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COVID-19 and Aging

New study helps explain older adults' increased vulnerability

Pushpa Pandiyan

Researchers know that older adults can suffer serious symptoms from COVID-19, and Case Western Reserve's Pushpa Pandiyan is working to understand why.

Various factors are behind the immune system's weakening response to the virus as we age, said Pandiyan, PhD, an associate professor of biological sciences at the university's School of Dental Medicine.

Sifting through those factors and understanding how treatments and vaccines could help enhance immune function is a challenge. But after a recent study co-authored by Pandiyan and published online in Frontiers in Immunology, scientists may be a step closer to that goal.

Researchers have long known that our immune systems weaken over time. Some reasons are clear. As we age, for example, the thymus—a small organ in the chest where pathogen-fighting T cells develop—shrinks and eventually may stop doing its job.

With fewer new T cells, the body is less able to defeat new infections. Older adults can still rely on T cells produced when they were younger. But Pandiyan suspected the problem isn't just less T-cell production, but a decline in the quality of existing T cells.

In a pilot study, she examined blood samples from younger and older patients who had visited University Hospitals Cleveland Medical Center with mild cases of COVID-19 in early 2020, several months before vaccines became available.

The researchers took T cells from the samples and placed them in culture dishes with coronavirus amino acids known as peptides.

"The T cells of the older patients looked very exhausted," Pandiyan said. "They were not proliferating very well, and they were not making enough of the proteins required to fight infection."

She hypothesizes that the effectiveness of COVID-19 vaccines decreases with age because of T-cell exhaustion and a decline in sensors in the cells that signal inflammation. She is now working on follow-up studies to assess if that's the case.

If it is, that suggests vaccines for older adults could be altered to compensate for reduced T-cell function. "This knowledge," she said, "could help us change our treatment and vaccination strategies."

— TOMAS WEBER