Bispecific antibody neutralizes SARS-CoV-2 and its variants

Severe Acute Respiratory Syndrome Most studies testing monoclonal antibodies specific for the use of coronavirus 2 (SARS-CoV-2) antigen Memory B cells from plasma provided with probes from plasma blasts and recovered SARS-CoV-2 individuals. However, given the rise of new variants of concern around the world, there is a high incentive to produce more antibody-based tools against SARS-CoV-2.

new bioRxiv* A preprint study led by Joshua Tan of the National Institute of Allergy and Infectious Diseases of the National Institutes of Health produces bispecific antibodies using a new method of cross-linking antibodies with their neighbors. Spike protein Uses dual N-terminal domain / receptor binding domain specificity.

How they did it

The researchers collected SARS-CoV-2-specific monoclonal antibodies from plasmablasts and memory B cells from 126 patients infected with COVID-19. Samples were collected in New York City in April 2020, showing that the immune response reflects the first wave of a pandemic. They got together. A total of 119 antibodies targeted the SARS-CoV-2 peplomer, 106 targeted the receptor binding domain, and 122 targeted the N-terminal domain.

Plasma was tested for neutralizing ability to detect a wide range of neutralizing titers from <40 to 765. Efficacy was weakly correlated with antibody levels in peplomer, receptor-binding domains, and N-terminal domains. Also, some plasma samples were incapable of neutralizing despite high antibody levels.

To develop monoclonal antibodies with high specificity for the SARS-CoV-2 epitope, researchers used a single-cell assay to screen for antibodies to plasma blast and memory B cells. The assay extracted a total of 169 monoclonal antibodies targeting SARS-CoV-2 from plasmablasts and 47 from 12 Memory B cells. Approximately 59 of the monoclonal antibodies target the receptor-binding domain, 64 targets the N-terminal domain, and 46 do not target either, suggesting that the antibody can detect the entire peplomer.

Plasmablastic cells and memory B cells produce highly effective neutralizing antibodies

Researchers have found that most monoclonal antibodies have no neutralizing effect, but 21 antibodies have shown strong efficacy against SARS-CoV-2.

Immunoglobulin A (IgA) isotype antibodies showed excellent neutralization. Twenty-one antibodies submitted under the immunoglobulin G (IgG) isotype targeted several peplomer regions. 16 targeted the receptor binding domain and 5 targeted the N-terminal domain.

The mean potency from antibodies produced from plasma cells or memory B cells is similar, indicating that both produce potent antibodies.

Using high-throughput surface plasmon resonance, antibodies specific for the receptor binding domain showed higher affinity than N-terminal domain-specific monoclonal antibodies. N-terminal domain-specific monoclonal antibodies from plasma cells had lower affinity than antibodies from memory B cells.

Researchers have found that the most potent monoclonal antibodies have a low affinity for the N-terminal domain.

Ability to bind antibodies to COVID-19 mutants

Approximately 28 of the 37 receptor-binding domain-specific monoclonal antibodies and 3 of the 20 N-terminal domain-specific antibodies bind 90% or more to the B.1.1.7 mutant. Was there.

Only 10 antibodies specific for the receptor binding domain and 2 antibodies specific for the N-terminal domain retained full binding to the B.1.351 mutant. Researchers suggest that the results provide more evidence that the B.1.351 mutant is more successful in antigenic escape.

SARS-CoV-2 bispecific antibody

Considering that most monoclonal antibodies bind to non-overlapping sites, we tested the potential for synergistic effects between the antibodies. They integrated the specificity of the antibody to produce 10 bispecific antibodies that combined the variable region of a potent neutralizer with two linkers.

Bispecific antibodies that could target the receptor-binding domain and the N-terminal domain retained binding to both domains. When testing bispecific antibodies in the SARS-CoV-2 assay, five antibodies (CV503_521_GS, CV521_1182_GS, CV1206_521_GS, CV521_503_GS, and CV503_664_EL) neutralized SARS-CoV-2.

“In particular, CV1206_521_GS neutralizes SARS-CoV-2 more than 100 times more potent than the cocktail of its constituent antibodies CV1206 and CV521. CV1206_521_GS uses its inner and outer Fab domains to use adjacent peplomer proteins. It was found that it bridges NTD and RBD. It has a mechanism of action that is not available with conventional mAbs, even when used in combination. “

Researchers suggest that the combination of bispecific antibodies can provide promising results that can further enhance neutralization.

When tested against peplomer of B.1.1.7 and B.1.351 variants, only bispecific antibodies, in which two components lost their binding to the variant, could not bind. This suggests that this antibody form is more resistant to spike mutations than typical monoclonal antibodies.

All bispecific antibodies neutralized the D614G strain, most bispecific antibodies, including CV521, neutralized the B.1.1.7 variant, and 6 of the 9 bispecific antibodies Neutralized B.1.351.

Important Notices

* bioRxiv Publish preliminary scientific reports that should not be considered definitive as they are not peer-reviewed, guide clinical practice / health-related behaviors, and should not be treated as established information.