Antigen drift combined with antigen original sin will be the worst outcome.
In the early August, a report on the British government emergency advisory group claimed that COVID-19 could have an antigen drift in the future, with a mortality rate of 35%.
The news not only raised a staggering death rate of 35%, but also lit up an unfamiliar word – “antigen drift”.
One version of the widely circulated news, but no matter which version of the newsletter, it seems that it can’t make things clear.
What did the British emergency Advisory Group say? Why do you say that? Fortunately, they released the full text of the report document, about 35% and antigen drift.
Let’s see what the original text says.
In the 4 case, the possibility is different.
When the report comes out, the number of infected people around the world is about 175 million.
Now it has exceeded 200 million.
Compared with the state of the report, COVID-19 may have changed.
For example, when the report was created in the United Kingdom, the key report of CDC in the United States has not yet been released.
See related articles for details: is the vaccine still effective against delta strain? The starting point of the CDC report itself is to predict possible changes in the epidemic situation, assess the possibility of changes, and propose solutions to these changes.
The report predicted 4 cases, almost all based on the analysis of the variation of the novel coronavirus.
The 4 cases are: 1., there are 1.
variants that can greatly increase lethality, such as raising the lethality to the height of SARS (10%) or MERS (35%).
This possibility is evaluated as high and feasible in reality.
There are mutants that completely escape the existing vaccine.
This possibility is evaluated as almost certain.
Mutant strains resistant to antiviral drugs.
This possibility is evaluated as: general, feasible in reality.
It is not evaluated as a high possibility because there is no large-scale use of antiviral drugs for novel coronaviruss.
The virus weakened and the viral load decreased after infection.
This possibility is evaluated as impossible in the short term and possible in the long term.
Generally speaking, this prediction is relatively pessimistic and does not think that the virus will weaken in the short term.
On the contrary, due to the current epidemic prevention methods, the virus is more likely to become immune escape and death, and even change in drug resistance after human beings strengthen antiviral drug treatment.
What does antigen drift mean? The core idea of the whole report revolves around virus mutation.
Among them, “antigen drift” is a word that has been highlighted by the domestic media.
What does this mean? In fact, in the report, two concepts were put forward: one is antigen drift (antigendrift), the other is antigen transfer (antigenshift), all of which are variants of the antigen (COVID-19) here.
The definition of antigen transfer (antigenshift) in the report is that COVID-19 is inserted into the sequence of the spike genes from other coronaviruses.
According to the analysis of the report, the more likely source is coronavirus with high prevalence in the population, and the possibility of inserting dangerous virus such as mers is low because the latter has low prevalence.
The report believes that another longer-term possibility of antigen shift is that people transmit the virus to animals, the virus mutates in animals, and the mutated virus is transmitted back to humans.
A recent study suggested that a large number of COVID-19 antibody positive samples were found in common white tailed deer in the United States.
It is not clear what threat this situation will bring to human epidemics.
Nature’s report on the discovery of novel coronavirus antibody positive in American white tailed deer herd the possibility of the above two changes is considered to be possible in reality.
If the transferred spike gene sequence is brand-new, it will have a high impact on humans.
If the inserted spike gene sequence is popular in humans and many people may have immunity to it, the impact may be small.
Antigen shift, the report points out that this gradual or intermittent accumulation of antigen variation will eventually make the existing vaccine ineffective.
In a broad definition, the change of antigen drift is less than that of antigen shift.
In the context of influenza, the latter is easy to cause a pandemic, while the former has less influence.
However, in this report, antigen drift may have no less impact than antigen shift.
In this link, the researchers put forward a worst-case possibility, that is, antigen drift may lead to significant antigenicsin, which makes it difficult for humans to produce effective antibodies by re vaccination.
What is antigen original sin? Antigenicsin means that after the antibody is triggered by infection with the virus or vaccination, the body cannot produce targeted antibodies to the new antigen – that is, the mutated new virus – but will only produce the previous antibodies.
If the previous antibodies have been ineffective against the new mutant virus, this will happen – on the one hand, the mutant virus does whatever it wants in the human body because there is no targeted antibody, on the other hand, the body continues to produce useless antibodies to try to fight the virus.
What’s worse, once this happens, the new vaccine can’t make the body produce new antibodies.
The problem of antigenic original sin was raised by two Swiss scholars last year.
In this viewpoint discussion, they proposed that the phenomenon of antigenic original sin may lead to ade.
This paper also puts forward the hypothesis that children have no pre-existing immunity, so the disease is mild.
Not long ago, the research of the University of Hong Kong on comparing T-cell immunity in children and adults supported the views of the two Swiss scholars on pre-existing immunity（ For details, see the related article: the symptoms are lighter after the infection of the novel coronavirus in children, University of Hong Kong reveals the specific reasons.
The report on the original sin of the United Kingdom reported that the antigen drift and gene mutation in COVID-19 could not be prevented.
Since there is no report that the novel coronavirus virus has the original antigen problem, the Advisory Group believes that the possibility of an original antigen is less likely.
How did the 35% death rate come from? High lethality itself is a direction of variation.
35% is just an example of mers in this report.
In reality, higher or lower lethality variation than 35% may occur.
But generally speaking, changing to a more deadly direction is a more likely direction according to the report.
This variation is different from the above variation of increasing transmission ability or immune escape ability.
Antigen drift or antigen shift mainly occurs on spike proteins, that is, the green ones in the figure below exist in these prominent parts on the surface of the virus, while lethal variation is more likely to occur inside the virus, For example, it occurs in polymerase proteins or accessory proteins.
Coronavirus model: these genes in nature virus determine the replication speed of the virus, the speed at which the virus is detected by cells, and even affect the resistance of cells to the virus (see related article: Nature: why is delta mutant so dangerous for details).
This variation may come from the host or from other different viruses.
And there has been a precedent among coronaviruses..