摘要：SummaryThe Delta variant had spread globally in 2021 and caused more serious disease than the original virus and Omicron variant. In this study, we investigated several virological features of Delta spike protein (SPDelta), including protein maturation, its impact on viral entry of pseudovirus and cell-cell fusion, and its induction of inflammatory cytokine production in human macrophages and dendritic cells. The results showed that SPΔCDeltaexhibited enhanced S1/S2 cleavage in cells and pseudotyped virus-like particles (PVLPs). Further, SPΔCDeltaelevated pseudovirus entry in human lung cell lines and significantly enhanced syncytia formation. Furthermore, we revealed that SPΔCDelta-PVLPs had stronger effects on stimulating NF-κB and AP-1 signaling in human monocytic THP1 cells and induced significantly higher levels of proinflammatory cytokine, such as TNF-α, IL-1β, and IL-6, released from human macrophages and dendritic cells. Overall, these studies provide evidence to support the important role of SPΔCDeltaduring virus infection, transmission, and pathogenesis.Graphical abstractDisplay OmittedHighlights•SARS-CoV-2 Delta-SP exhibits enhanced cleavage and more efficient pseudovirus entry•Delta-SP enhances syncytia formation in A549 cells expressing ACE2•Delta-SP stimulates higher NF-κB and AP1 signaling pathway activities•Delta-SP stimulates higher proinflammatory cytokine production in MDMs and MDDCsVirology; Molecular biology
