Cross-Reactive Immunity Found Between Common Coronaviruses and SARS-CoV-2

A collaborative team from Charité—the University of Medicine of Berlin, the Berlin Institute of Health at Charité, and the Max Planck Institute for Molecular Genetics—have shown that previous exposure to coronaviruses can enhance the body’s immune response to SARS-CoV-2, both during natural infection and following vaccination. The researchers, whose work has been published in Science, also report that this cross-reactive immunity decreases with age. 

For the current study, the researchers recruited individuals with no prior exposure to SARS-CoV-2, testing them at regular intervals to establish whether they had contracted the infection. Out of a total of nearly 800 participants who were recruited from mid-2020 onwards, 17 persons tested positive. The researchers studied the affected individuals’ immune systems in detail. Their analyses showed that the immune response against SARS-CoV-2 also included the mobilization of T helper cells which had been generated in response to endemic common cold viruses. 

In both the endemic viruses and the new coronavirus, this site was characterized by sequence similarities that were particularly well preserved. “During infections with the more harmless coronaviruses, the immune system builds up a kind of protective ‘universal coronavirus’ memory,” explains the study’s corresponding author, Claudia Giesecke-Thiel. “Once exposed to SARS-CoV-2, these memory cells are reactivated and kick-start the response against the new pathogen. This could help accelerate the initial immune response to SARS-CoV-2 and limit viral propagation during the early stages of the infection and is therefore likely to have a positive effect on the course of the disease.”

In a second part of the study, the researchers analyzed T helper cells in approximately 570 healthy individuals. They were able to show that cross-reactive immunity declines in older adults. In fact, both the number of cross-reactive T cells and the strength of their binding interactions were shown to be lower in older participants than in younger participants. According to the authors, this decline in cross-reactive immunity is caused by normal, age-related changes.