title: Influenza virus-model membrane interaction. A morphological approach using modern cryotechniques.
abstract: The membrane fusion activity of influenza virus was characterized morphologically using a model system composed of a highly purified influenza B virus suspension and ganglioside-containing zwitterionic liposomes. Electron microscopical analysis was performed after a combination of fast-freezing with either freeze-fracture or freeze-substitution-thin sectioning, ensuring maximal time resolution and avoiding preparation artifacts. In a parallel fluorescence 'lipid mixing' fusion assay, influenza virus-membrane fusion was characterized biochemically. Biochemical and morphological data are in full agreement, indicating negligible membrane fusion activity at neutral pH and high fusion activity at low pH. The freeze-fracture morphology strongly suggests a local point contact between viral and liposomal membrane at neutral pH, and a local point fusion mechanism for influenza virus-membrane fusion upon lowering of the pH. Fusion is followed by lipid mixing, lateral diffusion of viral spike proteins and exposure of viral contents at the inner liposomal surface.
authors.affiliation: Institute of Molecular Biology and Medical Biotechnology, University of Utrecht, The Netherlands.
authors.forename: K N
authors.initials: KN
authors.lastname: Burger
authors.forename: G
authors.initials: G
authors.lastname: Knoll
authors.forename: A J
authors.initials: AJ
authors.lastname: Verkleij
mesh_terms: D005614:Freeze Fracturing; D006863:Hydrogen-Ion Concentration; D009981:Influenza B virus / Q000502:physiology*; D008081:Liposomes; D008561:Membrane Fusion; D014759:Viral Envelope Proteins / Q000502:physiology
chemical_list: D008081:Liposomes; D014759:Viral Envelope Proteins