The way in which the equine hepatitis virus behaves in horses could represent a powerful model to gain insights into similar infections in humans, according to researchers.
Insights into equine hepatitis infections will help scientists understand the evolution of such viruses, and in particular the way the hepatitis C virus in humans evades the immune system, they say.
More than 70 million people worldwide are infected with hepatitis C. The disease is treatable, but it is often not recognised.
In 80 per cent of cases, it takes chronic courses and can lead to liver damage and even liver cancer.
Even 30 years after the discovery of hepatitis C in humans, there is still no vaccine available. Reasons for this include its high mutation rate, which allows the virus to escape immune recognition.
“The reason why the virus often doesn’t clear up is that the virus is constantly changing and thus escapes the immune system,” explains Dr Daniel Todt, with the Virology Department at Ruhr University Bochum in Germany.
“The immune system forms antibodies that always lag behind the virus for a while and have the ability to combat a variant that was in the body about two weeks before.”
This evolution of the virus within the host is therefore of particular interest to the researchers.
Writing in the journal Virus Evolution, they said distinct hepaciviruses have been isolated from a range of species, each with a narrow host range. The equine hepacivirus is the closest known relative of the hepatitis C virus in humans.
To date, there have been no suitable models to deal with these questions in animal experiments.
In their quest for a so-called surrogate model for research into the human hepatitis C virus, the scientists analysed samples from horses that were taken in cooperation with Germany’s University of Veterinary Medicine Hannover (TiHo).
“If you compare hepatitis viruses that can infect different species, it is striking that the human virus and the virus that is infectious for horses are genetically close relatives,” explains André Gömer, a PhD student at TiHo’s research training group VIPER, and lead author of the paper.
The researchers analysed the surface proteins of viruses from humans and horses in the course of infection and compared the results.
“In the horse virus, a region that we call hypervariable is missing,” explains Gömer.
It changes particularly quickly and protects an area of the virus that helps it infect host cells. This could be one reason why the infection in horses, unlike in humans, is rarely chronic.
“These findings help us to better understand the tactics of the hepatitis C virus and to find out which areas of the virus are the most relevant,” Todt says.
The equine hepatitis virus infection of horses could therefore represent a powerful model to gain insights into hepaciviral evolution and hepatitis C virus immune evasion, they said.
André Gömer, Richard J P Brown, Stephanie Pfaender, Katja Deterding, Gábor Reuter, Richard Orton, Stefan Seitz, C- Thomas Bock, Jessika M V Cavalleri, Thomas Pietschmann, Heiner Wedemeyer, Eike Steinmann, Daniel Todt, Intra-host analysis of hepaciviral glycoprotein evolution reveals signatures associated with viral persistence and clearance, Virus Evolution, Volume 8, Issue 1, 2022, veac007, https://doi.org/10.1093/ve/veac007