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http://www.plosbiology.org/article/i...l.pbio.1001642
See also:
http://www.plosbiology.org/article/i...l.pbio.1001641
A good synopsis:
http://blogs.plos.org/biologue/2013/...-helping-hand/
The Extraordinary Evolutionary History of the Reticuloendotheliosis Viruses
Anna Maria Niewiadomska,
Robert J. Gifford
Abstract
The reticuloendotheliosis viruses (REVs) comprise several closely related amphotropic retroviruses isolated from birds. These viruses exhibit several highly unusual characteristics that have not so far been adequately explained, including their extremely close relationship to mammalian retroviruses, and their presence as endogenous sequences within the genomes of certain large DNA viruses. We present evidence for an iatrogenic origin of REVs that accounts for these phenomena. Firstly, we identify endogenous retroviral fossils in mammalian genomes that share a unique recombinant structure with REVs?unequivocally demonstrating that REVs derive directly from mammalian retroviruses. Secondly, through sequencing of archived REV isolates, we confirm that contaminated Plasmodium lophurae stocks have been the source of multiple REV outbreaks in experimentally infected birds. Finally, we show that both phylogenetic and historical evidence support a scenario wherein REVs originated as mammalian retroviruses that were accidentally introduced into avian hosts in the late 1930s, during experimental studies of P. lophurae, and subsequently integrated into the fowlpox virus (FWPV) and gallid herpesvirus type 2 (GHV-2) genomes, generating recombinant DNA viruses that now circulate in wild birds and poultry. Our findings provide a novel perspective on the origin and evolution of REV, and indicate that horizontal gene transfer between virus families can expand the impact of iatrogenic transmission events.
Author Summary
Retroviruses are characterized by their ability to insert a DNA copy of their genome into the chromosomes of infected cells. Occasionally, retroviruses insert into ?germline? cells and are subsequently inherited as host alleles called endogenous retroviruses (ERVs). Vertebrate genomes contain thousands of ERV sequences derived from ancient retroviruses, and these viral sequences serve as molecular ?fossils? that can be used to explore how retroviruses have evolved over millions of years. Here we combine an analysis of the retroviral ?fossil record? with a phylogenetic and historical investigation to determine the origin of a group of avian retroviruses called reticuloendotheliosis viruses (REVs). We present evidence to demonstrate that rather than arising from natural infections of birds, REVs are in fact derived from mammalian retroviruses that were accidentally introduced into avian hosts during experimental studies of a malaria parasite in the late 1930s. Remarkably, REVs have subsequently inserted into the genomes of two large DNA viruses that infect birds, generating chimeric viruses that now circulate naturally in poultry and wild birds.
Citation: Niewiadomska AM, Gifford RJ (2013) The Extraordinary Evolutionary History of the Reticuloendotheliosis Viruses. PLoS Biol 11(8): e1001642. doi:10.1371/journal.pbio.1001642
Academic Editor: Bill Sugden, University of Wisconsin-Madison, United States of America
Received: February 25, 2013; Accepted: July 19, 2013; Published: August 27, 2013
Copyright: ? 2013 Niewiadomska, Gifford. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Anna Maria Niewiadomska,
Robert J. Gifford
Abstract
The reticuloendotheliosis viruses (REVs) comprise several closely related amphotropic retroviruses isolated from birds. These viruses exhibit several highly unusual characteristics that have not so far been adequately explained, including their extremely close relationship to mammalian retroviruses, and their presence as endogenous sequences within the genomes of certain large DNA viruses. We present evidence for an iatrogenic origin of REVs that accounts for these phenomena. Firstly, we identify endogenous retroviral fossils in mammalian genomes that share a unique recombinant structure with REVs?unequivocally demonstrating that REVs derive directly from mammalian retroviruses. Secondly, through sequencing of archived REV isolates, we confirm that contaminated Plasmodium lophurae stocks have been the source of multiple REV outbreaks in experimentally infected birds. Finally, we show that both phylogenetic and historical evidence support a scenario wherein REVs originated as mammalian retroviruses that were accidentally introduced into avian hosts in the late 1930s, during experimental studies of P. lophurae, and subsequently integrated into the fowlpox virus (FWPV) and gallid herpesvirus type 2 (GHV-2) genomes, generating recombinant DNA viruses that now circulate in wild birds and poultry. Our findings provide a novel perspective on the origin and evolution of REV, and indicate that horizontal gene transfer between virus families can expand the impact of iatrogenic transmission events.
Author Summary
Retroviruses are characterized by their ability to insert a DNA copy of their genome into the chromosomes of infected cells. Occasionally, retroviruses insert into ?germline? cells and are subsequently inherited as host alleles called endogenous retroviruses (ERVs). Vertebrate genomes contain thousands of ERV sequences derived from ancient retroviruses, and these viral sequences serve as molecular ?fossils? that can be used to explore how retroviruses have evolved over millions of years. Here we combine an analysis of the retroviral ?fossil record? with a phylogenetic and historical investigation to determine the origin of a group of avian retroviruses called reticuloendotheliosis viruses (REVs). We present evidence to demonstrate that rather than arising from natural infections of birds, REVs are in fact derived from mammalian retroviruses that were accidentally introduced into avian hosts during experimental studies of a malaria parasite in the late 1930s. Remarkably, REVs have subsequently inserted into the genomes of two large DNA viruses that infect birds, generating chimeric viruses that now circulate naturally in poultry and wild birds.
Citation: Niewiadomska AM, Gifford RJ (2013) The Extraordinary Evolutionary History of the Reticuloendotheliosis Viruses. PLoS Biol 11(8): e1001642. doi:10.1371/journal.pbio.1001642
Academic Editor: Bill Sugden, University of Wisconsin-Madison, United States of America
Received: February 25, 2013; Accepted: July 19, 2013; Published: August 27, 2013
Copyright: ? 2013 Niewiadomska, Gifford. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
See also:
http://www.plosbiology.org/article/i...l.pbio.1001641
The Mongoose, the Pheasant, the Pox, and the Retrovirus
Lucie Etienne,
Michael Emerman
Abstract
Paleovirology is the study of ancient viruses. The existence of a paleovirus can sometimes be detected by virtue of its accidental insertion into the germline of different animal species, which allows one to date when the virus actually existed. However, the ancient and the modern often connect, as modern viruses have unexpected origins that can be traced to ancient infections. The genomes of two species of mongooses and an egg-laying mammal called an echidna show that a virus currently present in poultry, the reticuloendotheliosis virus (REV), is actually of ancient exotic mammalian origin. REV apparently spread to poultry through a circuitous route involving the isolation of malaria parasites from a pheasant from Borneo housed at the Bronx Zoo that was contaminated with REV. Repeated passage of this virus in poultry adapted the virus to its new host. At some point, the virus got inserted into another virus, called fowlpox virus, which has spread back into the wild. Although REV may still exist somewhere in a mammalian host, its modern form links an 8 million-year-old infection of the ancestor of a mongoose to a virus that now is circulating in wild birds through malaria studies in the mid-20th century. These lessons of ancient and modern viruses have implications for modern human pandemics from viral reservoirs and for human interventions that may come with unintended consequences.
Citation: Etienne L, Emerman M (2013) The Mongoose, the Pheasant, the Pox, and the Retrovirus. PLoS Biol 11(8): e1001641. doi:10.1371/journal.pbio.1001641
Published: August 27, 2013
Copyright: ? 2013 Etienne, Emerman. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Funding: Supported by NIH grant AI30937 (ME) and an amfAR Mathilde Krim Fellowship in Basic Biomedical Research #108499-53-RKGN to LE. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing interests: The authors have declared that no competing interests exist.
Abbreviations: CoV, coronavirus; EVE, endogenous viral element; MYA, million years ago; SARS, severe acute respiratory syndrome; REV, reticuloendotheliosis virus; SIV, simian immunodeficiency virus
Lucie Etienne,
Michael Emerman
Abstract
Paleovirology is the study of ancient viruses. The existence of a paleovirus can sometimes be detected by virtue of its accidental insertion into the germline of different animal species, which allows one to date when the virus actually existed. However, the ancient and the modern often connect, as modern viruses have unexpected origins that can be traced to ancient infections. The genomes of two species of mongooses and an egg-laying mammal called an echidna show that a virus currently present in poultry, the reticuloendotheliosis virus (REV), is actually of ancient exotic mammalian origin. REV apparently spread to poultry through a circuitous route involving the isolation of malaria parasites from a pheasant from Borneo housed at the Bronx Zoo that was contaminated with REV. Repeated passage of this virus in poultry adapted the virus to its new host. At some point, the virus got inserted into another virus, called fowlpox virus, which has spread back into the wild. Although REV may still exist somewhere in a mammalian host, its modern form links an 8 million-year-old infection of the ancestor of a mongoose to a virus that now is circulating in wild birds through malaria studies in the mid-20th century. These lessons of ancient and modern viruses have implications for modern human pandemics from viral reservoirs and for human interventions that may come with unintended consequences.
Citation: Etienne L, Emerman M (2013) The Mongoose, the Pheasant, the Pox, and the Retrovirus. PLoS Biol 11(8): e1001641. doi:10.1371/journal.pbio.1001641
Published: August 27, 2013
Copyright: ? 2013 Etienne, Emerman. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Funding: Supported by NIH grant AI30937 (ME) and an amfAR Mathilde Krim Fellowship in Basic Biomedical Research #108499-53-RKGN to LE. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing interests: The authors have declared that no competing interests exist.
Abbreviations: CoV, coronavirus; EVE, endogenous viral element; MYA, million years ago; SARS, severe acute respiratory syndrome; REV, reticuloendotheliosis virus; SIV, simian immunodeficiency virus
http://blogs.plos.org/biologue/2013/...-helping-hand/
A Virus Emerges ? with a Human Helping Hand
By Roli Roberts
Posted: August 29, 2013
...
Reticuloendotheliosis is a nasty disease of domesticated fowl that seems to have come from nowhere, and is also known to affect wild bird populations. Read the research article and the Primer to get the full detective story and to find out how the paleovirologists traced the path of REV through tissue samples, sequence databases and the scientific literature, but here?s what they think happened (contains plot-spoilers!):
a) A retrovirus undergoes an ancient genome-splicing event, and starts infecting mammals tens of millions of years ago, leaving fossil traces in their genomes.
b) At least 8 million years ago, one of its active descendants infects a range of Madagascan carnivore species, including some mongoose-like animals. There?s no evidence of its presence in birds until the 20th century.
c) Somehow this virus ends up in a Borneo fireback pheasant in the Bronx Zoo in 1937. The implication is that the menagerie brings together exotic animals (and their viruses) that have previously never encountered each other, perhaps helping the virus jump from mammal to bird, becoming REV in the process.
d) Malaria researchers manage to isolate the malarial parasite Plasmodium lophurae from this pheasant, and they keep the parasite stock going by infecting chickens, ducks and turkeys, presumably also transmitting the viral contaminant.
e) At some point in this process, the ancient mammalian retroviral genome gets incorporated into the genomes of two bird viruses ? a pox virus and a herpes virus.
f) These viruses (REV and its derivatives) cause outbreaks in domestic and wild birds over the last 50 years, often triggered by contaminated vaccines, resulting in anaemia, suppression of the immune system and cancer.
By Roli Roberts
Posted: August 29, 2013
...
Reticuloendotheliosis is a nasty disease of domesticated fowl that seems to have come from nowhere, and is also known to affect wild bird populations. Read the research article and the Primer to get the full detective story and to find out how the paleovirologists traced the path of REV through tissue samples, sequence databases and the scientific literature, but here?s what they think happened (contains plot-spoilers!):
a) A retrovirus undergoes an ancient genome-splicing event, and starts infecting mammals tens of millions of years ago, leaving fossil traces in their genomes.
b) At least 8 million years ago, one of its active descendants infects a range of Madagascan carnivore species, including some mongoose-like animals. There?s no evidence of its presence in birds until the 20th century.
c) Somehow this virus ends up in a Borneo fireback pheasant in the Bronx Zoo in 1937. The implication is that the menagerie brings together exotic animals (and their viruses) that have previously never encountered each other, perhaps helping the virus jump from mammal to bird, becoming REV in the process.
d) Malaria researchers manage to isolate the malarial parasite Plasmodium lophurae from this pheasant, and they keep the parasite stock going by infecting chickens, ducks and turkeys, presumably also transmitting the viral contaminant.
e) At some point in this process, the ancient mammalian retroviral genome gets incorporated into the genomes of two bird viruses ? a pox virus and a herpes virus.
f) These viruses (REV and its derivatives) cause outbreaks in domestic and wild birds over the last 50 years, often triggered by contaminated vaccines, resulting in anaemia, suppression of the immune system and cancer.