Spanish researchers from the Institut de Recerca Sant Joan de Déu and the Universitat Internacional de Catalunya (UIC Barcelona) have found a possible clue that would help clarify why children are less likely to be infected with the SARS-CoV-2 coronavirus or to develop a COVID -19 severe. The key would be in the soluble enzyme angiotensin-converting enzyme 2 (sACE2) present in children’s saliva, which 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 in 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 thought that sACE2 could play a protective role against SARS-CoV-2, by binding to the virus and neutralizing it 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 Dr. Carmen Muñoz, coordinator of the ‘Infectious Diseases’ group. and Microbiome’ of the IRSJD and professor and professor of the Department of Medicine of the UIC Barcelona. “This could be another of the factors that explains why the 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 mainly found in the saliva of children. According to the authors of the work, it could be useful to investigate whether elevated levels of sACE2 can predict the risk of infection, or if they can be used as biomarkers to identify people who are more susceptible to infection.
“The results of our study are promising and suggest that measuring sACE2 levels in saliva could be a useful tool to identify people at higher risk of COVID-19 infection. Still, we need more research to better understand the relationship between sACE2 levels and COVID-19 infection. Since other variables such as age, gender, weight and other biological factors may possibly influence the levels of sACE2 in saliva”, concludes Dr. Pedro Brotons, IRSJD researcher and also professor in the Department of Medicine at UIC Barcelona .
Source: Sant Joan de Déu Research Institute
