In patients with COVID-19, the immune system’s T cells learn to recognize and target the new coronavirus.
But some people who were never infected with the virus nonetheless have T cells that also recognize it.
Researchers had suspected that in these individuals, past exposure to other coronaviruses, such as those that cause the common cold, had somehow primed their T cells to recognize and attack this new coronavirus (SARS-CoV-2), and new research appears to confirm that.
In studies of human blood samples collected well before the new coronavirus was discovered, researchers found T cells that were equally reactive against the new virus and four types of common cold coronaviruses.
The strongest T cell responses to the new coronavirus were associated with the spike protein the virus uses to enter human cells. “We knew there was pre-existing reactivity, and this study provides very strong direct molecular evidence that memory T cells can ‘see’ sequences that are very similar between common cold coronaviruses and SARS-CoV-2,” coauthor Alessandro Sette of the La Jolla Institute for Immunology said in a statement.
It is plausible to think that previous exposure to common cold viruses might contribute to variations in COVID-19 severity, researchers said on Tuesday in the journal Science.