Updated: December 22, 2020 12:22:34 am
People wait on the esplanade at Paddington Station in London, after the announcement that London will move to Level 4 Covid-19 restrictions starting at midnight on Saturday, December 19, 2020 (Stefan Rousseau, PA via AP) .
Written by Apoorva Mandavilli
Like vaccines start offering hope To emerge from the pandemic, officials in Britain last weekend sounded an urgent alarm over what they called a highly contagious new variant of the coronavirus circulating in England.
Citing the rapid spread of the virus through London and surrounding areas, Prime Minister Boris Johnson imposed the country’s tightest blockade since March.
“When the virus changes its method of attack, we must change our method of defense,” he said.
London train stations were filled with crowds of people struggling to get out of the city when the restrictions went into effect. On Sunday, European countries began closing its borders to travelers from the UK, hoping to shut down the new iteration of the pathogen.
In South Africa, a similar version of the virus has emerged, sharing one of the mutations seen in the British variant, according to the scientists who detected it. This virus has been found in up to 90% of the samples whose genetic sequences have been analyzed in South Africa since mid-November.
Scientists are concerned about these variants but not surprised by them. Researchers have recorded thousands of small modifications in the genetic material of the coronavirus as it has passed around the world.
Some variants become more common in a population simply by luck, not because the changes somehow overload the virus. But as it becomes more difficult for the pathogen to survive, due to vaccines and increasing immunity in human populations, researchers also hope that the virus will obtain useful mutations that allow it to spread more easily or escape detection by the virus. immune system.
“It’s a real warning that we need to pay more attention,” said Jesse Bloom, an evolutionary biologist at the Fred Hutchinson Cancer Research Center in Seattle. “Certainly, these mutations are going to spread, and definitely, the scientific community, we need to monitor these mutations, and we need to characterize which ones have effects.”
The British variant has around 20 mutations, including several that affect how the virus attaches to and infects human cells. These mutations may allow the variant to replicate and transmit more efficiently, said Muge Cevik, an infectious disease expert at the University of St. Andrews in Scotland and a scientific adviser to the British government.
But the estimate of higher transmissibility (British officials said the variant was up to 70% more transmissible) is based on models and has not been confirmed in laboratory experiments, Cevik added.
“In general, I think we need to have a little more experimental data,” he said. “We cannot completely rule out the fact that some of this transmissibility data could be related to human behavior.”
Also in South Africa, scientists were quick to note that human behavior was driving the epidemic, not necessarily new mutations whose effect on transmissibility had not yet been quantified.
The British announcement also raised concerns that the virus could evolve to become resistant to vaccines that are recently being released. Concerns center on a couple of alterations in the viral genetic code that can make it less vulnerable to certain antibodies.
A woman walks down a rain-soaked Oxford Street in London. (The New York Times: Andrew Testa)
But several experts called for caution, saying it would take years, not months, for the virus to evolve enough to render current vaccines impotent.
“No one should worry that there is going to be a single catastrophic mutation that suddenly crushes all immunity and antibodies,” said Bloom. “It is going to be a process that occurs on a time scale of several years and requires the accumulation of multiple viral mutations. It’s not going to be like an on-off switch. “
The scientific nuance mattered little to Britain’s neighbors. Concerned about the possible influx of travelers carrying the variant, the Netherlands said it would suspend flights from Great Britain from Sunday until January 1.
Italy also suspended air travel, and Belgian officials on Sunday enacted a 24-hour ban on arrivals from the UK by air or train. Germany is drawing up regulations limiting travelers from Great Britain and South Africa.
Other countries are also considering bans, including France, Austria and Ireland, according to local media. Spain has asked the European Union for a coordinated response to the flight ban. Governor Andrew Cuomo of New York asked the Trump administration to consider banning flights from Britain.
In England, transport officials said they would increase the number of police officers monitoring centers such as train stations to ensure that only essential trips are made. The country’s health secretary, Matt Hancock, on Sunday called those who were packing trains as “clearly irresponsible.”
He also said the restrictions Johnson imposed could be in place for months.
Like all viruses, the coronavirus changes shape. Some genetic changes are inconsequential, but some can give you a head start.
Scientists especially fear the latter possibility. The vaccination of millions of people can force the virus to make new adaptations, mutations that help it evade or resist the immune response. There are already small changes in the virus that have arisen independently multiple times around the world, suggesting that the mutations are helpful to the pathogen.
The mutation that affects antibody susceptibility, technically called a 69-70 deletion, meaning letters are missing from the genetic code, has been seen at least three times: in Danish minks, in people from Britain, and in an immunosuppressed patient. which became much less sensitive to convalescent plasma.
“This thing is broadcasting. It is acquiring. It is adapting all the time, ”said Dr. Ravindra Gupta, a virologist at the University of Cambridge who last week detailed the recurrent appearance and spread of the deletion. “But people don’t want to hear what we say, that is, this virus will mutate.”
A woman passes a suitcase next to a Christmas tree on the esplanade of Waterloo Station in central London, Sunday, December 20, 2020 (Victoria Jones, PA via AP).
The new genetic deletion changes the spike protein on the coronavirus surface, which it needs to infect human cells. Variants of the virus with this deletion emerged independently in Thailand and Germany in early 2020 and became prevalent in Denmark and England in August.
Several recent articles have shown that the coronavirus can evolve to avoid recognition of a single monoclonal antibody, a mixture of two antibodies, or even convalescent serum administered to a specific individual.
Fortunately, the entire body’s immune system is a much more formidable adversary.
The Pfizer-BioNTech and Moderna vaccines induce an immune response only to the spike protein carried by the coronavirus on their surface. But each infected person produces a large, unique and complex repertoire of antibodies against this protein.
“The fact is, you have thousands of bigwigs targeting the virus,” said Kartik Chandran, a virus expert at Albert Einstein School of Medicine in New York. “No matter how the virus twists and turns, it is not that easy to find a genetic solution that can actually combat all these different antibody specificities, not to mention the other arms of the immune response.”
In summary: it will be very difficult for the coronavirus to escape the body’s defenses, despite the many variations it may adopt.
The escape of immunity requires a virus to accumulate a series of mutations, each of which allows the pathogen to erode the effectiveness of the body’s defenses. Some viruses, like influenza, accumulate these changes relatively quickly. But others, like the measles virus, pick up almost none of the alterations.
Even the influenza virus takes five to seven years to collect enough mutations to completely escape immune recognition, Bloom noted. His lab released a new report on Friday showing that common cold coronaviruses also evolve to escape immune detection, but over many years.
The scale of infections in this pandemic can rapidly generate diversity in the new coronavirus. Still, a vast majority of people around the world have yet to become infected, and that has given scientists hope.
“It would be a bit surprising to me if we saw active selection for immune escape,” said Emma Hodcroft, a molecular public health researcher at the University of Bern in Switzerland.
“In a population that is still largely naive, the virus just doesn’t need to do that yet,” he said. “But it’s something we want to watch out for in the long term, especially as we start vaccinating more people.”
Immunizing about 60% of the population in about a year and keeping the number of cases low while that happens will help minimize the chances of the virus mutating significantly, Hodcroft said.
Still, scientists will need to closely monitor the evolution of the virus to detect mutations that may give it an advantage over vaccines.
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