Genomics and Biology of Iflaviruses

Iflaviruses are insect viruses that form non-enveloped, icosahedral particles approximately 30 nm in diameter. The particles contain one copy of the single-stranded RNA genome, which has a positive polarity. The genome encodes one large polyprotein, which is post-translationally processed. The viral coat proteins are located in an N-terminal domain of the polyprotein, while the non-structural proteins, involved in replication and polyprotein processing, are present in the C-terminal region. The order of the individual proteins in the polyprotein is strictly conserved. Polyprotein translation may initiate at an internal ribosome entry site (IRES) in the 5' untranslated region (UTR) of the RNA. The 3' UTR is followed by a poly(A) tail. Based on genome organization, virion structure and phylogeny, iflaviruses form a distinct group in the order Picornavirales, justifying their classification in a virus family separate from for instance Dicistroviridae and Picornaviridae. The type species of the family Iflaviridae, genus Iflavirus, is infectious flacherie virus (IFV) of silkworms