Kosuke Okada

Integration of bovine leukemia virus DNA in the genomes of bovine lymphosarcoma cells.

Integration of bovine leukemia virus (BLV) in the genomes of infected cells was investigated in cattle with enzootic bovine leukosis (EBL) and sporadic bovine leukosis (SBL). Southern blot hybridization of BLV cDNA to Eco RI and Xba I restriction fragments of EBL tumor DNAs revealed that: 1) one to four or more copies of proviral DNA were integrated per genome; 2) the restriction pattern of the integrated proviral DNA was the same in two or three different tumors from the same animals; and 3) different patterns were observed among tumors from four different animals. These findings suggest the monoclonal origin of different tumors in an individual animal and the existence of multiple chromosomal integration sites of BLV provirus. DNAs from several SBL tumors were also analyzed with the same restriction enzymes, but with both representative and cDNA3′‐enricheds of BLV RNA. No hybridization bands reactive with representative BLV cDNA could be detected, while several bands appeared to hybridize with cDNA3′‐enriched.

Studies of Marek's disease herpesvirus and turkey herpesvirus specific common antigen which stimulates the production of neutralizing antibodies.

SummaryAn agar-gel precipitation antigen prepared from the skin (feather-Ag) of chicken infected with JM strain of Mareks disease herpesvirus (MDHV) and cell extracts of cultures infected with either Type 2 plaque producing agent (PPA) of MDHV or turkey herpesvirus (HVT) (Type 2-Ag, HVT-Ag) had 1 precipitation line in common. Hyperimmune sera to the common antigen (common-Ag) neutralized both cell-free virus of Type 2 PPA and HVT. However, these viruses were neutralized to a greater extent by homologous antiserum. Absorption of HVT antiserum or hyperimmune serum to Type 2 PPA with common-Ag reduced their neutralizing activity. This reduction was almost complete with homologous antigen but less complete with heterologous antigen. The location of antigen in Type 2 PPA and HVT infected cells was determined using hyperimmune serum to the common-Ag in fluorescent antibody tests. Antigen mainly occurred in the cytoplasm of cells corresponding to the rounded refractile cells in the plaques, whereas unfixed cells showed antigen on the cytoplasmic membrane. The common-Ag associated with MDHV or HVT infections might be a virus structural component which is associated with the envelope.

Electron microscopic autoradiography in the development of herpesvirus of turkey.

Quail fibroblast cultures inoculated with herpesvirus of turkey (Strain FC126) were incubated in the presence of3H-thymidine for various periods of time and examined by electron microscopy and electron microscopic autoradiography. The small nuclear particles did not become labeled with3H-thymidine, but those incorporated into the capsids (cross-shaped capsids) did. It was observed rarely that small enveloped particles (ca. 140–170 nm) in the perinuclear space were unenveloped in passing through the outer nuclear membrane into the cytoplasm. After exposure to3H-thymidine for 1 hour, virus particles in the nuclei became labeled, but most of them in the cytoplasm did not. However, the virus particles in the cytoplasm became labeled after chasing with unlabeled thymidine. The capsids in the cytoplasm were wrapped by electron opaque materials in adjoining what we called “flattened sacks.” Subsequently it was suggested that the capsids acquired the envelope and also peripheral spikes by passing through the membrane of the flattened sacks and thus became large enveloped particles (ca. 190–370 nm). Large enveloped particles in the cytoplasmic inclusions became labeled earlier than those in the extracellular space after chasing.

Cohelical arrangement of the DNA strand in the core of Marek's disease virus particles

SummaryElectron microscopic studies on Mareks disease virus demonstrated that fibrils of 20 to 30 Å were arranged in a cohelical configuration within an electronopaque band of about 100 Å thickness in the core of immature particles. These fibrils were presumed to be the DNA double helix itself. This configuration may represent an arrangement of the herpesvirus DNA.

Further study on the three-dimensional structure of the core of Marek's disease virus and herpesvirus of turkey.

SummaryThree-dimensional structures of the core of Mareks disease virus and herpesvirus of turkey were examined by the tilting apparatus of an electron microscope. Various types of the core found in the infected cells were considered to represent developmental stages of the viruses. The basic structure of the core consisted of a toroid surrounding a cylindrical mass, which was clearly demonstrated by tilting the core in two directions. A cylindrical mass spooled by more than two toroids, which seemed to constitute a spiral band of 10 to 20 nm, was demonstrated. The maturation process of the cores of the viruses was also discussed.