No abstract

Infectious pancreatic necrosis virus of fish, infectious bursal disease virus of chickens, Tellina virus and oyster virus of bivalve molluscs, and drosophila X virus of Drosophila melanogaster are naked icosahedral viruses with an electron microscopic diameter of 58 to 60 nm. The genome of each of these viruses consists of two segments of double-stranded RNA (molecular weight range between 2.6 x 10(6) and 2.2 x 10(6), and the virion, capsid proteins fall into three size class categories (large, medium, and small; ranging from 100,000 to 27,000) as determined by polyacrylamide slab gel electrophoresis. The hydrodynamic properties of the five viruses are similar as determined by analytical ultracentrifugation and laser quasi-elastic, light-scattering spectroscopy. The calculated particle weights range between 55 x 10(6) and 81 x 10(6). Tryptic peptide comparisons of 125I-labeled virion proteins showed that five viruses are different from each other, although there was considerable overlap in the peptide maps of the three aquatic viruses, indicting a degree of relatedness. Cross-neutralization tests indicated that drosophila X, infectious pancreatic necrosis, and infectious bursal disease viruses were different from each other and from oyster and Tellina viruses. The same test showed oyster and Tellina viruses to be related. The biochemical and biophysical properties of the five viruses cannt be included in the family Reoviridae or in any of the present virus genera.

No abstract

The genome segment B sequence of infectious pancreatic necrosis virus was determined for both the Jasper and Sp serotypes. The sequences are 2784 and 2630 bp long, respectively, and contain a single large open reading frame encoding the VP1 protein, the putative RNA-dependent RNA polymerase (RdRp) of IPNV. The proteins exhibit an 88% homology with each other, but only 41% with infectious bursal disease virus (IBDV) VP1, another member of the Birnaviridae. Despite the low overall homology between the IPNV and IBDV VP1 proteins, homologous regions were detected within the central portion of the proteins. The carboxy-proximal regions of the VP1, which contain very low amino acid homology, displayed evidence of conservation in structural features such as a hydrophilic, highly basic domain. Consensus sequences associated with GTP-binding proteins and RdRps were also detected in VP1. However, unlike the RdRps associated with single-stranded plus RNA viruses, the birnavirus RdRp lacks the Gly-Asp-Asp motif characteristic of this enzyme family.

No abstract

Intraperitoneal injection of virulent infectious pancreatic necrosis virus (IPNV) into yearling brook trout Salvelinus fontinalis induced an asynlptomatic, chronic w u s infection that persisted for at least 76 wk post-lnlection (wpl) in spite of the production of a strong humoral immune response. At 8 wpi, 100 % of the fish in one of the injected groups were IPNV camers, as determined by organ and feces samphng. At 76 wpi. 95 % of the fish remained IPNV carriers. Vertical transmission of IPNV to progeny occurred, but the fry mortality rate, the prevalence of IPNV-infechon, and mean IPNV titres were low. Hence, vertical transm~ssion 1s not recommended a s a criterion for evaluating the efficacy of broodstock immunization. The IPNV carner state in yearlings that had survived a &rect mmersion in IPNV as fry was equivalent to that induced in yearlings by injection, in terms of the number of IPNV-infected organs per fish and the prevalence and titre of IPNV in the visceral organs when fish were sampled at 73 and 76 wpi, respectively. However, the Injected yearlings mounted a stronger humoral immune response to IPNV that the fish surviving the direct unmersion. Smce the IPNV camer state induced by injechon was nearly indistinguishable from the natural IPNV carner state, intraperitoneal injechon can be used as a challenge protocol for broodstock immunization tnals.

No abstract

Full-length and truncated genome segment A-specific infectious pancreatic necrosis virus cDNA was subcloned into plasmid transcription vectors, and runoff transcripts were produced in vitro. These transcripts were translated in cell-free rabbit reticulocyte lysates and the translation products were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Virus-specific polypeptides were gel purified and mapped by partial proteolysis with N-chlorosuccinimide and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Peptide profiles were compared with those of the corresponding polypeptides purified from infectious pancreatic necrosis virus-infected cells or prepared by in vitro translation of denatured genomic RNA. The cDNA directed the synthesis of authentic pVP2, VP3, and NS polypeptides as well as a number of previously undescribed polypeptides. A 101,000-molecular-weight polypeptide was isolated and shown to be the unprocessed infectious pancreatic necrosis virus polyprotein. The NS polypeptide appears to be a virus-encoded protease responsible for the cleavage of pVP2 from the polyprotein. The carboxy terminus of NS was mapped to within three or four amino acids on the polyprotein. The most likely internal translation start sites responsible for NS and VP3 production in vitro were also mapped.