A Highly Specific Assay for the Detection of SARS-CoV-2-Reactive CD4+ and CD8+ T Cells in COVID-19 Patients.

Gaining detailed insights into the role of host immune responses in viral clearance is critical for understanding COVID-19 pathogenesis and future treatment strategies. Although studies analyzing humoral immune responses against SARS-CoV-2 were available rather early during the pandemic, cellular immunity came into focus of investigations just recently. For the present work, we have adapted a protocol designed for the detection of rare neoantigen-specific memory T cells in cancer patients for studying cellular immune responses against SARS-CoV-2. Both CD4+ and CD8+ T cells were detected after 6 d of in vitro expansion using overlapping peptide libraries representing the whole viral protein. The assay readout was an intracellular cytokine staining and flow cytometric analysis detecting four functional markers simultaneously (CD154, TNF, IL-2, and IFN-γ). We were able to detect SARS-CoV-2-specific T cells in 10 of 10 COVID-19 patients with mild symptoms. All patients had reactive T cells against at least 1 of 12 analyzed viral Ags, and all patients had Spike-specific T cells. Although some Ags were detected by CD4+ and CD8+ T cells, VME1 was mainly recognized by CD4+ T cells. Strikingly, we were not able to detect SARS-CoV-2-specific T cells in 18 unexposed healthy individuals. When we stimulated the same samples overnight, we measured significant numbers of cytokine-producing cells even in unexposed individuals. Our comparison showed that the stimulation conditions can profoundly impact the activation readout in unexposed individuals. We are presenting a highly specific diagnostic tool for the detection of SARS-CoV-2-reactive T cells.

Invariant natural killer T (iNKT) cells prevent autoimmunity, but induce pulmonary inflammation in cystic fibrosis.

BACKGROUND/AIMS: Inflammation is a major and critical component of the lung pathology in the hereditary disease cystic fibrosis. The molecular mechanisms of chronic inflammation in cystic fibrosis require definition. METHODS: We used several genetic mouse models to test a role of iNKT cells and ceramide in pulmonary inflammation of cystic fibrosis mice. Inflammation was determined by the pulmonary cytokine profil and the abundance of inflammatory cells in the lung. RESULTS: Here we provide a new concept how inflammation in the lung of individuals with cystic fibrosis is initiated. We show that in cystic fibrosis mice the mutation in the Cftr gene provokes a significant up-regulation of iNKT cells in the lung. Accumulation of iNKT cells serves to control autoimmune disease, which is triggered by a ceramide-mediated induction of cell death in CF organs. Autoimmunity becomes in particular overt in cystic fibrosis mice lacking iNKT cells and although suppression of the autoimmune response by iNKT cells is beneficial, IL-17(+) iNKT cells attract macrophages and neutrophils to CF lungs resulting in chronic inflammation. Genetic deletion of iNKT cells in cystic fibrosis mice prevents inflammation in CF lungs. CONCLUSION: Our data demonstrate an important function of iNKT cells in the chronic inflammation affecting cystic fibrosis lungs. iNKT cells suppress the auto-immune response induced by ceramide-mediated death of epithelial cells in CF lungs, but also induce a chronic pulmonary inflammation.