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1/ Growing research demonstrating importance of protective T-cells against SARS-CoV-2 combined w/ prior research on influenza viruses suggest that nasal mucosa T-cells may explain the rising number of "positive" PCR tests while deaths & hospitalizations remain low.
Here's why.
Here's why.
2/ We know a large percentage of the uninfected population already possess T-cells in the blood that recognize SARS-CoV-2.
It seems likely our nasal mucosa also possess these protective T-cells considering airborne spread of common cold coronaviruses. https://twitter.com/JamesTodaroMD/status/1292873236716433416?s=20
It seems likely our nasal mucosa also possess these protective T-cells considering airborne spread of common cold coronaviruses. https://twitter.com/JamesTodaroMD/status/1292873236716433416?s=20
3/ Substantial research on influenza viruses shows conditioned T-cells in the nasal mucosa is associated with rapid viral clearance and decreased transmission to the lungs upon reinfection.
https://www.jimmunol.org/content/167/6/3293
https://www.pnas.org/content/114/20/5225 https://immunology.sciencemag.org/content/2/12/eaam6970
https://www.jimmunol.org/content/167/6/3293
https://www.pnas.org/content/114/20/5225 https://immunology.sciencemag.org/content/2/12/eaam6970
4/ In a study from 2018, mice intranasally infected with a general coronavirus resulted in significantly decreased mortality upon subsequent exposure to SARS-CoV-1 (from 100% to 0%).
The authors attribute this to a protective T-cell response. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6124400/
The authors attribute this to a protective T-cell response. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6124400/
5/ Similarly, for SARS-CoV-2, our nasal mucosa may have protective T-cells from prior exposure to common cold coronaviruses.
These protective T-cells may not stop you from testing "positive", but may protect against symptoms and disease transmission.
I'll explain.
These protective T-cells may not stop you from testing "positive", but may protect against symptoms and disease transmission.
I'll explain.
6/ We now know that up to 90% of people with a "positive" PCR test may not actually be infectious.
The PCR test commonly used during this pandemic is too sensitive...meaning it is detecting a tiny amount of viral particles/fragments. https://www.nytimes.com/2020/08/29/health/coronavirus-testing.html
The PCR test commonly used during this pandemic is too sensitive...meaning it is detecting a tiny amount of viral particles/fragments. https://www.nytimes.com/2020/08/29/health/coronavirus-testing.html
7/ Protective nasal mucosa T-cells in these individuals may be the key to keeping viral loads very low.
That is, while T-cells are killing infected cells, there's enough virus present for a positive PCR test, but not enough present to result in symptoms or disease transmission.
That is, while T-cells are killing infected cells, there's enough virus present for a positive PCR test, but not enough present to result in symptoms or disease transmission.
8/ This has obvious implications on herd immunity.
If a substantial percent of the population already has protective T-cells, then the number of people vulnerable to COVID-19 drops dramatically.
This could explain why we see rising "cases", but few deaths and hospitalizations.
If a substantial percent of the population already has protective T-cells, then the number of people vulnerable to COVID-19 drops dramatically.
This could explain why we see rising "cases", but few deaths and hospitalizations.
9/ Furthermore, Sweden has been in a steady state of about 200 new positive COVID-19 cases a day since July despite reopening without masks.
Perhaps, through a swift spread of COVID-19, the vast majority of Sweden now have protective T-cells limiting viral spread and morbidity.
Perhaps, through a swift spread of COVID-19, the vast majority of Sweden now have protective T-cells limiting viral spread and morbidity.
10/ This area of research certainly needs to be explored further.
It is important, however, to not limit the scope of this research in terms of vaccine development, but to also assess in the context of natural herd immunity—which may already be present in many parts of the world
It is important, however, to not limit the scope of this research in terms of vaccine development, but to also assess in the context of natural herd immunity—which may already be present in many parts of the world
