title: SARS spike protein induces phenotypic conversion of human B cells to macrophage-like cells.
abstract: Massive aggregations of macrophages are frequently detected in afflicted lungs of patients with severe acute respiratory syndrome-associated coronavirus (SARS-CoV) infection. In vitro, ectopic expression of transcription factors, in particular CCAAT/enhancer-binding protein alpha (C/EBPα) and C/EBPβ, can convert B cells into functional macrophages. However, little is known about the specific ligands responsible for such phenotype conversion. Here, we investigated whether spike protein of SARS-CoV can act as a ligand to trigger the conversion of B cells to macrophages. We transduced SARS-CoV spike protein-displayed recombinant baculovirus (SSDRB), vAtEpGS688, into peripheral B cells and B lymphoma cells. Cell surface expression of CD19 or Mac-1 (CD11b) was determined by flow cytometry. SSDRB-mediated changes in gene expression profiles of B lymphoma cells were analyzed by microarray. In this report, we showed that spike protein of SARS virus could induce phenotypic conversion of human B cells, either from peripheral blood or B lymphoma cells, to macrophage-like cells that were steadily losing the B-cell marker CD19 and in turn expressing the macrophage-specific marker Mac-1. Furthermore, we found that SSDRB enhanced the expression of CD86, hypoxia-inducible factor-1α (HIF1α), suppressor of cytokine signaling (SOCS or STAT-induced STAT inhibitor)-3, C/EBPβ, insulin-like growth factor-binding protein 3 (IGFBP3), Krüpple-like factor (KLF)-5, and CD54, without marked influence on C/EBPα or PU.1 expression in transduced cells. Prolonged exposure to hypoxia could also induce macrophage-like conversion of B cells. These macrophage-like cells were defective in phagocytosis of red fluorescent beads. In conclusion, our results suggest that conversion of B cells to macrophage-like cells, similar to a pathophysiological response, could be mediated by a devastating viral ligand, in particular spike protein of SARS virus, or in combination with severe local hypoxia, which is a condition often observed in afflicted lungs of SARS patients.
authors.affiliation: Graduate Institute of Microbiology and Public Health, National Chung Hsing University, 250 Kuo Kuang Road, Taichung 40227, Taiwan.
authors.forename: Shu-Fen
authors.initials: SF
authors.lastname: Chiang
authors.forename: Tze-Yi
authors.initials: TY
authors.lastname: Lin
authors.forename: Kuan-Chih
authors.initials: KC
authors.lastname: Chow
authors.forename: Shiow-Her
authors.initials: SH
authors.lastname: Chiou
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology*; D002460:Cell Line; D020869:Gene Expression Profiling; D006801:Humans; D016393:Lymphoma, B-Cell / Q000276:immunology; D008264:Macrophages / Q000276:immunology*; D008297:Male; D008562:Membrane Glycoproteins / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D010641:Phenotype; D011994:Recombinant Proteins / Q000276:immunology; D045473:Severe acute respiratory syndrome-related coronavirus / Q000276:immunology*; D064370:Spike Glycoprotein, Coronavirus; D014759:Viral Envelope Proteins / Q000276:immunology*
chemical_list: D008562:Membrane Glycoproteins; D011994:Recombinant Proteins; D064370:Spike Glycoprotein, Coronavirus; D014759:Viral Envelope Proteins