While many agree on the importance of antibodies in SARS-CoV-2 infection, T cells have also taken the spotlight as a key contributor to immunity. Researchers, led by Dr. Tania Watts and Dr. Mario Ostrowski from the University of Toronto, found that SARS-CoV-2 recovered patients have strong T cell responses. This publication is part of their research funded by the Government of Canada through the COVID-19 Immunity Task Force and the Canadian Institutes for Health Research.
Using blood from people who have recovered from COVID-19, scientists analyzed whether specific SARS-CoV-2 proteins could trigger a T cell response and how this response compares to the T cell responses triggered by the influenza virus in the same individuals. Most individuals showed a memory SARS-CoV-2 response from one type of T cell called CD4+T cell at 4-12 weeks after initial symptoms. Furthermore, people that recovered from COVID-19 had high levels of an inflammatory marker called tumor necrosis factor (TNF) and less of interferon-gamma (IFN-γ) in response to SARS-CoV-2 proteins than in response to influenza.
All in all, CD4+T cells had higher inflammatory characteristics and showed a weaker capacity to help trigger antibody production as a response to SARS-CoV-2, which suggests that they provide less protection than the response generated by the influenza virus.
Law JC, Koh WH, Budylowski P, Lin J, Yue F, Abe KT, Rathod B, Girard M, Li Z, Rini JM, Mubareka S, McGeer A, Chan AK, Gingras AC, Watts TH, A Ostrowski M. Systematic examination of antigen-specific recall T cell responses to SARS-CoV-2 versus influenza virus reveals a distinct inflammatory profile. J Immunol. 2021 Jan 1;206(1):37-50. doi: 10.4049/jimmunol.2001067.