Even as the newly reported Omicron variant is poised to replace Delta as the dominant variant across the world, a study led by an Indian-origin researcher shows that many mutations in the variant allow it to bond with human cells far more efficiently than previous strains.
The Omicron variant was first identified in South Africa in late November, and has since spread rapidly to 106 countries. The variant is now the dominant strain in many countries including the US, the UK, Denmark among others.
Of all the variants of coronaviruses so far, Omicron is the most heavily mutated with more than 30 mutations on its spike protein, which the virus uses to enter human cells. The variant also harbours a high number of mutations in regions of the spike protein that antibodies recognise, potentially dampening their potency.
Researchers from the University of British Columbia, Canada, studied Omicron using cryo-electron microscopy -- a technique that provides images of the virus at incredibly high resolution.
The results, published pre-print and not peer-reviewed yet, showed that "Omicron has far greater binding affinity than the original SARS-CoV-2 virus" due to new bonds created between the virus and human cell receptors, Dr Sriram Subramaniam, lead scientist, was quoted as saying to the Daily Mail.
In addition, the researchers tested Omicron against human and monoclonal antibodies, finding that the variant is more resistant to these immune system particles than other variants.
"The Omicron variant is unprecedented for having 37 spike protein mutations - that's three to five times more mutations than any other variant," Subramaniam, a biochemistry professor at the University, was quoted as saying in a statement.
According to Subramaniam, the increased mutations on the spike protein are important for two reasons: "Firstly, because the spike protein is how the virus attaches to and infects human cells. Secondly, because antibodies attach to the spike protein in order to neutralise the virus."
The team probed Omicron's mutations through microscopic imaging, and found that some of the mutations create additional bonds between the virus and ACE2 receptors - a human cell receptor located throughout the body, the report said.
These new mutations appear to "increase binding affinity", Subramaniam said, indicating that Omicron can attach more strongly to human cells.
The researchers compared Omicron's binding affinity to that of the Delta variant and the original strain of the coronavirus.
"Overall, the findings show that Omicron has far greater binding affinity than the original SARS-CoV-2 virus, with levels more comparable to what we see with the Delta variant," Subramaniam said.
Subramaniam's team also examined the Omicron spike protein's ability to evade both human antibodies and antibodies from monoclonal antibody treatments.
This analysis confirmed real-world data, showing that Omicron is more capable of evading antibodies than previous variants - meaning that treatments are less successful, the report said.
"Notably, Omicron was less evasive of the immunity created by vaccines, compared to immunity stemming from natural infection in unvaccinated Covid patients," Subramaniam said, adding "this suggests that vaccination remains our best defence against the Omicron variant."
Both the Omicron variant's increased binding affinity and its capacity to evade antibodies are "likely contributing factors to its increased transmissibility," Subramaniam said.