Covid variant discovered in South Africa worries scientists

On January 15, US public health officials warned that a more contagious variant of the coronavirus responsible for Covid-19 could dominate infections in the United States by March. This ominous warning referred to B.1.1.7, a variant that was first identified in the UK.

But now, a week later, scientists are increasingly concerned about another variant that has emerged in South Africa.

There is evidence from several small studies, which have not yet been peer reviewed, that mutations in the South African variant – known as 501Y.V2 and already present in at least 23 countries – may have a higher risk of re-infection with Covid-19 in humans. who have been ill in the past and should still be immune to the disease.

Scientists have not confirmed that this variant is more contagious, although the evidence points in this direction. They are also concerned that 501Y.V2 has implications for Covid-19 treatments. Regeneron, a company that has developed a cocktail of two monoclonal antibodies as therapy for patients with the disease, reported that 501Y.V2 may be able to evade one of the antibodies from its mixture. The drug is still effective, but later mutations could make it less effective.

But perhaps most alarming is the prospect that mutations in the variant could limit the effectiveness of existing vaccines, one of the best tools we have for controlling the pandemic.

The results of these recent studies are “a serious indication that we need to take a close look at the effectiveness of vaccines,” Penny Moore, a virologist at the National Institute of Communicable Diseases in South Africa, told Vox. Taken together, they highlight the dangers of letting Covid-19 spread unchecked and also herald the challenges ahead as the virus continues to evolve.

What the 501Y.V2 variant of the coronavirus could mean for Covid-19 vaccines

Moore is the lead author of a recent study on 501Y.V2, published Tuesday as a pre-print on BioRxiv. She and her team in South Africa took blood plasma samples from 44 people who had been infected with the coronavirus in the country’s first wave of infections last summer, then checked how their existing antibodies responded to 501Y .V2 as well as older variants.

The researchers sorted the plasma samples into categories – high and low antibody concentrations. Although the antibodies may decrease after infection, this does not necessarily mean that the protection wears off completely. Another recent study showed that immunity from infection lasts for at least five months in most people, so the antibodies of those who have had the virus should still protect against earlier versions of the virus if anyone has had the virus. one is infected again.

In 21 cases – almost half – the existing antibodies were powerless against the new variant when exposed in test tubes. This was especially true for the plasma of people who had a previous mild infection and lower levels of antibodies to begin with.

The results suggest that a previous Covid-19 infection may not help individuals fend off the new variant if they are exposed, particularly if their previous case was mild or symptomless.

For Trevor Bedford, a scientist at the Fred Hutch Cancer Research Center, who was not involved in the research, the study also came as a possible warning sign regarding vaccines. As early as the fall of this year, manufacturers may have to start reformulating their vaccines to respond to changes in the virus’s genetic code, he wrote on Twitter:

The specific mutations that worry scientists the most

The 501Y.V2 variant carries a mutation of particular concern, known as E484K. This change appears in the part of the virus, the spike protein, that fits into the receptor of human cells. The spike protein is also the primary target of currently available mRNA vaccines from Pfizer / BioNTech and Moderna.

“This mutation sits right in the middle of a hotspot in the peak,” Moore said. And it has become notorious among virologists for its ability to evade anti-coronavirus antibodies.

Scientists have demonstrated how this can happen in other cell culture experiments. In another recently published BioRxiv preprint, Washington state researchers followed how mutations altered the efficiency of the antibody response in the convalescent plasma of 11 people – and also found that E484K had particularly potent antibody escape.

Other worrisome variants also carry the E484K mutation, including one first identified in Manaus, Brazil, known as P.1. And a case study suggests that re-infection in some people may be possible when exposed to the new variant.

In a pre-print, Brazilian researchers documented the case of a 45-year-old Covid-19 patient without comorbidities, who months after her first bout with the disease, was re-infected with the new variant. The patient had more serious illness the second time around. Although this is limited evidence, this “could have major implications for public health policies, surveillance and vaccination strategies,” the authors wrote.

The broader context of the study is also concerning: after more than three-quarters of Manaus’s population were estimated to be infected with the virus in a spring outbreak, cases are piling up again and hospitals fill up. Researchers suspect re-infections with the new variant could be the driving force.

“The news is not all gloomy”

But “the news is not all gloomy,” said University of Utah evolutionary virologist Stephen Goldstein. A pre-print, led by scientists at Rockefeller University, suggested that the vaccine’s antibodies may be more potent than antibodies from a previous infection. The researchers tested blood samples from 14 people who had received the Moderna vaccine and six who had been immunized with the Pfizer / BioNTech vaccine. The E484K mutation, and two others found in the South African variant, have been associated with a “small but significant” drop in antibody activity, the researchers found.

Yet, Goldstein said, the antibodies induced by the vaccine “are so high initially that the serum was still extremely potent against the mutant.”

To fully understand the threat that mutations pose to vaccines, we’ll need clinical trials involving vaccinated people, Moore said. “These studies point to a problem,” she added, “but how that translates into real life, we can’t tell.”

There are also huge variations in immune responses between people, Goldstein said. In the Washington article, the researchers found “vast person-to-person variation” in how mutations affected an individual’s antibody response.

“At the end of the day, there are reasons to be concerned about reduced efficiency, but efficiency will not fall off a cliff,” Goldstein said. “Vaccines are incredibly powerful. … Yes [they go] from 95% [efficacy] at 85%, or a little less, we are still in great shape. That’s why researchers and public health officials strongly advocate that everyone be vaccinated as quickly as possible.

Despite this, Moore warned, “From an immune leak standpoint, the variants first detected in Brazil and South Africa are of more concern, but this is only the beginning. This is our first indication that this virus can and does change. “

As we learn more, even the E484K mutation may not be shown to compromise vaccines. But there may be other changes in the virus lurking there or evolving that will escape even the antibodies induced by the vaccine. “So many people are now infected that this is an arms race – the virus now has every chance to mutate,” Moore said, “so he can take these steps to escape more easily. to the immune system. ”