The Other Side of Covid-19 Immunity
Not all immunity research has to do with antibodies
--
This week, research suggesting that antibodies to Covid-19 wane quickly after infection raised concerns about immunity to the coronavirus. Throughout the pandemic, much of the conversation about immunity has focused on antibodies: using antibody tests to look for them, filtering them out of convalescent plasma, and hoping that a vaccine will elicit enough of them. If antibodies disappear soon after recovery, they aren’t going to be that helpful.
But as I wrote yesterday in Elemental, antibodies are only one side of the immunity story. The other side has to do with T cells. Unlike antibodies, which fight an infection by targeting the pathogen itself, some T cells (called “killer T” cells) can do so by attacking the cells that are infected, and others (called “helper T” cells) help coordinate the attack on invaders and spur the production of more antibodies.
T cells in general haven’t been talked about as much, but they’re the focus of a lot of promising Covid-19 research. If antibodies end up being insufficient for fighting the coronavirus, T cells may be able to pick up the slack or offer complementary support. Helper T cells, in particular, are getting a lot of attention in Covid-19 research, in part because of their potential to help boost the production of waning antibodies.
So far, a lot of T-cell research has focused on figuring out whether people who have Covid-19 have helper T cells that can recognize SARS-CoV-2, or at least parts of it. As early as April, researchers from Berlin identified helper T cells in people hospitalized with Covid-19. The T cells they found specifically recognized the coronavirus’s increasingly notorious spike protein, which it uses to get into a cell. The researchers posted their preprint (a paper that hasn’t yet gone through the critical process of peer review) to the server medRxiv.
In May, research published in Cell showed similar findings: 10 people who had Covid-19 all had helper T cells that recognized the spike protein as well as other proteins on SARS-CoV-2. Even more notable was their finding that about 40% to 60% of people who never had a Covid-19 infection also had helper T cells that could recognize the coronavirus. This suggested…
