(W1139) INDUCTION OF PROINFLAMMATORY CYTOKINE RELEASE FROM HUMAN PLURIPOTENT STEM CELL-DERIVED MACROPHAGES BY EXOSOMAL ORF3A DERIVED FROM SARS-COV-2-INFECTED CELLS
Abstract: The emergence of SARS-CoV-2 variants remains a major global health concern. In severe COVID-19, exacerbated proinflammatory cytokine release is often associated with acute respiratory distress syndrome and poor prognosis. It is pivotally important to understand the mechanism that drives this pathogenic event. SARS-CoV-2 ORF3a is capable of inducing inflammasome activation and IL-1β secretion. Macrophages are thought to be major producers of proinflammatory cytokines. However, it remained debated if macrophages are susceptible to infection with SARS-CoV-2. The relevance of proinflammatory cytokine release from macrophages to SARS-CoV-2 biology and pathogenesis remains to be established. We hypothesized that certain secretory viral factors might be responsible for proinflammatory response in macrophages. In this study, we identified secretory ORF3a as a key player in proinflammatory cytokine release in macrophages derived from human pluripotent stem cells. In overexpression system, we detected secretory ORF3a in culture medium. Exosomal ORF3a was verified by Western blotting and immunoelectron microscopy. Exosomal ORF3a was capable of transferring to neighboring cells. Feeding ORF3a-containing exosomes derived from SARS-CoV-2-infecetd cells to PMA-differentiated macrophages triggered proinflammatory cytokine release. Taken together, our demonstration of exosomal ORF3a-mediated proinflammatory cytokine release lent support to the notion that SARS-CoV-2 could modulate host exosome biogenesis to facilitate pathogenic inflammation. Our findings also have implications in identifying biomarkers for novel diagnostic and therapeutic strategies to mitigate cytokine storm in severe COVID-19.
Funding Source: Supported by RGC (C7142-20GF and T11-709/21-N) and HMRF (22211042).
