Elderly patients face higher risk of severity and death from COVID-19

SARS-CoV-2, the virus responsible for causing COVID-19 can infect people of any age. However, elderly people face a greater risk of severity and death when compared to younger patients.

COVID-19

Image Credit: Andrii Vodolazhskyi/Shutterstock.com

A new study comparing the immune reaction among different age groups may explain the reason behind this. The study was recently published in mBio, an open-access journal of the American Society for Microbiology.

Elderly patients infected with COVID-19 have lower frequencies of the immune cells required to remove the virus from the body, discovered the team.

Elderly people have more severe diseases compared to young people, and we found that the cytotoxic part of immune control is not as efficient to respond to the virus in older people.”

Gennadiy Zelinskyy, PhD, Study Lead and Virologist, University Hospital Essen

Zelinskyy and his collaborators examined blood samples, collected from 30 individuals who had mild cases of COVID-19 infection, to track how T cells, which are needed to detect and remove the infected cells, react during SARS-CoV-2 infection.

The researchers looked at patients aged from the mid-20s to the late 90s. In all the patients, they found that acute SARS-CoV-2 infections resulted in lower numbers of T cells in the patients’ blood when compared to healthy persons.

According to Zelinskyy, this reduction has been one of many unwanted surprises from COVID-19 infection. As soon as they enter the body, most viruses cause an uptick in the immune system’s expansion of T cells.

These comprise “killer” T cells, which play a crucial role in eliminating cells infected by virus. These cells create cytotoxic molecules that kill the virus-infected cells in the body. However, if the immune system of a specific person creates a less number of these T cells, it will be less successful at combating a viral infection, added Zelinskyy.

In the COVID-19 subjects investigated by Zelinskyy and his collaborators, the team similarly discovered that the number of CD8+ T cells that produce cytotoxic molecules in response to the virus reduced with increased age, and that reduction was considerably higher, on average, in patients aged over 80.

Furthermore, the “killer” T cells taken from patients aged 80 to 96 created cytotoxic molecules at a lower frequency when compared to analogous cells from younger patients.

The SARS-CoV-2 virus binds to cells in the mouth or nose. And from there, it may reach the lungs and travel to other organs, activating a life-threatening infection.

Cytotoxic T cells really fight for control during this acute phase of infection.”

Gennadiy Zelinskyy, PhD, Study Lead and Virologist, University Hospital Essen

If the immune system of an elderly patient generates a less number of killer T cells, and these cells are insufficiently armed, they may be mounting an inadequate defense against the SARS-CoV-2 virus, Zelinskyy added. The viral particles will continue to spread and, consequently, the infection becomes worse.

The latest data indicate that cytotoxic T cells have an important role to play in the regulation of early infections; however, Zelinskyy warned that it is too early to know whether that connection can be exploited to develop an effective immunotherapy that utilizes such cells.

In earlier studies performed on mice affected by viral infections, Zelinskyy’s team discovered that a checkpoint inhibitor—an immunotherapy that stimulates the killer T cells and efficiently releases the brakes on the immune system—enhanced virus control initially but had the ability to later impact the various organs, including the lungs.

More research is required to gain a deeper understanding of the possible risks and benefits of disrupting the T cells as a means to manage SARS-CoV-2 and other types of viruses, Zelinskyy concluded.

Source:
Journal reference:

Westmeier, J., et al. (2020) Impaired Cytotoxic CD8+ T Cell Response in Elderly COVID-19 Patients. mBio. doi.org/10.1128/mBio.02243-20.

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