Immune warriors known as T cells help us fight some viruses, but their importance for battling SARS-CoV-2, the virus that causes COVID-19, has been unclear. Now, two studies reveal infected people harbor T cells that target the virus—and may help them recover. Both studies also found some people never infected with SARS-CoV-2 have these cellular defenses, most likely because they were previously infected with other coronaviruses.
“This is encouraging data,” says virologist Angela Rasmussen of Columbia University. Although the studies don’t clarify whether people who clear a SARS-CoV-2 infection can ward off the virus in the future, both identified strong T cell responses to it, which “bodes well for the development of long-term protective immunity,” Rasmussen says. The findings could also help researchers create better vaccines.
The more than 100 COVID-19 vaccines in development mainly focus on another immune response: antibodies. These proteins are made by B cells and ideally latch onto SARS-CoV-2 and prevent it from entering cells. T cells, in contrast, thwart infections in two different ways. Helper T cells spur B cells and other immune defenders into action, whereas killer T cells target and destroy infected cells. The severity of disease can depend on the strength of these T cell responses.
Using bioinformatics tools, a team led by Shane Crotty and Alessandro Sette, immunologists at the La Jolla Institute for Immunology, predicted which viral protein pieces would provoke the most powerful T cell responses. They then exposed immune cells from 10 patients who had recovered from mild cases of COVID-19 to these viral snippets….
