Coronavirus mutations: what we have learned so far

In early January, the first genomic sequence of SARS-CoV-2 (the virus that causes COVID-19) was released on a monica called “Wuhan-1”. This 30,000-character string (the genetic code A, T, C, G) marked the first day of the race to understand the genetics of this newly discovered coronavirus. Currently, an additional 100,000 coronavirus genomes sampled from COVID-19 patients in more than 100 countries have been added to Wuhan-1. Geneticists around the world are mining data to get answers. Where did SARS-CoV-2 come from? When did you start infecting humans? How does the virus mutate? Is it important? SARS-CoV-2 genomics, like the virus itself, has grown and become global.

The term “mutation” tends to remind us of the image of a dangerous new virus with enhanced ability to travel around the globe. And while mutations always appear and sometimes sweep, early mutations in SARS-CoV-2 are Virus Spreads almost unnoticed — mutations are a completely natural part of any organism, including viruses. The overwhelming majority do not affect the ability of the virus to spread or cause the disease.

Mutations only mean a difference. Genome character changes. Although the SARS-CoV-2 population was genetically essentially unchanged when it jumped into the first human host In late 2019, More than 13,000 of these changes are included in the 100,000 SARS-CoV-2 sequenced to date. However, the two viruses from two patients worldwide differ only on average 10 characters.. This is a small part of the virus’s genetic code totaling 30,000 characters, which means that all circulating SARS-CoV-2 can be considered part of a single clonal lineage.

Mutate slowly

It will take some time for the virus to acquire significant genetic diversity. SARS-CoV-2 mutates fairly slowly against the virus. Some changes every month; 2-6 times lower More than the number of mutations acquired by the influenza virus during the same period.

Nevertheless, mutations are the basis on which natural selection can act. The most common mutations do not make the virus work or have no effect. Nevertheless, there is a possibility that mutations may affect the infectivity of SARS-CoV-2 in the new human host. As a result, since the first SARS-CoV-2 genome was sequenced in Wuhan, intensive to determine if identifiable mutations could significantly alter viral function. Efforts have been made.

A notorious mutation in this context is an amino acid change in the SARS-CoV-2 spike protein, a protein that gives coronavirus a characteristic coronary process and allows it to attach to host cells. Changes in this single property in the viral genome D614G – It has been shown to increase viral infectivity of cells grown in the laboratory, but has no measurable effect on disease severity. This mutation is almost systematically found in the other three mutations, but all four are found in about 80% of the sequenced SARS-CoV-2 and are the most frequent set of mutations in the circulation. It has become.

Like other mutations, the D614G challenges increased in frequency because they happened to be in the virus that caused the early successful outbreak. Really give benefits In their career. Genomics works on UK datasets, but suggests a subtle role for the increasing D614G Strain growth rate Carrying it, we were able to find our own job No measurable effect At the time of transmission.

Simply carry around

D614G is not the only mutation found frequently. Strings of three mutations within the SARS-CoV-2 protein shell have also gradually appeared in the sequence data and are now found in one-third of the viruses. A single change at position 57 of the Orf3a protein, a known immunogenic region, occurs in a quarter. Other mutations are present in spike proteins, and countless others appear to have been induced by our activity Own immune response.. At the same time, there is no consensus that either of these or any other significantly alters the infectivity or pathogenicity of the virus. most mutation It is simply carried while SARS-CoV-2 continues to spread successfully.

However, replacement is not the only small edit that can affect SARS-CoV-2. Deletion of the SARS-CoV-2 accessory gene Orf7b / Orf8 Reduce toxicity SARS-CoV-2 can induce mild infection in patients. A similar Delete May have worked with Same way Related to SARS-CoV-1 Coronavirus Responsible for SARS that occurred in 2002-04. The move to less toxic SARS-CoV-2 is welcome news, but the removal of Orf8 has been around since the early days of the pandemic and does not appear to be increasing in frequency.

Adaptive changes can still occur, but all data available at this stage suggests that we have been facing the same virus since the onset of the pandemic. Chris Whitty, UK Chief Medical Officer, was right to pour cold water on the idea that the virus has. Mutated to a gentle one More than the cause of imposing a blockade on Britain in March. The potential reduction in the severity of symptoms seen during the summer is probably the result of improved treatment rather than changes in the virus-infected adolescents, containment measures (such as social distance), and the virus itself. However, while SARS-CoV-2 hasn’t changed significantly to date, we’re ready to keep pace by continuing to expand our tools to track and track its evolution.

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