A virus going through mutation is a natural part of its lifecycle. As coronavirus continues to mutate over time, studying its evolution can help scientists develop a vaccine. In a recent study, scientists explain how the human body is causing the virus to mutate while natural selection triggers it to fight back.
A team from the University of Bath and the University of Edinburgh in the UK published their findings in the Oxford Academic Journal. Their research describes that while SARS-CoV-2 mutates within the human body, natural selection of the virus allows it to cope up with the immune system trying to degrade coronavirus.
At the Milner Centre for Evolution, the team observed that humans are responsible for the virus' mutation due to the body's defense mechanism. They analyzed more than 15,000 virus genomes from international data and identified more than 6,000 mutations. From the genetic codes of the RNA letters A, C, U, and G - the basic building blocks that make up nucleic acids - they discovered that coronavirus had high rates of mutations with the U nucleobase.
Professor Laurence Hurst, Director of the Milner Centre for Evolution, said, "I have looked at mutational profiles for many organisms, and they all show some sort of bias, but I've never seen one as strong and strange as this." While the original genetic sequence contained CU and UC, the mutated sequence generated UU.
Natural Selection
Professor Hurst explained, 'It looks like mutation isn't random, but instead, we are attacking the virus by mutating it.' His team recognized the mutation as the work of the human protein APOBEC, which mutates viruses.
At the same time, the virus is fighting back against the mutation due to its natural selection or survival of the fittest. Coronavirus was found to be adapting to the body's immune defense mechanisms.
Explaining the importance of the U nucleobase, Professor Hurst said, 'the viruses that have too much U in them simply don't survive well enough to reproduce. We estimate that for every ten mutations that we see, there are another six we never get to see because those mutant viruses are too poor at propagating.'
Genetic Mutations
Genetic mutations that have may U sequences were less stable. The human immune system also contains proteins that can attack U residues, which results in killing weaker versions of the virus in the body.
It may also mean that although the body's APOBEC protein causes the virus to mutate, it may actually be degrading the virus. Therefore, the new data can help with vaccine designs.
Other researchers are attempting to make a synthetic, attenuated virus that replicated coronavirus so they can experiment on how to degrade it and help develop a vaccine. Professor Hurst said, "Knowing what selection favors and disfavors in the virus is really helpful in understanding what an attenuated version should look like. We suggest, for example, that increasing U content, as APOBEC does within our cells, would be a sensible strategy."
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