Why the mutated new coronavirus has increased infectivity

Popular Science: Why the Infectiousness of the Variant New Coronavirus Increases

Popularization of science: why the infectivity of the mutated new coronavirus has increased

Xinhua News Agency, Beijing, September 14 (Reporter Peng Qian) From Alpha, Beta, Gamma, to Delta, Miu strains.
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the endless mutated new coronaviruses continue to challenge the prevention and control of epidemics in various countries
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Among them, the delta strain has become the main variant strain circulating in most parts of the world, and it is more contagious

The cunning new coronavirus can evolve new dominant variants
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Data from the "Global Initiative for Influenza Data Sharing" platform, an international shared genetic sequence resource, shows that starting from January 2021, alpha strains have the first to occupy the advantage of spreading

The study found that, compared with the Alpha strain, the spike protein of the Delta strain can be cleaved by the host cell protease more efficiently to form a functional protein, which greatly improves the efficiency of the Delta strain invading cells and speeds up the process.
The speed of replication in the early stages of infection helps to establish the advantage of the Delta variant
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In addition to the increased infection ability, the immune escape ability of the mutant new coronavirus has also been enhanced
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Compared with the wild-type new crown virus, the neutralizing power of the serum neutralizing antibody against the Delta strain of patients recovered from the new crown is greatly reduced; the neutralizing effect of the vaccine and the monoclonal antibody drugs used for treatment on the Delta strain is correspondingly reduced

The latest research by the Tan Xu laboratory of the School of Pharmacy of Tsinghua University and the Jin Tengchuan laboratory of the School of Life Sciences of the University of Science and Technology of China found that in addition to antibody-mediated humoral immune escape, the escape of cellular immune responses mediated by killer T cells is also possible.
Promote the continuous spread of dominant variants of the new coronavirus
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Cellular immunity is another set of immune systems in the human body besides antibody immunity.
Its main function is to use white blood cells called killer T cells to specifically identify and remove human cells infected by pathogens, thereby blocking pathogen replication and Spread the immune effect
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Existing studies have shown that the cellular immune response is related to the severity and development of the new coronary disease
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The blood test of the infected person found that the new coronavirus-specific cells can be detected earlier than the neutralizing antibody, indicating that the cellular immune response begins to play a role in the early stage of the virus infection

However, researchers have discovered that some unique mechanisms of the mutated new coronavirus can help it escape cellular immunity, leading to a further increase in infectivity
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Through the high-throughput screening platform, researchers screened and identified four key epitopes related to cellular immunity specific to the new coronavirus, and found that the alpha, beta, gamma, and delta strains make at least one of the key antigens Epitope mutations help the virus escape the immune recognition of killer T cells

In addition, the researchers also screened invariant epitopes in different types of coronaviruses.
The invariance of these epitopes shows that they have important functions for coronaviruses
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Tan Xu, an associate professor at the School of Pharmacy of Tsinghua University, said that the escape of the mutated new coronavirus from the immune system has greatly increased the complexity of the global vaccination plan.
These constant epitopes provide a theoretical basis for the design of a new generation of coronavirus vaccines
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The new universal vaccine will not only activate the human body to produce neutralizing antibodies, but also mediate a wide range of cellular immune responses, reducing the risk of mutant viruses breaking through infection (referring to infections that occur after vaccination)

Focus on the new crown pneumonia epidemic