Scientists explore the efficacy of neutralizing antibodies against the SARS-CoV-2 omicron mutant

In a recent study published in Experimental Medicine JournalResearchers evaluated the effects of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-Neutralizing antibody About the SARS-CoV-2 Omicron variant.

Researchers around the world have been investigating the development of vaccines and treatments to prevent and treat coronavirus disease (COVID-19) in 2019. Various studies have also investigated the effectiveness of SARS-CoV-2 neutralizing antibody-based immunotherapy, leading to the use of several monoclonal antibodies (mAbs) to COVID-19.

About research

In this study, researchers reported the functional and molecular characteristics of human SARS-CoV-2 spike (S) mAbs derived from immunoglobulin G (IgG) and IgA memory B cells.

The team teamed up on IgG and IgM in convalescent individuals who tested COVID-19 positivity in the first wave of infection with SARS-CoV-2 Wuhan trimeric spike (tri-S) and receptor binding domain (RBD) proteins. Estimated serum reactivity. Enzyme-linked immunosorbent assay (ELISA). The researchers also evaluated the neutralizing activity of IgG and IgA antibodies found in purified serum samples against the SARS-CoV-2 Wuhan strain by the following method. In vitro Pseudo-neutralization assay.

In addition, the team selected convalescent individuals to obtain stained peripheral blood IgG and IgA memory B cells using fluorescently labeled tri-S and RBD. SARS-CoV-2 tri-S was used as a bait to capture single SARS-CoV-2 reactive B cells via cytometric sorting. From isolated SARS-CoV-2tri-S IgG and IgA memory B cells, the team developed a unique human mAb as a recombinant IgG1 antibody from selected B cells. Subsequently, ELISA and binding analysis based on flow cytometry were performed.

result

The findings show that serological samples from convalescent individuals with a history of SARS-CoV-2 infection during the first wave of the pandemic are high-titer anti-tri-S IgG, primarily IgG1. I showed that I showed. These titers also included antibodies that cross-reacted with the Middle East respiratory syndrome-related coronavirus (MERS-CoV) tri-S protein. The team also observed high levels of serum anti-RBD IgG associated with anti-tri-S antibody titers.

A correlation was found between the SARS-CoV-2 serum reactivity of IgG and the IgA antibody. Serum IgG and IgG antibodies obtained from patients with the highest anti-SARS-CoV-2tri-S antibody titers have strong ELISA binding to SARS-CoV-2 Wuhan nucleocapsid (N), RBD, and tri-S, S1. Was shown. And the S2 subunit. These antibodies were also cross-reactive with recombinant S proteins belonging to other beta CoVs such as SARS-CoV-1 and MERS-CoV.

The In vitro The sham neutralization assay has a 50% inhibition concentration (IC)₅₀) The purified IgA antibody was lower than the IgG antibody. Also, IC₅₀ IgA antibody levels were substantially inversely correlated with the respective binding levels exhibited by the SARS-CoV-2RBD and S1 proteins.

Binding analysis showed that 76% of purified mAbs selectively bind to SARS-CoV-2. Spike protein On the other hand, RBD-bound cells consisted of 11% tri-S IgA cells and 17% tri-S IgGB cells.In addition, the anti-RBDIgA titer was inversely correlated with IC₅₀ It is the neutralization value of IgA and is directly proportional to the frequency of RBDIgAB cells in the blood. The team also noted that several antibody clones were present in some COVID-19 convalescent individuals, suggesting the presence of inter-individual convergence of anti-SARS-CoV-2 antibody responses.

Epitope mapping analysis performed by ELISA using recombinant proteins showed that nearly 59% of anti-S mAbs efficiently bind to the S2 subunit, 17% to the N-terminal domain (NTD) and 1% to S1. Revealed to bind to a domain (CD). 7% relative to other regions present in the SARS-CoV-2 S protein. Approximately 0.99% of all anti-S antibodies targeting S2 recognized the tri-S protein but did not bind to the linear peptide covering the spikes. This indicates that several SARS-CoV-2 spike memory B cell antibodies targeted the conformation epitopes.

In particular, antibodies Cv2.1169 and Cv2.3194 showed reduced neutralization efficiency for the SARS-CoV-2 Omicron BA.1 subline compared to the SARS-CoV-2 delta mutant. On the other hand, Cv2.1169 and Cv2.3194 showed relatively stronger RBD binding to the Omicron BA.2 subline than BA.1. The two antibodies showed efficient blocking of BA.2 RBD binding to angiotensin converting enzyme 2 (ACE-2).

Overall, the study results show that antibodies Cv2.1169 and Cv2.3194 show strong neutralizing activity against SARS-CoV-2 Omicron BA.1 and BA.2 and are used clinically against COVID-19. It has been shown to be the most powerful cross-neutralizer to be found. .. Researchers believe that these antibodies may serve as potential candidates in the development of prophylactic and therapeutic approaches to SARS-CoV-2 infection.