Like the new coronavirus, some viruses that cause a cold (note that the cold is different from the flu) are also coronaviruses. In fact, many adults have been linked to these coronaviruses. Fortunately, infection with this coronavirus usually causes only mild respiratory symptoms. Perhaps even luckier, because the immune system has a remarkable “memory” ability, the small cold scares also allowour our immune cells to get to know the new coronavirus in advance.
Scientists at la Jolla Institute for Immunology reported their findings in a research paper published in the leading academic journal Science.
“We have now shown that in some humans, T-cell memories pre-existing for cold coronaviruses can cross-react to the new coronavirus in precise molecular structures.” Professor Daniela Weiskopf, one of the study’s co-authors, said: “This may help explain why some people experience mild symptoms after contracting a new crown, while others get very ill.” “
Professor Alessandro Sette, who co-led the study, added: “Immune responses can be translated into varying degrees of protection. Stronger or better T-cell responses may give you the opportunity to have a faster and stronger immune response. “
The new study builds on a set of results previously published in the journal Cell by Professor Sette and co-authors. They found that not only did patients infected with the new coronavirus produce a group of auxiliary T-cells specifically to identify the new coronavirus, but about 50 percent of those who had not been infected with the new coronavirus also had T-cells that knew the new coronavirus. In other words, their immune system recognized fragments of the virus that had never been seen before.
Since then, reports from different regions, including the Netherlands, Germany, the United Kingdom and Singapore, have shown that the phenomenon is not unique to a region, but a global phenomenon.
So, how are T-cells that “know the new crown” come about? Scientists speculate that it may have come from the cold coronavirus that people have been exposed to. In Professor Sette’s words, the coronaviruses that cause colds are “not dangerous cousins” of the new coronavirus.
To test whether exposure to these cold viruses causes immune memory against the new coronavirus, in the new study, scientists collected blood samples from healthy participants from 2015 to 2018 and studied T-cells that react specifically to the new coronavirus.
The researchers found that pre-existing memory T cells responded to a total of 142 epitopes on the new coronavirus. Further analysis showed that the participants who had not been exposed to the new coronavirus produced a series of memory T cells that were cross-reactive to the new coronavirus and four cold-causing coronaviruses (HCov-OC43, HCov-229E, HCoV-NL63, and HCoV-HKU1). The discovery means that fighting the cold coronavirus can indeed teach T-cells to recognize fragments of the new coronavirus.
The researchers found that memory T cells cross-reacted to 142 new coronavirus phenometry in blood samples from participants who had not been infected with the new coronavirus.
Professor Sette said: “We have known in the past that there is a pre-existing immune response, and this study provides strong direct molecular evidence that memory T cells can ‘see’ very similar sequences between the coronavirus and SARS-CoV-2. “
It is worth noting that the analysis showed that while some cross-reactive T cells targeted the S protein of the new coronavirus (the region where the new coronavirus identifies and binds to the host cell), some of the immune memory is targeted at other parts of the new coronavirus. The researchers explained that the findings are significant because most of the candidate vaccines are primarily targeted at the S protein, and the findings suggest that the inclusion of more new crown targets may increase the potential for cross-reactive use and further enhance vaccine effectiveness.