Bengaluru: Researchers from China have reported on a coronavirus called NeoCoV potentially being able to infect humans and cause a deadly disease, as identified in bat sequences.
However, the mutation required to infect humans has not been detected in this specific coronavirus naturally, and there are no human cases of the virus, which has been known to the scientific community for a decade. The research paper by Chinese scientists, including from Wuhan University and the Chinese Academy of Sciences, was uploaded on the biology preprint server bioRxiv Tuesday.
The paper outlined the molecular mechanism used by the virus to infect host cells in bats and in human cells in the lab, and identified a potential mutation that would make it possible for the virus to bind to human receptors.
This has led to some alarm in India, with the findings often misunderstood and the virus even being mistakenly categorised as a variant of SARS-CoV-2.
The NeoCoV virus is the closest known genetic relative to the MERS virus, leading to comparisons with the latter’s fatality rate of one in three infected people — but there’s no risk to humans from NeoCoV yet.
The World Health Organization (WHO) addressed the reports of NeoCoV Friday, stating that further study is required to assess whether the virus poses a threat to humans.
What does the paper say?
The research paper is a preprint, which means that it has not yet been peer reviewed or published in a journal. It outlines the differences between the receptors in bats and human cells for two viruses, NeoCoV and a closely related PDF-2180-CoV virus.
The preprint found that while the two viruses can easily use ACE2 receptors in bat cells to infect the flying mammals, they are unable to do so in human cells. The researchers identified the molecular mechanism that prevents the human cells from letting the virus latch on.
They then noticed that in the laboratory, when they artificially induced a mutation on the receptor binding motif — a small fragment of the virus that binds the spike protein to the ACE2 host cells — the virus was able to infect human cells.
This mutation, T510F, was edited into the protein unit by the scientists. When it was present, the virus latched on to experimental human cells more easily — but the mutation hasn’t been detected in any of the NeoCoV viral samples obtained naturally.
“NeoCoV can use ACE2 receptors of bats but they can’t use human ACE2 receptor unless a new mutation occurs,” summarised Dr Shashank Joshi of Maharashtra’s Covid task force.
Neo Cov demystified
1 NeoCov is an old virus closely related to MERS Cov which enter cells via DPP4 receptors
2. What's new : Neo cov can use ace2 receptors of bats but they can't use human ace2 receptor unless a new mutation occurs
Everything else is hype 🙏
— Dr. Shashank Joshi (@AskDrShashank) January 28, 2022
Additionally, the research team found that the virus couldn’t be destroyed by antibodies from Covid or MERS, which is to be expected. Therefore, the authors flagged the virus, stating that it is potentially a few mutations away from spilling over into humans and being capable of infecting us.
What is NeoCoV?
Despite the “neo” appellation, this isn’t a new or unknown virus. It was first identified in 2011 in a species of bat in South Africa called Neoromicia capensis, which led to the name of the virus. The virus was identified from bat fecal pellets, a common source for scientists to study viruses hosted by bats.
It was discovered in 2014 that NeoCoV is genetically 85 per cent similar to the MERS-CoV virus, making it the latter’s closest relative. In 2012, MERS-CoV had caused an epidemic with a fatality rate of 35 per cent.
There are four known types of coronaviruses: alpha, beta, gamma, and delta (different from the delta variant of SARS-CoV-2). Alphacoronaviruses and betacoronaviruses are the ones capable of causing infection in humans and other mammals, while the other two types have infected birds.
There are a total of seven human coronaviruses, including SARS-CoV-2, SARS-CoV, and MERS-CoV, and they are all either alpha or betacoronaviruses. NeoCoV is also a betacoronavirus.
Bats — which have immune response adaptations that allow them to host a wide variety of thousands of viruses in their bodies — are the largest reservoir of mammalian coronaviruses. The origins of coronaviruses that infect humans can be traced back to their closest relatives in bats.
What is the risk to humans?
There are no known human cases of NeoCoV, and it has not spilled over into the human population. Reports calling it deadly to one in three people refer to the fatality rate of its closest relative, MERS.
When a coronavirus — or any virus — jumps from one species to another, it undergoes genetic mutations that allow it to transform into a different strain that’s capable of infecting the new species. It’s then given a different name.
Every day, there are hundreds of viruses and plenty of coronaviruses that are a few mutations away from potentially infecting humans. Typically, such spillover events occur within intermediate host animals like pigs or camels, where more favourable mutations are acquired that make it easier for viruses to jump into humans.
Bats are subject to active monitoring and genome sequencing for potential viruses, and have been since before the current pandemic. Identification of a potential mutation that could allow a virus to infect humans is important to understand risk.
Further investigation is warranted to understand how easily such a mutation could occur. To do this, researchers will study the potential for mutation through human cells in the lab, and how quickly other, similar, mutations occur in natural settings.
Until that is done, the risk to humans is not fully understood. There are hundreds of viruses that pose a risk to humans every day, but spillover events, or the jumping of a virus from one species to another, does not commonly occur on a daily basis.
(Edited by Rohan Manoj)