A Korean research team has revealed the reason why the severity and death rate of the novel coronavirus infection (COVID-19) is significantly higher in the elderly 65 years and older. As the age increases, the protein that controls the body’s defenses is overexpressed and macrophages, which are immune cells, are over-activated, attacking normal cells and causing severe inflammation. It is expected to help the development of a treatment for severe COVID-19 necessary for the elderly.
The Institute for Basic Science announced on the 12th that a research team led by Choi Young-ki, director of the Center for New Variant Virus Research Center at the Korea Institute of Virology, proved that the severity and transmission rate of COVID-19 infection among the elderly are higher than those of younger people through animal experiments.
The research team compared the pathogenicity of ferrets, a weasel mammal, by infecting them with the Corona 19 virus by dividing them into 6 months or less, 1 year or more, 2 years or less, and 3 years or more. As a result of the analysis, ferrets under 6 months of age did not spread to other animals in close contact with low pathogenicity and low proliferative properties. Pathogenicity refers to the ability to cause disease through infection.
On the other hand, older ferrets over 3 years of age had a high rate of infecting other animals due to their high virus proliferation. A large number of viral ribonucleic acid (RNA) positive cells were detected in the lungs, and the severity was also high, including severe lung lesions.
To determine the exact cause of this phenomenon, the research team analyzed the gene expression pattern of infected lung tissue by RNA sequencing. As a result, expression of various genes for tissue regeneration following rapid immune response was increased in young ferrets.
However, in older ferrets, symptoms of inflammatory cytokines increased significantly from the early stage of infection, and immune cells were over-activated, resulting in severe inflammation. Cytokines are glycoproteins that are used as signaling substances to control and stimulate the body’s defense system. Excessive expression causes a ‘cytokine storm’ that attacks not only viruses but also normal cells.
The experimental results were very similar to the immunological changes seen in COVID-19 patients who suffered severe or died. As a result of comparing the genomes of severe COVID-19 patients and elderly ferrets, it was found that type 1 interferon, a cytokine, and M1 macrophage hyperactivity, a type of immune cell, are factors that cause severe disease in the elderly.
Choi Young-ki, head of the center, said, “This is the first test to prove that there is a big difference in the pathogenicity and transmission rate of the Corona 19 virus depending on the age of the host. do,” he said. The research results were published on the 10th in the online edition of the international academic journal ‘Nature Communications’.
Correspondent Kim Min-soo, Dong-A Science reborn@donga.com
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