Spanish researchers from the Sant Joan de Déu Research Institute and the International University of Catalonia (UIC Barcelona) have found a possible clue that would help clarify why the children are less likely to be infected with the SARS-CoV-2 coronavirus or develop severe COVID-19. The key would be in the soluble enzyme angiotensin-converting enzyme 2 (sACE2) present in the children’s salivawhich could have implications for infection prevention and control, according to the results of the study published in the journal Scientific Reports.
ACE2 (angiotensin-converting enzyme 2) is a protein found on the surface of cells in various tissues in the human body, including the lungs. When the virus responsible for COVID comes into contact with us, it binds to the ACE2 protein, allowing it to enter our cells, replicate, and trigger infection. In addition, ACE2 also has an important role in regulating blood pressure and inflammation in the body, factors that can impact the severity of COVID.
This enzyme is also found in its soluble form, sACE2, which is released in small amounts into the blood and other body fluids, such as saliva. Unlike the ACE2 enzyme found in tissues, sACE2 is not bound to the cell surface and is free to circulate. It is believed that sACE2 could play a protective role against SARS-CoV-2by binding to the virus and neutralizarlo before it can infect cells.
sACE2 levels in saliva that prevent coronavirus infection
The researchers analyzed data from a sample of families living together in confined homes during the spring of 2020 in the Barcelona metropolitan area, which included adults who had suffered a SARS-CoV-2 infection and their children under the age of 15 who lived with them. Study participants were tested for both sACE2 and SARS-CoV-2 using western blot and nasopharyngeal RT-PCR screening, respectively.
Saliva samples from 161 participants—both children and adults—were analyzed and found that 96.3% of the samples contained the soluble protein sACE2. In addition, different forms of the protein were identified in the saliva of infected adults and children, and in the saliva of uninfected children.
“Children who had not been infected by SARS-CoV-2 had a higher concentration of sACE2 in saliva samples than infected children and adults”
“We observed that children who had not been infected by SARS-CoV-2 had a higher concentration of sACE2 in saliva samples than infected children and adults,” explained the Dr. Carmen Muñoz, coordinator of the IRSJD’s ‘Infectious Diseases and Microbiome’ group and professor in the Department of Medicine at the UIC Barcelona. “This could be another one of the factors that explain why children presented milder symptoms”.
These findings suggest that the release of adequate concentrations of sACE2 in saliva could have a protective effect against SARS-CoV-2 and specifically, forms of the soluble protein have been identified that are found mainly in the saliva of children. According to the authors of the paper, it could be useful to investigate whether elevated levels of sACE2 can predict infection riskor if they can be used as biomarkers to identify people most susceptible to infection.
“The results of our study are promising and suggest that measurement of sACE2 levels in saliva could be a useful tool for identify people most at risk of COVID-19 infection. Still, we need more research to better understand the relationship between sACE2 levels and COVID-19 infection. Since possibly other variables such as age, gender, weight and other biological factors may influence the levels of sACE2 in saliva”, concludes the Dr. Pedro Brotonsresearcher at the IRSJD and also a professor in the Department of Medicine at UIC Barcelona.
Fuente: Sant Joan de Déu Research Institute