What you need to know

In a small study supported by the National Institute of Allergy and Infectious Diseases (NIAID), severe cases of COVID-19 were shown to cause long-lasting changes to the immune system.

Researchers found that severe cases of COVID-19 can change which genes are turned on or off in certain stem cells. The study focused on stem cells that produce white blood cells, a part of the immune system. The stem cells of people who recovered from severe COVID-19 produced more white blood cells — which then produced more inflammatory signals — than the cells of healthy counterparts.

What did the researchers do?

The researchers received blood samples from 38 people recovering from severe COVID-19 and 19 healthy people. They identified differences in gene expression between the recovering and healthy participants’ stem cells. The gene expression in the recovering participants’ stem cells was associated with higher production of white blood cells. The white blood cells created by recovering participants also seemed to produce more chemicals that trigger inflammation, compared with the white blood cells of healthy participants. These changes lasted for up to 1 year after the participants recovered from severe COVID-19.

The researchers aimed to find out whether one inflammatory chemical messenger, called IL-6, can cause the changes to gene expression. When the researchers tested blocking IL-6 in the cells of people with COVID-19, there were fewer changes to their stem cells’ gene expression than in the cells of people who had recovered from COVID-19 without blocking IL-6. When IL-6 was blocked in mouse models with a disease similar to COVID-19, murine hepatitis virus 1 (MHV-1), the mice had fewer changes to gene expression and less organ damage from the disease than mice that had not had IL-6 blocked.

Why is this research important?

Many people are at increased risk of severe COVID-19, including older adults, pregnant people, and people with weakened immune systems.

Because this was a small study, researchers did not establish a direct association between changes to gene expression and poor health outcomes. But the study shows one way that severe COVID-19 can have a long-term impact on the immune system, and its results can inform future research on possible treatments.

Where can I go to learn more?

Severe COVID-19 may lead to long-term innate immune system changes

• A study supported by NIAID reported epigenetic changes in the immune system after severe COVID-19.

NIH Launches Clinical Trials for Long COVID Treatments

• NIH’s Researching COVID to Enhance Recovery (RECOVER) Initiative is investigating possible Long COVID treatments.

Factors That Affect Your Risk of Getting Very Sick from COVID-19

• The Centers for Disease Control and Prevention shares information related to COVID-19 risks.

Sources

Cheong, J., Ravishankar, A., Sharma, S., Parkhurst, C. N., Grassmann, S. A., Wingert, C. K., Laurent, P., Ma, S., Paddock, L., Miranda, I. C., Karakaslar, E. O., Nehar-Belaid, D., Thibodeau, A., Bale, M. J., Kartha, V. K., Yee, J. K., Mays, M. Y., Jiang, C., Daman, A. W., … Josefowicz, S. Z. (2023). Epigenetic memory of coronavirus infection in innate immune cells and their progenitors. Cell, 186(18), 3882-3902.e24. https://doi.org/10.1016/j.cell.2023.07.019