None of the SARS-CoV-2 genetic mutations appear to increase transmission

There are no currently documented mutations SARS-CoV-2 According to a study led by researchers at University College London, the virus increases its proliferation capacity in humans.

Analysis of the virus genome with over 46,000 people COVID-19 From 99 countries is published today (November 25, 2020) Nature communication.

The first and corresponding authors are Dr. Lucy van Dorp (UCL Genetics Institute) said: “The number of SARS-CoV-2 genomes generated for scientific research is staggering. We found out early in the pandemic that we needed new approaches to analyze huge amounts of data near real-time to flag new mutations in the virus that might affect its transmission or symptom severity.

“Luckily, we found that none of these mutations are spreading COVID-19 more quickly, but we have to be vigilant and continue to monitor new mutations, especially as vaccines are rolled out.”

Coronaviruses like SARS-CoV-2 are of a type Royal army Viruses, which can all develop mutations in three different ways: accidentally copying errors during viral replication, through interactions with other viruses that infect the same cell (recombination or recombination), or They may be induced by host HNA modification systems that are part of host immunity (eg a person’s own immune system).

Most mutations are neutral, while others may be beneficial or harmful to the virus. Both neutral and beneficial mutations may be more common as they pass through descendant viruses.

UCL, Sierrad and Universite de la Réunion and the research team University of Oxford, Analyzed a global dataset of virus genomes from 46,723 people with COVID-19, collected by the end of July 2020.

Researchers have so far identified 12,706 mutations in SARS-CoV-2, the virus COVID-19. For 398 of the mutations, there is strong evidence that they occurred repeatedly and independently. Among them, the researchers awarded 185 mutations that have occurred independently at least three times during the epidemic.

To test whether the mutation enhances the transmission of the virus, the researchers modeled the evolutionary tree of the virus, and analyzed whether a particular mutation within a given branch of the evolutionary tree is becoming increasingly common – namely , Testing whether a virus develops for the first time after mutation, that virus’s progeny outperform closely related SARS-CoV-2 viruses without that particular mutation.

Researchers have found no evidence that any common mutation is increasing the infectivity of the virus. Instead, they found that most of the common mutations are neutral for the virus. This includes a mutation in a virus spike protein called D614G, which has been widely reported as a common mutation that may make the virus more contagious. New evidence suggests that this mutation is not actually significantly associated with increased transmission.

Researchers found that most of the common mutations appear to be induced by the human immune system, not as a result of the virus being adapted for its novel human host. This situation is contrary to another analysis of the same team when SARS-COV-2 subsequently jumped from humans to farmland.

Dr. Van Dorp said: “When we analyzed the virus genome from the mink, we were surprised to see the same mutation appearing in different mink farms repeatedly, rarely before in humans after those same mutations. Gone. “

Lead author Professor François Balloux (UCL Genetics Institute) said: “We can well remember this period of early adaptation to the virus in humans. We first speculated that SARS-CoV-2 jumped into humans in October or November 2019, but in the first genome we have a date in late December. By that time, viral mutations important for infectivity in humans can emerge and drive us away from them. “

It should only be expected that a virus will mutate into different lineages and eventually segregate, as it is more common in human populations, but it is not necessary that any lineages will emerge that are more infectious or harmful.

Dr. Van Dorp said: “The virus seems well adapted for transmission between humans, and it may have already reached its fitness optimum in the human host by the time it was identified as a novel virus . “

Researchers warn that imminent introduction of vaccines is likely to lead to new selective pressures on the virus to avoid recognition by the human immune system. This may lead to the emergence of vaccine-escape mutants. The team stressed that the computational framework they developed should prove useful for the timely detection of possible vaccine-escape mutations.

Professor Baloux concluded: “The news on the vaccine front sounds very good. This virus may well receive vaccine-escape mutations in the future, but we believe we will be able to flag them immediately, which will allow vaccines to be updated when needed. “

Reference: 25 November 2020, Nature communication.
DOI: 10.1038 / s41467-020-19818-2

The study was supported by the Newton Fund UK-China NSFC initiative and the Biotechnology and Biological Sciences Research Council (BBSRC).

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