The new coronavirus infects and replicates in the cells of the salivary glands

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A study conducted at the University of São Paulo suggests that tissues specializing in the production and secretion of saliva serve as reservoirs for SARS-CoV-2, increasing its infectious potential (electron microscope image showing the new coronavirus inside of the salivary glands (credit: Bruno Matuck / USP)

In Brazil, researchers at the Faculty of Medicine of the University of São Paulo (FM-USP) have found that SARS-CoV-2 infects and replicates in the salivary glands.

Analysis of samples of three types of salivary gland obtained during a minimally invasive autopsy procedure performed on patients who died of COVID-19 complications at Hospital das Clínicas, the FM-USP hospital complex, showed that tissues specialized in the production and secretion of saliva serve as reservoirs. for the coronavirus novel.

FAPESP supported the study and it was reported in an article published in the journal Journal of Pathology.

The researchers said the discovery helps explain why the virus is so abundant in saliva and has allowed scientists to develop diagnostic tests based on the saliva of COVID-19.

“This is the first report on the ability of a respiratory virus to infect and replicate in the salivary glands. Until now it was thought that only viruses that caused highly prevalent diseases such as herpes used salivary glands as reservoirs. discovery may help explain why SARS-CoV -2 is so contagious, “said Bruno Fernandes Matuck, a PhD. candidate for the USP Dental School and first author of the article, told Agência FAPESP.

A previous study by the same group had already shown the presence of SARS-CoV-2 RNA in the periodontal tissue of patients who died of COVID-19.

Because SARS-CoV-2 is highly infectious compared to other respiratory viruses, they hypothesized that it may replicate in salivary gland cells and therefore be present in saliva without coming into contact with nasal and pulmonary secretions. Previous research detected ACE2 receptors in salivary gland ducts. The SARS-CoV-2 peak protein binds to ACE2 in order to invade and infect cells. More recently, other research groups have conducted animal studies showing that other receptors, apart from ACE2, such as transmembrane protease serine 2 (TMPRSS2) and furin, both present in the salivary glands, are targets of SARS-CoV-2.

To test this hypothesis in humans, ultrasound-guided autopsies were performed on 24 patients who died of COVID-19, with a mean age of 53 years, to extract tissue samples from the parotids, submandibular, and minor salivary glands.

He underwent molecular analysis (RT-PCR), which detected the presence of the virus in more than two-thirds. Immunohistochemistry, a form of immunostaining in which antibodies bind to the antigen in the tissue sample, activates a dye and the antigen can be seen under a microscope, also demonstrated the presence of the virus in the tissue. Finally, examination under an electron microscope detected not only the presence of the virus, but also its replication in the cells and the type of organelle it uses to replicate.

“We observed several viruses clustered in saliva cells, which proved to replicate. They weren’t passively in those cells, ”Matuck said.

The mouth as a direct point of entry

Researchers now plan to see if the mouth can be a direct entry point for SARS-CoV-2, since ACE2 and TMPRSS2 are found in various parts of the cavity, as well as in the gum tissue and oral mucosa. . In addition, the mouth has a larger contact area than the nasal cavity, which is widely considered the main route of entry for the virus.

“We will partner with researchers at the University of North Carolina in the United States to map the distribution of these receptors in the mouth and quantify them. in oral tissues, ”said Luiz Fernando Ferraz da Silva, professor at FM-USP and principal investigator of the project.

“The mouth could be a viable medium for the to enter the body directly, ”Matuck said.

Another idea is to find out if older people have more ACE2 receptors in their mouths than younger ones, given the decrease in salivary secretion with age. However, the researchers found a high viral load even in elderly patients, who have less salivary tissue.

“These patients had almost no salivary tissue, almost just fat . Still, the viral load was relatively high, “Matuck said.


Scientists find evidence that the new coronavirus infects the cells in the mouth


More information:
Bruno Fernandes Matuck et al, Salivary glands are a target of SARS – CoV – 2: a source of saliva contamination, The Journal of Pathology (2021). DOI: 10.1002 / path.5679

Citation: New coronavirus infects and replicates salivary gland cells (2021, July 7) recovered July 7, 2021 at https://medicalxpress.com/news/2021-07-coronavirus-infects-replicates -salivary-gland.html

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