In the immune arsenal, antibodies offer best long-term hope against COVID

When it comes to long-lasting protection against COVID-19, antibodies are our biggest allies, a new Yale University study shows.

Since the emergence of the SARS-CoV-2 virus, the relative contributions of the different parts of our immune system arsenal—particularly those of T cells, which destroy infected cells from the inside, and B cells, which produce antibodies that clean up free-floating virus outside of cells—during and after infection has remained unclear.

To better understand, scientists in the lab of Yale’s Akiko Iwasaki, the Waldemar Von Zedtwitz Professor of Immunobiology, conducted a series of experiments on mice to determine which immune system responses played the most important role at different stages of COVID-19 cases.

“While T cells play a role during acute infections, our antibodies are crucial for long-term protection against re-infection,” said Benjamin Goldman-Israelow, a postdoctoral researcher in Iwasaki’s lab and lead author of the study.

The paper was published Sept. 2 in the journal Science Immunology.

During acute infections, both types of adaptive, or learned, immune responses play key roles in combatting infections. Mice that lack T cells but have antibody protection and those without antibodies but that have healthy T cells both combatted infection equally well, researchers found.

However, in mice lacking what are known as “memory” T cells—a kind of reserve cell that remains in the body after infection—antibodies alone provided more than adequate protection after mice were reinfected with SARS-CoV-2, the virus that causes COVID-19, or the highly immune evasive Beta variant. This antibody protection was also seen in in mice which had received a vaccine.

Goldman-Israelow stressed that previous research has shown that people who received mRNA-based vaccines produce more antibodies than those who were naturally infected. And naturally infected people who then receive a vaccination produce even more, perhaps providing greater protection against re-infection.

While this study found the key importance of circulating antibodies in protection, the newly emerged Delta variant appears to overcome this systemic immunity to cause more breakthrough infections, he said.

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