Cells against SARS-CoV-2 detected in non-exposed individuals

Although researchers around the world rush to develop a vaccine against the virus that causes COVID-19, and some pin their hopes on the idea that enough people will recover from infections to achieve herd immunity in the meantime, questions about whether exposure to the virus induces immunity to it have lingered. If the virus itself does not prompt resistance, a vaccine against it might not either, according to The Scientist.

Although it doesn’t provide a conclusive answer, a study published yesterday (May 14) in Cellappears to be good news on the immunity front. Researchers at the La Jolla Institute for Immunology in California took blood from 20 adults who’d recovered from COVID-19 and exposed the samples to proteins from the SARS-CoV-2 virus. All of the patients had CD4+ helper T cells that recognized the virus’s spike protein, and 70 percent of them had CD8+ killer T cells that responded to the same protein. “Our data show that the virus induces what you would expect from a typical, successful antiviral response,” says co-author Shane Crotty in an institute press release.

The authors also tested blood samples collected between 2015 and 2018 to see whether people who were never exposed to SARS-CoV-2 might nevertheless have some immunity to it. They detected CD4+ T cell responses to SARS-CoV-2 in about half of those samples, which they suggest could be due to exposure to other coronaviruses that cause a cold.

“One reason that a large chunk of the population may be able to deal with the virus is that we may have some small residual immunity from our exposure to common cold viruses,” said viral immunologist Steven Varga of the University of Iowa.