The SARS-CoV-2 mutant partially evades humoral immunity, but does not evade the T cell response.

As the coronavirus disease (COVID-19) pandemic continues to cause havoc around the world, vaccination efforts are promising for lowering infection rates.However, the emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) mutants threatens to mutate major antigen targets. Effectiveness of Approved vaccine.

Researchers at the Department of Virus Sciences, Erasmus MC, National Institute of Public Health and Environment, Amsterdam UMC, and Weil Medical College at Cornell University study humoral and cell-mediated immune responses against wild SARS-CoV-2, B.1.1. Did. .7 variant (UK variant) and B.1.351 variant (South Africa variant) of healthcare workers vaccinated with BNT162b2 (Pfizer-BioNTech) mRNA.

Studies published in the journal Scientific immunochemistry, It has been shown that some SARS-CoV-2 mutants can partially evade infection or vaccination-induced humoral immunity. Nevertheless, T cell activation is unaffected by mutations in the B.1.1.7 and B.1.351 mutants.

SARS-CoV-2 mutant and immune response

The outbreak of Severe Acute Respiratory Syndrome (SARS) in 2003 was successfully contained by non-pharmaceutical intervention. However, controlling the spread of SARS-CoV-2 (a less pathogenic but highly contagious virus) is much more difficult and encourages the rapid development of vaccines.

At some point in the pandemic process, many countries around the world have imposed measures to control social restrictions, blockades, and the spread of the virus. Some of these restrictions include school closures, home isolation, Contact tracing, Universal masking, and mass testing. To date, the number of cases has continued to increase, reaching 170.3 million confirmed cases worldwide.

Very few countries have succeeded in controlling SARS-CoV-2 infection, and many are facing a resurgence, partly due to the emergence of new highly infectious variants. Variant of concern that is widespread today includes the B.1.1.7 (or UK) variant. B.1.351 (or South Africa) variant. And P.1. Variant (or Brazil). Two new variants, known as B.1.427 and B.1.429 variants, were also discovered in California in February 2021.

Most of the world relies on the acquisition of immunity to SARS-CoV-2 infection by vaccination and the adaptive immune response to natural infection. The duration of this immunity is still unknown, but it gives hope that the world may acquire herd immunity in the future.

Adaptive immune system

An adaptive immune response is immunity from exposure to an antigen from either a pathogen or vaccination. It is activated when the innate immune system is unable to control infection.

The basic components of the adaptive immune system include B cells, CD4 + T cells, and CD8 + T cells, all of which contribute to the control of infection.

In SARS-CoV-2 infection, the exact correlation of defense remains unclear, but circulating antibodies and memory immune cells are thought to be important for protection from COVID-19.Virus specific Neutralizing antibody Targets the receptor binding domain (RBD) of the peplomer (S) protein, which is consistent with the presence of SARS-CoV-2 specific CD4 + circulating follicular T cells. They can prevent the interaction between the virus and the host cell.

In addition, when reinfection occurs, memory B cells and T cells proliferate suddenly to control the infection. Non-neutralizing antibodies may then also contribute to Fc receptor-mediated elimination of virus-infected cells via death. This is called antibody-dependent cellular cytotoxicity (ADCC).

However, with the advent of variant strains of concern, there are concerns that they may lead to reinfection or breakthrough infections. This can pose a threat to efficacy in vaccination efforts around the world due to mutants that evade the immune system or neutralizing antibodies induced by vaccination.

S-specific CD4 + T cell activation

In the current study, researchers aim to study the humoral and cell-mediated immune response against wild-type SARS-CoV-2 and two strains of concern, B.1.1.7 and B.1.351. I was saying.

The team collected serum and peripheral blood mononuclear cells (PBMC) from healthcare workers vaccinated with Pfizer-BioNTech or BNT162b2. They evaluated humoral and cell-mediated immune responses.

The study included a total of 121 health care workers who were vaccinated with the Pfizer-BioNTech vaccine. Of these, 23 healthcare workers recovered from mild COVID-19 and showed high levels of SARS-CoV-2-specific functional antibody and virus-specific T cell recall after a single vaccination. It was. However, those who had not been infected with SARS-CoV-2 in the past required two vaccinations to reach comparable levels of humoral and cell-mediated immune responses.

South African variants or B.1.351 variants were less recognized and were not neutralized at antibody levels. A single vaccination of previously negative COVID-19 participants did not cause the appearance of cross-reactive neutralizing antibodies in most patients.

The team also noted that there was no significant difference in the CD4 + T cell response to wild-type and that two mutant strains of concern were detected.

Overall, this study found that vaccination with the BNT16b2b mRNA vaccine was a potent SARS-CoV-2 specific neutralizing antibody, in both those who had never received recovered COVID-19 and COVID-19. It has been shown to induce CD4 + and CD8 + T cells, and ADCC-mediated antibodies.

In addition, the study confirmed that a single vaccination with the BNT162b2 mRNA vaccine was sufficient to induce a strong immune response in patients who had recovered at both humoral and cellular levels.

Future research is needed to assess how sterile immunity is needed to reach herd immunity and block the circulation of SARS-CoV-2. Continued surveillance monitors the incidence of breakthrough infections and the duration of vaccine-induced immunity, “the researchers concluded in the study.