A bispecific T cell engager strategy targeting the SARS-CoV-2 spike to control SARS-CoV-2 infection

In a recent study published in communication biology In the same journal, researchers control severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection using a bispecific T-cell engager to target the SARS-CoV-2 spike protein. described a new strategy for

study: A spike-targeted, bispecific T-cell engager strategy provides dual-layered protection against SARS-CoV-2 infection in vivo. Image credit: Tsuguliev/Shutterstock.com

Background

Rapid development of vaccines and monoclonal antibodies has successfully limited severity and mortality during the 2019 coronavirus disease (COVID-19) pandemic, but new variants with immune-evading mutations Emergences continue to raise concerns on a regular basis.

Antiviral technologies consisting of small molecules that target SARS-CoV-2 viral entry and replication are under investigation, and some, such as Paxlovid, are approved for clinical use. Neutralizing antibody Early clinical use was also very successful against SARS-CoV-2.

Many of these antibody therapies target the angiotensin-converting enzyme 2 (ACE-2) receptor, the primary receptor for SARS-CoV-2 entry.

But emerging spike protein mutations continue to pose challenges efficacy of Neutralizing antibodies and novel approaches are needed in addition to existing small molecule inhibitors and neutralizing antibodies to combat emerging SARS-CoV-2 variants.

A bispecific antibody targeting two epitopes and a bispecific fusion protein with a soluble ACE-2 arm and an antibody arm have also been developed that simultaneously target evasive immune mutations while exerting a neutralizing effect. We are improving.

About research

In this study, researchers developed a bispecific T-cell engager (S-BiTE) that targets the SARS-CoV-2 spike protein.

This fusion protein consists of an extracellular ACE-2 domain that blocks viral entry and an anti-CD3ε (cluster of differentiation 3ε) single-chain variable fragment (scFv) that activates T cells to eliminate virus-producing cells. .

ACE-2 extracellular ligand was used to identify cells expressing the SARS-CoV-2 spike protein. live Cells infected with SARS-CoV-2. The monovalent extracellular domain of ACE-2 shows high affinity for the SARS-CoV-2 spike Fc fusion protein receptor binding domain (RBD).

Compared to the bivalent parental anti-CD3 antibody, the monovalent anti-CD3ε scFv has a lower affinity for CD3ε and therefore does not bind and activate T cells in the absence of the SARS-CoV-2 spike protein.

Perform a T-cell activation assay using co-cultured cells expressing the SARS-CoV-2 spike protein in vitro Test the ability of S-BiTE to activate T cells. The cytotoxicity of S-BiTE was also compared with that of ACE-2-human immunoglobulin g (IgG1) Fc fusion protein.

Furthermore, we tested the efficacy of S-BiTE in preventing viral shedding using a pseudotyped SARS-CoV-2 production system. Cytotoxicity of S-BiTE was also tested live.

Additionally, the safety profile of S-BiTE was tested using a mouse model, confirming that it does not cause unwanted depletion or activation of T cells.

Mesenchymal stem cells have been engineered to stably express S-BiTE, and the preferential biodistribution of mesenchymal stem cells in the lung may be useful in the treatment of SARS-CoV-2-induced pneumonia. It also shows the possibility of using S-BiTE.

The efficacy of S-BiTE in eliminating cells expressing the spike protein was further tested against the delta mutant spike protein using live virus-infected cells.

result

As a result, S-BiTE competes with membrane receptors to block entry of free SARS-CoV-2 into permissive cells, while simultaneously activating potent T-cell-mediated cytotoxicity to eliminate virus-infected cells. was reported.

Moreover, S-BiTE was equally effective against both the original SARS-CoV-2 strain and the delta mutant, indicating potential efficacy and application against emergency immune-evading SARS-CoV-2 mutants. I’m here.

Treatment of a humanized mouse model of SARS-CoV-2 infection with S-BiTE resulted in viral load More effective than neutralizing antibody alone.

The use of humanized mouse models to test safety profiles also reported no significant differences in immune cell subtypes, unwanted depletion or activation of T cells, or immune cell infiltration into major tissues. bottom.

The first of the two major advantages of using S-BiTE over standard neutralizing antibody therapy is the use of ACE-2 as the targeting moiety, which is responsible for nearly all SARS-CoV-2 mutations. effective for the body.

A second advantage comes from using anti-CD3ε to activate T cells and eliminate virus-infected cells. This is significantly more effective than antibody-mediated cytotoxicity.

Conclusion

Overall, the results of this study suggest that S-BiTE prevents viral entry by competing with ACE-2 membrane receptors and activating T-cell cytotoxicity, effectively killing SARS-CoV-2-infected cells. Reported to be removed.

S-BiTE technology can be further optimized by selecting target moieties, improving safety and neutralization capabilities, and improving efficacy against emerging SARS-CoV-2 variants.