A coronavirus variant that originated in mid-2020 and became the dominant strain in California, not only spreads more easily than its predecessors, but also evades antibodies generated by COVID-19 vaccines or previous infection, and it is associated with serious illness and death, researchers have investigated. said.
In a study that helps explain the state’s dramatic increase in COVID-19 cases and deaths – and pose further problems – scientists at UC San Francisco said the group of mutations that characterize the home-based strain described it as a “variant of concern ”should indicate. equivalent to those of the United Kingdom, South Africa and Brazil.
“The devil is already here,” said Dr. Charles Chiu, who led the UCSF team of geneticists, epidemiologists, statisticians, and other scientists in an extensive analysis of the new variant, which they call B.1.427 / B.1.429. “I wish it was different. But science is science. ”
Californians, along with the rest of the country, have witnessed the emergence of a more transmissible coronavirus variant from the UK, known as B.1.1.7. But they need to know that a competitive strain that is likely to be just as worrying has already been established and is likely to account for 90% of the state’s infections by the end of next month, said Chiu, a researcher and physician for infectious diseases. said.
The UK and California variants are each armed with improved capabilities, and the likelihood of them spreading to the same population increases the spectacle of a return to infections and deaths, Chiu said. It also opens the door to a “nightmare scenario”: that the two viruses will meet in a single person, swap their mutations and create an even more dangerous strain of the SARS-CoV-2 virus.
The new evidence that the California variant could make people sicker, and vaccines less effective, should make more intensive efforts to dispel infections, Chiu said. It should include both social measures, such as the masking and restrictions on public activities, and a campaign of rapid vaccinations, he added.
The new analysis is currently being reviewed by the San Francisco County Public Health Department and the state, which collaborated on the new research. It is expected to post on MedRxiv later this week, a website that allows new research to be shared before it is formally published.
Over five months from September 1, the California strain, sometimes referred to as 20C / L452R, rose from total haze to more than 50% of all coronavirus samples subjected to genetic analysis in the state. Compared to strains that were most important here in early fall, the new strain appears to have a greater ability to spread, Chiu said.
Exactly how much more transmissible the California tribe is remains an open question, he added. But the evidence that it is more contagious comes from various sources.
Samples collected from different provinces, and using different collection methods, indicate that the variant is 19% to 24% more transferable. But in some circumstances its advantage was far greater: in one outbreak of nursing homes, B.1.427 / B.1.429 spread at a rate six times that of its predecessors.
Researchers have also discovered uniform patterns of expansion of the variant in provinces across the country. When infection rates rose, they usually did so along with growing evidence of the presence of the California tribe.
The improved tendency to disperse the variant was also evident in laboratory results. An analysis of viral samples from across the state showed that compared to people infected with other strains of SARS-CoV-2, those infected with the California strain had viral loads in the nasopharynx that were twice as was high.
This in turn made it most likely that each person infected with the new strain would infect more people.
The genome of B.1.427 / B.1.429 contains three mutations that affect the important ear protein, which the virus uses to sneak into human cells and converts it into factories for its own production. One of the three mutations, called L452R, affects the so-called receptor binding domain, which helps to attach the virus more firmly to target cells.
This adaptation has not been seen in coronavirus variants that have caused concern elsewhere.
In a UCSF lab, scientists found that the L452R mutation alone made the stress more harmful in California. A coronavirus designed to have only the mutation is capable of infecting human lung tissue at least 40% more easily than the variant lacking the mutation. Compared to the so-called wild-type strains, the engineered virus was more than three times more contagious.
In the laboratory, the California strain has also been shown to be more resistant to neutralizing antibodies generated in response to COVID-19 vaccines as well as by a previous coronavirus infection.
Compared to existing variants, the reduction in protection was ‘moderate … but significant’, the researchers said.
The coronavirus strain currently prevalent in South Africa, which evades concerns about the defense of the immune system, has been shown to reduce the effect of neutralizing antibodies by a factor of 6.2. With the California strain, the effect of these antibodies was reduced by a factor of two.
“I expect over time that this is going to have an effect on the vaccination,” Chiu said. Although the extent of the effect varies from sample to sample and is less pronounced than with the South African tribe, “it is still worrying,” he said.
Unsurprisingly, the new study also suggested that the California variant may have greater virulence.
The observation is based on the medical charts of 324 patients hospitalized in UCSF, a relatively small sample. Nevertheless, the researchers found that the 21% of these patients infected with B.1.427 / B.1.429 were more likely than their peers to be admitted to the ICU, and that they would die 11 times more. This finding persisted even after researchers adjusted for the age, gender, and ethnicity of the patients.
However, Chiu warns that this increased risk of death may not be a sign that the variant is inherently more lethal. On the contrary, it may simply be a reflection of the greater portability that is causing hospitals to become so overwhelmed and that health care resources are so scarce that more deaths have resulted – especially in Southern California.
Dr Marc Suchard, an expert in detecting infectious diseases at UCLA, said some of the team’s findings are likely to be refined as more virus samples are genetically sorted and more data comes to light.
“It is critical that we actively pursue the virus as cases are diagnosed in our condition,” said Suchard, who was not involved in the UCSF work. “I am pleased to see such a collaboration between academics and California public health departments to identify the emergence of a previously unidentified lineage.”