Figure: Atomic structure of the Omicron variant spike protein (purple) bound to the human ACE2 receptor (blue)
.
Source: UBC School of Medicine
"Understanding the molecular structure of the viral spike protein is important as it can help us develop more effective therapeutic Omicron and related variants in the future," said lead author Sriram Subramaniam, Ph.
D.
, professor in UBC's Department of Biochemistry and Molecular Biology.
By analyzing the mechanism by which this virus infects human cells, we can develop better treatments—disrupting this process and rendering the virus ineffective
.
"
The spike protein located on the outside of the coronavirus enables SARS-CoV-2 to enter human cells
.
The Omicron variant had an unprecedented 37 mutations in its spike protein, three to five times more than the previous variant
.
Structural analysis revealed that some mutations (R493, S496 and R498) established new salt bridges and hydrogen bonds between the spike protein and the human cell receptor ACE2
.
The researchers concluded that these new bindings appeared to increase the binding affinity, the strength of the virus's binding to human cells, while the other mutation (K417N) decreased the strength of this binding
.
Dr Subramaniam said: "Overall, the findings suggest that Omicron has greater binding affinity than the original virus, at levels more similar to what we have seen with the Delta virus variant
.
It is noteworthy that despite such a wide range of mutations , Omicron variants have evolved to retain the ability to bind to human cells
.
"
The researchers conducted further experiments showing that the Omicron spike protein exhibited increased antibody evasion
.
Compared to the previous variant, Omicron showed measurable escape in all six mAb tests, five of which escaped completely
.
The variant also showed an increase in evasion of antibodies collected from vaccinated individuals and from unvaccinated COVID-19 patients
.
Notably, Omicron evaded less immunity from vaccines than immunity from natural infection in unvaccinated patients
.
This shows that vaccination remains our best defense
.
Dr.
Subramaniam said
.
Based on the observed increases in binding affinity and antibody avoidance, the researchers say the spike protein mutation may be a factor that increases the ability of the Omicron variant to spread
.
As a next step, Dr.
Subramaniam said, his research team will use this knowledge to support the development of more effective treatments
.
"An important focus of our team is to better understand the binding of neutralizing antibodies, as well as therapeutics that are effective across the full spectrum of variants, and how these approaches can be used to develop anti-variant therapies
.
"
article title
SARS-CoV-2 Omicron Variant: ACE2 Binding, Cryo-EM Structure of Spike Protein-ACE2 Complex and Antibody Evasion
