Now that vaccines are beginning to give hope of a pandemic, British authorities warned last weekend of a new highly contagious variant of the coronavirus circulating in England.
Taking as a reference the rapid spread of the virus in and around London, Prime Minister Boris Johnson imposed the strictest blockade on the country in March.
“If the virus changes its method of attack, we need to change our method of defense,” he said.
A crowd trying to get out of town when the restrictions came into force packed the stations in London. On Sunday, European countries began closing their borders to travelers from the United Kingdom, hoping to block the road to the new version of the pathogen.
In South Africa, a similar version of the virus has emerged which, according to the scientists who detected it, shares one of the mutations observed in the British version. This virus has been found in up to 90% of samples whose genetic sequences have been analyzed in South Africa since mid-November.
Scientists are worried about these variants, but they are not surprised. Researchers have seen thousands of small changes in the genetic material of coronavirus as it has spread around the world.
Some variants become more common in a population just by chance, not because the changes in some way overload the virus. However, as the pathogen becomes more difficult to survive due to vaccines and the growing immunity of human populations, researchers also hope that the virus will get useful mutations that will allow it to spread more easily or escape detection. . of the 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. “Undoubtedly, these mutations will spread, and ultimately the scientific community needs to monitor these mutations and describe which ones have effects.”
The British variant has around twenty mutations, including a few that affect how the virus attaches and infects human cells. These mutations may allow the variant to replicate and transmit more efficiently, said Muge Cevik, an infectious disease expert at St. Paul University. Andrew of Scotland and Scientific Adviser to the British Government.
However, the estimate of higher transmissibility (British officials said the variant was up to 70 percent more transmissible) is based on modeling and has not been confirmed in laboratory experiments, Cevik added.
“Overall, I think we need to have a little more experimental data,” he said. “We cannot completely rule out that some of this transmissibility data may be related to human behavior.”
In South Africa, scientists have also quickly pointed out that human behavior has driven the epidemic, not necessarily new mutations, the effect of which on transmissibility has not yet been quantified.
The British announcement raised concerns that the virus could evolve to become resistant to newly released vaccines. Concerns are focused on some changes in the virus’s genetic code that could make it less vulnerable to certain antibodies.
However, several experts have called for caution, saying the virus will take years, not months, to evolve enough to make current vaccines impotent.
“No one should worry about the possibility of a single catastrophic mutation that suddenly destroys all immunity and antibodies,” Bloom said. It will be a process that will happen in a few years and requires the accumulation of multiple viral mutations. It doesn’t work like an on-off switch, “he added.
The scientific nuance mattered little to the United Kingdom’s neighbors. The Dutch, worried about the possible influx of passengers carrying the variant, said they would suspend flights from the United Kingdom on Sunday, December 20, 2020 until January 1, 2021.
Italy has also suspended air travel, and on Sunday Belgian officials adopted a 24-hour ban on arrivals from the UK by plane or train. Germany is drafting a regulation restricting travel from the UK and South Africa.
According to local media, other countries are also considering bans, including France, Austria and Ireland. Spain has asked the European Union for a coordinated response to the flight ban. New York Governor Andrew Cuomo has called on the Trump administration to consider banning flights from Britain.
In England, transport officials have said they will increase the number of police officers guarding terminals, such as railway stations, to ensure that only essential journeys are made. On Sunday, National Health Secretary Matt Hancock said the people packing the trains were “undoubtedly irresponsible.”
He added that the restrictions imposed by Johnson could be in place for months.
Like all viruses, coronavirus is a metamorph. Some genetic changes are inconsistent, but others can give you an advance.
Scientists are particularly afraid of the latter possibility. 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 occurred independently on various occasions around the world, suggesting that mutations are useful to the pathogen.
The mutation that affects susceptibility to antibodies (deletion of technical name 69-70, referring to the missing letters in the genetic code) was observed at least three times: in the Danish mink, in people in the United Kingdom and in an immunosuppressed patient who became much more less sensitive to convalescent plasma.
“It simply came to our notice then. It is widespread. It adapts all the time, ”said Ravindra Gupta, a virologist at the University of Cambridge, who last week detailed the recurring appearance and spread of the erasure. “But people don’t want to hear what we’re saying, meaning this virus will move,” he added.
The new genetic deletion modifies the spike protein (known as the S protein) found on the surface of the coronavirus, which the virus needs to infect human cells. Variants of the virus with this elimination appeared independently in Thailand and Germany in early 2020 and became widespread in Denmark and England in August.
Several recent articles have shown that coronavirus can evolve to avoid being recognized by a single monoclonal antibody, a mixture of two antibodies, or even a convalescent serum given to a specific individual.
Fortunately, the body’s immune system as a whole is a much more formidable adversary.
Pfizer-BioNTech and Moderna vaccines induce an immune response only to S protein located on the surface of the coronavirus. However, each infected person produces a wide, unique and complex repertoire of antibodies against this protein.
“Suppose we have a thousand high-caliber weapons targeting the virus,” said Kartik Chandran, a virus expert at the Albert Einstein School of Medicine in New York. “No matter how the virus twists, it’s not so easy to find a genetic solution that can actually fight all these different specificities of antibodies, not to mention the other arms of the immune response.
In short: the coronavirus will be very difficult to get rid of the body’s defenses, despite the many variants it can adopt.
Loss of immunity requires a virus to accumulate a number of mutations, each of which allows the pathogen to erode the body’s defense. Some viruses, such as the flu, accumulate these changes relatively quickly. But others, such as the measles virus, have almost no changes.
Even the flu virus takes five to seven years to collect enough mutations to completely escape immune recognition, Bloom said. His lab released a new report on Friday, December 18, which shows that common cold coronaviruses are also evolving to get rid of the immune system, but this has been happening for many years.
The scale of infections in this pandemic can generate rapid diversity in the new coronavirus. However, the vast majority of people around the world have not yet become infected, and this has given scientists hope.
“I would be a little surprised to see active selection for immune escape,” said Emma Hodcroft, a molecular public health researcher at the University of Bern in Switzerland. “The virus doesn’t have to do this yet in a population that hasn’t been largely exposed, but it’s something we want to take care of in the long run, especially when we start vaccinating more people,” he said. .
Immunizing about 60 percent of the population over the course of a year and keeping the number of cases low while it happens will help minimize the chances of the virus moving significantly, Hodcroft said.
However, scientists will need to closely monitor the evolution of the virus to detect mutations that may give it an advantage over vaccines.