An offshoot of the Delta coronavirus variant that is efficient at evading the immune system needs to be closely monitored, scientists have warned, amid fears it could acquire further mutations that make it better suited to infecting humans.
The variant possesses the infamous E484K mutation, located in the virus’ spike protein, which is associated with circumventing the body’s antibody response.
Testing from the UK Health Security Agency (UKHSA) has shown that Delta with E484K reduces the neutralising effect of antibodies in a similar way to Beta, which also carries the same mutation.
As of 8 November, 152 cases of the variant had been detected across England, Scotland and Wales - an increase of 59 since the middle of October. These occurred “mostly in three self-limiting outbreaks,” UKHSA said.
There are no signs that Delta with E484K, otherwise known as Delta-plus, is set to become dominant in the UK, but scientists have warned it may further evolve to become more problematic - especially with infection rates and the prevalence of the virus so high.
Dr Stephen Griffin, a virologist at Leeds University, said the variant “has an advantage in that it’s immunity-evading” but the presence of E484K “appears to come at a cost” to the virus’ transmissibility.
“It certainly isn’t fitter than the original Delta that took hold in the UK,” he added. “But it has persisted, albeit at a low level.”
If the variant was to acquire additional mutations of concern that work in tandem with E484K, there “could be trouble,” said Dr Griffin.
Delta-plus could prove to be more troublesome in a highly-vaccinated population, though there are too many different factors at play - such as waning immunity, oscillating infection rates and the booster rollout - to say with any confidence what will happen, said Aris Katzourakis, a professor of evolution and genomics at Oxford University.
“We really don’t know what the changing vaccine landscape will do,” he said. “Now with everyone vaccinated in the UK (almost), its possible Delta with E484K will dominate even if it offers a small advantage. This could be a step up to a worse direction.”
Professor Francois Balloux, director of the Genetics Institute at University College London, echoed this sentiment.
“Delta-plus strains may become more competitive once essentially everyone in the population has acquired immunity,” he said. “Another possibility might be for Delta to acquire other mutations that could reduce the cost of carrying E484K - i.e. compensatory mutations.”
Meaghan Kall, an epidemiologist at UKHSA, said that the variant was “definitely one to watch”.
It’s continuing transmission comes at a time of high Covid prevalence in the UK, with 38,263 new infections reported on Monday.
Against this backdrop, there is an increased risk of the virus “taking another dangerous step forward” in terms of its evolution, said Dr Griffin.
“The recipe in the UK is wrong,” he said. “If you have a partially vaccinated population and high prevalence, then you’re giving it enough of a challenge to change but not enough to suppress it.
“The unlikely then becomes more likely over time.
“And with this virus, it doesn’t have to go back to the drawing broad when it changes. It can accumulate things that, at the time may not be advantageous, but in the future could be. If it acquired a new mutation that allowed E484K to be tolerated and the virus therefore retained its transmissibility, then we’d be in danger.”
Prof Katzourakis said he was concerned at the prospect of the N501Y mutation - a key component of the genetic make-up of Alpha - emerging in Delta-plus.
“If we start seeing E484K and N501Y in the same virus, I would start worrying a lot more,” he said.
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