New study shows mRNA vaccine harnesses T-cell power to combat COVID-19 in lungs

By Gian Galassi, UW News

The effectiveness of mRNA vaccines in reducing disease severity and hospitalization from COVID-19 is well established. Now, new research from the University of Wisconsin School of Veterinary Medicine advances our understanding of how these vaccines protect the lungs following breakthrough infections from emerging variants of SARS-CoV-2, the virus that causes COVID-19.

Published on Oct. 5 in the journal JCI Insight, the study is the first to directly demonstrate the role of memory CD8 T cells in mRNA vaccine-induced immunity to COVID-19. Memory CD8 T cells are a specialized type of white blood cell that rapidly respond when re-exposure to a pathogen occurs.

They are often referred to as “trained assassins” because they control viral infections by targeting and then destroying virally infected cells. This study, conducted in mice, shows that memory CD8 T cells were necessary and sufficient in controlling SARS-CoV-2, independent of antibodies. Researchers demonstrated this by showing how the protection afforded by mRNA vaccines was lost in mice when memory T cells were depleted prior to SARS-CoV-2 infection.

Scientists widely accept that CD8 T cells provide a more robust form of protection because the viral fragment they target to kill infected cells does not change considerably with each new viral variant. Antibodies on the other hand, typically lose their ability to prevent infection because the part of the virus they target changes with each new mutation. Read more…