Spike proteins conjure up the controversy surrounding COVID-19 and mRNA vaccines, but the infamous spike protein isn’t just helpful in spreading viruses — it can be weaponized to help stop them.
Aphids, a longtime enemy of farmers and those who grow plants, are known for their ability to wreak havoc on plants. Their voracious appetites for sap not only cause damage to plants, but these tiny pests are a vector — or transmitters of disease, particularly impacting cash crops such as soy and cotton.
Researchers at the U.S. Department of Agriculture’s Agricultural Research Service have found a weapon against the aphids’ harmful effects within the very viruses that they spread.
This is where spike proteins come into play. The irregular shape not only plays a starring role in transmitting coronavirus but is critical to transmitting other viruses, including those that afflict crops.
Poleroviruses, in particular, infect many economically important crops, including those used in biofuel; they are also an emerging threat to cotton.
The secret to combatting those viruses, and others with similar traits, appear to be turning their own structure against them.
Michelle Heck, a research molecular biologist at the ARS Emerging Pests and Pathogens Research explained, “Using X-ray crystallography, we know what that spike protein looks like on that virus,” she said. “That was a major breakthrough because these viruses have been studied for a very long time, since the 1960s, and no one has been able to look at the structure.”
Heck likens the proteins of a virus to the engine of a car. When you put all the pieces of the engine on the floor, you can recognize some of their purposes, but when you open the hood of the car, you can see how everything works.
“When you solve the structure of a protein, it allows you to see how the protein machine works,” says Heck.
With that knowledge in hand, Heck and, Jennifer Wilson, a research molecular biologist at the ARS Corn, Soybean, and Wheat Quality Research in Ohio were able to devise an ingenious approach to preventing aphids from spreading the lethal plant viruses: they manufactured free spike proteins like the ones that normally appear on the surface of viruses, only this time, there was no virus — only the spike protein itself.
They then fed the loose proteins to aphids. Essentially, Heck explained, the free-floating proteins blocked the viruses from infecting aphids by binding with receptors in the aphids’ cells. Normally, when a virus infects an aphid, the spike proteins on the surface of the virus latch into place by binding to those receptors; with the receptors already occupied by the manufactured spike proteins, there is nothing for the virus spike proteins to latch on to.
The results were so significant that Heck, Wilson, and their team published a paper about them in Nature Communications, a leading scientific journal. They are, according to Heck, “revolutionary because there is no way to block the transmission of these viruses by aphids yet.”
This solution could dramatically reduce disease transmission and do so relatively safely compared to treatments like pesticides, which often have toxic side effects.
“The spike protein isn’t toxic,” said Heck. “It’s in the food supply because these viruses are ubiquitous. There are so many viruses related to this one; our analysis showed that this structure is probably the blueprint for this particular protein in all of these related viruses.”
This may be useful for combatting other crop-killing diseases as well.
And there’s more: in addition to preventing the aphids from spreading the viruses, Heck found that the loose spike proteins were highly lethal to the insects, opening up even more possibilities: “This could be used as a novel insecticide that also blocks transmission,” said Heck. “You get a 1-2 punch: in the aphids that you don’t kill, the transmission would be blocked.” The most promising route to deliver the spike proteins to aphids would likely be through crop plants themselves — by making, Heck said, “a transgenic plant expressing this spike protein.”
She noted that transgenic crops are accepted and used in some agricultural sectors. Two new graduate students in Heck’s laboratory, Stephanie Preising, and Michael West-Ortiz, are leading research to test ways in which transgenic plants can be used alongside non-transgenic plants to protect the non-transgenic plants from getting infected.
Like all novel solutions, the free spike proteins will be tested to ensure they would be safe before being used in any live applications. For now, though, Heck believes she has the beginnings of a powerful new tool against one of agriculture’s tiny but mighty, foes,” says Kathryn Markham, ARS Office of Communications.
