Since the start of the COVID-19 pandemic in early 2020, a series of variants of the SARS-CoV-2 have emerged around the world. In the early stages of the epidemic, a new coronavirus containing a mutation in the spike protein D614G dominated the world. The scientific community generally believes that the D614G mutation makes the virus easier to spread. Recently, the most eye-catching is the fast-spreading mutants found in the United Kingdom, South Africa, and Brazil. Scientists suspect that the specific mutation combination of these mutants may affect the virus' transmission ability, pathogenicity, and immune evasion ability. These issues are still under further study.

In terms of mutation speed, SARS-CoV-2 is not top-notch. On the contrary, compared with many other viruses, its speed is about half of the influenza virus and a quarter of HIV. The approximately 30,000 base RNA genomes will have about two base mutations per month.

However, the epidemic has lasted for more than a year, which means that the SARS-CoV-2 inevitably mutates and accumulates, and then develops into a diverse evolutionary tree with countless branches.

Compared with the original virus, the infectivity and pathogenicity of many mutant strains (each strain carrying a specific mutation) has not changed much, so they were not concerned very much. There are three rapidly spreading variants that have attracted much attention, which were first found in the United Kingdom, South Africa, and Brazil, respectively, with some unusual mutations. They share a mutation called N501Y, which is in the receptor binding domain (RBD) ( of the spike protein on the virus surface. RBD is essential for the SARS-CoV-2 infection in that the virus uses RBD to bind to the ACE2 receptor on the surface of human cells to enter the cell. Cell and animal model studies have shown that the mutation of N501Y may enable the SARS-CoV-2 to bind more closely to the ACE2 receptor and enhance the virus infectivity.

The N501Y mutation alone is not that terrible. However, there are an unusually large number of other mutations, some of which are also on the spike protein. It is possible that the superposition of these multiple mutations—rather than a single mutation—causes substantial changes in virus characteristics, such as higher transmission capacity.

Around November and December 2020, scientists found that the proportion of mutant strains with N501Y mutations in infected people increased significantly. The fact that similar mutations appeared in three separate variants and spread rapidly makes scientists suspect that these variants may have an evolutionary advantage.

There are 8-10 mutations superimposed on the spike protein of the South African and Brazilian variants. The most worrying thing is that the spike protein is both the antigen of the vaccine and the target of antibody cocktail therapy (such as that developed by Regeneron Pharmaceuticals). These mutant strains are likely to become the pioneers of a new generation of SARS-CoV-2, which can evade antibody therapy, can escape the immune protection of vaccines, or even both.

Several well-known mutant strains are as follows.

* VOC202012/01: 23 mutations, firstly discovered in late December 2020 in the UK.
* 20C/501Y.V2: 21 mutations, firstly discovered in late December 2020 in South Africa.
* 20J/501Y.V3: 17 mutations, discovered on tourists from Brazil during a Japanese airport inspection in January 2021.
* COH.20G/501Y: N501Y mutation on the spike protein, but lacks most other mutations of the British variant B.1.1.7. Since late December 2020, N501Y variants have been detected in Columbus, Ohio, and other states.
* S:Q677H: Q677H mutation on spike protein, A85S mutation on M protein, and D377Y mutation on NP protein, frequently found in Ohio and many Midwestern states in the United States in December 2020 and January 2021.
* L452R, B1429

New variants will appear unless the epidemic is effectively controlled. At present, worldwide researchers are still working on virus mutation and virus traceability.

Author's Bio: 

a fan of biotechnology