May 8, 2021


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Strong T cell response is good news for the battle against Covid variants

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Covid-19 variants may be less dangerous for vaccinated people and recovered patients than previously thought, according to researchers who have found that the human body produces a strong cellular immune response to some of the more worrying new strains .

The American study, conducted by researchers at the La Jolla Institute for Immunology and the University of California, identified that T-cell responses in vaccinated or previously infected patients were just as robust to new variants of Covid-19 – including those first identified in Kent, Brazil, South Africa and California.

It is believed that T cells, which can “remember” past infections and kill pathogens if they reappear, have a great influence on how long people remain resistant to infections and diseases. They are of several different types, including killer T cells, helper T cells, and memory T cells. B lymphocytes, another essential type of white blood cell, produce antibodies.

The results are likely to alleviate some of the concerns about new strains thwarting the existing vaccine harvest.

“The data provides positive news in light of justified concerns about the impact of worrisome variants of Sars-Cov-2 on efforts to control and eliminate the current pandemic,” the document concludes. “Although circulating memory T cells are not expected to be effective in preventing Sars-Cov-2 infection, it is plausible that they may reduce the severity of Covid-19,” he said. declared.

The study, which has yet to be peer reviewed, found that the new variants had a “marginal impact” on helper and killer T cell responses when compared to the original Wuhan strain. The strains were tested against each other in the blood serum of people who had previously been infected and people who had received the Moderna and BioNTech / Pfizer vaccine.

The research comes after worrying data emerged from Brazil where the P. 1 variant, which has since spread to more than 25 countries, was found this week to cause a less efficient antibody response among those vaccinated and recovered than earlier versions of the virus.

In the Brazilian study, published Tuesday, the researchers tested the blood plasma of 20 people previously infected with Covid-19 and of eight people who received the CoronaVac vaccine, developed by the Chinese Sinovac, against the P. 1 variant.

The team from the University of São Paulo and the University of Campinas found that the P. 1 variant generated a six-fold decrease in antibodies compared to the variant that was circulating before it appeared at the end of the year. last. The flu shot was normally changed once it was found that a new variant in circulation reduced the level of antibodies produced by four or more times, the researchers said.

The study, which has yet to be peer reviewed, found that antibodies had difficulty binding to the all-important spike protein of P. 1, which it uses to enter human cells. The variant has more than 17 mutations, which alter its genetic sequence from the virus initially identified in Wuhan, including three involving changes in the spike protein.

Jeffrey Barrett, director of the Sars-Cov-2 genomics initiative at the Wellcome Sanger Institute, said the study showed there was “some reason for concern about vaccines that protect less well against P . 1 ”. But he also stressed that the function of T cells should not be overlooked.

The emergence of the P. 1 variant in the Brazilian city of Manaus was linked to an outbreak of cases earlier this year that overwhelmed the municipality’s health department. It quickly became the dominant strain of Covid-19 in the city and is now present in at least 17 of Brazil’s 26 states.

Like variants of the coronavirus that originated in the UK and South Africa, it was found to be more transmissible than strains circulating in early 2020.

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