BREAKING COVID-19 NEWS! Brazilian Researchers Find That Tonsils Are Major Sites Of SARS-CoV-2 Viral Persistence In Children!
: In a new study conducted by researchers at the University of São Paulo School of Medicine in Brazil, a startling revelation has emerged - tonsils, those seemingly innocuous lymphoid tissues located at the back of the throat, have been identified as major sites of SARS-CoV-2 viral persistence in children. This discovery not only sheds light on the mysterious nature of the virus but also raises crucial questions about the implications for children's health, potential transmission, and diagnostic challenges.
Already numerous studies and past COVID-19 News
coverages had shown that even asymptomatic COVID-19 infected children were actively spreading the SARS-CoV-2 virus and this study findings could help explain that phenomena.
The Study's Background
The study, conducted between October 2020 and September 2021, examined 48 children undergoing tonsillectomy for various reasons, including snoring/OSA (obstructive sleep apnea) and recurrent tonsillitis. What sets this study apart is that these children displayed no symptoms of COVID-19 and had no recent history of upper airway infections. Researchers utilized a battery of scientific techniques, including RT-qPCR, immunohistochemistry (IHC), flow cytometry, and neutralization assays, to probe for the presence of SARS-CoV-2 in nasal cytobrushes, nasal washes, and tonsillar tissue fragments.
The Shocking Findings
The results of the study were nothing short of startling. SARS-CoV-2 was detected in at least one specimen in 27% of the patients. What's even more intriguing is that immunohistochemistry revealed the presence of the viral nucleoprotein not only in epithelial surface cells but also in lymphoid cells located in both extrafollicular and follicular regions of adenoids and palatine tonsils. This suggests that SARS-CoV-2 can persist within these lymphoid tissues.
Even more concerning was the discovery that 53.8% of the SARS-CoV-2-infected tissues exhibited indications of viral replication. This was evident through the presence of the non-structural protein NSP-16, a critical component in the process of viral RNA capping, a crucial step for viral replication. This finding implies that the virus was actively replicating within the tonsils of these seemingly asymptomatic children.
The Cellular Targets of Infection
The study delved even further, identifying the specific cell types within the tonsils that SARS-CoV-2 was targeting. Flow cytometry revealed that CD20+ B lymphocytes were the most commonly infected cell type, followed by CD4+ lymphocytes and CD123 dendritic cells, CD8+ T lymphocytes, and CD14+ macrophages. This broad spectrum of cell types infected by SARS-CoV-2 in tonsils raises important questions about the impact on the immune system's functionality within these secondary lymphoid organs.
The Role of ACE2 and TMPRSS2
The study also unveiled higher expressions of ACE2 and TMPRSS2, two key proteins known to facilitate SARS-CoV-2 entry into host cells, in SARS-CoV-2-infected tonsils. This discovery suggests that the tonsillar infection
may lead to increased expression of these entry receptors, making children more susceptible to SARS-CoV-2 infection in these lymphoid tissues. Additionally, the study found that SARS-CoV-2 antigen was not limited to tonsils alone but was also detected in nasal cells within the olfactory region, further highlighting the virus's capacity for persistent infection in various upper respiratory tract tissues.
Implications for SARS-CoV-2 Pathogenesis
The implications of these findings are profound. Firstly, it indicates that SARS-CoV-2, in its various lineages, can infect tonsils and adenoids in a significant proportion of children undergoing tonsillectomy. This challenges the prevailing understanding of COVID-19 primarily affecting the lower respiratory tract, highlighting the importance of upper respiratory tract tissues, especially in children.
Moreover, the fact that tonsils may serve as sites of prolonged infection, even in the absence of COVID-19 symptoms, raises questions about the potential consequences. The infection of B and T lymphocytes, dendritic cells, and macrophages within these lymphoid organs could potentially disrupt the immune response, impairing the body's ability to mount an effective defense against the virus.
The Silent Spread and Diagnostic Confusion
One of the most concerning aspects of this discovery is the silent spread of SARS-CoV-2 in children. Many of the children studied had no clear symptomatic phase, making them asymptomatic carriers. This is consistent with previous reports suggesting that children are more likely than adults to have mild or asymptomatic SARS-CoV-2 infections. However, the asymptomatic shedding of SARS-CoV-2 in respiratory secretions from these children presents a considerable challenge. It not only poses a risk of transmission within schools and households but also raises concerns about diagnostic confusion when symptoms of acute respiratory infections occur due to other viral causes.
The Unknowns and Future Directions
Several questions remain unanswered. The study did not determine the initial exposure time to SARS-CoV-2 for these children, and most lacked a clear symptomatic phase. Additionally, the study did not assess virus-specific CD8+ T cell responses, which may play a role in SARS-CoV-2 persistence. The long-term impact of SARS-CoV-2 infection on lymphocytes and antigenic specificities in secondary lymphoid organs remains unknown.
In conclusion, the discovery that tonsils can harbor SARS-CoV-2, even in asymptomatic children, adds a new layer of complexity to our understanding of the virus's pathogenesis. It highlights the potential role of hypertrophic tonsils as sites of persistent infection, possibly involving ongoing viral activity. The presence of various SARS-CoV-2 lineages in tonsils suggests that this tropism is not limited to specific viral strains.
These findings underscore the importance of continued research into the impact of SARS-CoV-2 on the immune system and the potential consequences of persistent infection in children. It is crucial to further investigate the immunoinflammatory consequences of SARS-CoV-2 infection in lymphoid tissues and to explore the long-term effects on children's health.
As the COVID-19 pandemic continues to evolve, studies like this one remind us that there is still much to learn about the virus and its interactions with the human body. It is imperative that we remain vigilant, continue to conduct rigorous research, and adapt our strategies to combat this formidable adversary.
The study findings were published in the peer reviewed journal: Microbiology Spectrum.
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