Scientists have developed a method of using protein fragments to prevent the spread of orthotospoviruses, a widespread group of agricultural pathogens that are currently untreatable.

A patent application for this protein-driven approach was published March 11 by the U.S. Patent and Trademark Office. The method works by blocking transmission of viruses by thrips, which are small herbivorous insects.

"If you prevent the virus from returning to the thrips' mouth, you interrupt its transmission to plants," said inventor Ioannis Tzanetakis, a plant virology professor at University of Arkansas.

Orthotospoviruses cause wilting and spotting of the leaves and reduced vegetable yield, and eventually death to the plant. They impact both food and ornamental plants, and there is no treatment available for plants infected with these viruses. The only way to stop them from spreading is to remove and destroy infected plants.

These viruses are a growing threat to agriculture. While the economic impact of orthorospoviruses as a collective group has not been clearly determined, annual losses from the Tomato spotted wilt virus are estimated to be at least $1 billion. This is just one of more than 20 orthotospovirus species, and new ones are frequently emerging. Because they affect major food crops such as soybeans and tomatoes, these viruses also pose a threat to global food security.

The invention was discovered by chance while Tzanetakis and Jing Zhou, his Ph.D. student and co-inventor, were attempting to control transmission of the virus that causes vein necrosis in soybeans.

"It is the most prevalent virus of soybean in the U.S.," Tzanetakis said.

Instead of stopping just one virus, the team stumbled on a much more general technique that could potentially be applicable to all orthotospoviruses, a group that contains dozens of pathogens affecting hundreds of plants. But as of now, the method has only been tested in soybeans.

While its ultimate target is the viruses, the treatment works primarily on thrips, which ingest the virus when feeding on infected plants and then spread it to other plants.

In a related 2019 study in the Journal of General Virology, Tzanetakis and his team fed thrips several polypeptides that had been determined to be involved in the attachment of the virus to the thrips. The peptides bound to receptors in the thrips' cells, interrupting the virus and reducing transmission by two-thirds.

"It's a keylock approach," Tzanetakis said. "If you already have a key in the lock, the virus can't get his key in there."

While the polypeptides have shown great potential to reduce transmission of these viruses to plants, the invention is in the very early stages. The pending patent includes the polypeptides themselves, which could be formulated into a biopesticide that would be applied to plants. It also includes transgenic soybean plants, or plants that have been genetically modified to produce the polypeptides. 

Either of these delivery methods could prevent the spread of viruses, but which ends up seeing large-scale commercial production will depend on feasibility.

"I think probably a transgenic approach would be better for this one because those peptides are fairly expensive to manufacture," said Tzanetakis.

It's unlikely the average consumer will be purchasing a can of these polypeptides for their backyard garden any time soon. The invention is expected to be more applicable on a large industrial scale.

And while there is still a lot to learn about how to use these polypeptides in a variety of plants, the inventors are optimistic that their work will one day create a formulation that can block many viruses at once.

"It will take a lot more research to determine what's going on," Tzanetakis said. "But the results imply that that this may be a generic way to target multiple disease-causing viruses."

The application for the patent, "Peptides that Block Transmission of Orthotospoviruses and Methods of Using the Same," was filed June 26, 2020 to the United States Patent and Trademark Office. It was published March 11, 2021 with the application number US2021071196. The earliest priority date was June 26, 2019. The inventors of the pending patent are Ioannis Tzanetakis and Jing Zhou, University of Arkansas System. The assignee is the Board of Trustees of the University of Arkansas.