What we know about Sars-CoV-2 mutations

Hyperaxion May 7, 2020

Understanding the genetic variations of the new coronavirus may be essential for the development of a vaccine for Covid-19.

Understanding the mutations in Sars-CoV-2 is essential for the development of drugs or even a vaccine against Covid-19. This is precisely why the genetic variations of the new coronavirus have been studied by specialists from around the world.

What we know about Sars-CoV-2 mutations
(Credit: TPHeinzPixabay).

Among these researches is one from University College London, in England, published this Wednesday (6) on Infection, Genetics and Evolution. Researchers have identified 198 mutations that appear to have occurred independently in different parts of the world – which may give clues as to how the microorganism is adapting.

“All viruses naturally mutate,” Francois Balloux, one of the researchers, said in a statement. “Mutations in themselves are not a bad thing and there is nothing to suggest SARS-CoV-2 is mutating faster or slower than expected. So far we cannot say whether SARS-CoV-2 is becoming more or less lethal and contagious.”

Mutations are small changes in an organism’s genetic code that can cause it to develop new characteristics. According to the University College London team, the changes identified in the new coronavirus are not evenly distributed across its genome: some parts of the microorganism’s genetic code tend to vary more than others.

“A major challenge to defeating viruses is that a vaccine or drug might no longer be effective if the virus has mutated,” explained Balloux. “If we focus our efforts on parts of the virus that are less likely to mutate, we have a better chance of developing drugs that will be effective in the long run.”

(Credit: Oswaldo Cruz Foundation).

Europe and North America

When the new coronavirus infects our body, a spike protein on the surface of Sars-CoV-2 binds to a “receptor” protein located outside human cells, which allows the organism to enter our body. According to a study by the Los Alamos National Laboratory, in the United States, this protein has already undergone at least 14 mutations.

In a pre-published version of the article, made available on BioRxiv in late April, the researchers explain that the most worrying change in the protein is one that was named D614G. Scientists report that this is the most common mutation in patients in Europe and North America, where Covid-19 has spread rapidly.

“We were concerned that if the D614G mutation can increase transmissibility, it might also impact severity of disease,” they write in the article. Fortunately, although the mutation appears to make the virus more transmissible, the researchers say that “there was no significant correlation” between people infected with this variant and the development of more severe Covid-19 conditions.

“Although the functional significance of the changes observed have yet to be fully characterised, the study shows that SARS-CoV-2 can alter its genetic structure in multiple ways as it spreads around the world, a finding likely to have important implications for vaccine development,” wrote Jonathan Stoye, head of division of virology at The Francis Crick Institute, who was not involved in the study, in a comment.

Sars-CoV and Sars-CoV-2

In 2002 and 2003, a “relative” of the new coronavirus was responsible for causing an epidemic of severe acute respiratory syndrome (SARS) in China. At the time, a Sars-CoV mutation made it less harmful to humans – and this may have happened to its “cousin”, Sars-CoV-2.

Research by Arizona State University, in the United States, revealed a mutation of the new coronavirus in which 81 of the 30,000 components of the microorganism’s genetic code have disappeared. The study, published in the Journal of Virology last Friday (01), argues that the mutation is similar to the one that occurred with the SARS virus years ago.

A genome deletion was found that removes 27 protein building blocks, called amino acids, from the SARS-CoV-2 accessory protein ORF7a.
A genome deletion was found that removes 27 protein building blocks, called amino acids, from the SARS-CoV-2 accessory protein ORF7a. (Credit: Efrem Lim, ASU Biodesign Institute).

Scientists believe that the Sars-CoV mutation in 2003 weakened it and that, in turn, was an evolutionary advantage for the microorganism. It may seem contradictory, but the idea is this: a weaker version of the virus causes a less severe condition, allowing the infected to survive and infect more people – which is advantageous for the microorganism, as it allows the species to spread.

“One of the reasons why this mutation is of interest is because it mirrors a large deletion that arose in the 2003 SARS outbreak,” noted Efrem Lim, the research leader, in a statement to the press.

Only 16,000 versions of Sars-CoV-2 have been studied, a number that represents less than 0.5% of the strains in circulation – there are over 3.5 million confirmed cases of Covid-19 worldwide, and each infected could present a unique version of the new coronavirus. Still, experts are optimistic about what they have discovered.

“Being able to analyse such an extraordinary number of virus genomes within the first few months of the pandemic could be invaluable to drug development efforts, and showcases how far genomic research has come even within the last decade,” said Dr. Lucy van Dorp, a researcher at University College London. “We are all benefiting from a tremendous effort by hundreds of researchers globally who have been sequencing virus genomes and making them available online.”

Related topics:

Coronavirus Covid-19

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