Covid-19: E484K, the mutation that raises questions for vaccines - France 24

Paris (AFP)

The English variant is a real eye-catcher, but it is nevertheless a mutation present in other versions of the coronavirus that worries scientists from the point of view of vaccination against Covid-19, because it could affect its effectiveness.

Called E484K, this mutation is carried by variants that have emerged in South Africa and more recently in Brazil and Japan, but not by the English variant, whose worldwide expansion is making headlines.

However, this mutation "is the most worrying of all" in terms of the immune response, said Ravi Gupta, professor of microbiology at the University of Cambridge, interviewed by AFP.

Variants are different versions of the original coronavirus, which appear over time due to various mutations.

A normal phenomenon in the life of a virus, because mutations occur when it replicates.

Numerous mutations of Sars-CoV-2 have been observed since its appearance, the vast majority without consequence.

However, some may give it an advantage for its survival, including greater transmissibility.

The variants that have emerged in England, South Africa and Japan (the latter via travelers from Brazil) share a mutation called N501Y.

Located on the coronavirus spike protein (a spike that allows it to enter cells), this mutation is suspected of making these variants more contagious.

There are suspicions of a different nature hanging over the E484K mutation.

Laboratory tests have shown that it seemed capable of reducing recognition of the virus by antibodies, and therefore its neutralization.

- "Immune escape"

"As such, it can help the virus bypass the immune protection conferred by a previous infection or by vaccination", explains Prof. François Balloux, of University College London, quoted by the British organization Science Media Center.

It is this prospect of "immune evasion" that worries scientists, with the question of the effectiveness of vaccines in their sights.

On January 8, BioNTech and Pfizer, makers of the world's leading vaccine, assured that it was effective against the N501Y mutation.

But their lab checks did not focus on E484K.

They are therefore not sufficient to conclude that the efficacy of the vaccine will be the same against the variants which carry it as against the classical virus.

In addition, a study published on January 6 describes the case of a Brazilian woman sick with Covid in May, then reinfected in October by a variant carrying the E484K mutation.

This second infection, more severe than the first, could be a sign that the mutation caused a poorer immune response in the patient.

However, there is no indication that E484K is sufficient to make variants resistant to current vaccines, scientists say.

- "Beginning of problems" -

Indeed, even if it turns out that this target is less well recognized by the antibodies, other components of the variants will in principle remain within their reach.

"Even if you decrease in efficiency, you will normally still have a neutralization of the virus," said AFP Vincent Enouf, of the National Reference Center for Respiratory Viruses at the Institut Pasteur in Paris.

"I do not think that this mutation alone is problematic for vaccines", adds immunologist Rino Rappuoli, researcher and scientific manager of the pharmaceutical giant GlaxoSmithKline (GSK), interviewed by AFP.

He co-signed a study released on December 28.

Its objective was to observe in the laboratory the emergence of a variant, by placing the virus in the presence of the plasma of a patient cured of Covid for several weeks.

After less than three months, an antibody resistant variant appeared.

He carried three mutations, including E484K.

"We must develop vaccines and antibodies capable of controlling emerging variants", concludes this study.

The E484K mutation "could be the beginning of the problems" for vaccines, judges for his part Professor Gupta.

"At this stage, they should all remain effective, but what worries us is the prospect of future mutations which would be added" to those we are already observing, he develops, calling for "to vaccinate the as quickly as possible anywhere in the world ".

Faced with the emergence of new variants, several laboratories have ensured that they were able to quickly provide new versions of their vaccine if necessary.

© 2021 AFP