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

Abstract

A small icosahedral unenveloped virus (PC84) was discovered in connective tissue cells of several organs in diseased Mediterranean shore crabs, Carcinus mediterraneus. Nuclei of infected cells were very dense except in some clear areas where viral particles, about 25 nm in diameter, were observed. Numerous virions, identical in size, were also present in the cytoplasm of such cells. Isopycnic centrifugation in a CsCl gradient generated two bands of full viral particles: L and H particles showing, respectively, buoyant densities of 1.25 and 1.34 g/cm 3. Negatively stained with PTA, L and H virions were 29–31 nm in diameter. H particles appeared more fragile than L particles; preparations of H particles contain numerous apparently empty virions. No noticeable ultrastructural difference was noted. A preliminary study of the viral genome indicates the presence of DNA in the two types of particles. By reaction to formaldehyde as well as by thermal denaturation, viral DNA in situ was shown to be at least partially double stranded. The molecular weight of the L particles' DNA was 1.4 × 10 6, as determined by agarose gel electrophoresis. By SDS-PAGE, at least four virion polypeptides with molecular weights of 84, 80, 42, and 26 × 10 3 were detected in L particles and two polypeptides with molecular weights of 80 and 42 × 10 3 were detected in H particles. Although some of these characters are not those of Parvoviridae, this agent could be provisionally related only to this family.