Common Colds Train The Immune System To Recognize Covid-19

August 25, 2020

Previous infection with the common cold virus can train the immune system to recognize SARS-CoV-2, the virus that causes COVID-19, according to a new study.

The study, published Aug. 4 in the journal Science, found that immune cells called T-cells can recognize the common cold coronavirus, as well as specific sites on SARS-CoV-2 – including the part of the infamous “spike” protein it uses to bind to and invade human cells.

This existing immune system “memory” may explain why some people have less severe COVID-19 infections compared to others; however, the authors stress that this hypothesis is “highly speculative” and more research is needed to confirm it. That’s because it’s not yet known exactly how much of a role T cells play in the fight against COVID-19 – T cells are just part of the complex molecules and cells that make up our immune system.

“We have now shown that in some people, pre-existing T-cell memories against the common cold coronavirus can cross-recognize SARS-CoV-2 down to its precise molecular structure,” study co-lead author Daniela Weiskopf, an assistant professor at the La Jolla Institute of Immunology in California, said in a statement.

Study co-lead author Alessandro Sette, a professor at the La Jolla Immunology Institute, said in the statement that this “immune reactivity may translate into varying degrees of protection against COVID-19.” Having a strong T-cell response, or a better T-cell response, may give you the opportunity to initiate a faster, stronger response.”

Previous studies have shown that up to 50 percent or more of people who have never been exposed to COVID-19 have T cells that recognize SARS-CoV-2. This ability has been seen in people around the world in the Netherlands, Germany, the United Kingdom and Singapore. Scientists speculate that this existing immunity may be due to previous infections with other coronaviruses, especially those that cause common cold infections.

In the new study, researchers analyzed blood samples collected from people between 2015 and 2018, well before COVID-19 first appeared in Wuhan, China.

These blood samples contained T cells that responded to more than 100 specific sites on SARS-CoV-2. The researchers showed that these T cells also responded to similar sites on four different coronaviruses that cause common cold infections.

“This study provides very strong direct molecular evidence that memory T cells can ‘see’ very similar sequences between the common cold coronavirus and SARS-CoV-2,” said Sette.

In addition to binding to spiking proteins, T cells also recognize other viral proteins beyond spikes.

Currently, most COVID-19 vaccine candidates target spiking proteins, but the new findings suggest that adding other proteins to the vaccine in addition to spikes may take advantage of this T-cell cross-reactivity and potentially enhance the vaccine’s effectiveness, although more research is needed to prove this, the researchers said.

The authors note that their finding of cross-reactivity with T cells is different from what is seen with neutralizing antibodies – another weapon of the immune system that prevents pathogens from infecting cells. The authors say that based on previous studies, neutralizing antibodies against common cold viruses are specific to these viruses and have not shown cross-reactivity with SARS-CoV-2.