Figure 1 (Top) Negative contrast electron micrograph of infectious bursal disease virus (IBDV) particles (courtesy of J. Lepault). Bar represents 100 nm. (Bottom left) A three-dimensional model of the IBDV virion derived from X-ray crystallography (courtesy of F. Rey). (Bottom right) Diagrammatic representation of an IBDV particle, which has a single T=13 icosahedral shell.
Figure 2 Schematic representation of the gene arrangement in genome segment A of birnaviruses representative of the family: infectious bursal disease virus (IBDV), blotched snakehead virus (BSNV), infectious pancreatic necrosis virus (IPNV), Drosophila birnavirus (DBV), Tellina virus 1 (TV-1), rotifer birnavirus (RBV) and Drosophila X virus (DXV). Polyprotein (ORF2) cleavage sites are indicated by a vertical bar and their positions by the P1/P′1 number. The location and size of the small ORFs (ORF1) are indicated below the polyprotein ORF. Numbers in parentheses at the 5′ ends indicate the length of the 5′-non-coding region.
Figure 3 Schematic representation of the genome of infectious bursal disease virus (IBDV) illustrating processing of the encoded proteins. Numbers in parentheses indicate the nucleotide lengths of the two genomic segments.
Figure 4 A distance tree representing the phylogenetic relationships of VP2 in the various genera and genetic clusters of the family. Alignment was performed with MUSCLE and phylogenetic analysis with PhyML using default parameters. Internal branches with bootstrap support above 80% are highlighted. The tree was inferred by maximum likelihood on the amino-acid sequences of the capsid protein. Tellina virus 1 (TV-1), Drosophila birnavirus (DBV) and rotifer birnavirus (RBV) are separate from each other and from the four genera. The protein accession numbers used for comparison were (top to bottom): TV-1: CAI74981, RBV: CAX33877, YTAV: BAA25005, WB: AF342727, VR299: AF343572, Ab: AF342729, Ca1: AF342732, TV-2: AF342731, NZ-10: ACG56371, SP: AF342728, Hecht: AF342730, Ca2: AF342733, Ca3: AF342734, IBDV-OH: AAC55351, IBDV-P2: CAA58851, BSNV: AJ459382, DBV: ACU32790, and DXV: AAB16798.