According to new research, immunity to COVID-19 is likely to last a very long time, probably a lifetime as well, since coronavirus induces Memory B cells. The study was conducted by infectious disease experts at the University of Rochester Medical Center. It was also found that seasonal common colds may provide us with some protection from the coronavirus as well.
The study was published in mBio. It is the first study that shows that the SARS-CoV-2 virus, which causes COVID-19, induces memory B cells. Memory B cells are long-living immune cells. They detect pathogens and create antibodies to destroy them, and remember them for the future as well. The next time this pathogen enters the body, memory B cells fight them and stop their spread.
Since memory B cells can last in the body for several decades, it may be possible that they could also protect COVID-19 survivors from reinfections for a long time. However, further research is needed to make a more accurate observation.
Cross-reactivity of memory B cells
This is also the first study that reports the cross-reactivity of memory B cells. This means that Memory B cells that once attacked cold-causing coronavirus also recognize the SARS-CoV-2 virus. According to the authors of the study, this could mean that those who have been infected by a common coronavirus, which is mostly everyone, might have a degree of pre-existing immunity to COVID-19.
Mark Sangster, Ph.D., a research professor of Microbiology and Immunology at URMC, is the lead author of the study. “When we looked at blood samples from people who were recovering from COVID-19, it looked like many of them had a pre-existing pool of memory B cells that could recognize SARS-CoV-2 and rapidly produce antibodies that could attack it,” he said.
The researchers studied blood samples from 26 people that were recovering from mild to moderate COVID-19. They compared it with blood samples of 21 healthy donors whose samples were collected 6-10 years ago, long before they could have been infected with COVID-19.
They studied the level of memory B cells in these blood samples. They also studied the level of antibodies that target specific parts of the Spike protein, which is present in all coronavirus and serves an important role in helping the virus infect cells.
Even though the spike protein looks and acts differently in all coronavirus, one of its components, the S2 subunit is uniform across all of the viruses. Memory B cells cannot differentiate between the Spike S2 subunits of the different coronaviruses and attack each one of them. The study found it to be true for beta coronaviruses. It’s a subclass which includes two cold-causing viruses along with SARS, MERS and SARS-CoV-2.
The limitation of this study is that it doesn’t show the level of protection given by the cross-reactivity of memory B cells and how it influences recovery in patients.
David Topham, Ph.D., the Marie Curran Wilson and Joseph Chamberlain Wilson Professor of Microbiology and Immunology at URMC, runs the lab where this study was conducted. He said, “That’s next, Now we need to see if having this pool of pre-existing memory B cells correlates with milder symptoms and shorter disease course — or if it helps boost the effectiveness of COVID-19 vaccines.”