Source: One Zero
A new study suggests a 100% immunization rate
Last month, a river in South Korea turned red with the blood of 47,000 pigs. The animals had been culled in an effort to halt the spread of African swine fever (ASF), a deadly virus for which there is no known cure or commercially available vaccine. Practically every pig that becomes infected with it dies within 10 days.
Although the disease cannot harm humans, it has decimated China’s pig herds and is now spreading in Southeast Asia and Eastern Europe. It is thought to have led to the deaths of a quarter of the world’s domestic pigs this year. Hundreds of millions of animals have been either killed by the virus or preemptively culled.
The president of Germany’s national meat industry association recently told the newspaper ‘Bild’ that products like sausages would “definitely” be more expensive in 2020.
In China, the price of pork has risen sharply, affecting trade elsewhere. The president of Germany’s national meat industry association recently told the newspaper Bild that products like sausages would “definitely” be more expensive in 2020.
And yet there is a glimmer of hope. When the ASF epidemic exploded in China in August 2018, the world’s scientists hunkered down in an effort to develop a successful vaccine. Now, a research group in New York has published very promising, albeit early, results.
The experiments, conducted by scientists at the Department of Homeland Security’s Plum Island Animal Disease Center, have not yet been peer reviewed. But they are, potentially, significant: Every pig treated with a prototype vaccine avoided developing significant signs of ASF, and all of them appeared well-protected from it after 28 days.
“We’re pretty excited,” says Douglas Gladue, one of the study’s co-authors, via phone. “I think it will be possible to commercialize the vaccine.”
The vaccine was made by creating a mutant form of the wild ASF virus — the same strain known to be causing the current epidemic in Asia. For a virus, ASF contains a large amount of genetic material — far more than, say, Ebola. That makes it all the more difficult to find a vaccine, because it means there are lots of proteins in the virus that interact with the host’s immune system.
But the Plum Island team found a weakness. They deleted a single gene in the virus’s genome called I177L. Research published last year by researchers in Spain revealed that this gene is linked to a protein in the virus membrane, but little is known about its function.
The Plum Island team found that removing the gene resulted in a vaccine that was extremely successful in early tests. Groups of five pigs at a time were vaccinated with the mutant strain. Their immune systems began to produce antibodies to fight infection, and all the pigs remained essentially free of ASF symptoms despite being exposed later to the complete virus. Plus, unvaccinated pigs in the groups also remained free of symptoms, suggesting that using the vaccine doesn’t put other animals at risk.
If verified in further tests in larger pig herds, the vaccine would represent a “breakthrough,” says Volker Gerdts, director and CEO of VIDO-InterVac, the University of Saskatchewan’s international vaccine center, via phone.
“I think it will be possible to commercialize the vaccine.”
Previous attempts to create a vaccine used a modified version of the ASF virus, but the results were poor. Either the pigs weren’t well-protected and developed symptoms anyway, or the immunized animals spread so much viral material that they became dangerous to nonvaccinated pigs.
While more work is needed to see how the new vaccine performs in larger herds, Gerdts says the Plum Island work shows it might just be possible to make a safe and effective vaccine for ASF. If the results withstand further scrutiny and safety tests, a vaccine could still take a couple years before it’s ready for commercial use.
Chris Netherton, of the Pirbright Institute in the U.K., agrees that the early results are promising. He notes that the form of the virus created by deleting that single gene, I177L, is unlike previous mutant forms created by other researchers. This is because it triggers a strong immune response, preventing the complete ASF virus from being able to replicate in inoculated pigs.
“That’s why it’s so interesting,” says Netherton via phone.
Netherton is working on a different kind of ASF vaccine, which involves giving pigs a number of extracted proteins from the virus to see if this will make them immune to it. He says this hasn’t been quite as successful as the Plum Island group’s efforts so far.
ASF was first described in Kenya in 1921, but for much of the 20th century, scientists around the world failed to take the disease seriously, with the worst outbreaks confined to Africa.
“A lot of our folks here [in the United States] said this is really not an issue for us, this is an African issue, we don’t trade with Africa — you know, all this stuff,” says Daniel Rock, a former Plum Island Animal Disease Center scientist who is now a professor of pathobiology at the University of Illinois, Urbana-Champaign.
But the boom of ASF in China has been a “game-changer,” he adds, via phone. “African swine fever now is out of Africa forever. It’s an endemic disease in over half the world’s pig population.”
Gerdts adds, “What we’re seeing in Asia right now and how it affects domestic pigs in their herds, that is catastrophic. If we don’t come up with a vaccine for it, I can’t see how this thing eventually is going to go away.”