After covid-19, how immune is the person to the virus? 1:20
(CNN) –– The immune system of some people who have not been exposed to the coronavirus may have some familiarity with the pathogen, possibly helping to reduce the severity of the disease if that individual is infected with covid-19, a study suggests. recent.
The study, published in the journal Nature on Wednesday, found that in a sample of 68 healthy adults in Germany, who were not exposed to covid-19, 35% had T cells in their blood that were reactive to the virus.
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T cells are part of the immune system and help protect the body from infection. T cell reactivity suggests that the immune system may have had some previous experience in fighting a similar infection, and you can use that memory to help fight a new infection.
So how can there be reactive T cells in your immune systems without ever having covid-19? These were "probably acquired in previous infections with endemic coronaviruses," the researchers from various institutions in Germany and the United Kingdom explained in the new study. Activating this memory of T cells corresponding to another similar infection to respond to a new infection is called "cross reactivity".
"The big question is ... what could be the role of those T cells?"
The new research included analysis of blood samples from 18 covid-19 patients, ages 21 to 81, and healthy donors, ages 20 to 64, who live in Germany. The study found that coronavirus-reactive T cells were detected in 83% of covid-19 patients.
Although the researchers found pre-existing cross-reactive T cells in healthy donors, the report clarifies that the impact those cells could have on the outcome of covid-19 disease is still unknown.
The study findings certainly require more research, said Dr. Amesh Adalja, principal investigator for the Johns Hopkins University Center for Health Safety, who was not involved in the new study.
How long does convalescent plasma immunity last?"In this study, there appears to be a significant proportion of individuals who have this cross-reactive T-cell immunity from other coronavirus infections that may have some impact on how they cope with the new coronavirus. I think the big question is trying to jump from the fact that they have these T cells to understand what the role of those T cells might be, ”Adalja analyzed.
"We know, for example, that children and younger adults are relatively safe from the serious consequences of this disease, and I think a hypothesis could be that the pre-existing T cells that exist may be much more numerous or more active in cohorts. younger than in older cohorts, "the doctor completed.
"And if you could compare people with severe and mild diseases, and try to look at T cells in them and ask yourself, 'Are people with severe disease less likely to have cross-reactivated T cells and, by comparison, Can people with mild illness have more cross-reactive T cells? I think there is a biological possibility in that hypothesis, "he added. "However, it is clear that the presence of T cells does not prevent people from becoming infected, but then does it moderate the severity of the infection? That seems to be the case. "
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So far in the coronavirus pandemic, much attention has been paid to covid-19 antibodies and their role in building immunity against the disease.
But infectious disease expert Dr. William Schaffner, professor of preventive medicine and infectious diseases at Vanderbilt University School of Medicine in Nashville and who was not involved in the new study, said T cells cannot be overlooked .
"Here's a study suggesting that there may actually be some cross-reactivity - some preparation against the pump if you will - due to conventional coronaviruses that cause colds in humans, and there may be some cross-reactivity with the virus from covid-19 that is causing so much damage. That is intriguing in itself because we had thought from an antibody perspective that there was not a lot of crossover at all, ”Schaffner explained.
“It is not entirely surprising because they are all members of the same family. It is as if they were cousins, "he said. “Now we have to see if there is any impact of this on clinical practice… Does this make it more or less likely that the person infected with covid-19 will actually develop a disease? Does it have any implications for the development of vaccines? ”She added.
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"Almost everyone in the world has had an encounter with a coronavirus"
Adalja said she was not surprised to see this T-cell cross reactivity in study participants who were not exposed to the new coronavirus, called SARS-CoV-2.
"SARS-CoV-2 is the seventh human coronavirus ever discovered, and four of the human coronaviruses are what we call community-acquired coronaviruses. Those four are responsible for 25% of our common colds, ”explained Adalja. "Almost everyone in the world has had an encounter with a coronavirus, and since they are all part of the same family, some cross-reaction immunity develops."
The new study published in Nature isn't the only one that suggests a certain level of pre-existing immunity to the new coronavirus in some people.
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Alessandro Sette and Shane Crotty, both from the University of California, San Diego, wrote in a comment, published in the journal Nature earlier this month, that "20-50% of unexposed donors show significant reactivity to the SARS antigen -CoV-2 ”, based on separate research, but noted that the source and clinical relevance of reactivity remains unknown.
Sette and Crotty noted that “it has now been established that pre-existing immune reactivity to SARS-CoV-2 exists to some extent in the general population. It is assumed, but has not yet been proven, that this could be due to immunity to the common cold coronaviruses. ”
Antibodiescovid-19 Immunity Pandemic
