Simian foamy virus
Encyclopedia
The simian foamy virus is a spumavirus
closely related to the Human Immunodeficiency Virus, HIV
, the virus that can lead to AIDS
. 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 through hunting
bushmeat
.
About 70-90% of non-human primates born in captivity have SFV. Animals with SFV do not display symptoms or become ill. However, recent research suggests that some primates that contract SFV would become pre-disposed to other viruses. People who have had contact with non-human primates can become infected with SFV.
in African apes and monkeys, there is not enough evidence that it causes any harm to the population. Its ability to cross over to humans was proven in 2004 by a joint United States
and Cameroon
ian team which found the retrovirus
in gorillas, mandrill
s and guenon
s; unexpectedly they also found it in 10 of 1,100 local Cameroon
residents. Of those found infected the majority are males who had been bitten by a non-human primate.
While this only accounts for 1% of the population, this detail is alarming to some groups that fear the outbreak of another AIDS-like epidemic
.
SFV causes cell
s to fuse with each other to form so called syncytia
, or more figurative, "giant cells" and look, on a slide, like foamy bubbles, hence its name. It has been tentatively linked to several diseases but without any real evidence.
The SFV sequence examination of species and sub species within each clade of the phylogenetic tree of the primates indicated co-speciation of SFV and the primate hosts as well. There was a strong linear relationship between the branch lengths for the host and SFV gene trees which indicated synchronous genetic divergence in both data sets.
By using the molecular clock, it was observed that the substitution rates for the host and SFV genes were very similar. The substitution rates for host COII gene and the SFV gene were found out to be (1.16 ± 0.35) X 10−8 and (1.7 ± 0.45) X 10−8 respectively. This is the slowest rate of substitution observed for RNA viruses and is closer to that of DNA viruses and endogenous retroviruses. This rate is quite different from that of exogenous RNA viruses such as HIV and influenza A virus (10−3 to 10−4 substitutions per site per year).
Recent studies have shown that humans who hunt wild primates, including chimpanzees, can acquire SFV infections. Since the long-term consequences of these cross-species infections are not known, it is important to determine to what extent wild primates are infected with simian foamy viruses. In this study, researchers tested this question for wild chimpanzees by using novel non-invasive methods. Analyzing over 700 fecal samples from 25 chimpanzee communities across sub-Saharan Africa, the researchers obtained viral sequences from a large proportion of these communities, showing a range of infection rates from 44% to 100%.
Major disease outbreaks have originated from cross-species transmission of infectious agents between primates and humans, making it important to learn more about how these cross-species transfers occur. The high SFV infection rates of chimpanzees provide an opportunity to monitor where humans are exposed to these viruses. Identifying the locations may help determine where the highest rates of human–chimpanzee interactions occur. This may predict what other pathogens may jump the species barrier next.
Spumavirus
A spumavirus or foamyvirus is a genus 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...
closely related to the Human Immunodeficiency Virus, HIV
HIV
Human immunodeficiency virus is a lentivirus that causes acquired immunodeficiency syndrome , a condition in humans in which progressive failure of the immune system allows life-threatening opportunistic infections and cancers to thrive...
, the virus that can lead to AIDS
AIDS
Acquired immune deficiency syndrome or acquired immunodeficiency syndrome is a disease of the human immune system caused by the human immunodeficiency virus...
. Its discovery in primates has led to some speculation that HIV may have been spread to the human species in Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
through contact with blood
Blood
Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....
from apes, monkeys, and through hunting
Hunting
Hunting is the practice of pursuing any living thing, usually wildlife, for food, recreation, or trade. In present-day use, the term refers to lawful hunting, as distinguished from poaching, which is the killing, trapping or capture of the hunted species contrary to applicable law...
bushmeat
Bushmeat
Bushmeat initially referred to the hunting of wild animals in West and Central Africa and is a calque from the French viande de brousse. Today the term is commonly used for meat of terrestrial wild animals, killed for subsistence or commercial purposes throughout the humid tropics of the Americas,...
.
About 70-90% of non-human primates born in captivity have SFV. Animals with SFV do not display symptoms or become ill. However, recent research suggests that some primates that contract SFV would become pre-disposed to other viruses. People who have had contact with non-human primates can become infected with SFV.
Description
Although the simian foamy virus is endemicEndemic (epidemiology)
In epidemiology, an infection is said to be endemic in a population when that infection is maintained in the population without the need for external inputs. For example, chickenpox is endemic in the UK, but malaria is not...
in African apes and monkeys, there is not enough evidence that it causes any harm to the population. Its ability to cross over to humans was proven in 2004 by a joint United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
and Cameroon
Cameroon
Cameroon, officially the Republic of Cameroon , is a country in west Central Africa. It is bordered by Nigeria to the west; Chad to the northeast; the Central African Republic to the east; and Equatorial Guinea, Gabon, and the Republic of the Congo to the south. Cameroon's coastline lies on the...
ian team which found the retrovirus
Retrovirus
A retrovirus is an RNA virus that is duplicated in a host cell using the reverse transcriptase enzyme to produce DNA from its RNA genome. The DNA is then incorporated into the host's genome by an integrase enzyme. The virus thereafter replicates as part of the host cell's DNA...
in gorillas, mandrill
Mandrill
The mandrill is a primate of the Old World monkey family, closely related to the baboons and even more closely to the drill. Both the mandrill and the drill were once classified as baboons in genus Papio, but recent research has determined they should be separated into their own genus, Mandrillus...
s and guenon
Guenon
The guenons are the genus Cercopithecus of Old World monkeys. Not all the members of this genus have the word "guenon" in their common names, and because of changes in scientific classification, some monkeys in other genera may have common names that do include the word "guenon"...
s; unexpectedly they also found it in 10 of 1,100 local Cameroon
Cameroon
Cameroon, officially the Republic of Cameroon , is a country in west Central Africa. It is bordered by Nigeria to the west; Chad to the northeast; the Central African Republic to the east; and Equatorial Guinea, Gabon, and the Republic of the Congo to the south. Cameroon's coastline lies on the...
residents. Of those found infected the majority are males who had been bitten by a non-human primate.
While this only accounts for 1% of the population, this detail is alarming to some groups that fear the outbreak of another AIDS-like epidemic
Epidemic
In epidemiology, an epidemic , occurs when new cases of a certain disease, in a given human population, and during a given period, substantially exceed what is expected based on recent experience...
.
SFV causes cell
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....
s to fuse with each other to form so called syncytia
Syncytium
In biology, a syncytium is a large cell-like structure; filled with cytoplasm and containing many nuclei. Most cells in eukaryotic organisms have a single nucleus; syncytia are specialized forms used by various organisms.The term may also refer to cells that are connected by specialized membrane...
, or more figurative, "giant cells" and look, on a slide, like foamy bubbles, hence its name. It has been tentatively linked to several diseases but without any real evidence.
Co-speciation of SFV and Primates
The phylogenetic tree analysis of SFV polymerase and mitochondrial cytochrome oxidase subunit II (COII has been shown as a powerful marker used for primate phylogeny) from African and Asian monkeys and apes provides very similar branching order and divergence times among the two trees, supporting the co-speciation. Also, it was found that the substitution rate in the SFV gene is extremely slow i.e the SFV has evolved at a very low rate (1.7 X 10−8 substitutions per site per year). These results suggest that SFV has been co-speciated with Old World primates for about 30 million years, making them the oldest known vertebrate RNA viruses.The SFV sequence examination of species and sub species within each clade of the phylogenetic tree of the primates indicated co-speciation of SFV and the primate hosts as well. There was a strong linear relationship between the branch lengths for the host and SFV gene trees which indicated synchronous genetic divergence in both data sets.
By using the molecular clock, it was observed that the substitution rates for the host and SFV genes were very similar. The substitution rates for host COII gene and the SFV gene were found out to be (1.16 ± 0.35) X 10−8 and (1.7 ± 0.45) X 10−8 respectively. This is the slowest rate of substitution observed for RNA viruses and is closer to that of DNA viruses and endogenous retroviruses. This rate is quite different from that of exogenous RNA viruses such as HIV and influenza A virus (10−3 to 10−4 substitutions per site per year).
Prevalence
Researchers in Cameroon, the Democratic Republic of Congo, France, Gabon, Germany, Japan, Rwanda, the United Kingdom, and the United States have found that simian foamy virus (SFV) is widespread among wild chimpanzees throughout equatorial Africa. Details are published July 4 in the open-access journal PLoS Pathogens.Recent studies have shown that humans who hunt wild primates, including chimpanzees, can acquire SFV infections. Since the long-term consequences of these cross-species infections are not known, it is important to determine to what extent wild primates are infected with simian foamy viruses. In this study, researchers tested this question for wild chimpanzees by using novel non-invasive methods. Analyzing over 700 fecal samples from 25 chimpanzee communities across sub-Saharan Africa, the researchers obtained viral sequences from a large proportion of these communities, showing a range of infection rates from 44% to 100%.
Major disease outbreaks have originated from cross-species transmission of infectious agents between primates and humans, making it important to learn more about how these cross-species transfers occur. The high SFV infection rates of chimpanzees provide an opportunity to monitor where humans are exposed to these viruses. Identifying the locations may help determine where the highest rates of human–chimpanzee interactions occur. This may predict what other pathogens may jump the species barrier next.