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Scientists have identified antibodies that neutralise Omicron and other variants of coronavirus by targeting areas that remain essentially unchanged as the virus mutates.
The research, published in the journal Nature, may help design vaccines and antibody treatments that will be effective against not only Omicron but other variants that may emerge in the future.
"This finding tells us that by focusing on antibodies that target these highly conserved sites on the spike protein, there is a way to overcome the virus' continual evolution," said David Veesler, an associate professor at the University of Washington School of Medicine in the US.
About Omicron Variant
The Omicron variant has an unusually high number of 37 mutations in the spike protein, which the virus uses to enter and infect the human cells.
It is thought that these changes explain in part why the variant has been able to spread so rapidly, to infect people who have been vaccinated and to reinfect those who have previously been infected.
"The main questions we were trying to answer were: how has this constellation of mutations in the spike protein of the Omicron variant affected its ability to bind to cells and to evade the immune system's antibody responses," Veesler said.
To assess the effect of these mutations, the researchers engineered a disabled, nonreplicating virus, called a pseudovirus, to produce spike proteins on its surface, as coronaviruses do.
They then created pseudoviruses that had spike proteins with the Omicron mutations and those found on the earliest variants identified in the pandemic.
The researchers first looked to see how well the different versions of the spike protein were able to bind to protein on the surface of cells, that the virus uses to latch onto and enter the cell. This protein is called the angiotensin converting enzyme-2 (ACE2) receptor.
They found the Omicron variant spike protein was able to bind 2.4 times better than spike protein found in the virus isolated at the very beginning of the pandemic.
They also found that the Omicron version was able to bind to mouse ACE2 receptors efficiently, suggesting Omicron might be able to "ping-pong" between humans and other mammals.
The researchers then looked at how well antibodies against earlier isolates of the virus protected against the Omicron variant.
The team found that antibodies from people who had been infected by earlier strains and from those who had received one of the six most-used vaccines currently available all had reduced ability to block infection.
Testing Antibodies from different people
Antibodies from people who had been infected, recovered and then had two doses of the vaccine also had reduced activity, but the reduction was less, about fivefold, clearly demonstrating that vaccination after infection is useful.
However, when they tested a larger panel of antibodies that have been generated against earlier versions of the virus, the researchers identified four classes of antibodies that retained their ability to neutralise Omicron.
Members of each of these classes target one of four specific areas of the spike protein present in not only SARS-CoV-2 variants but also a group of related coronaviruses, called sarbecoviruses.
These sites on the protein may persist because they play an essential function that the protein would lose if they mutated. Such areas are called "conserved."
The finding that antibodies are able to neutralise via recognition of conserved areas in so many different variants of the virus suggests that designing vaccines and antibody treatments that target these regions could be effective against a broad spectrum of variants, Veesler added.