title: Quantitation of malaria parasite-erythrocyte cell-cell interactions using optical tweezers.
abstract: Erythrocyte invasion by Plasmodium falciparum merozoites is an essential step for parasite survival and hence the pathogenesis of malaria. Invasion has been studied intensively, but our cellular understanding has been limited by the fact that it occurs very rapidly: invasion is generally complete within 1 min, and shortly thereafter the merozoites, at least in in vitro culture, lose their invasive capacity. The rapid nature of the process, and hence the narrow time window in which measurements can be taken, have limited the tools available to quantitate invasion. Here we employ optical tweezers to study individual invasion events for what we believe is the first time, showing that newly released P. falciparum merozoites, delivered via optical tweezers to a target erythrocyte, retain their ability to invade. Even spent merozoites, which had lost the ability to invade, retain the ability to adhere to erythrocytes, and furthermore can still induce transient local membrane deformations in the erythrocyte membrane. We use this technology to measure the strength of the adhesive force between merozoites and erythrocytes, and to probe the cellular mode of action of known invasion inhibitory treatments. These data add to our understanding of the erythrocyte-merozoite interactions that occur during invasion, and demonstrate the power of optical tweezers technologies in unraveling the blood-stage biology of malaria.
authors.affiliation: Cavendish Laboratory, University of Cambridge, Cambridge, United Kingdom.
authors.forename: Alex J
authors.initials: AJ
authors.lastname: Crick
authors.affiliation: Wellcome Trust Sanger Institute, Hinxton, Cambridge, United Kingdom.
authors.forename: Michel
authors.initials: M
authors.lastname: Theron
authors.affiliation: Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom.
authors.forename: Teresa
authors.initials: T
authors.lastname: Tiffert
authors.affiliation: Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom.
authors.forename: Virgilio L
authors.initials: VL
authors.lastname: Lew
authors.affiliation: Cavendish Laboratory, University of Cambridge, Cambridge, United Kingdom. Electronic address: pc245@cam.ac.uk.
authors.forename: Pietro
authors.initials: P
authors.lastname: Cicuta
authors.affiliation: Wellcome Trust Sanger Institute, Hinxton, Cambridge, United Kingdom. Electronic address: jr9@sanger.ac.uk.
authors.forename: Julian C
authors.initials: JC
authors.lastname: Rayner
mesh_terms: D001696:Biomechanical Phenomena; D002448:Cell Adhesion / Q000502:physiology; D004910:Erythrocyte Membrane / Q000469:parasitology / Q000502:physiology; D004912:Erythrocytes / Q000469:parasitology* / Q000502:physiology*; D006790:Host-Parasite Interactions; D006801:Humans; D052940:Merozoites / Q000502:physiology*; D052898:Optical Tweezers; D010963:Plasmodium falciparum / Q000502:physiology*