What is the “unique strategy” that the Delta variant has for evading antibodies

Since its emergence in India, the Delta variant of the coronavirus has caused concern among health authorities in countries to which it has spread, precisely because of its rapid expansion and greater contagiousness.

Detected in October 2020, he grew to date in nearly 100 countries and is already predominant in circulation in the US, UK, Germany, Portugal and Singapore, where it even displaced other variants that were more contagious than the original virus.

However, a recent prepress study concluded that the Delta variant of SARS-CoV-2 has a “unique strategy” to facilitate infection and evade antibodies.

Like other viruses, the new coronavirus multiplies by infiltrating and “hijacking” cells before exploding to continue the cycle in a process known as “cellless” infection. But infected cells can also fuse with uninfected cells before they separate, and viruses such as hepatitis C that spread in this way tend to be relatively more resistant to neutralizing antibodies.

Researchers from the Genotype to Phenotype Japan consortium have found that a mutation in the spike protein Delta, which the coronavirus uses to infect humans, increases its ‘fusiogenicity’, that is, its ability to spread from cell to cell.

In addition, the blood cells of infected cells that form are significantly larger than those of people infected with other strains., saw the study authors, who concluded that changing the viral replication preference from cell-free infection to cell-to-cell infection “may be a unique strategy” of the Delta variant to evade antiviral immunity , as published Financial Time.

In addition, if more comprehensive studies are lacking, they believe that the greater fusiogenicity associated with the mutation could also be responsible for the greater virulence of Delta, as well as the “unusual symptoms” it causes.

During the study, hamsters infected with a virus carrying the mutation “showed significant weight loss” compared to those infected with other variants, the researchers added.

Yes study recently published in the magazine Nature found that the Delta variant barely responded to a dose of the vaccine, which confirmed previous research suggesting that the variant might bypass the immune system to some extent, albeit less so than the beta, the variant of the coronavirus first identified in South Africa.

French researchers analyzed the effectiveness of antibodies produced by natural infection and by coronavirus vaccines to neutralize alpha, beta and delta variants, as well as a variant similar to the original version of the virus. To do this, they analyzed blood samples from 103 people infected with the coronavirus. The study found that the Delta variant was much less sensitive than alpha in samples from unvaccinated people in this group. One dose of the vaccine significantly increased sensitivity, suggesting that people who have recovered from COVID-19 still need to be vaccinated to protect themselves from certain variants.

The team also analyzed samples from 59 people after receiving the first and second doses of AstraZeneca or Pfizer-BioNTech vaccines. Only 10% of blood samples from individuals immunized with a dose of AstraZeneca or Pfizer-BioNTech vaccines were found to be able to neutralize the Delta and beta variants in laboratory experiments.. However, a second dose increased this figure to 95%. There were no major differences in the levels of antibodies generated by the two vaccines.

The researchers concluded that: “A single dose of Pfizer or AstraZeneca was little or no effective against the beta and Delta variants. Overall, data from Israel and the UK support this conclusion, although these studies suggest that one dose of the vaccine is still sufficient to prevent hospitalization or death of the virus. Although researchers are studying the possibility of Delta bypassing vaccine protection, to date the vaccines remain effective and it is recommended that the device be supplemented to reduce infections and serious hospitalizations.

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