Vaccines against the Sars-CoV-2 coronavirus give hope to contain the pandemic. At the same time, however, new mutations are developing, for example in Great Britain, Brazil and South Africa. To what extent do the existing vaccines also help against these variants of the virus? Researchers have now investigated this for two mutations that occur in these variants. Their result: At least as far as these two mutations are concerned, the mRNA vaccine from BioNTech / Pfizer offers sufficient protection. Although the protective antibody titer against the E484K mutation of the Brazilian and South African variants is somewhat lower, it is probably high enough to effectively fight the virus.
The further the coronavirus spreads, the more common mutations are. In particular, if parts of the population are already immune to the original type of virus, for example because they have already gone through an illness, so-called escape mutations can occur. The virus changes in such a way that it can still escape attacks by the immune system. Many of these mutations affect the shape of the so-called spike protein, which the virus uses to dock on the cells. On the one hand, these surface structures are the distinguishing features for the immune system. On the other hand, they determine certain properties of the virus, including its infectivity.
Blood serum from vaccinated people also neutralizes new virus variants
Researchers around Xuping Xie from the University of Texas have now simulated various mutations of Sars-CoV-2 in the laboratory and checked to what extent the BioNTech vaccine also helps against the new virus variants. To do this, they created so-called pseudoviruses – viruses that are not infectious but have the molecular structure of Sars-CoV-2 – and tested them with the blood serum of 20 people who had been vaccinated. One focus was on the one hand on the N501Y mutation, which occurs in both the British and South African variants, and on the other hand on the E484K mutation, which is found in the Brazilian and South African virus strains. For this mutation, it has already been proven that the effect of antibodies from the plasma of recovered Covid-19 patients is weakened. It is therefore considered an incipient “escape” mutation. Xie and colleagues tested this mutation in combination with other mutations that are typical of the South African variant.
The tests showed: The blood serum of the vaccinated also neutralized the mutated viruses. In the case of pseudoviruses with the E484K mutation, the titer was somewhat lower than that of the original form of the virus and the N501Y mutation. “But the differences were small,” report the researchers. It can therefore be assumed that people who have been immunized with the BioNTech vaccine are also protected against the mutations that have emerged in Great Britain and South Africa and spread from there worldwide. With regard to possible protection against the Brazilian variant, the researchers are not yet able to make any clear statements, as it contains E484K but not N501Y.
Future adjustments to the vaccine are conceivable
However, the researchers also point out the limitations of their study. The pseudoviruses did not contain the full set of mutations that occur in the virus variants. How exactly the mutations affect the biological properties of Sars-CoV-2 is so far only partially known. However, the fact that the vaccinee’s blood serum was able to neutralize particularly frequent mutations in laboratory tests strongly suggests that this would also work outside the laboratory.
Another point that limits the validity of the study is that so far it can only be guessed how high the titer against the virus actually has to be in order to protect against infection. These assumptions are based, among other things, on empirical values with regard to the flu vaccination. “Clinical data are needed to be able to draw firm conclusions about the effectiveness of vaccines against the virus variants,” said the researchers.
According to all previous knowledge, according to Xie and colleagues, it can be assumed that the BioNTech vaccine protects against the British and South African variants of Sars-CoV-2. Nevertheless: “The ongoing evolution of Sars-CoV-2 requires continuous monitoring of the importance of mutations for the effectiveness of the vaccine,” said the researchers. At the same time, preparations should be made to adapt the vaccine to future mutations. “For Covid-19, such vaccine updates would be made easier by the flexibility of messenger RNA-based vaccine technology,” they write.
Source: Xuping Xie (University of Texas) et al., Nature Medicine, doi: 10.1038 / s41591-021-01270-4