While this might sound crazy to some it seems researchers are now suggesting some of us may have the altered T cells that react to the new coronavirus without ever having come down with the new coronavirus at all. I know, that might seem like a lot but it does make more sense than you’d expect. 

According to the study, researchers suggested that T cells in some people reacted to different coronaviruses that cause things like the common cold thus forcing them to change overall. That leading them to be more reactive to the new coronavirus without the person ever having been in contact with COVID-19 as a whole. This could explain a lot but of course, more research will need to be done on the topic. 

The abstract for this specific study goes as follows:

Many unknowns exist about human immune responses to the SARS-CoV-2 virus. SARS-CoV-2 reactive CD4+ T cells have been reported in unexposed individuals, suggesting pre-existing cross-reactive T cell memory in 20-50% of people. However, the source of those T cells has been speculative. Using human blood samples derived before the SARS-CoV-2 virus was discovered in 2019, we mapped 142 T cell epitopes across the SARS-CoV-2 genome to facilitate precise interrogation of the SARS-CoV-2-specific CD4+ T cell repertoire. We demonstrate a range of pre-existing memory CD4+ T cells that are cross-reactive with comparable affinity to SARS-CoV-2 and the common cold coronaviruses HCoV-OC43, HCoV-229E, HCoV-NL63, or HCoV-HKU1. Thus, variegated T cell memory to coronaviruses that cause the common cold may underlie at least some of the extensive heterogeneity observed in COVID-19 disease.

For this research those working on the study looked at blood samples from the year 2015 to the year 2018, this for those who do not know is long before COVID-19 was first found. These scientists found within that blood that some of those people had memory T cells that could recognize COVID-19 as well as several other types of coronavirus. The other types being ones that cause common colds. 

Science Daily wrote as follows on the topic:

The research, published Aug. 4, 2020 in Science, may explain why some people have milder COVID-19 cases than others — though the researchers emphasize that this is speculation and much more data is needed.

“We have now proven that, in some people, pre-existing T cell memory against common cold coronaviruses can cross-recognize SARS-CoV-2, down to the exact molecular structures,” says LJI Research Assistant Professor Daniela Weiskopf, Ph.D., who co-led the new study with LJI Professor Alessandro Sette, Dr. Biol. Sci. “This could help explain why some people show milder symptoms of disease while others get severely sick.”

“Immune reactivity may translate to different degrees of protection,” adds Sette. “Having a strong T cell response, or a better T cell response may give you the opportunity to mount a much quicker and stronger response.”

The new work builds on a recent Cell paper from the Sette Lab and the lab of LJI Professor Shane Crotty, Ph.D., which showed that 40 to 60 percent of people never exposed to SARS-CoV-2 had T cells that reacted to the virus. Their immune systems recognized fragments of the virus it had never seen before. This finding turned out to be a global phenomenon and was reported in people from the Netherlands, Germany, the United Kingdom and Singapore.

Scientists wondered if these T cells came from people who had previously been exposed to common cold coronaviruses — what Sette calls SARS-CoV-2’s “less dangerous cousins.” If so, was exposure to these cold viruses leading to immune memory against SARS-CoV-2?

For the new study, the researchers relied on a set of samples collected from study participants who had never been exposed to SARS-CoV-2. They defined the exact sites of the virus that are responsible for the cross-reactive T cell response. Their analysis showed that unexposed individuals can produce a range of memory T cells that are equally reactive against SARS-CoV-2 and four types of common cold coronaviruses.

This discovery suggests that fighting off a common cold coronavirus can indeed teach the T cell compartment to recognize some parts of SARS-CoV-2 and provides evidence for the hypothesis that common cold viruses can, in fact, induce cross-reactive T cell memory against SARS-CoV-2.

“We knew there was pre-existing reactivity, and this study provides very strong direct molecular evidence that memory T cells can ‘see’ sequences that are very similar between common cold coronaviruses and SARS-CoV-2,” says Sette.

What do you think about all of this? I for one think it is a very interesting find and as we understand it more and more we will know whether it is truly something that is happening or not overall. This pandemic is not over yet and well, the more we understand about COVID-19 the better.

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