Abstract
The nucleotide sequence of sacbrood virus (SBV) which causes a fatal infection of honey bee larvae has been determined. The genomic RNA of SBV is longer than that of typical mammalian picomaviruses (8854 nucleotides) and contains a single, large open reading frame (201-8774) encoding a polyprotein of 2858 amino acids. Sequence comparison with other virus polyproteins revealed regions of similarity to characterized helicase, protease and RNA-dependent RNA polymerase domains; structural genes were located at the 5' terminus with non-structural genes at the 3' end. Picornavirus-like agents of insects have two distinct genomic organizations; some resemble mammalian picornaviruses with structural genes at the 5' end and non-structural genes at the 3' end, and others resemble caliciviruses in which this order is reversed; SBV thus belongs to the former type. Sequence comparison with mammalian, insect and plant picorna-like viruses suggested that SBV is most closely related to infectious flacherie virus (IFV) of the silk worm, which possesses an RNA of similar size and gene order, although this relationship is distant. A reverse transcription-polymerase chain reaction (RT-PCR) has been developed using SBV specific primers which was able to amplify part of the polymerase gene from all the strains in SBV tested and to distinguish between SBV and black queen cell virus (BQCV). Partial sequence information was also obtained from BQCV and acute bee paralysis virus (ABPV).