La Jolla Institute for Immunology (LJI) researchers are examining how the immune system develops its responses against common cold coronaviruses (CCCs) to get an early look at SARS-CoV-2 immunity.
Apparently resulting from repeated exposure to CCCs in childhood, a new LJI study just published in Cell Host & Microbe found that adults had lasting memory responses of CCC-fighting antibodies and T cells. Because of this immune cell army, CCC infections in adults often occur infrequently and are seldom severe.
Leading scientists believe that the COVID-19 booster shots that are currently available may be crucial for long-term protection against SARS-CoV-2, the virus that causes COVID-19, and that these findings may offer a clue as to how immunity might be built up against it.
What do coronaviruses have in common?
With the Omicron 5 subvariant on the loose, more and more people are suffering from breakthrough infections and reinfections.
“Everyone is wondering where this is going to go. Will we need to keep getting boosters or redesigning the vaccines?” says LJI Professor Alessandro Sette, Dr.Biol.Sci.
These important considerations led Sette and his coworkers to examine whether coronaviruses provide the immune system with any unique difficulties. The researchers instead looked at long-term immunological memory of common cold coronaviruses because SARS-CoV-2 has only been in circulation for a short two years and has continued to mutate during that time.
They had to evaluate samples from persons who had never been exposed to SARS-CoV-2 in order to avoid muddying the data. Fortunately, blood samples were taken for a prior study conducted at LJI before to the epidemic. It was safe to assume that because the patients in this group were all young adults, they had several exposures to CCC.
Well-trained immune cells remember coronaviruses
The common cold seems to afflict young children frequently, as everyone with young children is aware. These infections in childhood stimulate a robust immunological memory. Kids’ immune systems are educated as they travel through the germ-filled early school environment.
Adults have persistent immunological memory, according to the study, and typically only contract CCCs every eight years or so. “The immune response is remarkably stable and durable, over time,” says LJI Instructor Ricardo Da Silva Antunes, Ph.D., who co-led the study with Sette.
SARS-CoV-2 is different from CCCs, but they have many structural similarities, and previous work at LJI suggests the immune system recognizes similarities between different coronaviruses.
For the new study, the LJI researchers also showed that antibodies and T cells from this group of healthy adults could cross-react with SARS-CoV-2. This cross-reactivity supports the hypothesis that the immune system perceives CCCs and SARS-CoV-2 in a similar manner, and may even protect a person from severe COVID-19.
As community immunity increases, reinfections should become less frequent over time, and COVID-19 symptoms should be less severe if the pattern of CCC immunity holds true for SARS-CoV-2.
The rise of new SARS-CoV-2 variants may complicate the process of building immunity, but “there is certainly reason to assume that eventually, this will be the end result; but we are not there yet,” says Sette.
Don’t lower your defenses yet
SARS-CoV-2 has a good possibility of remaining active. “Endemism” refers to a pathogen that persists at a constant level in a population and does not interfere with daily life. However, endemic illnesses remain a danger. Although most people don’t experience a life-threatening episode of the flu due to its endemic nature, the influenza virus nonetheless claimed 53,544 American lives in just 2020 (and that was a lower number than usual).
Sette and Da Silva Antunes stress that endemic SARS-CoV-2 would still be serious. They concur that the best course of action at this time is for people to keep up with their booster doses based on their research on CCC immunity.
“At this stage of the pandemic, we’re still mounting that immunity to SARS-CoV-2,” says Da Silva Antunes.
“It’s really important to get the vaccine boosters the third and fourth doses,” adds Sette.
Additional authors of the study, “Immunological memory to Common Cold Coronaviruses assessed longitudinally over a three-year period pre-COVID19 pandemic,” include Esther Dawen Yu, Tara M. Narowski, Eric Wang, Emily Garrigan, Jose Mateus, April Frazier, Daniela Weiskopf, Alba Grifoni and Lakshmanane Premkumar.
The National Institute of Allergy and Infectious Diseases (NIAID) of the National Institutes of Health (grants U01AI141995, U19AI142742, and U54CA260543; and contract number 75N93019C00065) supported this research.
