A new study published in Science explored this question. Although the researchers cautioned it is too premature to tell, they did find that certain cells in the human body — “memory T cells” — that recognize common cold coronaviruses can also recognize COVID-19 in some people.
“This could help explain why some people show milder symptoms of coronavirus while others get severely sick,” said co-author of the study Daniela Weiskopf, Ph.D. in a University news release.
The researchers at La Jolla Institute for Immunology (LJI) investigated memory T cells, which are part of our immune system. The researchers explained in a press release that these cells remember viruses the body has encountered throughout a person’s life. When the body gets exposed to that virus again, the memory T cells are able to identify that foreign invader and activate the immune system to fight off it off.
“Immune reactivity may translate to different degrees of protection,” Alessandro Sette, co-author of the study and LJI professor, said in the release. “Having a strong T cell response, or a better T cell response may give you the opportunity to mount a much quicker and stronger response.”
The researchers in the new study collected samples from participants who had never been exposed to SARS-CoV-2 to see if they had a cross-over immunity reaction from previous common cold coronavirus exposure. Their findings showed that participants not exposed to COVID-19 can produce memory T cells that are equally reactive against SARS-CoV-2 and four other common cold coronaviruses.
“We have now proven that, in some people, pre-existing T cell memory against common cold coronaviruses can cross-recognize SARS-CoV-2, down to exact molecular structures,” Weiskopf, an LJI research assistant professor, stated in the release.
“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,” Sette added.
The new study expanded on a previous report from LJI Professor Shane Crotty, Ph.D., and the Sette Lab which found 40 to 60% of people never exposed to COVID-19 had T cells that reacted to the SARS-CoV-2 virus, the news release stated. Similar study findings were revealed globally, including a study out of Singapore.
The researchers found that while some cross-reactive T cells targeted the SARS-CoV-2’s spike protein, which is how the virus reportedly binds to a human’s cells, the pre-existing memory T cells also target other SARS-CoV-2 proteins, according to the release. Co-study author Sette said this is significant because most vaccine candidates target mainly the spike protein, and taking advantage of this cross-reactivity to other proteins could potentially enhance vaccine potency.
Sette said the study findings are speculative and much more data is needed.
“The jury is still out (some would say the trial hasn’t even started) on this matter,” Dr. Aaron E. Glatt, an epidemiologist, and a fellow of the Infectious Diseases Society of America told Fox News in an email.
“Very preliminary albeit very interesting studies suggest there may be some benefit, and some papers have even suggested that prior influenza vaccination might provide some protection, but I would certainly not rely on any prior infection to assume any significant immunity to COVID-19 at this time,” cautioned Glatt, who is also a professor of medicine at the Icahn School of Medicine at Mount Sinai. “Everyone still needs to mask and social distance appropriately.”