Since the end of the year, a variant of SARS-CoV-2 has spread in England at a much faster rate than the others. Reported in September, this variant named VUI202012 / 01 is now in the majority in several regions of England.
It has since crossed the Channel and a few cases have been reported in France, the first having been reported in Tours on December 25. What consequences could this new variant have on the way out of the crisis that the arrival of vaccines made us foresee?
Is it more contagious?
The variant of a virus is a version that has undergone a number of mutations that remain as it spreads and forms a new branch of the virus. As Isabelle Imbert, virologist and teacher-researcher at Aix-Marseille University explains, “This is not the first time that SARS-CoV-2 has mutated. Like any RNA virus, there is selection pressure. When he manages to find mutations that give him a gain, he will keep them. “ But the speed of spread of VUI202012 / 01 quickly prompted researchers to look into its contagiousness.
Other external parameters such as favorable weather in the areas where it has developed could have been the cause of its over-representation in the UK data. But researchers are less and less doubtful of the greater contagiousness of this variant to explain its rapid spread.
“There are still two weeks, the preliminary results only suggested it but since, from English epidemiological data, we can clearly say that the English variant is more infectious, which does not mean that it is more pathogenic or more virulent. It infects cells better ” says the virologist.
Studies of London School of Tropical Medicine and of English Institute of Public Health PHE being validated tend to confirm this higher contagiousness. They estimate it at more than 50% compared to that of other pre-existing variants of the virus.
Of the twenty mutations in this variant, nine are located on the Spike protein, which is the virus’s key to entering cells. One hypothesis that could explain its greater contagiousness would be that these mutations would allow the virus to enter cells more efficiently.
Barrier actions and measures to fight the virus are therefore even more advisable to stop the spread of the virus.
Are vaccines effective?
For the moment, the effectiveness of vaccines and in particular those with messenger RNA is not called into question by the arrival of this variant because it is very close to the first strain of Wuhan: “There are twenty mutations in total on its genome and that represents 29 nucleotides out of the 30,000 nucleotides that make up the genome of the virus”, according to the virologist.
But, for vaccines, variant mutations on the Spike protein need to be taken more seriously. The principle of RNA vaccines is in fact to make our cells manufacture this protein, which will be recognized by our body as being non-self and will trigger the production of an antibody soup. In particular, so-called neutralizing antibodies which will recognize different areas of the Spike protein and attach themselves to it. This will allow them to block a future attack on cells by the virus.
“Since there are currently only nine changes to this key, we can be optimistic in saying that we have a whole arsenal of neutralizing antibodies. There is currently no indication that the vaccine could be less effective ”, reassures Isabelle Imbert.
RNA vaccines have another advantage: “Compared to a protein vaccine, RNA vaccines are technically faster to produce. Thus, if necessary, we can modify the vaccine according to the evolutions of the virus ”, adds the virologist.
How to detect it?
The United Kingdom discovered the predominance of this variant in different parts of its population because it uses the sequencing of viral genomes in a very important way. This technique is the only one capable of identifying mutations in the virus. But France has not developed such a sufficiently efficient sequencing network.
Sequencing is in any case ill-suited to rapid detection. But there is another possibility for, not really identifying the new variant, but obtaining a strong indication of its presence or not. And this using RT-PCR tests.
PCR tests work by looking to detect two to three viral genetic sequences. These target sequences may be different depending on the test manufacturer. Or uThe French team has shown that, for certain variants, including the famous English variant, one of the three targets of the manufacturer’s test Thermo Fischer is affected by mutations and is not detected.
In other words, if the ThermoFischer test is positive for the other two targets but negative for the mutated target, there is a good chance that this reflects an infection with the English variant. And conversely: a positivity on the three targets rules out the variant with a high probability. What, therefore, proceed to a mass screening by confirming, by sequencing in a second step, only the samples suspected of containing the variant.
This technique is interesting as long as France does not have a sequencing network as efficient as it is across the Channel, but the deployment of such a network would greatly facilitate the monitoring of this variant within the borders of France.
–
