According to USP, the discovery indicates a new way for Sars-CoV-2 to interfere with the immune response and a potential source of transmission
Researchers from FMRP-USP (Faculty of Medicine of Ribeirão Preto, University of São Paulo) identified that respiratory viruses, including Sars-CoV-2, can remain and replicate in the tonsils, adenoids and secretions of children without symptoms of the disease or history of recent infection.
From the analysis of tonsils and adenoids surgically removed from 48 children aged 3 to 11 years, the researchers detected RNA and protein from the viruses in tonsils, nasal washes and respiratory secretions of children with tonsillar hypertrophy and without symptoms of respiratory diseases and Covid.
The results published in the magazine Microbiology Spectrum showed that different strains of the covid virus infected 1/4 of the children who participated in the study.
The discovery of the persistence of Sars-CoV-2 in the tonsils and adenoids, in addition to contributing to the understanding of covid, indicates a new way of interference of the virus in the immune response and a potential source of transmission of the disease to the community, even from of asymptomatic people.
The investigation had support from Fapesp (São Paulo State Research Support Foundation) through a broad study that seeks to understand the biology, pathogenesis and prospection of emerging viruses.
“We did not imagine finding so many viruses in the tonsils (tonsils and adenoids) taken from children who had no symptoms or history of respiratory infection. It is unusual to know that, in the same child, several persistent respiratory viruses can be detected and, among them, different strains of Sars-CoV-2″said Eurico Arruda, professor of virology at the college and author of the study.
“So, it is the virus from a cold from 6 months ago, together with another from a more recent infection, which are being collected in the tonsils”. The research had the collaboration of the otorhinolaryngology team at FMRP-USP, led by professor Fabiana Valera and Carolina Miura.
“However, it is also in the tonsils, as our study showed, where the Sars-CoV-2 virus is able to persist for longer, replicate and be secreted. The replication and potential transmission of covid-19, even in asymptomatic people, may indicate a new way for the virus to interfere with the immune response. This is because tonsils and adenoids are secondary organs of the lymphoid system, where defense cells such as lymphocytes, for example, act.”said Arruda.
Researchers believe that the infection of B and T lymphocytes, macrophages and dendritic cells by Sars-CoV-2 may interfere with the mounting of immune responses in these secondary lymphoid organs. “It was not possible, however, to identify how long the viruses persist in the tonsils analyzed”said Arruda.
Sars-CoV-2 RNA was detected by RT-qPCR (acronym in English for Reverse Transcription and Quantitative Polymerase Chain Reaction) in more than one sample from some of the children positive for the virus, with viral loads ranging from hundreds to thousands of copies per copy of messenger RNA for RNase-p (a normal ribonucleic acid in the cell, which alters transporter RNA molecules), suggesting that the children may have undergone tonsillectomy at different times post-infection.
The discovery reinforces the importance of vaccinating children.
“We showed that the virus persists in the tonsils, even in children who did not show any symptoms of respiratory infection. This highlights the importance of vaccination for this age group, which was the last to have the vaccine offered and has not yet achieved good coverage rates.”said Ronaldo Martins, author of the study.
It’s not just in children
Arruda stated that, although the study was carried out by analyzing children’s tonsils, the persistence of Sars-CoV-2 in these lymphoid organs is also observed in adults.
“This study was carried out on tonsils removed from children, as this is a much more common surgery in children than in adults. However, in another study, we were able to analyze tonsils taken from an adult, and the result was the same. Therefore, it is a finding that has the potential to change our understanding of the pathophysiology of Covid-19 and other respiratory diseases.”he stated.
“The unusual thing is the find itself. If these children can occasionally replicate and transmit the virus via secretions, they could become the focus of outbreaks.”said Arruda.
The researcher also stated that the finding reinforces the role of the tonsils in harboring a variety of viruses.
“The results of our study suggest that secondary lymphoid tissue is capable of harboring a much greater quantity of viruses. In our study we only tested respiratory viruses, and we did not test dengue, zika, chikungunya, yellow fever and other viruses, which may be persisting in these tissues”he said.
With information from Fapesp Agency.
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