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SFROM THE In early 2020, medical researchers have been chasing COVID-19. One of its most important goals is to understand the immune response to SARS–CORV-2, the virus that causes it. Finding out what a good response looks like and how long it lasts is crucial. The answers will reveal whether people who have recovered from the disease are protected from a second infection and will also indicate how difficult it will be to develop a vaccine.
There is a lot to worry about. Over the past year, many reports have shown rapidly decreasing levels of covid-specific antibodies after the initial outbreak caused by an infection. Antibodies are parts of the immune system that directly attack the virus. They are expected to participate in any long-term protection against re-infection. If they disappear quickly, that seems, at first glance, like bad news. Concerns also highlight the fact that immunity to the types of coronavirus that cause the symptoms described as “a cold” is short-lived, and that there are already a number of proven cases of reinfection with SARS–CORV-2.
However, antibodies tell only part of the story. Another important actor is T-cell (in the photo above). Instead of attacking viruses directly, T-Cells attack infected cells to stop virus reproduction. The balance of importance of the antibody and TThe cellular arms of the immune system vary with the disease in question. And, when it comes to this particular infection, although almost all patients who contract SARS–CORV-2 are believed to create T-cells in response, understanding their meaning has been elusive.
This is largely due to TCells are more difficult to measure than antibodies, so they are studied less frequently. Shamez Ladhani, a consulting epidemiologist at Public Health England, a government health protection agency, who has worked on new long-term research on these cells, says it took nearly three weeks to count them in the 100 patients his study analyzed. . The effort was worth it, however, because it has shed new light on the duration of this form of immunity to SARS–CORV-2 could be.
To a T?
Dr. Ladhani’s project is part of a larger effort focused on healthcare workers that Public Health England began in March. More than 2,000 people have donated blood samples every month since then. The 100 that he and his colleagues have studied are a subset of these. In a paper just published as preprint, but not yet peer-reviewed, they say that six months after infection all of these patients, even those who had only had mild symptoms, or none at all, still had detectable levels of T-Cells directed against the virus. Although your antibodies might have disappeared, T-Cells remained at the scene.
These findings bode well for the idea that T“Cells offer long-term protection against re-infection,” says Eleanor Riley, a professor of immunology at the University of Edinburgh. And Paul Moss, a hematologist at the University of Birmingham, says his experience with other viruses leads him to wait. TThe cell response that Dr. Ladhani has observed will last many more months than the six it has persisted so far. In SARS–CORV-1, the name now given to the virus that caused the SARS Outbreak, in 2002-03, it was found that this form of cellular immunity lasted in some people for more than a decade. The long-lived nature of such T-The response of the cells fits with the observation that, so far, reinfections seem rare.
Dr. Moss says the implication of the new study is that those seeking COVID-19 vaccines should prioritize the production of T-cells. There is more good news here. Two of the leading candidates: one from a collaboration between Pfizer, an American pharmaceutical company, and BioNTech, a German biotechnology firm, and the other from a second joint effort, between AstraZeneca, a British-Swedish pharmaceutical company, and the Jenner Institute from Oxford University: Do exactly this, while also stimulating the production of antibodies. Speaking in July when the first results of the AstraZeneca-Oxford vaccine were published, Adrian Hill, the head of the Jenner Institute, wanted to highlight how “excellent” T-Cellular response created by your vaccine. “That’s what this type of vaccine does,” he explained. “That’s what it’s designed for.”
The meaning of T-cells was obvious to Pfizer and BioNTech as well. In July they shifted the focus of their efforts in response to data suggesting that an experimental vaccine they had previously considered secondary was causing strong T-Responses of cells. The next few weeks are likely to produce results on whether one or more of these purported vaccines actually provides protection against COVID-19. Let the two main candidates provoke strong TThe cellular response is cause for optimism that vaccination is on the right track.
As for the disappearance of antibodies, here too there may be reason for optimism. The fact that the levels of these proteins drop rapidly after infection, when they are no longer needed, should not surprise us. It may not matter either. The immune system could well be prepared to produce them again in large quantities, if it is reunited SARS–CORV-2. It’s also worth remembering that even if researchers can’t detect antibodies, that doesn’t mean they aren’t there at all.
As winter approaches in the northern hemisphere, the scientific fight against covid-19 feels more urgent than ever. But, while it is true that science has not yet blocked the exit doors of the pandemic, there are now at least some rays of light emerging around the door. ■
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This article appeared in the science and technology section of the print edition under the title “Teed up.”
