Scientists have been wondering for months whether exposure to seasonal coronaviruses that cause colds can prevent people from getting serious cases of COVID-19.
The protection will explain why children, who get more of these colds, are less severely affected by SARS-CoV-2, the coronavirus that causes COVID-19. But a new study, published Tuesday (February 9) in the journal Cell, antibodies against such seasonal coronaviruses do not detect SARS-CoV-2 infection or reduce the severity of the disease.
There are four coronavirus which circulate in the human population and cause symptoms of colds – and most people have been exposed to it many times during their lifetime (especially as children) and have thus developed antibodies against them. Researchers have conducted a number of studies over the past year to determine if these antibodies can also bind to SARS-CoV-2 and protect against infection or serious illness.
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“We have found that many people possess antibodies that could bind to SARS-CoV-2 before the pandemic, but these antibodies could not prevent infections, ”said senior author Scott Hensley, associate professor of microbiology at the Perelman School of Medicine at the University of Pennsylvania. said in a statement. The antibodies also could not stop serious diseases.
This is a different conclusion from that of a similar study published in the journal Science in December, a small group of people – and a larger percentage of children compared to adults – had antibodies from previous coronavirus infections that could neutralize or disarm the SARS-CoV-2.
It is ‘no surprise’ that the new study finds that these antibodies cannot prevent infection, led George Kassiotis, an immunologist at The Francis Crick Institute in the UK, who led the other study published in Science in December. has been published. Antibodies that work against multiple coronaviruses are only present in a few individuals and at very low levels, Kassiotis said. Children become much more ill with colds than adults, which means that their antibodies against common cold coronaviruses do not even stop it. [from] get more colds – it would be pretty weird if they could stop them from catching the pandemic virus, “he said.
That is not the question, he said. On the contrary, researchers want to know if these antibodies can change the disease once you have contracted the virus, to protect you from serious symptoms, Kassiotis told WordsSideKick. “The new study suggests[s] they do not, but I do not think it is conclusive. ‘
Antibody Archive
In the new study, Hensley and his team analyzed serum samples collected in 2017 to determine the level of antibodies versus seasonal antibodies carried by the general population. Blood samples were taken from 263 children at the Children’s Hospital of Philadelphia and from 168 adults at the Penn Medicine Biobank.
Most of these samples contain antibodies against seasonal coronaviruses, but only 20% of them contain antibodies that could also bind to the ability of SARS-CoV-2 protein (the weapon that the virus uses to invade human cells) or the nucleocapsid protein. (a protein that is essential for repeating the virus).
They then analyzed 502 other serum samples taken from humans before the pandemic; half of these people tested positive for SARS-CoV-2 after the pandemic, and half did not and were used as a control group. Similarly, they found that more than 20% of these samples contained coronavirus antibodies that could bind to SARS-CoV-2. However, people with these antibodies still developed SARS-CoV-2. There is no correlation between the level of these antibodies and the severity of COVID-19 they developed, the study found.
In the third part of the experiment, they analyzed serum samples from 27 patients hospitalized with COVID-19 and found that the infection increased the body’s antibodies against seasonal coronaviruses. Another study published in the journal in December 2020 Clinical infectious diseases also found that these antibodies have no neutralizing effects. However, Kassiotis’ study found that some antibodies that can bind to SARS-CoV-2 can neutralize the virus.
It is not clear whether these differences are due to differences in the way they tested their samples, or other factors such as geographical differences, the authors wrote. Kassiotis believes this is because the researchers used a less sensitive test and therefore did not identify enough people (two in the year before the pandemic and 11 in total) with antibodies that could bind to the peak protein. “These numbers are far too small for any meaningful conclusion.”
In any case, even if larger studies confirm that seasonal coronavirus antibodies are not protective, it does not mean that there are no other species immune cell, except for antibodies that persist from cold infections in the past, which may play a protective role and which have not yet been tested, according to the statement. For example, T cells that respond to the original SARS-COV-1 virus remain for decades, and some also bind to SARS-CoV-2, a July 2020 study in the journal Nature found.
“Although antibodies from previous coronavirus infections may not prevent SARS-CoV-2 infections, it is possible that memory B cells and T cells may provide some protection or at least reduce the severity of COVID-19, said Hensley. said. “Studies need to be completed to test the hypothesis.”
Originally published on Live Science.