title: Infectious bursal disease virus is an icosahedral polyploid dsRNA virus.
abstract: Viruses are a paradigm of the economy of genome resources, reflected in their multiplication strategy and for their own structure. Although there is enormous structural diversity, the viral genome is always enclosed within a proteinaceous coat, and most virus species are haploid; the only exception to this rule are the highly pleomorphic enveloped viruses. We performed an in-depth characterization of infectious bursal disease virus (IBDV), a non-enveloped icosahedral dsRNA virus with a bisegmented genome. Up to 6 natural populations can be purified, which share a similar protein composition but show higher sedimentation coefficients as particle density increases. Stoichiometry analysis of their genome indicated that these biophysical differences correlate with the copy number of dsRNA segments inside the viral capsid. This is a demonstration of a functional polyploid icosahedral dsRNA virus. We show that IBDV particles with greater genome copy number have higher infectivity rates. Our results show an unprecedented replicative strategy for dsRNA viruses and suggest that birnaviruses are living viral entities encompassing numerous functional and structural characteristics of positive and negative ssRNA viruses.
authors.affiliation: Department of Structure of Macromolecules, Centro Nacional de Biotecnología/CSIC, Cantoblanco, 28049 Madrid, Spain.
authors.forename: Daniel
authors.initials: D
authors.lastname: Luque
authors.forename: Germán
authors.initials: G
authors.lastname: Rivas
authors.forename: Carlos
authors.initials: C
authors.lastname: Alfonso
authors.forename: José L
authors.initials: JL
authors.lastname: Carrascosa
authors.forename: José F
authors.initials: JF
authors.lastname: Rodríguez
authors.forename: José R
authors.initials: JR
authors.lastname: Castón
mesh_terms: D001703:Biophysics / Q000379:methods; D036022:Capsid Proteins / Q000737:chemistry; D007243:Infectious bursal disease virus / Q000737:chemistry* / Q000502:physiology*; D008027:Light; D008854:Microscopy, Electron; D008954:Models, Biological; D011003:Ploidies; D012330:RNA, Double-Stranded / Q000737:chemistry*; D012367:RNA, Viral / Q000737:chemistry; D012542:Scattering, Radiation; D015678:Viral Structural Proteins / Q000737:chemistry; D019065:Virus Assembly
chemical_list: D036022:Capsid Proteins; D012330:RNA, Double-Stranded; D012367:RNA, Viral; D015678:Viral Structural Proteins