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Recombinant SARS-CoV-2 RBD Mutants

Creative Diagnostics now can provide SARS-CoV-2 Spike/RBD Mutants which were expressed in HEK293 cells. Antigens are post-translationally modified (glycosylation and phosphorylation) and more closely resembling the native viral proteins that can overcome specificity issues in COVID-19 serology assays.

Some of these antigens have higher affinity to human ACE2. Antigens made by Creative Diagnostics are manufactured to the highest quality standards and are performance guaranteed for the applications listed on the detailed datasheets.

A recent study from Los Alamos National Laboratory has identified a major mutation on SARS-CoV-2 Spike initially emerged in European countries. This D614G mutation has rapidly become dominant in these regions, suggesting this mutation may make the SARS-CoV-2 virus more transmissive. It's critical to understand the biology of this variant, particularly in the context of vaccine and drug design.

HEK293 Expressed Recombinant SARS-CoV-2 Spike/RBD Mutants:

The Spike protein of SARS-CoV-2 facilitates the viral entry into target cell exploiting Angiotensin-converting enzyme 2 (ACE2) receptor. The receptor binding domain (RBD) of the SARS-CoV-2 S protein plays the key role in the tight binding to human ACE2 for viral entry.

RBD is considered highly conserved because it is the only domain that binds human ACE2 and initiates cell entry. Surprisingly, through polymorphism analysis and divergence analysis, the RBD sequence is as diverse as other regions of the S protein. Among the 1609 SARS-CoV-2 strains with whole genome sequences available in the public databases, 32 strains contained amino acid mutations in the RBD.

Most mutants had only one amino acid change compared to the originally reported genome (SARS-CoV-2 Wuhan-Hu-1). High frequencies of RBD mutations were identified: 6 V367F mutants from France and Hong Kong, 13 V483A and 7 G476S mutants from the U.S.A.

Fig. 1: Spatial location of the mutant amino acids and the fragment 510-524.

Molecular dynamics simulation indicates three RBD mutant types (N354D and D364Y, V367F, W436R) exhibited significantly lowered binding free energy (ΔG), suggesting a significantly increased affinity to human ACE2, which indicates that these mutants may have acquired increased infectivity to humans.

Fig. 2: RMSF of the nine mutants were compared to that of the prototype. Red arrows denote the fragment of residues 510-524. Black arrows denote the fragment of residues 475-485.

Since the RBD contains important antigenic epitopes, frequent mutations in RBD, especially the change of amino acid properties, may weaken the binding affinity of the antibody raised against the prototype strain. This may lead to the decline of vaccine efficacy and need to be further validated.

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