As the 2019-nCoV coronavirus epidemic continues to expand, virologists are striving to better understand this new virus in order to develop avenues of prophylaxis and treatment. Recently, a team of researchers has shown that the genome of 2019-nCoV is 80% identical to that of the coronavirus responsible for SARS. A similarity that could make it possible to use the therapeutic protocols developed within the framework of SARS against the 2019-nCoV coronavirus.
The new coronavirus that is spreading in China appears to be similar to SARS in two important ways: the two viruses share 80% of their genetic code and both originate from bats. These are the conclusions of a pair of studies published in the journal Nature, which delve into the genome of the Wuhan coronavirus (2019-nCoV), which has infected more than 20,000 people and has killed more than 400 since December.
” In essence, it is a version of SARS that spreads more easily but causes less damage. This indicates that the treatments and vaccines developed for SARS should work for the Wuhan virus. Said Ian Jones, a virologist at the University of Reading in the UK.
The sequencing of the genome of the different coronaviruses
Many coronaviruses are zoonoses, which means they can spread to humans from animals. In the case of SARS and the new coronavirus (officially named 2019-nCoV), the bats were the original hosts. They then infected other animals with their droppings or saliva, and the unintentional intermediaries transmitted the virus to humans.
(A): Metagenomic analysis of 2019-nCoV. (B): Genomic organization of 2019-nCoV. (C): Similarities between 2019-nCoV and other strains of coronavirus. Credits: Peng Zhou et al. 2020
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Between November 2002 and July 2003, SARS killed 774 people and infected 8,098 in 29 countries. To determine the origin of the new coronavirus, scientists examined the full genomes of the coronavirus samples taken from patients at the start of the epidemic.
2019-nCoV: a coronavirus similar to SARS
In the first study, a team led by researchers from the Wuhan Institute of Virology examined virus samples from seven patients who initially reported severe pneumonia. Six of the patients worked at the Huanan seafood wholesale market in Wuhan, China, where the outbreak is believed to have started in December.
About 70% of the samples were almost identical to each other and their genetic sequence was 79.5% similar to SARS. The researchers behind this study also discovered that 2019-nCoV is almost identical to other coronaviruses circulating in Chinese bat populations – 96% of the genetic codes match.
Genomic organizations of 2019-nCoV (top), a common coronavirus strain (betacoronavirus, medium) and SARS. Between 2019-nCoV and SARS, the researchers found an 80% genetic similarity. Credits: Fan Wu et al. 2020
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A second study, led by scientists from Fudan University in Shanghai and the China Center for Disease Control and Prevention, examined a 41-year-old man who also worked in the market. He entered a hospital in Wuhan on December 26 with symptoms of respiratory illness and fever. An analysis of the virus that infected him showed that it is 89% similar to a group of SARS-type coronaviruses called betacoronaviruses, which had previously been found in Chinese bats.
How does coronavirus infect human cells?
Vincent Munster, virologist at Rocky Mountain Laboratories, previously stated that only betacoronaviruses can jump in humans and settle in our respiratory tract. Indeed, not all coronaviruses have the same shape.
The circular shell of the virus is studded with pointy proteins that help it attach to a host cell. If the shape of the spikes does not match the receptors on a potential host’s cells, the virus cannot spread. But when a coronavirus mutates, the shape of these proteins is altered, which sometimes allows the virus to attach to a new host.
Zheng-Li Shi, the lead author of the study who examined seven virus samples, showed that SARS and the new coronavirus can bind to the same receptor, called ACE2. This may explain the patients’ pneumonia symptoms.
Similarities between 2019-nCoV and SARS: they offer a possibility of treatment
Because SARS and 2019-nCoV bind to human cells in the same way, the authors of the new studies say that the potential treatments for the former could also work for the latter. No specific treatment or vaccine has been developed for SARS or this coronavirus, but researchers have worked on certain preclinical drugs and vaccines for SARS. This work could probably be applied to this virus.
However, they stated that the ability to use SARS antibodies to treat 2019-nCoV has yet to be confirmed – for now, this is only a guess. The study authors also suggested two other potential ways to treat the new coronavirus.
On the same subject: It’s official: a new human organ has been classified
Phylogenetic tree showing the correspondences between the genomes of different coronaviruses. The genetic similarities between 2019-nCoV and SARS could allow the use of treatments developed for the second on the former. Credits: Peng Zhou et al. 2020
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Patients who have previously been infected with 2019-nCoV have produced antibodies – proteins used by our immune system to fight bacteria and viruses – which have the potential to neutralize the virus. Another type of anti-coronavirus antibody produced in horses has also been shown to neutralize 2019-nCoV, the authors add. This horse antibody has also been used to fight the SARS virus.
A still unknown intermediate animal host
However, experts have yet to confirm the animal species that allowed the new coronavirus to spread from bats to humans. ” We still don’t know if another species served as an intermediate host to amplify the virus, or what species that host could have been. “Explains Michael Skinner, virologist at theImperial College London. But the new study by Shi and his colleagues offers some clues.
Genetic information from the new coronavirus indicates that it can bind to the ACE2 receptor in humans, as well as the same receptor in bats, pigs, and civets – a weasel-like mammal that served as intermediate species for SARS. This information, combined with the similarity of the virus to other bat coronaviruses, suggests that these three species may be intermediaries.
” The direct transmission of CoV from bats to people is also theoretically possible ” according to Johns Hopkins Center for Health Security. On January 22, a group of scientists who publish the journal Journal of Medical Virology suggested that the intermediate species in the coronavirus outbreak could be the Chinese cobra.
But Skinner said the new information about his genome indicates that the virus is not really compatible with some of the more exotic hosts that were considered earlier in the epidemic. However, the only way to know where the virus comes from is by taking DNA samples from animals sold at the Huanan market and from bats in the area.
Sources: Nature 1 and 2
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