According to a preliminary study, the SARS-CoV-2 coronavirus can infect cells in the mouth, which could promote the spread of the virus both in the body and to others, according to a preliminary study. .
In the new study, published October 27 on the pre-printed medRxiv database, the researchers predicted which oral tissue was most likely to be most vulnerable to SARS-CoV-2, the virus that causes. COVID-19. So the team tested RNA – a genetic material that tells the cell’s protein factories what to build – for the different types of cells in the mouth. They found that, compared to other oral tissues, the cells of the salivary glands, tongue, and tonsils carry the most RNA that binds to proteins that the coronavirus needs to infect cells. Specifically, they include the ACE2 receptor, where the virus plugs in, and an enzyme called TMPRSS, which allows the virus to fuse its membrane with that of the host cell and slide inside.
The researchers continued to take saliva samples from the COVID-19 patient and found that, since the mouth cells shed in our saliva, they were able to detect the infected cells floating around. in the sample. The more viruses they find, the more likely a patient has loss of smell and loss of taste as one of their symptoms, although the saliva of some asymptomatic people also contains cells. infected. Additionally, the team examined oral tissue of deceased COVID-19 patients, and they found more evidence of infection in the vulnerable cell types they flagged.
“Our research shows that the mouth is an infectious pathway as well as an incubator for the SARS-CoV-2 virus that causes COVID-19,” said Dr. Kevin Byrd, a research scholar and manager of The Oral and Skull Study at the American Academy of Dental Research and Science Association, told Live Science in an email.
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Theoretically, a SARS-CoV-2 infection in the mouth could cause changes in saliva production or quality, contributing to symptoms of loss of taste, he said. Future research may reveal how this oral infection affects disease course in COVID-19 patients, as well as how those infected cells contribute to the spread of coronavirus between humans. .
“Seeing the presence of the virus in the salivary glands, I think that’s what,” said Dr. Alessandro Villa, assistant professor and head of Sol Silverman Oral Medicine Clinic at the University of California, San Francisco. new. while studying. “It is interesting to me as a clinician.”
That said, the study looked at only a few dozen people, Villa said. “The number is definitely small, so it will be interesting to see what happens if you look at more patients and more tissue,” he said.
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Thankfully, the study authors helped create a tool that could make future studies of oral infections easier. Specifically, they created a map of different cells in the mouth that essentially serves as a map of what and where the cells contain RNA. Byrd and his co-author, Dr. Blake Warner, a clinical investigation assistant in the Saliva Disorders Unit at the National Institute of Oral and Dental Research, an affiliate of the National Institutes of Health, worked with an organization called Human Cell Atlas to organize and refine data.
“This new atlas provided us with a way to analyze 50 types of oral cells … at the same time for the ‘front doors’ that viruses use to enter cells to infect cells,” Byrd said. . The atlas helped them pinpoint the cells most at risk for SARS-CoV-2 infection, and then the team tested their work on saliva samples and cadaveric tissue of patient.
While the study presents a convincing case that SARS-CoV-2 infects cells in the mouth, a number of questions remain unanswered.
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First, research is unable to show how much of the virus found in saliva actually comes from infected mouth cells. It’s possible that some of the virus originated elsewhere, such as the nose or lungs, Byrd said. “We have, however, found that these undervalued but widely distributed salivary glands” – the so-called tiny salivary glands – “can produce viruses of their own after being infected,” he said. infection”. The team confirmed this by examining the coronavirus RNA levels in cells using PCR, a type of test commonly used to detect and diagnose COVID-19, as well as a technique. The so-called in situ hybrid also detects genetic material.
“We hypothesize this is the main source of the virus in saliva,” Byrd told Live Science. This should be confirmed in more patients with COVID-19.
In addition, we still do not know how the function of the salivary glands changes after infection with coronavirus. “If saliva production is somehow compromised, one can speculate that one may experience alterations in taste or taste loss,” because saliva carries molecules to the taste receptors. tongue, Villa said. “Again, that’s a theory,” Villa said. SARS-CoV-2 infection in the mouth may also contribute to other symptoms, such as dry mouth and blistering in mucous membranes, the study authors wrote.
A better understanding of how coronavirus infects oral cells, at the molecular level, could help improve treatments for patients with these symptoms, Byrd said. Several clinical trials are also investigating whether mouthwash can help prevent or treat COVID-19 infection; According to ClinicalTrials.gov, the UCSF researchers plan to conduct such an experiment and Villa is working with another team to organize an additional trial of several types of washers, he told Live Science.
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Meanwhile, new research raises an important point: People without symptoms can carry a lot of the virus in their saliva. In the two asymptomatic people included in the study, the virus was found in their saliva 14 days after the first positive test, even though they tested negative for the virus in the nose and throat at that time. The study does not address whether the detected virus still exists, meaning it can infect cells.
“This study highlights the importance of public health measures we know are effective – masks, away from society and hand washing – whether you have symptoms or not,” Byrd said. As to how oral infection fits into the big picture of COVID-19, “there’s a lot to learn about where SARS-CoV-2 started, travels in our bodies and is eventually eliminated” he said.
Originally published on Live Science.