title: Proteomic analysis of the cyst stage of Entamoeba histolytica.
abstract: BACKGROUND
  The category B agent of bioterrorism, Entamoeba histolytica has a two-stage life cycle: an infective cyst stage, and an invasive trophozoite stage. Due to our inability to effectively induce encystation in vitro, our knowledge about the cyst form remains limited. This also hampers our ability to develop cyst-specific diagnostic tools.
  
  
  OBJECTIVE
  Three main aims were (i) to identify E. histolytica proteins in cyst samples, (ii) to enrich our knowledge about the cyst stage, and (iii) to identify candidate proteins to develop cyst-specific diagnostic tools.
  
  
  METHODS
  Cysts were purified from the stool of infected individuals using Percoll (gradient) purification. A highly sensitive LC-MS/MS mass spectrometer (Orbitrap) was used to identify cyst proteins.
  
  
  RESULTS
  A total of 417 non-redundant E. histolytica proteins were identified including 195 proteins that were never detected in trophozoite-derived proteomes or expressed sequence tag (EST) datasets, consistent with cyst specificity. Cyst-wall specific glycoproteins Jacob, Jessie and chitinase were positively identified. Antibodies produced against Jacob identified cysts in fecal specimens and have potential utility as a diagnostic reagent. Several protein kinases, small GTPase signaling molecules, DNA repair proteins, epigenetic regulators, and surface associated proteins were also identified. Proteins we identified are likely to be among the most abundant in excreted cysts, and therefore show promise as diagnostic targets.
  
  
  CONCLUSIONS
  The proteome data generated here are a first for naturally-occurring E. histolytica cysts, and they provide important insights into the infectious cyst form. Additionally, numerous unique candidate proteins were identified which will aid the development of new diagnostic tools for identification of E. histolytica cysts.
authors.affiliation: Division of Infectious Disease and International Health, University of Virginia Health System, Charlottesville, Virginia, United States of America. ika3t@virginia.edu
authors.forename: Ibne Karim M
authors.initials: IK
authors.lastname: Ali
authors.forename: Rashidul
authors.initials: R
authors.lastname: Haque
authors.forename: Abdullah
authors.initials: A
authors.lastname: Siddique
authors.forename: Mamun
authors.initials: M
authors.lastname: Kabir
authors.forename: Nicholas E
authors.initials: NE
authors.lastname: Sherman
authors.forename: Sean A
authors.initials: SA
authors.lastname: Gray
authors.forename: Gerard A
authors.initials: GA
authors.lastname: Cangelosi
authors.forename: William A
authors.initials: WA
authors.lastname: Petri
mesh_terms: D002648:Child; D002675:Child, Preschool; D002853:Chromatography, Liquid; D004748:Entamoeba histolytica / Q000737:chemistry* / Q000302:isolation & purification; D004749:Entamoebiasis / Q000469:parasitology; D005243:Feces / Q000469:parasitology; D005260:Female; D006801:Humans; D008297:Male; D020543:Proteome; D033761:Spores, Protozoan / Q000737:chemistry* / Q000302:isolation & purification; D053719:Tandem Mass Spectrometry
chemical_list: D020543:Proteome