Post-COVID impairment of memory T cell responses to community-acquired pathogens can be rectified by activating cellular metabolism

Infection rates involving bacterial and viral pathogens have increased precipitously after the COVID-19 pandemic. While it has been speculated that higher infection rates resulted from increased hospitalizations throughout the pandemic or greater use of antibiotics, precisely why rates remain high today has remained unexplained. Mitochondrial dysfunction is known to occur post-COVID and may disrupt immune responses. Within T cells, SARS-CoV-2 infection is linked to low mitochondrial membrane potential, increased mitochondrial apoptosis, and decreased mitochondrial respiration, which together impact cellular activation and function beyond the acute phase of illness. Here, we demonstrate that decreased mitochondrial function in T cells post-COVID may contribute to higher infection susceptibility by metabolically immobilizing T cell memory responses. Using donor-matched peripheral blood samples from 31 COVID-naïve individuals who subsequently contracted COVID-19, we tracked how influenza A (IAV), Staphylococcus aureus (SA), and Varicella-zoster virus (VZV) T memory cell responses are impacted by COVID-19 infection. We found that gene expression linked to T cell activation decreased but mitochondrial redox-pathway genes increased in CD4 memory T cells post-COVID. However, mitochondrial flux and reactive oxygen species production were limited in a plurality of post-COVID memory T cells after stimulation with IAV, SA, and VZV. Furthermore, we found a disordered relationship between memory T cell mobilization of glycolysis, fatty acid metabolism, and oxidative phosphorylation pathways post-COVID which was partially rescued by pharmacological activation of mitochondrial pathways within antigen-specific T cells. Collectively, these findings indicate that COVID-19 infection may have lasting effects on inhibiting T cell memory responses to commonly encountered community-acquired pathogens, with significant implications for the clinical care of immunologically vulnerable populations in the post-pandemic era.