SARS-CoV-2 induces inflammatorycytokine release, which may be exacerbated by immunecheckpoint blockade

ABSTRACT

Cancer patients infected with the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have ahigher mortality rate compared to non-cancer patients. Recent anticancer treatment, including immunotherapy, isassociated with severe infection including development of acute respiratory distress syndrome (ARDS) and highlevels of cytokine release resulting in cytokine storm. Immune checkpoint inhibitors (ICIs) are approved for use inmultiple cancer types and function by blocking the interaction between PD-1 and its ligand PD-L1, activatingantitumor cytotoxic immune cells. However, ICIs can also increase inflammatory cytokine secretion, which maypredispose to the development of cytokine storm. In fact, we have shown via single-cell cytokine secretion analysisthat pembrolizumab (anti-PD-1 antibody) increases cytokine secretion by polyfunctional strength index, a measureof the percentage of cells secreting multiple functional cytokines. Therefore, we hypothesize that ICIs may worseninflammatory cytokine secretion and potentiate cytokine storm and downstream complications in COVID-19 patients.Peripheral blood mononuclear cells (PBMCs) were isolated via Ficoll density gradient centrifugation from healthydonors, head and neck cancer (HNC) patients, and COVID-19-infected cancer patients. Flow cytometry wasperformed on patient PBMCs, after staining for viability and immune cell markers including CD3, CD8, CD19, andCD45. PBMCs were also activated overnight with low-dose IL-2, cocultured with Cal27 or HN5 cell lines, andsubjected to various treatment conditions. For non-COVID-19 patients, PBMCs were exposed to 25 nM SARS-CoV-2 recombinant spike (S) protein, a virulent protein associated with cytokine storm, or control prior to drug treatments.Preliminary flow cytometry analysis showed that a COVID-19-positive patient with thyroid cancer had an increasedproportion of CD8+ cells compared with a COVID-negative ovarian cancer patient and healthy donor. RecombinantSARS-CoV-2 S protein caused increased secretion of IL-6, IL-2, perforin, and MIP-1b from PBMCs isolated fromboth healthy donors and HNC patients, which was measured by IsoLight Codeplex bulk cytokine analysis or ELISA.We have previously shown that metformin, a commonly prescribed antidiabetes drug, decreases the proportion ofcells that secrete inflammatory cytokines such as IL-6, which is thought to be an important cytokine for cytokinestorm. Interestingly, we observed that metformin treatment resulted in decreased IL-6 secretion from PBMCsisolated from a COVID-19-positive patient. Results from this project suggest that ICIs may potentiate cytokine storm, and ongoing investigation will be informative to oncologists as to whether ICI treatment should be postponed insevere COVID-19 infections. In addition, metformin may be a novel potential treatment for COVID-19 patients toprevent and treat cytokine storm.