PC 84, a parvo-like virus from the crab Carcinus mediterraneus: pathological aspects, ultrastructure of the agent, and first biochemical characterization

White tail disease of the giant freshwater prawn, Macrobrachium rosenbergii: separation of the associated virions and characterization of MrNV as a new type of nodavirus

White tail disease of the farmed freshwater prawn, Macrobrachium rosenbergii, is the cause of mortalities in the French West Indies, China and India. Two different sized particles, both developing in the cytoplasm of target cells, are found associated with diseased animals. These two viruses were separated, purified and subsequently characterized. The larger one, called MrNV, is icosahedral in shape and 27 nm in diameter. Its genome is composed of two fragments of linear single-stranded RNA (ss-RNA), of 2.9 and 1.3 kb, respectively and its capsids exhibited a single polypeptide of 43 kDa. These characteristics and the partial sequence of a cloned fragment of RNA-1 suggest this agent is a member of the family Nodaviridae, but with differences from both the genera Alphanodavirus and Betanodavirus. The smaller virus, named XSV, is icosahedral in shape, 15 nm in diameter, possesses a linear ss-RNA genome of about 0.9 kb, and its capsid exhibits two polypeptides of 16 and 17 kDa, respectively. The relationships between these two viruses remain unknown.

Viral infections of aquatic animals with special reference to Asian aquaculture

Worldwide, the number of communicable diseases of animals raised in aquaculture continue to increase. Viral infections of cultivated shellfish, crustacea, and finfish have been frequently recognized in the past few years. In the Asian regions, penaeid shrimp and several teleost fish underwent epizootics associated with heavy losses in aquaculture. Baculoviruses are particularly harmful to shrimp and prawns. Herpes-, irido-, reo-, or rhabdovirus-like agents can cause outbreaks in fish farms. Viral diseases are important limiting factors in the expansion of aquaculture. However, studies on viral infections of aquatic animals have been focused primarily on economically important farmed fish. Therfore, certain viral diseases of teleost fish are relatively well understood. In contrast, our knowledge of viral infections of farmed aquatic invertebrates is still very spare. Although a great number of viruses have been detected in farmed molluscs and crustaceans, the pathogenicity and epizootiology of most of the agents is not known.

Expression of densonucleosis virus GmDNV in Galleria mellonella larvae: size analysis and in vitro translation of viral transcription products

The RNA of densonucleosis virus type 1 (GmDNV), isolated from GmDNV-infected Galleria mellonella larvae, was shown by Northern blotting to contain five polyadenylated, viral-specific RNA species with sizes of 1.8, 2.4, 3.5, 4.0, and 5.0 kb. Poly(A)-containing RNA from whole larvae and hybrid-selected viral RNA were translated in a rabbit reticulocyte lysate system and the translation products were coelectrophoresed with proteins extracted from CsCl-purified virus. All four virion-associated proteins, namely p49, p55, p65, and p94, were present in the in vitro-translated products. However, in the majority of the experiments the most abundant translation product was a 30K polypeptide which is absent from virion extracts. The most abundant viral protein is p49, and the 49K polypeptide was also the most abundant translation product in about 30% of the preparations. The 1.8 kb transcript, which constitutes about half of the total viral RNA, is only slightly larger than the template required for a 30K polypeptide, suggesting that the latter may be a primary translation product of the smallest RNA transcript. The similarities in gene expression between densoviruses and mam malian parvoviruses are discussed.