While the variant BA.5, or Omicron 5, is now taking over in many countries around the world, including Italy, where it is fueling the summer wave of infections, experts have already identified a sub-lineage to keep an eye on. It does not derive from BA.5 but somehow “starts over” from BA.2. It is no coincidence that it has been classified in genome databases as BA.2.75. Confirmed cases, as the Corriere della Sera, they are very few, just about forty on the 4th of July. What is worrying is its already international diffusion with a larger group of cases in India (46 according to the data uploaded to the platform Nextstrain). In fact, at least one was sequenced and deposited in Australia, Canada, Germany, United Kingdom and New Zealand. In short, it is difficult for everyone to be wrong.
According to Tom Peacockvirologist of the Department of Infectious Diseases of Imperial College London BA.2.75 shares 45 mutations with the highly contagious BA.5 while 15 are new and original. There are eight mutations in the Spike protein, five concentrated in particular in the N-terminal domainwhich the virus uses to bind to human cells (BA.5 has three) via the human receptor Angiotensin Converting Enzyme 2 (hACE2). Four more they are precisely located on the receptor binding domain.
Two essential mutations with respect to BA.2: G446S And R493Q. The former is located in one of the most potent antibody escape sites induced by current vaccines which still neutralize BA.2. Therefore one is theorized increased ability to dodge the protection induced by neutralizing antibodies the result of vaccination or recent recovery. Except in the case of have been exposed to BA.1, the main Omicron so to speak: the advantage therefore concentrated towards those population groups infected with other strains or, obviously, never infected. However, it must always be remembered that protection against serious illness is mainly controlled by cell-mediated immune responsesthat is, from memory B and T lymphocytes and cytotoxic lymphocytes, capable of recognizing spike protein epitopes other than those targeted by antibodies and which fortunately change less frequently.
It is clear that current vaccines, while effective against serious disease, risk not being enough anymore. New products are needed, such as the bivalent of Moderna coming in the fall, to keep pace with a virus that is very far from the original Wuhan pathogen. If a sub-lineage, at least pathogenic (and it is not taken for granted that this happens), infects with a replication rate worthy of measles or chickenpox and manages to easily reinfect those who are protected or cured, it is clear that the vaccination campaign, also in terms of awareness and involvement of the populations, risks getting wrapped up.
It is difficult for the moment to say more about the new sub-variant, one of the thousands that have appeared so far. The contagiousness will eventually be seen from the progression in epidemiological terms while the lethality from what should happen in hospitals. “I think the new sub-variant is worth keeping an eye on as it could be even more contagious than Omicron” wrote the virologist Matteo Bassetti, director of the infectious disease center of the San Martino hospital in Genoa, on Twitter. “Watch out, without alarm.”
Omicron 5, with which symptoms the variant that will soon predominate in Italy manifests itself
Omicron 5 variant, the basic precautions not to get infected in the summer
Source: Vanity Fair
