in west and central African rainforest countries).
in diameter and 300 nm
in length and carries its genome
in a single, linear, double-stranded segment of DNA. By comparison, Rhinovirus
is 1/10 as large as a typical Poxviridae virion.
does is to bind to a receptor on the host cell surface; the receptors for the poxvirus are thought to be Glycosaminoglycans (GAGs). After binding to the receptor, the virus enters the cell where it uncoats. Uncoating of the virus is a two step process. Firstly the outer membrane is removed as the particle enters the cell; secondly the virus particle (without the outer membrane) is uncoated further to release the core into the cytoplasm
. The pox viral genes
are expressed in two phases. The early genes are expressed first. These genes encode the non-structural protein
, including proteins necessary for replication of the viral genome
, and are expressed before the genome is replicated. The late genes are expressed after the genome has been replicated and encode the structural proteins to make the virus particle. The assembly of the virus particle occurs in the cytoskeleton
of the cell and is a complex process that is poorly understood but is currently being researched. Considering the fact that this virus is large and complex, replication is relatively quick taking approximately 12 hours until the host cell dies by the release of viruses.
The replication of poxvirus is unusual for a virus with double-stranded DNA
genome (dsDNA) because it occurs in the cytoplasm Poxvirus encodes its own machinery for genome transcription, a DNA dependent RNA polymerase, which makes replication in the cytoplasm possible. Most dsDNA viruses require the host cell's proteins to perform transcription. These host proteins are found in the nucleus
, and therefore most dsDNA viruses carry out a part of their infection cycle within the host cell's nucleus.
es in the skin. Modern viral classification
is based on phenotypic characteristics; morphology, nucleic acid type, mode of replication, host organisms, and the type of disease they cause. The smallpox
virus remains as the most notable member of the family.
The following genera are currently included here:
Ramses V who is thought to have died from smallpox nearly 2000 years BCE. Smallpox was thought to have been transferred to Europe around the early 8th century and then to the Americas in the early 16th century. It is widely accepted that the main defeat of the Aztecs was due to a smallpox epidemic and within two years over 3.2 million Aztecs died. This death toll can be attributed to the American population's complete lack of sensitization to the virus as children. A century after Edward Jenner showed that the less potent cow pox could be used to effectively vaccinate against the more deadly smallpox, a worldwide effort to vaccinate everyone against smallpox began with the ultimate goal to rid the world of the plague-like epidemic. The World Health Organization (WHO) declared the virus officially eradicated in 1977 and after nine years, in 1986, all virus samples were destroyed or transferred to two approved WHO reference labs: at the headquarters of the federal Centers for Disease Control and Prevention
(the C.D.C.) in Atlanta, Georgia (the United States) and at the Institute of Virus Preparations in Moscow. Post September 11, 2001 the American and UK governments have had increased concern over the use of smallpox, or a small pox like disease, in bio-terrorism.
Virus
A virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses infect all types of organisms, from animals and plants to bacteria and archaea...
es that can, as a family, infect both vertebrate
Vertebrate
Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...
and invertebrate
Invertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...
animals.
Four genera of poxviruses may infect humans: orthopox, parapox, yatapox, molluscipox.
Orthopox: smallpox
Smallpox
Smallpox was an infectious disease unique to humans, caused by either of two virus variants, Variola major and Variola minor. The disease is also known by the Latin names Variola or Variola vera, which is a derivative of the Latin varius, meaning "spotted", or varus, meaning "pimple"...
virus (variola), vaccinia
Vaccinia
Vaccinia virus is a large, complex, enveloped virus belonging to the poxvirus family. It has a linear, double-stranded DNA genome approximately 190 kbp in length, and which encodes for approximately 250 genes. The dimensions of the virion are roughly 360 × 270 × 250 nm, with a mass of...
virus, cowpox
Cowpox
Cowpox is a skin disease caused by a virus known as the Cowpox virus. The pox is related to the vaccinia virus and got its name from the distribution of the disease when dairymaids touched the udders of infected cows. The ailment manifests itself in the form of red blisters and is transmitted by...
virus, monkeypox
Monkeypox
Monkeypox also known as cockpox is an exotic infectious disease caused by the monkeypox virus. The disease was first identified in laboratory monkeys, hence its name, but in its natural state it seems to infect rodents more often than primates...
virus;
Parapox: orf virus, pseudocowpox, bovine papular stomatitis virus;
Yatapox: tanapox
Tanapox
Tanapox , was first seen among individuals in the flood plain of the Tana River in Kenya during two epidemics of acute febrile illness accompanied by localized skin lesions.-Epidemiology:...
virus, yaba monkey tumor virus
Yaba monkey tumor virus
Yaba monkey tumor virus is a type of poxvirus.It is closely related to tanapox.It is named for Yaba, Lagos....
;
Molluscipox: molluscum contagiosum virus
Molluscum contagiosum
Molluscum contagiosum is a viral infection of the skin or occasionally of the mucous membranes. It is caused by a DNA poxvirus called the molluscum contagiosum virus . MCV has no animal reservoir, infecting only humans. There are four types of MCV, MCV-1 to -4; MCV-1 is the most prevalent and...
(MCV).
The most common are vaccinia (seen on Indian subcontinent) and molluscum contagiousum, but monkeypox infections are rising (seen in west and central African rainforest countries).
Structure
Poxviridae viral particles (virions) are generally enveloped (external enveloped virion- EEV), though the intracellular mature virion (IMV) form of the virus, which contains different envelope, is also infectious. They vary in their shape depending upon the species but are generally shaped like a brick or as an oval form similar to a rounded brick because they are wrapped by the endoplasmic reticulum. The virion is exceptionally large, its size is around 200 nmNanometre
A nanometre is a unit of length in the metric system, equal to one billionth of a metre. The name combines the SI prefix nano- with the parent unit name metre .The nanometre is often used to express dimensions on the atomic scale: the diameter...
in diameter and 300 nm
Nanometre
A nanometre is a unit of length in the metric system, equal to one billionth of a metre. The name combines the SI prefix nano- with the parent unit name metre .The nanometre is often used to express dimensions on the atomic scale: the diameter...
in length and carries its genome
Genome
In modern molecular biology and genetics, the genome is the entirety of an organism's hereditary information. It is encoded either in DNA or, for many types of virus, in RNA. The genome includes both the genes and the non-coding sequences of the DNA/RNA....
in a single, linear, double-stranded segment of DNA. By comparison, Rhinovirus
Rhinovirus
Human rhinoviruses are the most common viral infective agents in humans and are the predominant cause of the common cold. Rhinovirus infection proliferates in temperatures between 33–35 °C , and this may be why it occurs primarily in the nose...
is 1/10 as large as a typical Poxviridae virion.
Replication
Replication of the poxvirus involves several stages. The first thing the virusVirus
A virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses infect all types of organisms, from animals and plants to bacteria and archaea...
does is to bind to a receptor on the host cell surface; the receptors for the poxvirus are thought to be Glycosaminoglycans (GAGs). After binding to the receptor, the virus enters the cell where it uncoats. Uncoating of the virus is a two step process. Firstly the outer membrane is removed as the particle enters the cell; secondly the virus particle (without the outer membrane) is uncoated further to release the core into the cytoplasm
Cytoplasm
The cytoplasm is a small gel-like substance residing between the cell membrane holding all the cell's internal sub-structures , except for the nucleus. All the contents of the cells of prokaryote organisms are contained within the cytoplasm...
. The pox viral genes
Gênes
Gênes is the name of a département of the First French Empire in present Italy, named after the city of Genoa. It was formed in 1805, when Napoleon Bonaparte occupied the Republic of Genoa. Its capital was Genoa, and it was divided in the arrondissements of Genoa, Bobbio, Novi Ligure, Tortona and...
are expressed in two phases. The early genes are expressed first. These genes encode the non-structural protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
, including proteins necessary for replication of the viral genome
Genome
In modern molecular biology and genetics, the genome is the entirety of an organism's hereditary information. It is encoded either in DNA or, for many types of virus, in RNA. The genome includes both the genes and the non-coding sequences of the DNA/RNA....
, and are expressed before the genome is replicated. The late genes are expressed after the genome has been replicated and encode the structural proteins to make the virus particle. The assembly of the virus particle occurs in the cytoskeleton
Cytoskeleton
The cytoskeleton is a cellular "scaffolding" or "skeleton" contained within a cell's cytoplasm and is made out of protein. The cytoskeleton is present in all cells; it was once thought to be unique to eukaryotes, but recent research has identified the prokaryotic cytoskeleton...
of the cell and is a complex process that is poorly understood but is currently being researched. Considering the fact that this virus is large and complex, replication is relatively quick taking approximately 12 hours until the host cell dies by the release of viruses.
The replication of poxvirus is unusual for a virus with double-stranded DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...
genome (dsDNA) because it occurs in the cytoplasm Poxvirus encodes its own machinery for genome transcription, a DNA dependent RNA polymerase, which makes replication in the cytoplasm possible. Most dsDNA viruses require the host cell's proteins to perform transcription. These host proteins are found in the nucleus
Cell nucleus
In cell biology, the nucleus is a membrane-enclosed organelle found in eukaryotic cells. It contains most of the cell's genetic material, organized as multiple long linear DNA molecules in complex with a large variety of proteins, such as histones, to form chromosomes. The genes within these...
, and therefore most dsDNA viruses carry out a part of their infection cycle within the host cell's nucleus.
Taxonomy
The name of the family, Poxviridae, is a legacy of the original grouping of viruses associated with diseases that produced poxPox
A pox is a type of disease, often caused by an animal virus, characterised by pockmarks. The term may be used to refer to disease.Pox, as a disease, may refer to:*Poxviruses...
es in the skin. Modern viral classification
Virus classification
Virus classification is the process of naming viruses and placing them into a taxonomic system. Similar to the classification systems used for cellular organisms, virus classification is the subject of ongoing debate and proposals. This is mainly due to the pseudo-living nature of viruses, which...
is based on phenotypic characteristics; morphology, nucleic acid type, mode of replication, host organisms, and the type of disease they cause. The smallpox
Smallpox
Smallpox was an infectious disease unique to humans, caused by either of two virus variants, Variola major and Variola minor. The disease is also known by the Latin names Variola or Variola vera, which is a derivative of the Latin varius, meaning "spotted", or varus, meaning "pimple"...
virus remains as the most notable member of the family.
The following genera are currently included here:
- Subfamily Chordopoxvirinae
- Genus AvipoxvirusAvipoxvirusAvipoxvirus is a member of the Poxviridae family. The Poxviridae family is the family of viruses which cause the victim organism to have poxes as a symptom. This pox virus is one that affects birds only. Poxviruses have generally large genomes, and other such examples include smallpox and monkeypox...
; type species: Fowlpox virus; species: Canarypox virusCanarypox virusCanarypox virus is an avipoxvirus and etiologic agent of canarypox, a disease of wild and captive birds that can cause significant losses. Canarypox can enter human cells, but it cannot survive and multiply in human cells. There is a live viral vaccine available ....
, Fowlpox virus, Juncopox virus, Mynahpox virus, Pigeonpox virus, Psittacinepox virus, Quailpox virus, Sparrowpox virus, Starlingpox virus, Turkeypox virus - Genus Capripoxvirus; type species: Sheeppox virus; species: Goatpox virus, Lumpy skin disease virus, Sheeppox virus
- Genus Cervidpoxvirus; type species: Deerpox virus W-848-83; species: Deerpox virus W-848-83
- Genus Leporipoxvirus; type species: Myxoma virusMyxoma virusThe Myxoma virus causes Myxomatosis in rabbits and was used as a pest control in Australia.- Structure :Virions are enveloped, have a surface membrane with lateral bodies. The envelope contains host-derived lipids and self-synthesized glycolipids. They are brick shaped and are about 250 nm in...
; species: Hare fibroma virus, Myxoma virusMyxoma virusThe Myxoma virus causes Myxomatosis in rabbits and was used as a pest control in Australia.- Structure :Virions are enveloped, have a surface membrane with lateral bodies. The envelope contains host-derived lipids and self-synthesized glycolipids. They are brick shaped and are about 250 nm in...
, Rabbit fibroma virus, Squirrel fibroma virus - Genus Molluscipoxvirus; type species: Molluscum contagiosum virusMolluscum contagiosumMolluscum contagiosum is a viral infection of the skin or occasionally of the mucous membranes. It is caused by a DNA poxvirus called the molluscum contagiosum virus . MCV has no animal reservoir, infecting only humans. There are four types of MCV, MCV-1 to -4; MCV-1 is the most prevalent and...
; species: Molluscum contagiosum virusMolluscum contagiosum virusThe Molluscum contagiosum virus or MCV is a species of virus in the poxvirus family, which causes the disease Molluscum contagiosum in humans. Virions have a complex structure and is consistent with the structure of the poxvirus family: an envelope, surface membrane, core, and lateral bodies... - Genus OrthopoxvirusOrthopoxvirusOrthopoxvirus is a genus of poxviruses that includes many species isolated from mammals, such as Camelpox virus, Cowpox virus, Ectromelia virus, Monkeypox virus, and Volepox virus, which causes mousepox. The most famous member of the genus is Variola virus, which causes smallpox...
; type species: Vaccinia virus; species: Camelpox virus, Cowpox virus, Ectromelia virusEctromelia virusEctromelia virus is a virus of the family Poxviridae and the genus Orthopoxvirus that causes mousepox, a disease of mice. It has only been seen in mouse colonies kept for research purposes. Mousepox causes skin lesions and generalized disease, which can be fatal. It is the only poxvirus to...
, Monkeypox virusMonkeypox virusMonkeypox virus is the virus that causes the disease monkeypox in both humans and animals. It was first identified in 1958 as a pathogen of crab-eating macaque monkeys being used as laboratory animals. The crab-eating macaque is often used for neurological experiments...
, Raccoonpox virus, Taterapox virus, Vaccinia virus, Variola virus, Volepox virus - Genus ParapoxvirusParapoxvirusParapoxviruses belong to the Poxviridae family. Like all members of that family, they are oval, relatively large, double-stranded DNA viruses. Parapoxviruses have a unique spiral coat that distinguishes them from other poxviruses. Parapoxviruses infect vertebrates.Not all parapoxviruses are...
; type species: Orf virus; species: Bovine papular stomatitis virus, Orf virus, Parapoxvirus of red deer in New Zealand, Pseudocowpox virus - Genus Suipoxvirus; type species: Swinepox virus; species: Swinepox virus
- Genus Unassigned; species: Squirrel poxvirus
- Genus YatapoxvirusYatapoxvirusYatapoxvirus is a grouping of poxvirus.It includes Tanapox and Yaba monkey tumor virus....
; type species: Yaba monkey tumor virusYaba monkey tumor virusYaba monkey tumor virus is a type of poxvirus.It is closely related to tanapox.It is named for Yaba, Lagos....
; species: Tanapox virus, Yaba monkey tumor virusYaba monkey tumor virusYaba monkey tumor virus is a type of poxvirus.It is closely related to tanapox.It is named for Yaba, Lagos....
- Genus Avipoxvirus
- Subfamily Entomopoxvirinae
- Genus Alphaentomopoxvirus; type species: Melolontha melolontha entomopoxvirus; species: Anomala cuprea entomopoxvirus, Aphodius tasmaniae entomopoxvirus, Demodema boranensis entomopoxvirus, Dermolepida albohirtum entomopoxvirus, Figulus subleavis entomopoxvirus, Geotrupes sylvaticus entomopoxvirus, Melolontha melolontha entomopoxvirus
- Genus Betaentomopoxvirus; type species: Amsacta moorei entomopoxvirus 'L'; species: Acrobasis zelleri entomopoxvirus 'L', Amsacta moorei entomopoxvirus 'L', Arphia conspersa entomopoxvirus 'O', Choristoneura biennis entomopoxvirus 'L', Choristoneura conflicta entomopoxvirus 'L', Choristoneura diversuma entomopoxvirus 'L', Choristoneura fumiferana entomopoxvirus 'L', Chorizagrotis auxiliars entomopoxvirus 'L', Heliothis armigera entomopoxvirus 'L', Locusta migratoria entomopoxvirus 'O', Oedaleus senigalensis entomopoxvirus 'O', Operophtera brumata entomopoxvirus 'L', Schistocera gregaria entomopoxvirus 'O'
- Genus Gammaentomopoxvirus; type species: Chironomus luridus entomopoxvirus; species: Aedes aegypti entomopoxvirus, Camptochironomus tentans entomopoxvirus, Chironomus attenuatus entomopoxvirus, Chironomus luridus entomopoxvirus, Chironomus plumosus entomopoxvirus, Goeldichironomus haloprasimus entomopoxvirus
- Genus Unassigned; species: Diachasmimorpha entomopoxvirus
Vaccinia virus
The prototype of poxvirus family is vaccinia virus, which has been used as a successful vaccine to eradicate smallpox virus. Vaccinia virus is also used as an effective tool for foreign protein expression to elicit strong host immune response. Vaccinia virus enters cells mainly by cell fusion, although currently the receptor is not known. Virus contains three classes of genes, early, intermediate and late, that are transcribed by viral RNA polymerase and associated transcription factors. Vaccinia virus replicates its genome in cytoplasm of the infected cells and after late gene expression virion morphogenesis produces IMV that contains envelope, although the origin of the envelope membrane is still unknown. IMV is transported to Golgi to be wrapped additional two membrane to become intracellular enveloped virus (IEV). IEV transports along microtubules to reach cell periphery and fuse with plasma membrane to become cell-associated enveloped virus (CEV) that triggers actin tails on cell surfaces or is releared as EEV.History
Diseases caused by pox viruses, especially smallpox, have been known about for centuries. One of the earliest suspected cases is that of Egyptian pharaohPharaoh
Pharaoh is a title used in many modern discussions of the ancient Egyptian rulers of all periods. The title originates in the term "pr-aa" which means "great house" and describes the royal palace...
Ramses V who is thought to have died from smallpox nearly 2000 years BCE. Smallpox was thought to have been transferred to Europe around the early 8th century and then to the Americas in the early 16th century. It is widely accepted that the main defeat of the Aztecs was due to a smallpox epidemic and within two years over 3.2 million Aztecs died. This death toll can be attributed to the American population's complete lack of sensitization to the virus as children. A century after Edward Jenner showed that the less potent cow pox could be used to effectively vaccinate against the more deadly smallpox, a worldwide effort to vaccinate everyone against smallpox began with the ultimate goal to rid the world of the plague-like epidemic. The World Health Organization (WHO) declared the virus officially eradicated in 1977 and after nine years, in 1986, all virus samples were destroyed or transferred to two approved WHO reference labs: at the headquarters of the federal Centers for Disease Control and Prevention
Centers for Disease Control and Prevention
The Centers for Disease Control and Prevention are a United States federal agency under the Department of Health and Human Services headquartered in Druid Hills, unincorporated DeKalb County, Georgia, in Greater Atlanta...
(the C.D.C.) in Atlanta, Georgia (the United States) and at the Institute of Virus Preparations in Moscow. Post September 11, 2001 the American and UK governments have had increased concern over the use of smallpox, or a small pox like disease, in bio-terrorism.
External links
- Electron micrographs of Orthopoxvirus and Parapoxvirus GeneraGenusIn biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
, including the smallpoxSmallpoxSmallpox was an infectious disease unique to humans, caused by either of two virus variants, Variola major and Variola minor. The disease is also known by the Latin names Variola or Variola vera, which is a derivative of the Latin varius, meaning "spotted", or varus, meaning "pimple"...
virus, have been collected by the International Committee on Taxonomy of VirusesInternational Committee on Taxonomy of VirusesThe International Committee on Taxonomy of Viruses is a committee which authorizes and organizes the taxonomic classification of viruses. They have developed a universal taxonomic scheme for viruses and aim to describe all the viruses of living organisms. Members of the committee are considered to...
in their Poxviridae picture gallery. - Detailed genomic and bioinformatic information on Poxviruses on NIH-funded database.
- NCBI Taxonomy Page.
- Poxviridae at the Viral Bioinformatics Resource Center.
- Poxviridae Genomes database search results from the Poxvirus Bioinformatics Resource Center.
- Viralzone: Poxviridae
- Virus Pathogen Database and Analysis Resource (ViPR): Poxviridae