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Laboratory test reveals which variant can escape antibodies

by archyw

Vaccination must be expedited. Variant P.1 is able to escape neutralizing antibodies generated by immune response from previous infection by other covid-19 virus strains.

Laboratory tests revealed that the P.1 variant of the coronavirus is able to evade neutralizing antibodies generated by an immune response from a previous infection with other covid-19 virus strains. The conclusion comes from an international study, with the participation of researchers from USP, which analyzed plasma samples from patients who had the disease, and also from people immunized by the CoronaVac vaccine. The researchers emphasize that the results were obtained in vitro, not in patients, and the study does not include other types of immune responses in the body, reinforcing that vaccination should be accelerated. The study is described in an article published in the scientific journal The Lancet on July 8th.

William Marciel de Souza (Personal Archive)

Neutralization assays for the P.1 variant, with the full set of mutations, were performed after incubation with plasma from 21 covid-19 convalescent blood donors and a total of 53 people who received the chemically inactivated virus vaccine CoronaVac. “Plasma samples from 18 people who received a single dose and 38 who received two doses of the vaccine were included, all collected between 17 and 38 days after immunization”, explains researcher William Marciel de Souza, from the Faculty of Medicine from Ribeirão Preto (FMRP) from USP, first author of the article. “We also included plasma samples from 15 people who received two doses of the vaccine 134 to 260 days before collection.”

The neutralization results for P.1 were compared with the results obtained for an isolate of the B strain of the virus, which circulated at the beginning of the pandemic in Brazil last year. “One of the neutralization assays revealed that the plasma of convalescent covid patients has a neutralizing capacity 8.6 times lower than that of the P.1 variant isolates”, points out Souza.

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Souza notes that clinical studies have shown that the CoronaVac vaccine is effective against severe forms of covid-19, reducing hospitalizations and deaths. “It is necessary to remember that this is the main objective of a vaccine”, he says. “In this way, we reiterate that vaccination campaigns must be accelerated.”

CoronaVac vaccine was evaluated under three different conditions. “First, we evaluated the plasmas collected between 20 and 23 days after a single dose, and most of the plasmas had a result below the detection limit of the tests used”, reports the researcher. “For people who received two doses, with plasma collection done between 17 and 38 days after the second dose, they had neutralizing antibody levels greater than just one dose.”+ More

However, when the researchers looked at samples collected between 134 and 260 days after the second dose, the level of neutralizing antibodies was below the detection limit for P.1, and low for the B strain. the P.1 strain can escape neutralization by antibodies generated in response to a stimulus induced by sars-cov-2 variants that circulated at the beginning of the pandemic”, highlights Souza.

“We believe that genomic surveillance of the sars-cov-2 virus and the combined performance of neutralization trials can help guide vaccination programs, including updates to the vaccine strategy, if needed in the future”, emphasizes the researcher. “We reiterate that all our findings were in vitro, not in patients. We also remember that neutralizing antibodies are one of the components of the immune response, other components such as cellular immunity were not evaluated in this study.”

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Souza notes that clinical studies have shown that the CoronaVac vaccine is effective against severe forms of covid-19, reducing hospitalizations and deaths. “It is necessary to remember that this is the main objective of a vaccine”, he says. “In this way, we reiterate that vaccination campaigns must be accelerated.”

The study was conducted by more than 50 researchers, and was led by the State University of Campinas (Unicamp), in collaboration with researchers from USP and other Brazilian research institutions, in addition to the University of Oxford, Imperial College of London (United Kingdom) and the Washington University School of Medicine (United States). The work had the support of the Foundation for Research Support of the State of São Paulo (Fapesp), National Council for Scientific and Technological Development (CNPq), Coordination for the Improvement of Higher Education Personnel (Capes), Financier of Studies and Research ( Finep), Ministry of Science and Technology and several other development agencies.


From the USP Journal


by Julio Bernardes | Text in Brazilian Portuguese

Exclusive Editorial PV / Tornado

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