Chewing gum mixed with a particular protein could be a low-cost way to help prevent the spread of the virus behind COVID-19, a recent study suggests.

The angiotensin-converting enzyme 2 (ACE2) protein, found on the surface of many human cells, acts as a gateway for the virus to infect them. If delivered to the mouth by chewing gum, however, ACE2 could instead trap the virus by binding to the spike protein it uses to infect cells. The protein in the gum could also bind to receptors on cells themselves, thereby blocking infection sites. This combination could prevent viruses from infecting cells in the oral cavity, researchers report in Molecular Therapy.

SARS-CoV-2, the virus that causes COVID-19, typically first infects human cells in the nose and throat. But the mouth is also a key reservoir of the virus in an infected person, scientists have found. The new study contends that inactivating the virus in the mouth’s mucous membranes and saliva could reduce infection in the adjoining nasopharyngeal area, too. If additional research bears out these findings, the gum might join face masks and hand sanitizer in the anti-COVID arsenal.

To study this strategy, a team led by University of Pennsylvania pharmaceutical researcher Henry Daniell genetically modified lettuce plants to produce a soluble form of ACE2 (which has been proved safe at high dosages in animals). The lettuce was then powdered and blended with cinnamon-flavored chewing gum.

The researchers tested the protein’s effectiveness in hamster cells modified to produce human ACE2 receptors. They found that a relatively small quantity of the protein, coming from the gum, was associated with a 95 percent reduction in the amount of cell penetration by a stand-in virus equipped with SARS-CoV-2 spike proteins. The amount of a similar stand-in virus inside unmodified monkey cells also dropped by 85 percent when exposed to the protein. Adding the gum to saliva samples and swabs of nasal and throat fluid from a handful of people infected with SARS-CoV-2 was associated with a more than 95 percent reduction in the virus amount.

Daniell says his team is awaiting approval from the U.S. Food and Drug Administration to test the gum’s effectiveness in humans. Testing with a chewing machine suggests the protein would be released over 10 minutes, and Daniell estimates protection would last four hours. He is also testing the chewing-gum approach against influenza.

A key consideration is whether this strategy works if infection first occurs outside the mouth. “The main entry route for COVID-19 is the nose,” says immunologist Danny Altmann of Imperial College London, who was not involved in the new study. “And the gum may have little effect at stopping the virus entering from that opening—unless it is found that it provides protection at the back of the throat.”

Even if the gum does not fully defend a chewer against infection, it might reduce spread by cutting down the amount of virus in an infected person’s mouth and thus reducing how much is available for transmission, says University of Leicester virologist Julian Tang, who also was not involved in the study.

In a best-case scenario, COVID-busting gum could be on store shelves in about six months, Daniell says. And one day four out of five doctors might recommend virus-busting gum for their patients.