TB and malaria drugs could hold key to fighting African swine fever, Chinese scientists say

Stephen Chen

Drugs developed to fight tuberculosis or malaria could help fight African swine fever, according to China’s top viral research agencies.

There is currently no cure for swine fever, which has devastated China’s domestic herds and caused a 70 per cent rise in pork prices due to the resulting shortages.

Since the first reported detection of the virus last summer, more than 1 million pigs have been culled, according to the Chinese government’s statistics.

Now the pandemic has spread to farms in every province and region, while 50 other countries have reported outbreaks, according the UN Food and Agriculture Organisation.

But the latest research suggests that the African swine fever virus has a critical structure that is similar to the microorganisms that cause malaria and TB in humans.

Drugs targeting these structures have already been developed for those diseases and they may hold the key to fighting African swine fever as well, according to a paper published in the journal mBio last week.

The new study, led by virology professor Gao Fu from the Chinese Centre for Disease Control and Prevention in Beijing, examines an enzyme that protects the DNA of the virus.

The E165R enzyme is a protein that can prevent and correct mistakes in the copying of genetic information – so if a drug can be developed to disable it, the virus will perish.

The problem is that similar enzymes can be found in many live forms and no one knew its exact structure in the viral strain of African swine fever.

Gao’s team painstakingly separated the protein from the virus. They then crystallised it with a special mixture of chemicals to make its three-dimensional structure sharper.

Using a high-definition electron microscope, they were able to study in detail the enzyme’s “active site”, where critical activities such as chemical reactions and molecular binding take place.

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Crucially, they discovered that its structure is almost identical to those that have been found in the bacteria or parasites that cause tuberculosis and malaria.

The chemicals that had been designed to inhibit the two human diseases “may also be effective for inhibiting E165R … activity or could serve as lead compounds for designing novel anti-[swine fever] drugs”, Gao’s team reported.

The study is not the only swine fever breakthrough made by Chinese scientists in recent months.

A separate team from the Chinese Academy of Sciences and Harbin Veterinary Research Institute published results in Science magazine last month revealing the overall structure of the virus in unprecedented detail, which has helped to develop a vaccine that remains to be tested.

The Chinese government also held a closed-door meeting with scientists and researchers from all over the world in Beijing last month.

One of the other possible treatments discussed was the use of herbal medicines that might increase pigs’ chances of survival and a safety evaluation of various vaccines that have been designed for use on humans.

But there was no solution that could be applied immediately on a mass scale, according to a senior scientist who took part in the meeting.

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The herbal medicine, for example, may work but is expensive, while the safety and effectiveness of the vaccines is as yet uncertain.

“We need to prepare for a long-term battle,” said the scientist who requested not to be named due to the sensitivity of the issue.

While the disease cannot be transmitted to humans it is deadly for pigs and the virus will not be an easy target.

In the 1960s, half a million pigs in Spain and Portugal were given an experimental vaccine that had proved effective in the laboratory.

It turned into a disaster.

About a quarter of the pigs became seriously ill or died from painful side effects including pneumonia. Part of the reason was that the scientists had underestimated the virus’s destructive power.

The African swine fever virus is a giant compared with other viruses and also has an extremely complex structure.

This means that the virus has more lines of defences against drugs, and can bypass immune systems through mutation.

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