Immune escape mutant: Anyone who has already had a coronavirus infection can still contract the Omicron BA.5 coronavirus variant, which is currently rampant in Germany. Because, as a study confirms, antibodies from those who have recovered hardly have any effect on this virus mutant.
The triple mRNA vaccination, on the other hand, can still neutralize BA.5, but the effect is weaker than previous corona variants. This immune escape of the new omicron variant could explain why the infection numbers are higher this summer.
The SARS-CoV-2 coronavirus has mutated again and again since the beginning of the corona pandemic. This resulted in virus mutants that are more contagious, but also variants such as omicron that partially elude our immune defenses through changes to their spike protein. In the meantime, Omikron has developed several sub-variants with BA.4 and BA.5, which have also been circulating in Germany for a few weeks and the spread of which is responsible for the current “summer wave”.
So far, however, it has been unclear whether the subvariants BA.4 and BA.5 are displacing the previously dominant corona viruses due to their better transferability or whether they are less well inhibited by antibodies.
Prerna Arora from the German Primate Center in Göttingen and her colleagues have now investigated how strong the immune escape effect is in these new omicron variants. For their study, they confronted the different omicron variants with antibodies from the blood serum of unvaccinated convalescents who had already experienced infections with the original omicron variant BA.1 or BA.2.
Antibodies from triple vaccinates with mRNA vaccine, vaccinates with subsequent infection and therapeutic antibody preparations were also tested.
The first result: Out of ten therapeutic antibody preparations tested, only two were able to at least partially inhibit the omicron variants BA.4 and BA.5. Only one of these preparations, bebtelovimab (LY-CoV1404), neutralized all omicron subvariants. “It is therefore important that new antibodies for therapy are developed promptly in order to be well prepared for future variants,” says Arora.
Even more important, however, is that the antibodies naturally formed during a coronavirus infection are only partially effective against the new omicron variants. Antibodies from unvaccinated people who had been infected with the omicron subvariants BA.1 or BA.2 in the spring were hardly active against BA.4 and BA.5, as the researchers report.
Apparently, the difference between these subvariants is large enough to miss a significant portion of the antibodies imprinted on the old variants.
This also explains why a particularly large number of those who have recovered are currently being infected again with the corona virus: Because their antibodies, which have been adapted to the earlier coronavirus variants, can no longer find many of their attachment points on the viral spike protein, they have no or only a limited effect. This makes it harder for the immune system to fight off the infection and the result is re-infection.
But what about the vaccination protection provided by the mRNA vaccines? According to the tests, the antibodies formed after triple mRNA vaccination are still effective against the new omicron variants, albeit somewhat weaker. Even with the original omicron type, the neutralization was around four times worse, with BA.4 and BA.5 it is around eight times lower, as Arora and her colleagues determined.
Similar results were also shown for antibodies that were formed after vaccination and subsequent breakthrough infection. This so-called hybrid immunity is considered to be particularly protective. In the tests, however, the inhibition of BA.4 and BA.5 was also significantly reduced in the antibodies of such patients.
According to the researchers, this confirms that BA.4 and BA.5 are immune escape variants of the coronavirus: The pathogen has adapted to the fact that many people have now either recovered or been vaccinated and carry antibodies against the virus . Because variants that evade this immune response have a better chance of replicating, mutants with this ability spread.
After all, the chances are good that our immune system can still largely prevent severe courses. Because in addition to the antibodies, the cellular immune response also fights the invading viruses – and this is less affected by the immune escape.
“The vaccination will still protect against a severe course, but the protection will probably be somewhat lower than with the previously circulating variants,” explains Arora’s colleague Markus Hoffmann.
Source: Deutsches Primatenzentrum GmbH – Leibniz Institute for Primate Research
This article was written by Nadja Podbregar
The original to this article “Immune escape: Why Omikron BA.5 becomes a danger in the body of recovered people” comes from scinexx.
