What reason caused some people infected with COVID-19 times?

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What reason caused some people infected with COVID-19 times?

What reason caused some people infected with COVID-19 times?  The Delta mutant strain of the new coronavirus that first appeared in India has attracted widespread attention in the world.

What is worrying is that the Delta mutant strain not only has a 100% increase in transmissibility, but also has stronger resistance to vaccines and treatments, making existing vaccines more resistant to The immune effect of the Delta mutant strain is not ideal, resulting in re-infection in patients who have been infected with the new coronavirus.

A recent study found that the neutralizing effect of the convalescent serum and vaccine on the Delta variant strain was reduced, and the results of the study provided a certain degree of explanation for the reason for the unsatisfactory immune effect.

Original title published in CELL

The serum of patients infected with Beta and Gamma mutant strains has a reduced neutralization effect on Delta and Kappa mutant strains.

At present, the two variants found in India are mainly Kappa and Delta, both of which belong to the B.1.617 strain. They are currently found in most parts of the world and become the main epidemic strains of COVID-19.

The study found that the neutralizing activity FRNT50 of patients infected with the Alpha mutant strain (B.1.1.7) was 765 against the standard strain (Victoria) and 179 against the Kappa mutant strain (B.1.617.1).

The neutralizing activity FRNT50 of the serum of patients infected with the Beta variant strain (B.1.351) was 424 against the standard strain and 236 against the Kappa variant strain.

The neutralizing activity FRNT50 of the serum of patients infected with the Gamma mutant strain (P.1) was 197 against the standard strain and 93 against the Kappa mutant strain.

Convalescent serum has reduced neutralization of Kappa mutant strains

Obviously, the neutralizing effect of the infected person’s serum on the Kappa mutant strain is not as good as that of the standard strain.

In the serum of previously infected persons, the neutralizing activity FRNT50 for the standard strain was 475, and for the Delta variant strain (B.1.617.2) it was 178.

The neutralizing activity FRNT50 of patients infected with Alpha mutant strains was 715 and 472 for Delta mutants.

The neutralizing activity FRNT50 of the sera of patients infected with the Beta mutant strain was 623 and 54 for the Delta mutant strain.

The neutralizing activity FRNT50 of the serum of patients infected with the Gamma variant strain was 307 against the Gamma variant strain and 27 against the Delta variant strain.

The neutralizing effect of the convalescent serum on the Delta mutant strain was significantly reduced

It can be seen from the difference of the experimental results that the Delta variant has a large difference in antigens from the Beta and Gamma variant strains, while the antigenic difference with the Alpha variant strain is relatively small. Therefore, the antibodies produced by recovered patients infected with Beta and Gamma variants have poor neutralizing effect on Delta variants.

After gene sequencing of the Delta mutant strain, it was also found to have high specificity, which further verified the large difference between the Delta mutant strain and the Beta and Gamma mutant strains, and the specificity of the antibody has reached the point where the mutant strains cannot be used universally. The reason may be related to the extra RBD amino acid mutations in Beta and Gamma variants.

Therefore, individuals who have been infected with Beta and Gamma variants, due to the lack of cross-neutralization of antibodies, are still at risk of re-infection with Delta variants.

The neutralization effect of the vaccine on the Delta variant is reduced

The neutralization test was performed with the serum of individuals who had been injected with two injections of Pfizer and Alicecam, and it was found that the neutralization effect of Kappa and Delta mutant strains was also reduced to varying degrees compared with the neutralization effect of the standard strain.

Due to the continuous mutations of the new coronavirus, the genetic sequencing of the virus is gradually established all over the world. However, the progress of genome testing in many regions is slow and cannot keep up with the speed of infection. Therefore, the diversity of the new coronavirus mutant strains is likely to be underestimated, and further Mutation and spread are likely to continue to occur.

Variant strains are extremely infectious and people at higher risk of disease, such as the elderly and patients with comorbidities, should be vaccinated with at least one shot. Although the antibody response is low or non-existent, a single dose of the vaccine may still provide protection effect. Of course, if conditions permit, two doses of immunization are better.

How to prevent repeated infections?

On the one hand, the Alpha mutant strain has a certain degree of cross-protection effect on all mutant strains. If a vaccine is made against the Alpha mutant strain, the vaccine may have a wide range of preventive effects, and it is expected that the neutralization effect on the Delta mutant strain will be good. However, the effect on Beta and Gamma mutant strains may be relatively poor.

On the other hand, the serum of people infected with the Gamma mutant strain even has a lower neutralizing ability to the self-mutated type. The neutralizing activity FRNT50 is 307, which is less than half of the neutralizing activity of the Alpha mutant strain on its own. Further research is needed to explain.

At present, people are also considering the use of enhanced vaccines to prevent further mutations of mutant strains such as Beta. Future vaccines are likely to require protection from the components of a variety of mutant strains, including at least the basic serum complexes of standard strains or Alpha variant.

In summary, this study provides a possible explanation for the phenomenon of repeated infections caused by the Delta mutant: not all antibodies can neutralize it. As the new coronavirus continues to mutate, it is likely that it will continue to mutate in the future. There are more such differences in effectiveness.

(source:internet, reference only)

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