In Brazil, researchers at the University of Sao Paulo School of Medicine (FM-USP) have discovered that SARS-CoV-2 infects and replicates the salivary glands.
Analysis of samples from three salivary glands obtained during a minimally invasive autopsy procedure performed on patients who died of COVID-19 complications at the FM-USP hospital complex Hospital Das Clinicas , Showed that tissues specialized in saliva production and secretion function as reservoirs. For the new coronavirus.
This study is supported by FAPESP Pathology Journal..
Researchers said the findings helped explain why the virus is so abundant in saliva and allowed scientists to develop saliva-based diagnostic tests for COVID-19.
“This is the first report of the ability of respiratory viruses to infect and replicate salivary glands. To date, it is believed that only viruses that cause highly prevalent diseases, such as herpes, used salivary glands as reservoirs. This finding may help explain the reason for SARS-CoV. -2 is highly infectious. ” He told Agência FAPESP that he was a candidate for a USP dental school and the first author of the article.
Previous studies by the same group have already demonstrated the presence of RNA from SARS-CoV-2 in periodontal tissue. Patients who died of COVID-19..
The hypothesis that SARS-CoV-2 is more infectious than other respiratory viruses, so it may replicate in salivary gland cells and be present in saliva without contact with nasal or lung secretions. I set it up. In a previous study, the ACE2 receptor was detected in the salivary gland duct. The SARS-CoV-2 spike protein binds to ACE2 to invade and infect cells. Recently, other research groups have conducted studies in animals and have shown that other receptors other than ACE2, such as transmembrane serine protease 2 (TMPRSS2) and furin, present in salivary glands are targets for SARS-CoV-2. I will.
To test this hypothesis in humans, ultrasound-guided autopsy was performed on 24 patients with an average age of 53 years who died of COVID-19 and tissue samples were taken from the parotid, submandibular, and minor salivary glands. I extracted it.
The· Tissue sample It was subjected to molecular analysis (RT-PCR) and the presence of the virus was detected in more than two-thirds. Immunohistochemistry (a form of immunostaining in which the antibody binds to the antigen in the tissue sample, the pigment is activated, and then the antigen can be seen under a microscope) also showed the presence of the virus in the tissue. .. Finally, electron microscopy detected not only the presence of the virus, but also the replication of the virus inside the cell and the type of organelle used for replication.
“I observed some viruses gathering in my saliva. Gland The cells showed that they were replicating there. They were passively absent from these cells, “Mattac said.
Mouth as a direct entrance
Given that ACE2 and TMPRSS2 are found not only in the gingival tissue and oral mucosa, but also in various parts of the cavity, researchers are now wondering if the mouth can be a direct entry point for SARS-CoV-2. I am planning to confirm. In addition, the mouth has a larger contact area than the nasal cavity, which is widely considered the main method of virus.
“We will work with researchers at the University of North Carolina in the United States to map and quantify the oral distribution of these receptors. Virus replication In oral tissue. ” Luis Fernando Ferraz da Silva, a professor at FM-USP and a senior researcher at the project, said.
“The mouth is Virus It goes directly into the body. “
Another idea is to find out if older people have more ACE2 receptors in their mouth than younger people, given that salivation decreases with age. Nonetheless, researchers have found high viral load even in older patients with low salivary tissue.
“These patients had little salivary tissue, only fat. Organization.. Still, the viral load was relatively high. ”
For more information:
Bruno Fernandes Matuck et al, Salivary Glands are Targets of SARS-CoV-2: Causes of Salivary Contamination, Pathology Journal (2021). DOI: 10.1002 / path.5679