A study explains the differences between omicron and its 'older sister', the alpha variant

The omicron and alpha variants of the coronavirus, the latter detected for the first time in the United Kingdom and recognized as worrisome on December 18, 2020 by the World Health Organization (WHO), share some mutations, which cause it to have similar behavior in some respects.

It was new research from the lab of Gary Whittaker, a professor of virology in the Department of Microbiology and Immunology at the Cornell University College of Veterinary Medicine (United States), which has revealed key information about omicron’s oldest sister variant, alpha.

The mutation that gave rise to alpha is very similar to the one that later created omicron, but with very different results in terms of severity of each, according to this research, published in the journal Science.

The scientists observed a major mutation in a key region of the alpha spike protein, called the furin cleavage site. This site is thought to be where much of the virus’ virulence comes from. However, “in reality, turned out to be relatively inconsequential“, apunta Whittaker.

Thus, although alpha had a notable mutation at the furin cleavage site, it had little effect on its ability to infect cells and cause disease.

Similarities Between Alpha and Omicron

Alpha and omicron share the same mutation at the furin cleavage site and, on a different genetic background, this may explain why the latter spreads so fast, but appears to cause less severe disease.

“Omicron has many of the same characteristics as alpha. What we have learned about the latter helps us understand the other and possible future variants“, apunta Whittaker.

Although alpha went unnoticed in many countries, its arrival was important from a scientific point of view. It was the first major mutation of the SARS-CoV-2 virus, which occurred at the furin cleavage site.

However, this change in alpha did not make a big difference in the impact of the variant as a disease: it took the arrival of delta, which had a different mutation at the same site, to turn the virus into a more lethal weapon.

Ómicron, “a step back in the evolutionary trajectory” of SARS-CoV-2

A health worker performs an antigen test on a man in Madrid.

Scientific evidence has shown that although the omicron variant is highly contagious, it is much less harmful. “It’s back to square one. It’s back to the same genetic change at the furin cleavage site that the alpha had. Essentially took a big step back in its evolutionary trajectory as a pathogen,” explains Whittaker.

This has been most evident in the variant’s ability to produce cell-to-cell fusion, a telltale sign used to determine the ability of the virus to cause virulence in its host.

“Alpha makes the cells fuse. Delta would fuse the cells even more… but then omicron comes along, and their host cells don’t fuse at all. has completely regressed“, details the scientist.

If the furin cleavage sites of alpha and omicron were essentially the same, why was alpha a more deadly variant than omicron? The answer must lie elsewhere in the genetic makeup of these variants, which scientists hope to be able to explain in the future.

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