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Older patients with this disease have a lower frequency of immune cells needed to remove the virus from the body. The study is published this week in mBio, the open access journal of the American Society for Microbiology.
“Older people have more severe disease than young people, and we found that the cytotoxic portion of immune control was not as efficient as responding to viruses in the elderly,” says virologist Gennadiy Zelinskyy, Ph.D., at University Hospital. Essen, in Germany, led the study. (Also read: Have you been cheated on? Avoid These 7 Words to Your Partner)
Zelinskyy and his colleagues analyzed blood samples from 30 people with mild cases of COVID-19 to observe how T cells, which are required for recognition and removal of infected cells, respond during SARS-CoV-2 infection. The patient’s age ranged from mid-20s to late 90s.
In all the patients, the investigators found that acute SARS-CoV-2 infection resulted in lower T cell counts in the patients’ blood, compared to healthy people.
This reduction has been one of the many unwanted surprises from COVID-19, said Zelinskyy. Most viruses, once they enter the body, trigger an increased expansion of immune system T cells. These include “killer” T cells, which play an important role in eradicating virus-infected cells.
They produce cytotoxic molecules that destroy infected cells in the body. But if a person’s immune system produces fewer of these T cells, Zelinskyy says, it will be less successful at fighting viral infections.
In the cohort of COVID-19 patients studied by Zelinskyy and his colleagues, the researchers also found that the number of CD8 + T cells that produce cytotoxic molecules in response to the virus decreased with age, and that decrease was significantly higher, on average. , in the patient above. 80. In addition, “killer” T cells from patients aged 80-96 years produce cytotoxic molecules at a lower frequency than similar cells from younger patients.
The SARS-CoV-2 virus attaches to cells in the nose or mouth. From there, it can spread to the lungs and travel to other organs, triggering a life-threatening infection. “Cytotoxic T cells really struggle to control during this acute phase of infection,” Zelinskyy said. (Also read: BLACKPINK’s Rose admits it is difficult to sing Hope Not, but finds a singing style)
If elderly patients’ immune systems produce fewer killer T cells, and these cells are not adequately armed, he said, they may mount an inadequate defense against SARS-CoV-2. Viral particles can continue to spread and as a result the infection gets worse.
New data suggest that cytotoxic T cells play a key role in early infection control, but Zelinskyy warns that it is too early to know whether this link can be harnessed to design effective immunotherapy using these cells.
In a previous study of viral infection in mice, his group found that checkpoint inhibitors – immunotherapy that activate killer T cells and effectively release brakes on the immune system – initially improved viral control but could potentially cause damage to the lungs and other organs.
Further research is needed, he said, to better understand the potential risks and benefits of disrupting T cells as a way to control SARS-CoV-2 and other viruses.
(tdy)
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