Transmissible gastroenteritis virus

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Transmissible gastroenteritis virus
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Electron micrograph of transmissible gastroenteritis coronavirus (TGEV)
Virus classification Red Pencil Icon.png
(unranked): Virus
Realm: Riboviria
Kingdom: Orthornavirae
Phylum: Pisuviricota
Class: Pisoniviricetes
Order: Nidovirales
Family: Coronaviridae
Genus: Alphacoronavirus
Subgenus: Tegacovirus
Species:
Alphacoronavirus 1
Virus:
Transmissible gastroenteritis virus
Isolates [1]

Transmissible gastroenteritis virus or Transmissible gastroenteritis coronavirus (TGEV) is a coronavirus which infects pigs. It is an enveloped, positive-sense, single-stranded RNA virus which enters its host cell by binding to the APN receptor. [2] The virus is a member of the genus Alphacoronavirus, subgenus Tegacovirus, species Alphacoronavirus 1 . [3] [4]

Contents

Proteins that contribute to the overall structure of TGEV include the spike (S), envelope (E), membrane (M) and nucleocapsid (N). The genomic size of coronaviruses ranges from approximately 28.6 kilobases. [5] Other coronaviruses that belong to the species Alphacoronavirus 1 are Feline coronavirus, Canine coronavirus and Feline infectious peritonitis virus.

Biology

TGEV belongs to the family Coronaviridae , genus Alphacoronavirus , species Alphacoronavirus 1. It is an enveloped virus with a positive single stranded RNA genome. TGEV has three major structural proteins, which are phosphoprotein (N), integral membrane protein (E1), and large glycoprotein (E2). The N protein encapsulates the genomic RNA, and the S protein forms viral projections.

The 3' segment of about 8000 nucleotides encodes subgenomic RNAs. The remaining part of the genome encodes viral replicase. The three largest gene sequence from 5' to 3' is in the order of E2 to E1 to N. There are about seven other open reading frames that are not structurally related. There are very little overlaps among the genes, and is densely packed. A negative strand is synthesized to serve as a template for transcribing RNAs of one genome size and several subgenome sized RNAs.

The E2 protein forms a petal-shaped 20 nm long projection from the virus's surface. The E2 protein is thought to be involved in pathogenesis by helping the virus enter the host cytoplasm. The E2 protein initially has 1447residues, and then a short hydrophobic sequence is cleaved. After glycosylation of the protein in the golgi, the protein is then incorporated into the new virus. There are several functional domains within the E2 protein. A 20 residue hydrophobic segment at the C-terminus anchors the protein in the lipid membrane. The rest of the protein is divided into two parts, a hydrophilic stretch that is inside the virus and a cysteine rich stretch that are possibly fatty acylation sites. The E1 protein is mostly embedded in the lipid envelop and hence plays an essential role in virus architecture. The E1 protein is postulated to interact with the lymphocyte membrane, which leads to the induction of IFN-coding genes.

Coronaviruses enter the host by first attaching to the host cell using the spike glycoprotein. The S protein interacts with the porcine aminopeptidase N (pAPN), a cellular receptor, to aide in its entry. The same cell receptor is also a point of contact for Human Coronaviruses. A domain in the S spike protein is recognized by pAPN, and transfection of pAPN occurs to nonpermissive cells and infects them with TGEV.

Morphology

The morphology of TGEV was mostly determined by electron microscopy techniques. The morphology is similar to myxovirus and oncogenic virus in that they have surface projections and an envelop. The viruses are mainly circular in shape with a diameter ranging from 100 to 150 nm including the surface projections. The projections were mainly petal-shaped attached by a very narrow stalk. The projections seemed to be very easily detached from the virus and were only found on select areas.

Pathology

TGEV infects pigs. In piglets less than 1 week old, the mortality rate is close to 100%. The pathology of TGEV is similar to that of other coronaviruses. Once the virus infects the host, it multiplies in the cell lining of the small intestine resulting in the loss of absorptive cells that in turn leads to shortening of villi. The infected swine then have reduced capability for digesting food and die from dehydration. [6]

Occurrence

TGE was prevalent in the US when it was originally discovered in the early 20th century. It became more scarce in the late 80's with the rise of porcine respiratory coronavirus (PRCV). It is thought that PRCV provides some immunity to TGE. [7]

Engineering TGEV coronavirus

The Transmissible Gastroenteritis Virus has been engineered as an expression vector. The vector was constructed by replacing the nonessential 3a and 3b ORF, which is driven by the transcription-regulating sequences (TRS) with green fluorescent protein. The resulting construct was still enteropathogenic, but with reduced growth. The infection of cells with this altered virus elicits a specific lactogenic immune response against the heterologous protein. The application of this vector is in the development of a vaccine or even gene therapy. The motivation for engineering the TGEV genome is that coronaviruses have large genomes, so they have room for insertion of foreign genes. Coronaviruses also infect the respiratory tract, and they can be used to target antigens to that area and generate some immune response.

Related Research Articles

<span class="mw-page-title-main">Coronavirus</span> Subfamily of viruses in the family Coronaviridae

Coronaviruses are a group of related RNA viruses that cause diseases in mammals and birds. In humans and birds, they cause respiratory tract infections that can range from mild to lethal. Mild illnesses in humans include some cases of the common cold, while more lethal varieties can cause SARS, MERS and COVID-19, which is causing the ongoing pandemic. In cows and pigs they cause diarrhea, while in mice they cause hepatitis and encephalomyelitis.

<span class="mw-page-title-main">SARS-related coronavirus</span> Species of coronavirus causing SARS and COVID-19

Severe acute respiratory syndrome–related coronavirus is a species of virus consisting of many known strains phylogenetically related to severe acute respiratory syndrome coronavirus 1 (SARS-CoV-1) that have been shown to possess the capability to infect humans, bats, and certain other mammals. These enveloped, positive-sense single-stranded RNA viruses enter host cells by binding to the angiotensin-converting enzyme 2 (ACE2) receptor. The SARSr-CoV species is a member of the genus Betacoronavirus and of the subgenus Sarbecovirus.

<i>Coronaviridae</i> Family of viruses in the order Nidovirales

Coronaviridae is a family of enveloped, positive-strand RNA viruses which infect amphibians, birds, and mammals. The group includes the subfamilies Letovirinae and Orthocoronavirinae; the members of the latter are known as coronaviruses.

<i>Nidovirales</i> Order of positive-sense, single-stranded RNA viruses

Nidovirales is an order of enveloped, positive-strand RNA viruses which infect vertebrates and invertebrates. Host organisms include mammals, birds, reptiles, amphibians, fish, arthropods, molluscs, and helminths. The order includes the families Coronaviridae, Arteriviridae, Roniviridae, and Mesoniviridae.

Avian coronavirus is a species of virus from the genus Gammacoronavirus that infects birds; since 2018, all gammacoronaviruses which infect birds have been classified as this single species. The strain of avian coronavirus previously known as infectious bronchitis virus (IBV) is the only coronavirus that infects chickens. It causes avian infectious bronchitis, a highly infectious disease that affects the respiratory tract, gut, kidney and reproductive system. IBV affects the performance of both meat-producing and egg-producing chickens and is responsible for substantial economic loss within the poultry industry. The strain of avian coronavirus previously classified as Turkey coronavirus causes gastrointestinal disease in turkeys.

<i>Human coronavirus NL63</i> Species of virus

Human coronavirus NL63 (HCoV-NL63) is a species of coronavirus, specifically a Setracovirus from among the Alphacoronavirus genus. It was identified in late 2004 in patients in the Netherlands. The virus is an enveloped, positive-sense, single-stranded RNA virus which enters its host cell by binding to ACE2. Infection with the virus has been confirmed worldwide, and has an association with many common symptoms and diseases. Associated diseases include mild to moderate upper respiratory tract infections, severe lower respiratory tract infection, croup and bronchiolitis.

<span class="mw-page-title-main">Canine coronavirus</span> Species of virus

Canine coronavirus (CCoV) is an enveloped, positive-sense, single-stranded RNA virus which is a member of the species Alphacoronavirus 1. It causes a highly contagious intestinal disease worldwide in dogs. The infecting virus enters its host cell by binding to the APN receptor. It was discovered in 1971 in Germany during an outbreak in sentry dogs. The virus is a member of the genus Alphacoronavirus and subgenus Tegacovirus.

<i>Murine coronavirus</i> Species of virus

Murine coronavirus (M-CoV) is a virus in the genus Betacoronavirus that infects mice. Belonging to the subgenus Embecovirus, murine coronavirus strains are enterotropic or polytropic. Enterotropic strains include mouse hepatitis virus (MHV) strains D, Y, RI, and DVIM, whereas polytropic strains, such as JHM and A59, primarily cause hepatitis, enteritis, and encephalitis. Murine coronavirus is an important pathogen in the laboratory mouse and the laboratory rat. It is the most studied coronavirus in animals other than humans, and has been used as an animal disease model for many virological and clinical studies.

Feline coronavirus (FCoV) is a positive-stranded RNA virus that infects cats worldwide. It is a coronavirus of the species Alphacoronavirus 1 which includes canine coronavirus (CCoV) and porcine transmissible gastroenteritis coronavirus (TGEV). It has two different forms: feline enteric coronavirus (FECV) that infects the intestines and feline infectious peritonitis virus (FIPV) that causes the disease feline infectious peritonitis (FIP).

<i>Alphacoronavirus</i> Genus of viruses

Alphacoronaviruses (Alpha-CoV) are members of the first of the four genera of coronaviruses. They are positive-sense, single-stranded RNA viruses that infect mammals, including humans. They have spherical virions with club-shaped surface projections formed by trimers of the spike protein, and a viral envelope.

<i>Deltacoronavirus</i> Genus of viruses

Deltacoronavirus (Delta-CoV) is one of the four genera of coronaviruses. It is in the subfamily Orthocoronavirinae of the family Coronaviridae. They are enveloped, positive-sense, single-stranded RNA viruses. Deltacoronaviruses infect mostly birds and some mammals.

<i>Gammacoronavirus</i> Genus of viruses

Gammacoronavirus (Gamma-CoV) is one of the four genera of coronaviruses. It is in the subfamily Orthocoronavirinae of the family Coronaviridae. They are enveloped, positive-sense, single-stranded RNA viruses of zoonotic origin. Coronaviruses infect both animals and humans.

<i>Human coronavirus 229E</i> Species of virus

Human coronavirus 229E (HCoV-229E) is a species of coronavirus which infects humans and bats. It is an enveloped, positive-sense, single-stranded RNA virus which enters its host cell by binding to the APN receptor. Along with Human coronavirus OC43, it is one of the viruses responsible for the common cold. HCoV-229E is a member of the genus Alphacoronavirus and subgenus Duvinacovirus.

Miniopterus bat coronavirus 1 is the first coronavirus found in bats, sampled in summer 2003 and published in February 2005.

Rhinolophus bat coronavirus HKU2 is a novel enveloped, single-stranded positive-sense RNA virus species in the Alphacoronavirus, or Group 1, genus with a corona-like morphology.

Scotophilus bat coronavirus 512 is an enveloped, single-stranded positive-sense RNA virus species in the Alphacoronavirus, or Group 1, genus with a corona-like morphology. It was isolated from a lesser Asiatic yellow house bat discovered in southern China.

<i>Coronavirus HKU15</i> Species of virus

Coronavirus HKU15, sometimes called Porcine coronavirus HKU15 is a virus first discovered in a surveillance study in Hong Kong, China, and first reported to be associated with porcine diarrhea in February 2014. In February 2014, PorCoV HKU15 was identified in pigs with clinical diarrhea disease in the U.S. state of Ohio. The complete genome of one US strain has been published. Since then, it has been identified in pig farms in Canada. The virus has been referred to as Porcine coronavirus HKU15, Swine deltacoronavirus and Porcine deltacoronavirus.

<span class="mw-page-title-main">Coronavirus diseases</span> List of Coronavirus diseases

Coronavirus diseases are caused by viruses in the coronavirus subfamily, a group of related RNA viruses that cause diseases in mammals and birds. In humans and birds, the group of viruses cause respiratory tract infections that can range from mild to lethal. Mild illnesses in humans include some cases of the common cold, while more lethal varieties can cause SARS, MERS and COVID-19. As of 2021, 45 species are registered as coronaviruses, whilst 11 diseases have been identified, as listed below.

<i>Orthornavirae</i> Kingdom of viruses

Orthornavirae is a kingdom of viruses that have genomes made of ribonucleic acid (RNA), those genomes encoding an RNA-dependent RNA polymerase (RdRp). The RdRp is used to transcribe the viral RNA genome into messenger RNA (mRNA) and to replicate the genome. Viruses in this kingdom also share a number of characteristics involving evolution, including high rates of genetic mutations, recombinations, and reassortments.

<i>Alphacoronavirus 1</i> Species of virus

Alphacoronavirus 1 is a species of coronavirus that infects cats, dogs and pigs. It includes the virus strains feline coronavirus, canine coronavirus, and transmissible gastroenteritis virus. It is an enveloped, positive-strand RNA virus which is able to enter its host cell by binding to the APN receptor.

References

  1. ↑ "ICTV 9th Report (2011) Coronaviridae". International Committee on Taxonomy of Viruses (ICTV). Retrieved 26 January 2019. Alphacoronavirus 1 Transmissible gastroenteritis virus Transmissible gastroenteritis virus virulent Purdue [AJ271965] (TGEV virulent Purdue) Species names are in italic script; names of subspecies and isolates are in roman script. Sequence accession numbers [ ] and assigned abbreviations ( ) are also listed.
  2. ↑ Fehr AR, Perlman S (2015). "Coronaviruses: an overview of their replication and pathogenesis". In Maier HJ, Bickerton E, Britton P (eds.). Coronaviruses. Methods in Molecular Biology. Vol. 1282. Springer. pp. 1–23. doi:10.1007/978-1-4939-2438-7_1. ISBN   978-1-4939-2438-7. PMC   4369385 . PMID   25720466. See Table 1.
  3. ↑ Woo, Patrick C. Y.; Huang, Yi; Lau, Susanna K. P.; Yuen, Kwok-Yung (24 August 2010). "Coronavirus Genomics and Bioinformatics Analysis". Viruses. 2 (8): 1804–1820. doi: 10.3390/v2081803 . ISSN   1999-4915. PMC   3185738 . PMID   21994708. Figure 2. Phylogenetic analysis of RNA-dependent RNA polymerases (Pol) of coronaviruses with complete genome sequences available. The tree was constructed by the neighbor-joining method and rooted using Breda virus polyprotein.
  4. ↑ "Taxonomy browser (Alphacoronavirus 1)". www.ncbi.nlm.nih.gov. Retrieved 29 February 2020.
  5. ↑ Thiel V, ed. (2007). Coronaviruses: Molecular and Cellular Biology (1st ed.). Caister Academic Press. ISBN   978-1-904455-16-5.[ page needed ]
  6. ↑ Harris, D. L. Hank. "Transmissible Gastroenteritis in Pigs". Merck Veterinary Manual. Merck. Retrieved 7 July 2019.
  7. ↑ Transboundary and Emerging Diseases of Animals. Iowa State University. 2016. ISBN   978-0-9846270-5-9.
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