title: Subviral Hepatitis B Virus Filaments, like Infectious Viral Particles, Are Released via Multivesicular Bodies.
abstract: In addition to infectious viral particles, hepatitis B virus-replicating cells secrete large amounts of subviral particles assembled by the surface proteins, but lacking any capsid and genome. Subviral particles form spheres (22-nm particles) and filaments. Filaments contain a much larger amount of the large surface protein (LHBs) compared to spheres. Spheres are released via the constitutive secretory pathway, while viral particles are ESCRT-dependently released via multivesicular bodies (MVBs). The interaction of virions with the ESCRT machinery is mediated by α-taxilin that connects the viral surface protein LHBs with the ESCRT component tsg101. Since filaments in contrast to spheres contain a significant amount of LHBs, it is unclear whether filaments are released like spheres or like virions. To study the release of subviral particles in the absence of virion formation, a core-deficient HBV mutant was generated. Confocal microscopy, immune electron microscopy of ultrathin sections and isolation of MVBs revealed that filaments enter MVBs. Inhibition of MVB biogenesis by the small-molecule inhibitor U18666A or inhibition of ESCRT functionality by coexpression of transdominant negative mutants (Vps4A, Vps4B, and CHMP3) abolishes the release of filaments while the secretion of spheres is not affected. These data indicate that in contrast to spheres which are secreted via the secretory pathway, filaments are released via ESCRT/MVB pathway like infectious viral particles.
  
  
  OBJECTIVE
  This study revises the current model describing the release of subviral particles by showing that in contrast to spheres, which are secreted via the secretory pathway, filaments are released via the ESCRT/MVB pathway like infectious viral particles. These data significantly contribute to a better understanding of the viral morphogenesis and might be helpful for the design of novel antiviral strategies.
authors.affiliation: Department of Virology, Paul-Ehrlich-Institut, Langen, Germany.
authors.forename: Bingfu
authors.initials: B
authors.lastname: Jiang
authors.affiliation: Department of Virology, Paul-Ehrlich-Institut, Langen, Germany.
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Himmelsbach
authors.affiliation: Department of Virology, Paul-Ehrlich-Institut, Langen, Germany.
authors.forename: Huimei
authors.initials: H
authors.lastname: Ren
authors.affiliation: Department of Immunology, Paul-Ehrlich-Institut, Langen, Germany.
authors.forename: Klaus
authors.initials: K
authors.lastname: Boller
authors.affiliation: Department of Virology, Paul-Ehrlich-Institut, Langen, Germany DZIF-German Center of Infection Research, Paul-Ehrlich-Institut, Langen, Germany Eberhard.Hildt@pei.de.
authors.forename: Eberhard
authors.initials: E
authors.lastname: Hildt
mesh_terms: D000736:Androstenes / Q000494:pharmacology; D045744:Cell Line, Tumor; D003599:Cytoskeleton / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D056827:Endosomal Sorting Complexes Required for Transport / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D056945:Hep G2 Cells; D006515:Hepatitis B virus / Q000235:genetics / Q000378:metabolism*; D022781:Hepatocytes / Q000821:virology; D006801:Humans; D018613:Microscopy, Confocal; D008854:Microscopy, Electron; D057146:Multivesicular Bodies / Q000187:drug effects / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*; D033921:Vesicular Transport Proteins / Q000378:metabolism; D014758:Viral Core Proteins / Q000172:deficiency / Q000235:genetics; D057074:Virus Release / Q000502:physiology*; D000099177:Tsg101 Protein
chemical_list: D000736:Androstenes; D004268:DNA-Binding Proteins; D056827:Endosomal Sorting Complexes Required for Transport; D014157:Transcription Factors; D033921:Vesicular Transport Proteins; D014758:Viral Core Proteins; D000099177:Tsg101 Protein; C488100:TXLNA protein, human; C006261:3-beta-(2-(diethylamino)ethoxy)androst-5-en-17-one