title: Inside the lifestyle of the virophage.
abstract: OBJECTIVE
  We sought to better characterize Sputnik, the first isolated virophage, and to analyze its parasitic lifestyle during co-infection with Marseillevirus (a new giant virus) in Acanthamoeba castellanii.
  
  
  METHODS
  A combination of electron microscopy, immunofluorescence microscopy, and real-time PCR was used to characterize the kinetics of the viral replication cycle. RT-PCR was performed to detect RNAs inside the Sputnik virions.
  
  
  RESULTS
  Sputnik is a new viral entity carrying an almost complete ready-to-use set of viral RNAs (20 out of 21). Sputnik does not replicate with Marseillevirus but delays its replication cycle. While Marseillevirus is successfully internalized by A. castellanii following co-infections with Mamavirus and Sputnik, it does not initiate a replication cycle. In contrast, both Marseillevirus and Mamavirus can replicate in the amoeba in case of co-infection, but the development of one is exclusive from the other inside a single amoeba cell.
  
  
  CONCLUSIONS
  This work provides new insight into the Sputnik replication cycle with another giant virus and confirms that Sputnik is a virophage. It shows new dimensions of the interactions existing among giant viruses.
authors.affiliation: Unité de recherche sur les maladies infectieuses et tropicales émergentes, URMITE CNRS-IRD UMR 6236, Faculté de Médecine, Marseille, France. christelle.desnues@univmed.fr
authors.forename: C
authors.initials: C
authors.lastname: Desnues
authors.forename: D
authors.initials: D
authors.lastname: Raoult
mesh_terms: D048248:Acanthamoeba castellanii / Q000821:virology*; D004267:DNA Viruses / Q000502:physiology*; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000032:analysis / Q000235:genetics; D012367:RNA, Viral / Q000032:analysis; D014771:Virion / Q000737:chemistry; D014779:Virus Replication
chemical_list: D012333:RNA, Messenger; D012367:RNA, Viral