Asymptomatic SARS-CoV-2 Infection in Children's Tonsils

ABSTRACT

Introduction: The SARS-CoV-2 pandemic killed over 6 million people worldwide. Children were described to have predominantly mild or asymptomatic infections and to be less exposed to the virus, at least for the initial variants. In the present study, we describe how SARS-CoV-2 can silently infect tonsils and adenoids in children undergoing adenotonsillectomy. Method(s) In this cross-sectional study we assessed children who underwent adenotonsillectomy between October 2020 and September 2021 in a secondary hospital in Brazil. All the caregivers denied any symptom of acute viral upper airway infection in the month prior to surgery. Briefly, nasal cytobrush (NC), nasal wash (NW) and tonsillar tissue fragments posttonsillectomy were tested by RT-PCR, immunohistochemistry (IHC), in situ immunofluorescence (IF), and flow cytometry. Result(s) A total of 48 children (18 females, median age 5.5 years) were enrolled. None of them had been vaccinated against COVID-19 at the time of surgery. Only 2 had a history of previous COVID-19 diagnosis, 3 and 5 months, respectively, before surgery. SARS-CoV-2 RNA was detected in 25% (12) of patients-20% in palatine tonsils, 16.27% in the adenoids, 10.41% in NC, and 6.25% in NW. IHC labeling showed viral nucleoprotein presence in both adenoids and palatine tonsils, in epithelial surface and lymphoid cells from extrafollicular and follicular regions. In 5 out of 7 patients, in situ IF showed the expression of ACE2 and TMPRSS2 and viral spike protein in the tonsillar tissue. Flow cytometry revealed that SARS-CoV-2 is predominantly observed in CD123+ dendritic cells (10.57% of all tested sites), followed by CD14+ monocytes (6.32%). Conclusion(s) According to these results, the prevalence of SARS-CoV-2 infection seems to be higher than expected and underdiagnosed in children at this age group. Palatine tonsils and adenoids are important sites of infection and may be a reservoir for the virus. Nevertheless, it is still unclear the impact of these results on virus transmission.