Virion RNA polymerases of two salmonid rhabdoviruses

Development of a walleye cell line and use to study the effects of temperature on infection by viral haemorrhagic septicaemia virus group IVb

A cell line, WE-cfin11f, with a fibroblast-like morphology was developed from a walleye caudal fin and used to study the intersection of thermobiology of walleye, Sander vitreus (Mitchill), with the thermal requirements for replication of viral haemorrhagic septicaemia virus (VHSV) IVb. WE-cfin11f proliferated from 10 to 32 °C and endured as a monolayer for at least a week at 1-34 °C. WE-cfin11f adopted an epithelial shape and did not proliferate at 4 °C. Adding VHSV IVb to cultures at 4 and 14 °C but not 26 °C led to cytopathic effects (CPE) and virus production. At 4 °C, virus production developed more slowly, but Western blotting showed more N protein accumulation. Infecting monolayer cultures at 4 °C for 7 days and then shifting them to 26 °C resulted in the monolayers being broken in small areas by CPE, but with time at 26 °C, the monolayers were restored. These results suggest that at 26 °C, the VHSV IVb life cycle stages responsible for CPE can be completed, but the production of virus and the initiation of infections cannot be accomplished.

Comparison of representative strains of infectious hematopoietic necrosis virus by serological neutralization and cross-protection assays

Infectious hematopoietic necrosis virus (IHNV) is a pathogen of young salmon and trout. Viral epizootics among these fish in private and public rearing facilities have been a problem in the northwestern United States from California to Alaska, and an IHNV vaccine has been sought by the aquaculture experts. Since an IHNV vaccine must be designed to immunize against all viral serotypes, an analysis of IHNV serotypes was made. A large number of viruses from widely separated geographic locations and different fish species had already been placed in one of five electropherotypes by the migration of the virion proteins in sodium dodecyl sulfate-polyacrylamide gels. Also, there was evidence that some of these virus isolates had differences in virulence for chinook salmon, rainbow trout, or kokanee salmon. Previous serological studies with polyclonal rabbit antisera and three IHNV isolates indicated that there was only one serotype (B. B. McCain, J. L. Fryer, and K. S. Pilcher, Proc. Soc. Exp. Biol. Med. 137:1042-1046, 1971). A substantial number of new IHNV isolations have been made since that study, and thus a more extensive comparison was made of 10 different IHNV isolates representing the five electropherotypes. This report shows that the glycoprotein from a single isolate of IHNV can induce a protective immune response in vivo to the five IHNV electropherotypes. Plaque reduction neutralization assays indicated that there was only one serotype. Thus, despite the differences observed in the migration of the structural proteins for IHNV isolated from separate geographic locations and different fish species, only one neutralizing virus type was identified.

Characterization of infectious hematopoietic necrosis virus mRNA species reveals a nonvirion rhabdovirus protein

The genome RNA and six mRNA species of infectious hematopoietic necrosis virus were analyzed by denaturing gel electrophoresis. The following molecular weights were determined: genome RNA, 3.7 X 10(6); mRNA 1, 2.26 X 10(6); mRNA 2, 5.63 X 10(5); mRNA 3, 4.84 X 10(5); mRNA 4 (containing two different mRNA species), 3.00 X 10(5); and mRNA 5, 1.95 X 10(5). Densitometer analyses of gels were used to calculate the molar ratios of the intracellular mRNA species: mRNA 1, 0.02; mRNA 2, 0.49; mRNA 3, 1.0; mRNA 4, 2.52; and mRNA 5, 0.41. Hybrid selection studies determined the mRNA coding assignments as follows: mRNA 1 encodes the viral polymerase, L; mRNA 2 encodes the glycoprotein, G; mRNA 3 encodes the nucleocapsid protein, N; mRNA 4 is composed of two comigrating mRNA species which encode the matrix proteins, M1 and M2; and mRNA 5 encodes a previously unrecognized viral protein which is induced in infected cells but is not present in mature virions. This nonvirion protein has been designated the NV protein.

Viral hemorrhagic septicemia of rainbow trout: selection of a thermoresistant virus variant and comparison of polypeptide synthesis with the wild-type virus strain

Serial passage of viral hemorrhagic septicemia virus at gradually increasing temperature selected for a variant virus that replicates at 25 degrees C and has a low pathogenicity for rainbow trout. Viral hemorrhagic septicemia virus-specific polypeptide synthesis was examined in epithelioma papulosum cyprini cells infected with either a wild-type strain or a thermoresistant variant. The wild-type N and M1 proteins were synthesized throughout the course of infection, whereas L, G, and M2 were more actively translated later in the replication cycle. The wild-type strain was more cytotoxic at 25 than at 14 degrees C despite the fact that no translation could be evidenced when the temperature was raised. When epithelioma papulosum cyprini cells were infected with the variant virus, the kinetic study was obstructed since protein synthesis was difficult to observe by the pulse method at a low multiplicity of infection and aborted when the multiplicity of infection was raised. The variant was less cytotoxic at 25 degrees C than wild-type virus.

The viral diseases of fish: a review through 1978. Part 1: Diseases of proven viral etiology

In this review, a survey is made of the published literature on the viral diseases of fish available up to and including the year 1978. It is divided into two main sections. Part 1 describes 11 diseases where a virus has been isolated and proven to be the causative agent. Part 2 discusses 16 diseases where there is reason to suspect viral etiology because of evidence deriving from electron microscopy or transmission experiments with bacteria-free filtrates of homogenates of diseased tissue, but where final proof of a causative relationship is lacking. The review attempts to provide the most significant information on the disease process itself, in most cases including external signs, fish species susceptible, pathology, geographic distribution, existence of carriers, methods of transmission, and control. It also gives the most recent and significant data concerning the nature of the causative virus, including its cultural, biological, and physicochemical properties, where such information is available.

Spring viremia of carp virus RNA and virion-associated transcriptase activity

An RNA-dependent RNA polymerase activity has been demonstrated for spring viremia of carp virus (SVCV). The optimal temperature for in vitro synthesis of RNA was 20 to 25 degrees C. The SVCV enzyme activity was stimulated when the methyl donor S-adenosyl-L-methionine was included in the reaction mixture. S-adenosyl-L-methionine was not particularly effective in stimulating the virion RNA polymerase activity of vesicular stomatitis virus or pike fry rhabdovirus. The 5' nucleotide of the SVCV viral RNA is pppAp.