title: Chikungunya virus fusion properties elucidated by single-particle and bulk approaches.
abstract: Chikungunya virus (CHIKV) is a rapidly spreading, enveloped alphavirus causing fever, rash and debilitating polyarthritis. No specific treatment or vaccines are available to treat or prevent infection. For the rational design of vaccines and antiviral drugs, it is imperative to understand the molecular mechanisms involved in CHIKV infection. A critical step in the life cycle of CHIKV is fusion of the viral membrane with a host cell membrane. Here, we elucidate this process using ensemble-averaging liposome-virus fusion studies, in which the fusion behaviour of a large virus population is measured, and a newly developed microscopy-based single-particle assay, in which the fusion kinetics of an individual particle can be visualised. The combination of these approaches allowed us to obtain detailed insight into the kinetics, lipid dependency and pH dependency of hemifusion. We found that CHIKV fusion is strictly dependent on low pH, with a threshold of pH 6.2 and optimal fusion efficiency below pH 5.6. At this pH, CHIKV fuses rapidly with target membranes, with typically half of the fusion occurring within 2 s after acidification. Cholesterol and sphingomyelin in the target membrane were found to strongly enhance the fusion process. By analysing our single-particle data using kinetic models, we were able to deduce that the number of rate-limiting steps occurring before hemifusion equals about three. To explain these data, we propose a mechanistic model in which multiple E1 fusion trimers are involved in initiating the fusion process.
authors: Department of Medical Microbiology, University Medical Center Groningen, University of Groningen, 9700 RB Groningen, The Netherlands.
authors: Mareike K S
authors: MKS
authors: van Duijl-Richter
authors: Centre for Synthetic Biology, Zernike Institute of Advanced Materials, University of Groningen, 9747 AG Groningen, The Netherlands.
authors: Jelle S
authors: JS
authors: Blijleven
authors: Centre for Synthetic Biology, Zernike Institute of Advanced Materials, University of Groningen, 9747 AG Groningen, The Netherlands.|School of Chemistry, University of Wollongong, Wollongong, NSW, 2522, Australia.
authors: Antoine M
authors: AM
authors: van Oijen
authors: Department of Medical Microbiology, University Medical Center Groningen, University of Groningen, 9700 RB Groningen, The Netherlands.
authors: Jolanda M
authors: JM
authors: Smit
mesh_terms: D002462:Cell Membrane / Q000378:metabolism / Q000821:virology; D065632:Chikungunya Fever / Q000378:metabolism / Q000821:virology*; D002646:Chikungunya virus / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D002784:Cholesterol / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D014771:Virion / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D053586:Virus Internalization
chemical_list: D002784:Cholesterol