Discovery of canine hepatitis C virus opens up new doors for research on deadly human pathogen
In a study to be published online this week in the Proceedings of the National Academy of Sciences, researchers report the discovery of a novel hepatitis C-like virus in dogs. The identification and characterization of this virus gives scientists new insights into how hepatitis C in humans may have evolved and provides scientists renewed hope to develop a model system to study how it causes disease.
The research was conducted at the Center for Infection and Immunity (CII) at Columbia University's Mailman School of Public Health, the University of Edinburgh, the Center for the Study of Hepatitis C and Pfizer Veterinary Medicine.
Human hepatitis C virus (HCV) affects approximately 200 million people worldwide. According to the Centers for Disease Control and Prevention (CDC), 3.2 million people in the United States are chronically infected. The majority of these patients do not know they are carrying the virus, thus serving as a source of infection for others. HCV, which can cause liver disease and liver cancer, is most often transmitted following large or repeated exposure to infected blood. Persons who use injection drugs; are HIV-positive; or are children of infected mothers have the highest risk of infection.
The discovery of canine hepatitis C virus (CHV) marks the first known instance of hepatitis-like infection in non-human primates and suggests that the virus may have been introduced into human populations through contact with dogs or some other related species more than 500 years ago, long after the domestication of dogs.
CHV belongs to a group of viruses known as hepaciviruses, which also includes GBV-B, a virus that causes hepatitis in tamarins, small monkeys from Central and South America. Among these viruses, HCV is most closely related to its canine counterpart, a finding that surprised first author Dr. Amit Kapoor, an investigator in the Center for Infection and Immunity and Assistant Professor of Pathology..
"Considering the origin of HIV," Dr. Kapoor explains, "we expected to find the closest homologs, or genetic relatives, of HCV in non-human primates. However, while we were analyzing samples from dogs involved in outbreaks of respiratory disease, we came upon a virus that was more similar to HCV than other viruses of the same family. So far, we have only detected CHV in sick animals, a few of which had died of unknown causes. Because of its close genetic similarity to HCV, we suggested the name of canine hepacivirus."
According to Dr. Charles Rice, Scientific and Executive Director of the Center for the Study of Hepatitis C at The Rockefeller University and one of the collaborators involved in the study, "the origins of HCV remain a mystery. These findings underscore the need to look beyond primates for clues to the origins of HCV."
Viral zoonoses, infections that are transmitted from animals to humans, account for about 70% of human emerging infectious diseases. Although transmission between species is uncommon, sustained contact over time can increase the likelihood that a virus adapted to infect humans will evolve. Since their domestication about 10,000 years ago, dogs have been close human companions. Whether humans and dogs were independently infected with an ancestral virus by another species or whether dogs infected humans (or vice versa) cannot be determined from this study. There is NO current risk that dogs can infect humans with either HCV or CHV.
Using a sequencing platform provided by Roche 454 Life Sciences and state-of-the-art-molecular techniques, Dr. Kapoor, together with scientists at the University of Edinburg, The Rockefeller University and Pfizer, determined that like HCV, CHV's genome contained RNA secondary structures called GORS that allow viruses to chronically infect their natural hosts. Moreover, the sequence of genes that encode proteins involved in virus infection and replication were very similar between HCV and CHV.
Until recently, studies into how hepatitis C causes disease in humans have been limited by the lack of animal and cell culture models. According to CII Director Dr. Ian Lipkin, "The identification and characterization of CHV signals the advent of a new tractable animal model for hepatitis C. This discovery provides new tools for understanding how this virus causes disease, and will facilitate drug and vaccine research and development."
Interesting. I just (tried to ) wade through an article on the development of Boceprevir and they were discussing how hard it was to test and research Hep C because we and chimps are the only animals that get it. And chimp spontaneously clear about 1/3 of the time. I still hate to think that they will use our canine friends for lab rats.
There are some very disconcerting virus' showing up in humans now vis-a-vis the bushmeat crisis. According to the CDC:
"Approximately three fourths of human emerging infectious diseases are caused by zoonotic pathogens (1). These include agents responsible for global mortality (e.g., HIV-1 and -2, influenza virus) and others that cause limited deaths but result in high case-fatality rates and for which no effective therapies or vaccines exist (e.g., Ebola virus, hantaviruses, Nipah virus, severe acute respiratory syndrome [SARS]-associated coronavirus)."
I agree now if I tell anyone I have it I'll say I got it from my doberman. Although exactly HOW you get it from a dog seems like it might be rather a gross story..........better just to say I did a lot of drugs in the 80s after all. :O
true story we had a cat named bubbles in the 70's that had hepatitis the vet told my mother she could try to save the cat or he could euthanize him, because he didn't think the cat would make it. My mom put the cat in a closet a walkin and kept him away from the other kitties and the family. she put on masks and gloves and tended to that cat for several months, handfed him rice and soft food, he recovered and the vet couldn't believe it. Just saying you never know
nygirl - ha ha this is true - actually in the middle of the night last night the thought did cross my mind that it would be just my luck to be reinfected by my dog once I am done treating. The odds are just about the same as how I originally contracted it.
Viral Outbreaks in Dogs Yield Clues on Origins of Hepatitis C
By CARL ZIMMER
Published: May 30, 2011
Hepatitis C is, in some ways, a high-profile disease. Worldwide, an estimated 200 million people are infected with the virus. Some of them will suffer cirrhosis, liver cancer and even death. Celebrities like Steven Tyler of Aerosmith and “American Idol” have spoken publicly of their infections.
But mysteries still shroud the disease. Typically spread through drug injections, blood transfusions and sexual contact, hepatitis C can quietly cause liver damage for 20 years or more before victims become aware that they are ill. “Worldwide, it’s causing devastation,” said Brian Edlin, an epidemiologist at SUNY Downstate Medical Center in Brooklyn.
Its origins are even more puzzling. Hepatitis C is a distinct disease from hepatitis A and B; it belongs to an entirely different virus family that includes diseases like West Nile fever and yellow fever. Scientists have searched for years for related viruses in animals to figure out how it evolved into a human disease.
“Identifying the species reservoir of hepatitis C — one of the most common and deadly of all human viruses — has been something of a holy grail in studies of viral evolution,” said Eddie Holmes, a virologist at Penn State University.
Now scientists have gotten an important clue, finding a close relative in an unexpected host: dogs.
The discovery, published in Proceedings of the National Academy of Sciences, “represents a major step forward,” said Dr. Holmes, who was not involved in the research.
The finding came as a surprise to all the scientists involved. Researchers at Pfizer were investigating virus outbreaks in dogs in shelters across the United States. They swabbed the noses of dogs sick with respiratory diseases and searched for viruses. In some cases they could not isolate a known virus, so they sent samples to the Center for Infection and Immunity at Columbia University, where researchers specialize in finding new viruses.
The Columbia center found that six of nine dogs in one outbreak and three of five in another shared the same unknown virus. Nasal swabs from 60 healthy dogs showed no sign of it.
Amit Kapoor, a Columbia virologist, compared the genetic material of the new virus to known ones. His analysis revealed it was closely related to the hepatitis C virus (HCV for short). “I was not expecting anything like HCV,” Dr. Kapoor said. Like many other researchers, he assumed that it had evolved from a primate virus, because chimpanzees can be experimentally infected with hepatitis C.
But as Dr. Kapoor and Peter Simmonds of the University of Edinburgh analyzed more genetic data, the link continued to hold. Dr. Kapoor and his colleagues have called the new virus canine hepacivirus, or CHV for short.
The Columbia researchers collaborated with hepatitis C experts at Rockefeller University in New York to compare the two viruses. Canine hepacivirus infects the airways of dogs and is present at low levels in the liver.
Based on the genetic similarity of the two viruses, the scientists estimate that they share a common ancestor that lived 500 to 1,000 years ago. “It’s really quite rough,” said W. Ian Lipkin, the director of the Center for Infection and Immunity and an author of the journal article. “This is not something that happened recently, but it didn’t happen hundreds of thousands of years ago.”
The researchers see three possibilities for the origin of the viruses. The least likely is that dogs acquired hepatitis C from humans. Another possibility is that dogs and humans both acquired the virus from an unknown animal. This is the sort of evolution that gave rise to the 2004 outbreak of SARS. At first scientists found the virus in the catlike palm civet of Southeast Asia. But later research revealed that the virus actually started out in bats and then spread to palm civets and humans.
A third possibility — one favored by Dr. Kapoor — is that the virus started in dogs, and then evolved into a liver-infecting disease in humans.
“The evidence we have favors an origin in dogs,” Dr. Kapoor said.
To test these alternatives, Dr. Kapoor and his colleagues plan to search for hepatitis C-like viruses in dogs from other countries, as well as in foxes and other species of carnivorous mammals.
Even before that mystery is resolved, however, researchers expect to see some benefits from the discovery of canine hepacivirus. In the current issue of the journal Nature, Dr. Edlin argues that much more needs to be done to fight the hepatitis C epidemic. Along with better surveillance, he sees a need for research into antiviral drugs as well as vaccines. (Currently there is no commercially available hepatitis C vaccine.) Researchers may now be able to study CHV in dogs to get insights into hepatitis C in humans.
would not surprise me at all, read an article earlier that there is a hepatitis virus in mice, dogs, turkeys and several others. I have had dogs all my life, but also have got them their vaccinations. I posted earlier that we had a cat that had hep and the vet said it was contagious. Thats why mom gloved up and wore a mask. Hep C had to come from somewhere, makes you think.
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