To take a look at the future of SARS-CoV-2 immunity, scientists at the La Jolla Institute of Immunology (LJI) are investigating how the immune system builds its defenses against common cold coronaviruses (CCCs).
According to a new LJI study, recently published in Cell Host & Microbe, adults have stable memory antibody and T-cell responses that fight CCC, presumably resulting from multiple exposures to CCC during childhood. Thanks to this army of immune cells, CCC infections in adulthood are usually infrequent and mild.
These findings may be a clue to how immunity can build against SARS-CoV-2, the virus that causes COVID-19, and leading researchers think that the COVID-19 booster shots available today may be critical for long-term immunity.
What do coronaviruses have in common?
With the Omicron 5 subvariant on the loose, more and more people are suffering from innovative infections and reinfections.
“Everybody’s wondering where this is going to go. Are we going to have to keep getting boosters or redesign the vaccines?” says LJI professor Alessandro Sette, Dr.Biol.Sci.
These big questions led Sette and his colleagues to wonder whether coronaviruses pose any special challenge to the immune system. SARS-CoV-2 has been circulating for just under two years and has continued to evolve during that time, so researchers looked at the long-term immune memory of common cold coronaviruses.
In order not to confuse the data, they had to analyze samples from people never exposed to SARS-CoV-2. Fortunately, they took blood samples for a previous study launched at LJI before the pandemic. The patients in this group were all young adults, and it was safe to assume that they had been exposed to CCC multiple times.
Well-trained immune cells remember coronaviruses
As anyone with young children knows, common colds seem to strike young children again and again. These childhood diseases cause a strong immune memory. As children go through the germinal gauntlet of early schooling, their immune systems are also schooled.
The researchers found that adults have a stable immune memory and tend to catch CCC only about every eight years. “The immune response is remarkably stable and durable over time,” says LJI instructor Ricardo Da Silva Antunes, Ph.D., who led the study with Sette.
SARS-CoV-2 is distinct from CCCs, but they have many structural similarities, and previous work at LJI suggests that 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 may help protect a person from severe COVID-19, and the finding reinforces the idea that the immune system sees CCCs and SARS-CoV-2 in a similar way.
If the pattern observed in CCC immunity holds true for SARS-CoV-2, as immunity builds in the population, reinfections should become less frequent over time and symptoms of COVID-19 should be less severe The rise of new variants of SARS-CoV-2 may complicate the process of building immunity, but “there’s certainly reason to assume that eventually this will be the end result; but we’re not there yet,” Sette says.
Don’t let your defenses down just yet
There is a good chance that SARS-CoV-2 is here to stay. A pathogen that maintains a stable level in a community and does not cause day-to-day disruption is called “endemic”. But endemic diseases remain a threat. Influenza is endemic, and while most people don’t have a life-threatening case of the flu, the flu virus still killed 53,544 Americans in 2020 alone (and that was less than the usual).
Sette and Da Silva Antunes emphasize that endemic SARS-CoV-2 would still be serious. Based on their CCC immunity data, they agree that the best strategy right now is for people to stay current on their booster shots.
“At this stage of the pandemic, we are still building this immunity to SARS-CoV-2,” says Da Silva Antunes.
“It’s very important to get the vaccine boosters: the third and fourth doses,” adds Sette.
Source:
Institute of Immunology La Jolla