Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), the causative agent of the current coronavirus disease 2019 (COVID-19) pandemic, causes respiratory infection in people of all ages.
Compared to adults, children are less frequently and severely affected by SARS-CoV-2. Although the exact reason for this is unclear, reduced expression of angiotensin converting enzyme receptor 2 (ACE2) and transmembrane serine protease 2 (TMPRSS2) in the airways of children might be a contributing factor.
To study: Tonsils are major sites of prolonged SARS-CoV-2 infection in children. Image Credit: Andrey_Popov / Shutterstock.com
Fond
Previous research has shown the presence of important respiratory viruses, including endemic coronaviruses, in the tonsils and adenoids of patients with chronic tonsillar disease. However, at the time of analysis, these patients had no recent symptomatic respiratory tract infections.
Additionally, the tonsils have been reported as sites of asymptomatic infections with respiratory viruses. In view of these results, a recent study published on the medRxiv* The preprint server assessed the presence of SARS-CoV-2 in children’s tonsils during the COVID-19 pandemic.
About the study
The current cross-sectional study was conducted between October 2020 and September 2021 at the University of São Paulo. Children aged 3 to 11 years with recurrent tonsillitis or obstructive sleep apnea who had undergone adenoidectomy or tonsillectomy were included in the study.
At the time of this survey, none of the children in Brazil had been vaccinated once morest COVID-19. Children with craniofacial malformations, immunodeficiencies, deposition diseases, suspected tonsil cancer and genetic syndromes were excluded from the study.
Clinicians obtained several specimens, such as bilateral nasal lavage, bilateral cytobrush from the olfactory area, peripheral blood for serological testing, and adenoid and palatine tonsil tissue, during participants’ surgery.
Study results
A total of 48 children (30 boys and 18 girls) participated in this study, of which 57.2% were Caucasian. The average age of the participants was 5.9 years.
About 50% of patients had no associated diseases; however, the remaining 50% of the cohort had previously been diagnosed with allergic rhinitis, recurrent otitis media, or mild asthma.
The patients’ parents said that none of their children had been treated with antibiotics for an average of 9.2 months before their surgery.
About 17% of the cohort were exposed to SARS-CoV-2 in their households forty days to six months before surgery. Additionally, two patients confirmed previous SARS-CoV-2 infection, while one patient lost his sense of smell and taste a month before surgery but tested negative for COVID-19 through the reaction test. polymerase chain (PCR). According to parents/guardians, the last acute upper respiratory tract infection requiring antibiotics occurred 1 to 24 (mean 9.2) months before surgery.
SARS-CoV-2 was identified in the upper respiratory tract samples of 25% of the tonsillectomy cohort, not all of whom reported a recent history of COVID-19. The authors were unable to determine the time of initial exposure to COVID-19.
SARS-CoV-2 genetic material was detected using quantitative reverse transcription PCR (qRT-PCR) in three samples from children with confirmed COVID-19. Because viral load varied widely from hundreds to thousands of copies per microgram of ribonucleic acid (RNA), the authors assumed that the participants underwent tonsillectomy at different times following infection.
However, the timing of exposure to COVID-19 remained unknown and most children were asymptomatic. The absence of this information prevented the authors from establishing an association between the duration of infection and viral loads at the time of tonsillectomy.
Serological analysis revealed that five out of twelve children were immunoglobulin G (IgG) positive; however, none were IgM-positive for COVID-19.
The presence of viral structural proteins was detected in the palatine tonsils and the adenoids, in particular in the lymphomononnuclear and epithelial cells of the different lymphoid compartments. Interestingly, two children in whom SARS-CoV-2 was detected in their tonsils also showed the presence of SARS-CoV-2 protein in cells in the olfactory region.
Through flow cytometry analysis, the SARS-CoV-2 antigen was identified in major tonsillar mononuclear cell (TMNC) types, including dendritic cells, macrophages, and B and T lymphocytes. -CoV-2 was detected in these cells and since infection of monocytes triggers inflammasomes, the authors hypothesized that SARS-CoV-2 infected cells in the tonsils would increase inflammation in previously inflamed tissues chronically.
Generally, ACE2 and TMPRSS2 proteins are highly expressed in the upper respiratory tract. The current study found higher expressions of these proteins in SARS-CoV-2 infected tonsils, suggesting that tonsil infection with COVID-19 promotes enhanced expression of ACE2 and TMPRSS2.
conclusion
The tonsils and olfactory epithelium might be sources of viral shedding in the nasal washes of asymptomatic COVID-19 children, which likely enabled these children to promote viral transmission in the community. In addition to epithelial cells, all major lymphomononnuclear cell types have been shown to harbor SARS-CoV-2.
Taken together, the present study revealed the presence of SARS-CoV-2 RNA and proteins in the nasal cytobrushes, tonsils and respiratory secretions of children with tonsillar hypertrophy, without exhibiting symptoms of COVID-19 .
*They import birds
medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be considered conclusive, guide clinical practice/health-related behaviors, or treated as established information.
