title: Secreted NS1 Protects Dengue Virus from Mannose-Binding Lectin-Mediated Neutralization.
abstract: Flavivirus nonstructural protein 1 (NS1) is a unique secreted nonstructural glycoprotein. Although it is absent from the flavivirus virion, intracellular and extracellular forms of NS1 have essential roles in viral replication and the pathogenesis of infection. The fate of NS1 in insect cells has been more controversial, with some reports suggesting it is exclusively cell associated. In this study, we confirm NS1 secretion from cells of insect origin and characterize its physical, biochemical, and functional properties in the context of dengue virus (DENV) infection. Unlike mammalian cell-derived NS1, which displays both high mannose and complex type N-linked glycans, soluble NS1 secreted from DENV-infected insect cells contains only high mannose glycans. Insect cell-derived secreted NS1 also has different physical properties, including smaller and more heterogeneous sizes and the formation of less stable NS1 hexamers. Both mammalian and insect cell-derived NS1 bind to complement proteins C1s, C4, and C4-binding protein, as well as to a novel partner, mannose-binding lectin. Binding of NS1 to MBL protects DENV against mannose-binding lectin-mediated neutralization by the lectin pathway of complement activation. As we detected secreted NS1 and DENV together in the saliva of infected Aedes aegypti mosquitoes, these findings suggest a mechanism of viral immune evasion at the very earliest phase of infection.
authors: Division of Dengue Hemorrhagic Fever Research, Department of Research and Development, Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand.|Graduate Program, Department of Immunology, Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand.
authors: Somchai
authors: S
authors: Thiemmeca
authors: Division of Dengue Hemorrhagic Fever Research, Department of Research and Development, Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand.
authors: Chamaiporn
authors: C
authors: Tamdet
authors: Division of Dengue Hemorrhagic Fever Research, Department of Research and Development, Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand.
authors: Nuntaya
authors: N
authors: Punyadee
authors: Medical Biotechnology Research Unit, National Center for Genetic Engineering and Biotechnology, National Science and Technology Development Agency, Bangkok 12120, Thailand.
authors: Tanapan
authors: T
authors: Prommool
authors: Division of Dengue Hemorrhagic Fever Research, Department of Research and Development, Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand.
authors: Adisak
authors: A
authors: Songjaeng
authors: Division of Dengue Hemorrhagic Fever Research, Department of Research and Development, Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand.|Medical Biotechnology Research Unit, National Center for Genetic Engineering and Biotechnology, National Science and Technology Development Agency, Bangkok 12120, Thailand.
authors: Sansanee
authors: S
authors: Noisakran
authors: Division of Dengue Hemorrhagic Fever Research, Department of Research and Development, Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand.|Medical Biotechnology Research Unit, National Center for Genetic Engineering and Biotechnology, National Science and Technology Development Agency, Bangkok 12120, Thailand.
authors: Chunya
authors: 0000-0003-1611-2667
authors: C
authors: Puttikhunt
authors: Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110.|Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO 63110.
authors: John P
authors: 0000-0003-2809-9308
authors: JP
authors: Atkinson
authors: Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110.|Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO 63110.|Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110; and.
authors: Michael S
authors: MS
authors: Diamond
authors: Department of Entomology, Armed Forces Research Institute of Medical Sciences, Bangkok 10400, Thailand.
authors: Alongkot
authors: A
authors: Ponlawat
authors: Division of Dengue Hemorrhagic Fever Research, Department of Research and Development, Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand; panisadee.avi@mahidol.ac.th.|Medical Biotechnology Research Unit, National Center for Genetic Engineering and Biotechnology, National Science and Technology Development Agency, Bangkok 12120, Thailand.
authors: Panisadee
authors: 0000-0003-0053-3045
authors: P
authors: Avirutnan
mesh_terms: D000330:Aedes / Q000821:virology; D000818:Animals; D002460:Cell Line; D003167:Complement Activation; D037582:Complement Pathway, Mannose-Binding Lectin; D003165:Complement System Proteins / Q000276:immunology / Q000378:metabolism; D003716:Dengue Virus / Q000276:immunology* / Q000472:pathogenicity; D006801:Humans; D057131:Immune Evasion; D037601:Mannose-Binding Lectin / Q000276:immunology* / Q000378:metabolism*; D011485:Protein Binding; D012463:Saliva / Q000821:virology; D013552:Swine; D017361:Viral Nonstructural Proteins / Q000737:chemistry / Q000378:metabolism*
chemical_list: D037601:Mannose-Binding Lectin; C079340:NS1 protein, Dengue virus type 2; D017361:Viral Nonstructural Proteins; D003165:Complement System Proteins