The devastating impact of the new corona variants is slowly becoming apparent. The British variant is causing a wave of infections and deaths worldwide. Is this just the beginning? Could even more dangerous variants emerge?
To the impact of future variants To be able to estimate, three properties are important: infectivity, how well the variant can evade our immune system, and lethality. Of these, infectivity is the most important. The current coronavirus, SARS-CoV-2, is much less deadly than, for example, the Ebola virus, but still leads to much more death because it spreads a lot more easily.
A hundred times more contagious
We still don’t understand why the British variant is at least 50 percent more contagious than other variants, says virologist Joe Grove from University College London. His work suggests that the spike proteins on the surface of the British variant are slightly better at penetrating human cells than those of the other variants.
The bad news is that Grove has found a corona variant in pangolins with a spike protein that is a hundred times better at penetrating human cells. This suggests that SARS-CoV-2 could become much more contagious. “Until recently, SARS-CoV-2 didn’t live in humans,” says Grove. “Now it is optimizing for humans and there is no reason to assume that it will stop there.”
Grove stresses that we cannot be sure that changes in the spike protein are responsible for the greater infectivity. One reason for this is that he did not use live viruses in his experiments. He wanted to prevent the virus from escaping from his lab.
Bypassing antibodies
The next important factor is the extent to which a virus variant evades our immune system. Our immune system protects us in two important ways. First, it produces T cells that sense and destroy infected cells before the virus can multiply. Second, our immune system makes antibodies that bind to the virus to stop infecting cells.
The most effective antibodies, called neutralizing antibodies, bind to the part of the spike protein that helps the virus enter cells. Mutations in this region allow the virus to bypass the antibodies to some extent. That’s what happened with the South African and Brazilian variant.
Time to adjust
There are limits to the further evolution of the virus. “The spike protein is a machine with moving parts that have important functions,” says Grove. If mutations destroy that machine, the virus can no longer infect cells.
It is also much more difficult for the virus to bypass the T cell response. T cells continue to work as long as they recognize part of the virus. Scientists think that T cell resistance develops much more slowly than antibody resistance. That gives us time to adjust the vaccines if necessary. “It seems that it is difficult for the virus to completely escape the T cells,” says virologist Andreas Bergthaler from the Research Center for Molecular Medicine in Austria.
Less deadly?
Finally, there is lethality. There is growing evidence that the British variant is slightly more deadly than previous variants. “There is a chance it will get worse,” says an evolutionary virologist Aris Katzourakis from the University of Oxford.
Virologists often say that viruses become less deadly when new variants emerge. But there’s no reason to think that’s the case for SARS-Cov-2, says Katzourakis. ‘The virus can easily spread before the host dies. So there is not that much selection pressure to be less lethal, ‘he says.
Cold
The good news is that the vaccines work even better than hoped. The coronavirus probably cannot completely bypass the protection provided by the vaccines. If more and more people become immune, the virus will turn into a cold virus, according to many experts, just like previous coronaviruses.
But because the majority of people worldwide are still waiting for a first injection, we are far from there. We will probably have to adjust the vaccines more than once in order to continue to provide protection. ‘That evolutionary arms race between the vaccine and the virus will go on for a while, ‘says Grove.
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