Bovine foamy virus

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Bovine foamy virus
Virus classification Red Pencil Icon.png
(unranked): Virus
Realm: Riboviria
Kingdom: Pararnavirae
Phylum: Artverviricota
Class: Revtraviricetes
Order: Ortervirales
Family: Retroviridae
Genus: Bovispumavirus
Species:
Bovine foamy virus

Bovine foamy virus (BFV) is a ss(+)RNA retrovirus that belongs to the genus spumaviridae. Spumaviruses differ from the other six members of family retroviridae, both structurally and in pathogenic nature. Spumaviruses derive their name from spuma the latin for "foam". The 'foam' aspect of 'foamy virus' comes from syncytium formation and the rapid vacuolization of infected cells, creating a 'foamy' appearance. [1] [2]

Contents

Discovery

The first foamy virus was isolated from liver structures of the Rhesus macaque in 1955. [3] [4] Bovine foamy virus was isolated in 1969 from cattle with lymphosarcoma. [5] At the time of its discovery little was known about the effects of the virus or whether it played a role in the development of lymphosarcoma in the cattle. Continued research has shown that the infection prevalence of BFV is 40-85% worldwide but lacks any significant pathogenic nature. [6] [5]

Structure/Morphology

An extremely simple diagram of a mature BFV virion Mature BFV Particle.png
An extremely simple diagram of a mature BFV virion

Bovine foamy virus is an enveloped, spherical virus. The virus particles are approximately 80-100 nm in diameter and contain single-strand, positive-sense RNA: ss(+)RNA. 20% of released virions contain double stranded DNA as a product of late stage reverse transcription. The outer membrane of the virus is covered with a variety of glycoproteins which allow it to interact with its surroundings. Just beyond the envelope is a buffer between the capsid and envelope, known as the protein matrix. The matrix is responsible for maintaining membrane shape as well as participating in the budding process. Inside the matrix lies the capsid, a protein shell that contains viral integrase, reverse-transcriptase and the nucleocapsid, inside of which lives the viruses' genetic material. [7] Due to the viruses' tendency to bud into the endoplasmic reticulum, the virions tend to display immature protein characteristics around the core as well as unique glycoptorien spikes on the surface of the membrane. BFV particles also possess electron-lucent membranes which are easily crossed by electrons. [1]

Viral genome

An extremely simple diagram of the bovine foamy virus genome BFV genome.png
An extremely simple diagram of the bovine foamy virus genome

BFV has a monopartite genome, meaning that its entire genome is stored in a single ssRNA(+)/dsDNA molecule. This molecule is linear dimeric genome contain approximate 12.3kb of information. The molecule possesses an 5'-cap and 3'poly-A tail. Each of these ends possesses a 600nt long sequence of terminals repeats (LTR). The U3, R ad U5 regions are contained within these LTRs. The 5' end possesses a primer binding site while the 3' end possesses a polypurine tract. [7]

Viral entry

Attachment

The process by which foamy viruses enter a cell lacks certain levels of characterization, however it is known that the virus particle first attaches to its host using the SU glycoprotein present on its envelope. [8] The binding receptor for foamy viruses is not entirely know, however it is known that the virus is capable of infecting a board spectrum of cells, meaning the binding receptor must be quite prevalent in most forms of cells. [9] Research has shown that the most likely candidate for a common receptor is heparan sulfate (HS), an extremely common glycosaminoglycan (GAG) present on the ECM of many cells. [9]

Fusion

Once internalized, the virus particle must fuse with the internal vesicle and allow its genetic material to escape into the cytoplasm. Viral fusion is mediated through the TM glycoprotein. The fusion process is imitated when the TM protein is cleaved by the changing levels of pH which in turns creates a conformation change in the protein, fusing the membrane of the virus with the internal vesicle. [9]

Replication cycle

Cycle overview

Once the viral particle has delivered its genetic material safely into the cytoplasm of its host, one of two things will occur. If the genetic payload of the virion was double stranded DNA, the viral DNA will directly integrate into the host's genome via the viral enzyme integrase. [1] [7] If the payload was ssRNA the RNA is first copied into sdDNA via reverse transcriptase and then integrated randomly into the host genome by integrase. The host cell then performs its natural replication functions, however while doing so it transcribes viral RNA which is then translated into precursor polyproteins. [7] At this point in the cycle, if any viral RNA is remaining, it will be transcribed into dsDNA, however it is too late to be integrated into the host-cell genome. This dsDNA is then randomly packaged into newly formed virions along with the ssRNA. From this point the viral particles begin to bud. Most bud into the endoplasmic reticulum which are then packaged and distributed to other cells. Some particles manage to escape through the membrane but this number is usually quite low. [7] [10] [11]

Unique features of the replication cycle

Being a spumavirus, bovine foamy virus has a unique life cycle, even when compared to other retroviruses. One of these differences is the mechanism used in the budding process. Rather than budding through the plasma membrane like a more traditional retrovirus, BFV and other foamy viruses bud using the endoplasmic reticulum. Another facet of BFV that makes it unique among other retroviruses is how late in the replication cycle reverse-transcription takes place. This results in some of virions containing DNA rather than typical RNA. This also results in some level of integration into the host cell DNA in uncommon ways. [10] For this reason, scientists have likened foamy viruses to viruses of the family Hepadnaviridae. Foamy viruses also contain structural genes that are distinct to their particular genus. The Gag protein is not always correctly cleaved into the mature form of the viral protein, as seen in other members of retrovirdae , which leads to the overall immature morphology of FV. [1] The Env budding associated protein found in the transmembrane domain of the viron contains an endoplasmic reticulum retention signal which contributes to its ability to bud into the ER. [1] [11]

Host interactions

The most obvious result of interactions between the virus and its host is the telltale formation of large numbers of vacuoles throughout the cytoplasm. This is referred to as vacuolization, and it is what gives the spumaviruses their name. Most infected cells also begin rapid syncytium formation. [1] Thought this effect in seen quite frequently, its cause is still yet to be determined. In some more rare instances, cell death has been recorded. [2]

Associated diseases

To date, no known pathogen is associated with bovine foamy virus.[ citation needed ]

Tropism

Bovine foamy virus is known to be capable of infecting a wide range of cells. [2] These include fibroblasts, epithelial cells and neural cells. Using techniques such as PCR, bovine foamy virus can be identified in most tissues of infected animals. [1]

Related Research Articles

<span class="mw-page-title-main">Retrovirus</span> Family of viruses

A retrovirus is a type of virus that inserts a DNA copy of its RNA genome into the DNA of a host cell that it invades, thus changing the genome of that cell. Once inside the host cell's cytoplasm, the virus uses its own reverse transcriptase enzyme to produce DNA from its RNA genome, the reverse of the usual pattern, thus retro (backwards). The new DNA is then incorporated into the host cell genome by an integrase enzyme, at which point the retroviral DNA is referred to as a provirus. The host cell then treats the viral DNA as part of its own genome, transcribing and translating the viral genes along with the cell's own genes, producing the proteins required to assemble new copies of the virus. Many retroviruses cause serious diseases in humans, other mammals, and birds.

<span class="mw-page-title-main">Viral protein</span>

A viral protein is both a component and a product of a virus. Viral proteins are grouped according to their functions, and groups of viral proteins include structural proteins, nonstructural proteins, regulatory proteins, and accessory proteins. Viruses are non-living and do not have the means to reproduce on their own, instead depending on their host cell's resources in order to reproduce. Thus, viruses do not code for many of their own viral proteins, and instead use the host cell's machinery to produce the viral proteins they require for replication.

Metaviridae is a family of viruses which exist as Ty3-gypsy LTR retrotransposons in a eukaryotic host's genome. They are closely related to retroviruses: members of the family Metaviridae share many genomic elements with retroviruses, including length, organization, and genes themselves. This includes genes that encode reverse transcriptase, integrase, and capsid proteins. The reverse transcriptase and integrase proteins are needed for the retrotransposon activity of the virus. In some cases, virus-like particles can be formed from capsid proteins.

<span class="mw-page-title-main">Viral replication</span> Formation of biological viruses during the infection process

Viral replication is the formation of biological viruses during the infection process in the target host cells. Viruses must first get into the cell before viral replication can occur. Through the generation of abundant copies of its genome and packaging these copies, the virus continues infecting new hosts. Replication between viruses is greatly varied and depends on the type of genes involved in them. Most DNA viruses assemble in the nucleus while most RNA viruses develop solely in cytoplasm.

Lentivirus is a genus of retroviruses that cause chronic and deadly diseases characterized by long incubation periods, in humans and other mammalian species. The genus includes the human immunodeficiency virus (HIV), which causes AIDS. Lentiviruses are distributed worldwide, and are known to be hosted in apes, cows, goats, horses, cats, and sheep as well as several other mammals.

<i>Gammaretrovirus</i> Genus of viruses

Gammaretrovirus is a genus in the Retroviridae family. Example species are the murine leukemia virus and the feline leukemia virus. They cause various sarcomas, leukemias and immune deficiencies in mammals, reptiles and birds.

Spumaretrovirinae, commonly called spumaviruses or foamyviruses, is a subfamily of the Retroviridae family. Spumaviruses are exogenous viruses that have specific morphology with prominent surface spikes. The virions contain significant amounts of double-stranded full-length DNA, and assembly is rather unusual in these viruses. Spumaviruses are unlike most enveloped viruses in that the envelope membrane is acquired by budding through the endoplasmic reticulum instead of the cytoplasmic membrane. Some spumaviruses, including the equine foamy virus (EFV), bud from the cytoplasmic membrane.

The genome and proteins of HIV have been the subject of extensive research since the discovery of the virus in 1983. "In the search for the causative agent, it was initially believed that the virus was a form of the Human T-cell leukemia virus (HTLV), which was known at the time to affect the human immune system and cause certain leukemias. However, researchers at the Pasteur Institute in Paris isolated a previously unknown and genetically distinct retrovirus in patients with AIDS which was later named HIV." Each virion comprises a viral envelope and associated matrix enclosing a capsid, which itself encloses two copies of the single-stranded RNA genome and several enzymes. The discovery of the virus itself occurred two years following the report of the first major cases of AIDS-associated illnesses.

<i>Pestivirus</i> Genus of viruses

Pestivirus is a genus of viruses, in the family Flaviviridae. Viruses in the genus Pestivirus infect mammals, including members of the family Bovidae and the family Suidae. There are 11 species in this genus. Diseases associated with this genus include: hemorrhagic syndromes, abortion, and fatal mucosal disease.

The murine leukemia viruses are retroviruses named for their ability to cause cancer in murine (mouse) hosts. Some MLVs may infect other vertebrates. MLVs include both exogenous and endogenous viruses. Replicating MLVs have a positive sense, single-stranded RNA (ssRNA) genome that replicates through a DNA intermediate via the process of reverse transcription.

Human foamy virus (HFV) is a retrovirus and specifically belongs to the genus Spumavirus. The spumaviruses are complex and significantly different from the other six genera of retroviruses in several ways. The foamy viruses derive their name from the characteristic ‘foamy’ appearance of the cytopathic effect (CPE) induced in the cells. Foamy virus in humans occurs only as a result of zoonotic infection.

<span class="mw-page-title-main">Viral envelope</span> Outermost layer of many types of the infectious agent

A viral envelope is the outermost layer of many types of viruses. It protects the genetic material in their life cycle when traveling between host cells. Not all viruses have envelopes.

Simian foamy virus (SFV) is a species of the genus Spumavirus that belongs to the family of Retroviridae. It has been identified in a wide variety of primates, including prosimians, New World and Old World monkeys, as well as apes, and each species has been shown to harbor a unique (species-specific) strain of SFV, including African green monkeys, baboons, macaques, and chimpanzees. As it is related to the more well-known retrovirus human immunodeficiency virus (HIV), its discovery in primates has led to some speculation that HIV may have been spread to the human species in Africa through contact with blood from apes, monkeys, and other primates, most likely through bushmeat-hunting practices.

Bovine immunodeficiency virus (BIV) is a retrovirus belonging to the genus Lentivirus. It is similar to the human immunodeficiency virus (HIV) and infects cattle. The cells primarily infected are lymphocytes and monocytes/macrophages.

Mason-Pfizer monkey virus (M-PMV), formerly Simian retrovirus (SRV), is a species of retroviruses that usually infect and cause a fatal immune deficiency in Asian macaques. The ssRNA virus appears sporadically in mammary carcinoma of captive macaques at breeding facilities which expected as the natural host, but the prevalence of this virus in feral macaques remains unknown. M-PMV was transmitted naturally by virus-containing body fluids, via biting, scratching, grooming, and fighting. Cross contaminated instruments or equipment (fomite) can also spread this virus among animals.

Entebbe bat virus is an infectious disease caused by a Flavivirus that is closely related to yellow fever.

Feline foamy virus or Feline syncytial virus is a retrovirus and belongs to the family Retroviridae and the subfamily Spumaretrovirinae. It shares the genus Felispumavirus with only Puma feline foamy virus. There has been controversy on whether FeFV is nonpathogenic as the virus is generally asymptomatic in affected cats and does not cause disease. However, some changes in kidney and lung tissue have been observed over time in cats affected with FeFV, which may or may not be directly affiliated. This virus is fairly common and infection rates gradually increase with a cat's age. Study results from antibody examinations and PCR analysis have shown that over 70% of felines over 9 years old were seropositive for Feline foamy virus. Viral infections are similar between male and female domesticated cats whereas in the wild, more feral females cats are affected with FeFV.

Equine foamy virus (EFV), also called foamy virus (FV), is virus in the genus Equispumavirus. It shares similarities, with respect to replication, with lentiviruses. EFV, along with other FVs are from the family Retroviridae and subfamily Spumaretrovirinae. Spumarivuses, such as EFV, are complicated retroviruses that have been characterized in many animals including nonhuman primates, cattle, cats. Additionally, these viruses have been identified in animals that most often carry lentiviruses.

<i>Sepik virus</i> Mosquito transmitted virus endemic to Papua New Guinea

Sepik virus (SEPV) is an arthropod-borne virus (arbovirus) of the genus Flavivirus and family Flaviviridae. Flaviviridae is one of the most well characterized viral families, as it contains many well-known viruses that cause diseases that have become very prevalent in the world, like Dengue virus. The genus Flavivirus is one of the largest viral genera and encompasses over 50 viral species, including tick and mosquito borne viruses like Yellow fever virus and West Nile virus. Sepik virus is much less well known and has not been as well-classified as other viruses because it has not been known of for very long. Sepik virus was first isolated in 1966 from the mosquito Mansoniaseptempunctata, and it derives its name from the Sepik River area in Papua New Guinea, where it was first found. The geographic range of Sepik virus is limited to Papua New Guinea, due to its isolation.

<i>Modoc virus</i> Species of virus

Modoc virus (MODV) is a rodent-associated flavivirus. Small and enveloped, MODV contains positive single-stranded RNA. Taxonomically, MODV is part of the Flavivirus genus and Flaviviridae family. The Flavivirus genus includes nearly 80 viruses, both vector-borne and no known vector (NKV) species. Known flavivirus vector-borne viruses include Dengue virus, Yellow Fever virus, tick-borne encephalitis virus, and West Nile virus.

References

  1. 1 2 3 4 5 6 7 Meiering, Christopher D.; Maxine L. Linial (January 2001). "Historical Perspective of Foamy Virus Epidemiology and Infection". Clinical Microbiology Reviews. 14 (1): 165–176. doi:10.1128/CMR.14.1.165-176.2001. ISSN   0893-8512. PMC   88968 . PMID   11148008.
  2. 1 2 3 Linial, Maxine L. (1999-03-01). "Foamy Viruses Are Unconventional Retroviruses". Journal of Virology. 73 (3): 1747–1755. doi:10.1128/JVI.73.3.1747-1755.1999. ISSN   0022-538X. PMC   104413 . PMID   9971751.
  3. ↑ Enders, J. F.; Peebles, T. C. (June 1954). "Propagation in tissue cultures of cytopathogenic agents from patients with measles". Proceedings of the Society for Experimental Biology and Medicine. 86 (2): 277–286. doi:10.3181/00379727-86-21073. ISSN   0037-9727. PMID   13177653.
  4. ↑ Rustigian, R.; Johnston, P.; Reihart, H. (January 1955). "Infection of monkey kidney tissue cultures with virus-like agents". Proceedings of the Society for Experimental Biology and Medicine. 88 (1): 8–16. doi:10.3181/00379727-88-21478. ISSN   0037-9727. PMID   14357329.
  5. 1 2 Malmquist, W. A.; Van der Maaten, M. J.; Boothe, A. D. (January 1969). "Isolation, immunodiffusion, immunofluorescence, and electron microscopy of a syncytial virus of lymphosarcomatous and apparently normal cattle". Cancer Research. 29 (1): 188–200. ISSN   0008-5472. PMID   4974302.
  6. ↑ Johnson, R. H.; de la Rosa, J.; Abher, I.; Kertayadnya, I. G.; Entwistle, K. W.; Fordyce, G.; Holroyd, R. G. (January 1988). "Epidemiological studies of bovine spumavirus". Veterinary Microbiology. 16 (1): 25–33. doi:10.1016/0378-1135(88)90124-1. ISSN   0378-1135. PMID   2833003.
  7. 1 2 3 4 5 SIB Swiss Insitiute of Bioinformatics. "Spuma Virus".
  8. ↑ taxonomy. "Taxonomy Browser". www.ncbi.nlm.nih.gov. Retrieved 2017-11-02.
  9. 1 2 3 Plochmann, Kathrin; Horn, Anne; Gschmack, Eva; Armbruster, Nicole; Krieg, Jennifer; Wiktorowicz, Tatiana; Weber, Conrad; Stirnnagel, Kristin; Lindemann, Dirk (September 2012). "Heparan Sulfate Is an Attachment Factor for Foamy Virus Entry". Journal of Virology. 86 (18): 10028–10035. doi:10.1128/JVI.00051-12. ISSN   0022-538X. PMC   3446549 . PMID   22787203.
  10. 1 2 Moebes, A.; Enssle, J.; Bieniasz, P. D.; Heinkelein, M.; Lindemann, D.; Bock, M.; McClure, M. O.; Rethwilm, A. (1997-10-01). "Human foamy virus reverse transcription that occurs late in the viral replication cycle". Journal of Virology. 71 (10): 7305–7311. ISSN   0022-538X. PMC   192074 . PMID   9311807.
  11. 1 2 Goepfert, P. A.; Wang, G.; Mulligan, M. J. (1995-08-25). "Identification of an ER retrieval signal in a retroviral glycoprotein". Cell. 82 (4): 543–544. doi:10.1016/0092-8674(95)90026-8. ISSN   0092-8674. PMC   7172326 . PMID   7664333.
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