Covid-19: What is the “Delta Plus” variant?

Last June, the Indian government indicated that a new mutation had been detected in the Delta variant of the SARS-CoV-2 coronavirus. This results in a change in the Spike protein, which serves as a "key" for the virus to enter the cells it infects.

Called "Delta Plus" because of this additional mutation, this new variant (also called AY.1 or B.1.617.2.1) was identified in India in 48 persons infected with the Delta variant (out of a total of over 45 samples analyzed). Delta Plus was classified as "variant of concern" by the Indian Ministry of Health, in particular because of increased transmissibility.

How does this variant differ from the Delta variant, and what is known about its ability to evade vaccine immunity?

The Delta variant

Initially detected in India, the Delta variant of the SARS-CoV-2 coronavirus is becoming majority everywhere on the planet, according to the World Health Organization. He notably played a major role in the violent second wave that hit India last spring.

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Various studies found that the Delta variant is able to replicate faster and spread more easily than other variants, and that it binds more strongly to receptors located on the surface of lung cells.

Separately, in a preliminary study that has not yet been peer reviewed, Indian researchers have discovered that this variant would have been at the origin of three quarters of infectious outbreaks in the city of Delhi in vaccinated people (8% of these infections would have been due to the Kappa - or B.1.617.1 variant, and 76% to the Delta variant - or B.1.617.2, the remainder being linked to other variants of the B.1 line).

How is the Delta Plus variant different from the Delta variant?

The new mutation of the Delta variant was initially detected in Europe in the month of March 2021.

In June, patients sick with Covid-19 were also found to be carriers of this new mutant, which has become a source of concern for the authorities, some indian scientists fearing that it is the cause of new infections.

However, the mutation of the Spike protein carried by the Delta Plus variant is not new. Known under the name “K417N”, it has already been described in the beta variant, initially detected in South Africa. The Beta variant carrying this mutation has been shown to be able to escape to some extent to antibodies induced by AstraZeneca vaccine. It could therefore be feared that some vaccines may not prove to be as effective against the Delta Plus variant as against the other variants.

Will the vaccines be effective against the Delta Plus variant?

According to the Indian Ministry of Health, the Delta Plus variant might possess a similar ability to evade immunity and to resist the effects of anti-Covid-19 therapies based on monoclonal antibodies.

This mutation is of concern because it is located on the Spike protein, a key component of the virus, which is used to enter human cells. Previous mutations affected the receptor binding domain of the Spike protein, which allows the virus to attach to receptors on the surface of said cells.

The mutations present in the Delta variant could already, to some extent, help it escape the immune system. Some vaccines have thus been shown to have slightly lower efficiency in front of him, a single dose offering reduced protection. However, a second dose of vaccine continued to produce sufficient amounts of antibodies to protect against symptomatic infections and prevent severe forms of the disease. It is important to remember that most Covid-19 vaccines do not provide absolute immunity, but limit the severity of the disease.

From British researchers thus showed that a dose of RNA vaccine from Pfizer was 33% effective against the Delta variant, and 88% after a second injection. In the case of AstraZeneca vaccine, the efficacy is 33% after the first dose, and 60% after the second.

The Delta Plus variant could be affected by similar reductions in efficacy, however the available data are still lacking to be able to confirm this. Studies are underway in India to test the efficacy of the vaccines currently used against this new variant.

It is important to note that the Delta Plus variant has not yet spread widely, and the World Health Organization has not yet classified it as a variant of concern.

What remains to be learned?

The emergence of variants with increased transmissibility capable of evading antibodies threatens the success of efforts to control and mitigate the pandemic. Countries with the lowest immunization rates are also at risk of further outbreaks.

The existence of these new mutations does not mean that new measures must be taken in the face of the epidemic. On the other hand, it is necessary to ensure that the number of people vaccinated continues to grow, to continue to comply with the recommendations in terms of behavior during an epidemic, and to improve genomic surveillance, in order to be able to follow more closely. the evolution of the SARS-CoV-2 coronavirus.The Conversation

Sunit K. Singh, Professor of Molecular Immunology and Virology, Institute of Medical Sciences, Banaras Hindu University

This article is republished from The Conversation under a Creative Commons license.

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