Researchers have found that people with long-term chronic obstructive pulmonary disease (Long-COVID) have immune and hormonal responses that are very different from those without symptoms. Their study, involving 268 people, showed significant differences in antibody and cortisol levels, providing implications for potential treatments. However, the complexity of Long-COVID poses challenges in developing effective treatments.
A new study by researchers at Yale School of Medicine and the Icahn School of Medicine at Mount Sinai shows that people who develop long-term symptoms of brain fog, confusion, pain and extreme fatigue after being infected with COVID-19 show different immune and hormonal responses compared to people who do not have long-term COVID.
Identifying these different responses could help scientists identify, for the first time, the cause of this often debilitating disease and explore potential treatments for it. In the United States, about 7.5% of people infected with the SARS-CoV-2 virus have Long-COVID.
"If you were a doctor and did routine laboratory tests on these patients, you wouldn't find these signals," said Akiko Iwasaki, co-first author of the paper and Sterling Professor of Immunobiology at Yale University.
For the study, researchers analyzed blood samples from 268 people who either had symptoms of Long-COVID for an average of a year; had been infected with COVID-19 but fully recovered; or had no known previous infection. The researchers observed clear differences between circulating antibodies and other immune system cells in Long-COVID patients and those in other groups.
The researchers also found that in those patients who exhibited long COVID, there was an increase in circulating antibodies that help the body fight non-COVID-19 viruses, particularly those known to protect against Epstein-Barr virus, a human herpes virus linked to a variety of cancers. Additionally, these patients also had significantly lower levels of cortisol, a steroid hormone released by the adrenal glands during stress.
The authors say that while the findings reveal key biological processes associated with Long-COVID, the complexity of individual responses means developing therapies to treat the disease will be difficult.
"There is currently no specific treatment for Long-COVID because it is a disease that penetrates complex systems such as immunity and hormonal regulation," said David Putrino, co-first author of the study, professor of rehabilitation and human performance at Icahn Sinai University and director of the Cohen Center for Complex Chronic Disease Rehabilitation.
However, Iwasaki said the new insights provide important clues that may help develop new diagnostics and treatments. "Once we have more information about these signals, we can start thinking about designing the right trials to treat this disease," she said.
The findings were recently published in the journal Nature.