Mucosal-Associated Invariant T (MAIT) Cells Are Highly Activated and Functionally Impaired in COVID-19 Patients

• Main Authors: Sebastian Deschler, Juliane Kager, Johanna Erber, Lisa Fricke, Plamena Koyumdzhieva, Alexandra Georgieva, Tobias Lahmer, Johannes R. Wissner, Florian Voit, Jochen Schneider, Julia Horstmann, Roman Iakoubov, Matthias Treiber, Christof Winter, Jürgen Ruland, Dirk H. Busch, Percy A. Knolle, Ulrike Protzer, Christoph D. Spinner, Roland M. Schmid, Michael Quante, Katrin Böttcher
• Format: Article
• Language: English
• Published: MDPI AG 2021-02-01
• Series: Viruses
• Subjects: COVID-19; SARS-CoV-2; mucosal-associated invariant T (MAIT) cells
• Online Access: https://www.mdpi.com/1999-4915/13/2/241

Coronavirus disease 2019 (COVID-19), caused by infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), comprises mild courses of disease as well as progression to severe disease, characterised by lung and other organ failure. The immune system is considered to play a crucial role for the pathogenesis of COVID-19, although especially the contribution of innate-like T cells remains poorly understood. Here, we analysed the phenotype and function of mucosal-associated invariant T (MAIT) cells, innate-like T cells with potent antimicrobial effector function, in patients with mild and severe COVID-19 by multicolour flow cytometry. Our data indicate that MAIT cells are highly activated in patients with COVID-19, irrespective of the course of disease, and express high levels of proinflammatory cytokines such as IL-17A and TNFa ex vivo. Of note, expression of the activation marker HLA-DR positively correlated with SAPS II score, a measure of disease severity. Upon MAIT cell-specific in vitro stimulation, MAIT cells however failed to upregulate expression of the cytokines IL-17A and TNFa, as well as cytolytic proteins, that is, granzyme B and perforin. Thus, our data point towards an altered cytokine expression profile alongside an impaired antibacterial and antiviral function of MAIT cells in COVID-19 and thereby contribute to the understanding of COVID-19 immunopathogenesis.