Differential control of mycobacterial growth ex vivo by COVID-19 patients is associated with CD8+ CD28+ T cells

Diseases caused by SARS-CoV-2 and Mycobacterium tuberculosis (M.tb) represent two public health emergencies. In severe presentations of disease, both pathogens may share a biological niche in the lower respiratory tract. There is significant potential for SARS-CoV-2 and M.tb infections to be co-present within individuals and modulate the respective outcomes of either infection. Here, we investigated how whole blood samples, as well as CD4+ and CD8+ T cells, from individuals hospitalised with acute COVID-19 disease respond to mycobacterial challenge. To do this, samples were assessed by ex vivo mycobacterial growth inhibition assays, immune cell phenotyping by mass cytometry, and whole blood cytokine responses to mycobacterial antigens assessed by flow cytometry. These studies identified a subgroup of COVID-19 patients whose blood had an enhanced capacity to inhibit mycobacterial growth. The ability to control mycobacterial growth was associated with the presence of a distinct non-M.tb-specific CD8+ CD28+ T cell population. This work improves our understanding of factors involved in mycobacterial control.