COVID-19 Immunology: Study Indicates That Prior Exposure To Common Cold Coronaviruses Creates Memory T Cells That Can Recognize SARS-CoV-2
Source: COVID-19 Immunology Aug 05, 2020 3 years, 11 months, 3 weeks, 1 day, 2 hours, 4 minutes ago
COVID-19 Immunology: A new study led by researchers from La Jolla Institute for Immunology (LJI) indicates that memory helper T cells that recognize common cold coronaviruses also recognize matching sites on SARS-CoV-2, the virus that causes COVID-19.
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According to the research paper, the immune system's 'memory' T cells keep track of the viruses they have seen before. This immune cell memory gives the cells a head start in recognizing and fighting off repeat invaders.
The study findings were published in the journal: Science.
https://science.sciencemag.org/content/early/2020/08/04/science.abd3871
The research findings may explain why some individuals have milder COVID-19 cases than others though the researchers emphasize that this is speculation and much more data is needed.
LJI Research Assistant Professor Dr Daniela Weiskopf, Ph.D., who co-led the new study with LJI Professor Dr Alessandro Sette, Dr. Biol. Sci. told Thailand Medical News, "We have now proven that, in some individuals, pre-existing T cell memory against common cold coronaviruses can cross-recognize SARS-CoV-2, down to the exact molecular structures. This could help explain why some people show milder symptoms of disease while others get severely sick."
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Dr Sette added, "Immune reactivity may translate to different degrees of protection. 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 research 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.
https://www.cell.com/cell/fulltext/S0092-8674(20)30610-3
This research finding turned out to be a global phenomenon and was reported in individuals from the Netherlands, Germany, the United Kingdom and Singapore.
Researchers wondered if these T cells came from people who had previously been exposed to common cold coronaviruses what Dr 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?
In this 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.
The new 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.
Dr Sette added, "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.”
Upon detail analysis, the researchers found that while some cross-reactive T cells targeted the SARS-CoV-2's spike protein, the region of the virus that recognizes and binds to human cells, pre-existing immune memory was also directed to other SARS-CoV-2 proteins.
This new finding is relevant, Dr Sette explains, since most vaccine candidates target mostly the spike protein. These findings suggest the hypothesis that inclusion of additional SARS-CoV-2 targets might enhance the potential to take advantage of this cross reactivity and could further enhance vaccine potency.
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