The new coronavirus has developed a series of worrying mutations, resulting in multiple new variants appearing around the world. Now, a new study sheds light on how the virus mutates so easily and why those mutations help it “escape” the body’s immune response.
The study’s researchers found that SARS-CoV-2, the virus that causes COVID-19, often mutates, simply excluding small pieces of its genetic code. Although the virus has its own “review” mechanism that corrects errors as the virus replicates, an exclusion will not appear on the reviewer’s radar.
“He’s diabolically smart,” senior study author Paul Duprex, director of the University of Pittsburgh’s Vaccine Research Center, told Live Science. “You can’t fix what’s not there.”
Furthermore, for SARS-CoV-2, these deletions often appear at similar points in the genome, according to the study, published on February 3 in the journal Science. These are the places where people’s antibodies bind and inactivate the virus. But because of these exclusions, certain antibodies can’t recognize the virus.
Duprex compared the exclusions to a string of accounts where an account is highlighted. This may not seem like much, but for an antibody, it is “completely different,” he said. “These little absences have a big, big effect.”
Sneaky Exclusions
Duprex and his colleagues first noticed these deletions in a patient who was infected with the coronavirus for an unusually long time – 74 days. The patient had a weakened immune system, which prevented them from eliminating the virus properly. During prolonged infection, the coronavirus started to evolve while playing “cat and mouse” with the patient Imune systemultimately developing deletions, the researchers said.
They wondered how common these exclusions were. They used a database called GISAID to analyze about 150,000 SARS-CoV-2 genetic sequences collected from samples worldwide. And a pattern emerged. “These deletions started to align in very different places,” said lead study author Kevin McCarthy, an assistant professor of molecular biology and molecular genetics at the University of Pittsburgh.
“We saw them continuously,” he said in samples of SARS-CoV-2 collected in different parts of the world at different times. It seemed that these strains of virus were independently developing these deletions due to “common selective pressure”, the researchers wrote in their article.
The researchers dubbed these sites “recurring exclusion regions”. They noticed that these regions tended to occur in spots on the virus peak protein where antibodies bind in order to disable the virus. “This gave us the first clue that, possibly, these exclusions were leading to ‘flight’ or evolution [of the virus] away from the antibodies that are binding, “said McCarthy.
Forecasting new variants
The researchers started their project in the summer of 2020, when the coronavirus was not thought to be undergoing a significant mutation. But the exclusions that appeared in his data said otherwise. In October 2020, they discovered a variant with these exclusions that would later be known as “United Kingdom variant, “or B.1.1.7. This variant gained global attention from December 2020, when it took off quickly in the UK.
“Our search for exclusion variants captured the first representative of what would become the B.1.1.7 line,” wrote the authors. The finding underscores the importance of closely monitoring the evolution of the virus, tracking these exclusions and other mutations.
“We need to develop the tools and strengthen our vigilance to look for these things and follow them … so that we can begin to predict what is going on,” said McCarthy.
Although the virus can mutate to escape some antibodies, other antibodies can still bind and inactivate the virus.
“Going after the virus in many different ways is how we defeat the shape-shifter,” Duprex said in a statement. “Combinations of different antibodies [i.e. different monoclonal antibody treatments] … Different types of vaccines. If there is a crisis, we will want these backups. “
The findings also show why it is important to wear a mask and implement other measures to prevent the virus from spreading – the more people it infects, the more likely it is to replicate and potentially mutate.
“Anything we can do to decrease the number of times it replicates … will give us a little time,” said Duprex.
Originally published on Live Science.