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Biomedical subjects

T Osato

Publications and source records attributed to T Osato.

At least 109 records · Page 6Linked to original sources
PubMed1978

Epstein-Barr virus and human chromosomes: close association of the resident viral genome and the expression of the virus-determined nuclear antigen (EBNA) with the presence of chromosome 14 in human-mouse hybrid cells.

Fourteen hybrid clones derived from the fused cultures of human lymphoblastoid FV5 cells and 5-bromodeoxyuridine-resistant mouse fibroblastic MCB2 cells grown in hypoxanthine/aminopterin/thymidine selective medium were examined for the presence of Epstein-Barr virus (EBV) DNA, the expression of the virus-determined nuclear antigen (EBNA), and the presence of human chromosomes, in the course of serial passage in vitro. Among the hybrid clones tested, 3 were positive for EBV DNA and EBNA, whereas the remaining 11 were totally negative. The chromosome investigations showed that human chromosome 14 was consistently involved in all three EBV genome-positive and EBNA-positive hybrid clones, but not in any negative clones. In 10 subclones isolated from 1 of the 3 positive clones, all of which contained only chromosome 14 of the human chromosomes, a concordant segregation of EBNA, EBA DNA, and chromosome 14 was evident. These findings suggest that the resident EBV genome is closely associated with chromosome 14 and the presence of this particular chromosome alone is sufficient for the maintenance and the expression of EBV genetic information in human lymphoblastoid cells.

Antigens, Viral↗
PubMed1978

Interaction between Epstein-Barr virus and type-C virus in human cells.

The interaction between EBV and type-C viruses was studied in our FVNC experimental system, in which EBV and type-C viral genomes are contained in each cell. The data indicate that the human lymphoid FVNC cells are sensitive to both EBV and type-C virus exposure, showing high frequencies of induction of both repressed viral genomes. The two different viral genomes may be associated with different chromosomes in individual cells.

Antigens, Viral↗
PubMed1978

Antibody-dependent autologous lymphocyte cytotoxicity against cells freshly transformed by Epstein-Barr virus.

Cytotoxicity against lymphocytes freshly transformed by EBV was studied in an autologous system by trypan blue exclusion of EBNA-positive cells and 51Cr-release assay. When EBV-tranformed lymphocytes were incubated with EBV-positive serum and autologous unfractionated lymphocytes or K-cells from sero-positive healthy donors, the transformed cells were significantly damaged. The cytotoxicity against newly produced EBNA-positive lymphocytes was also remarkable when sero-positive healthy donor lymphocytes were exposed to EBV, immediately followed by incubation with positive serum. In contrast, EBV-transformed cells incubated with autologous lymphocytes or T-cells alone were not significantly affected. EBV-positive serum alone was also not cytotoxic, regardless of inactivation. These results strongly suggest that antibody-dependent cellular cytotoxicity (ADCC) plays an important role in immunological defence against EBV oncogenesis in healthy humans. However, ADCC was not seen when immunosuppressed patients were examined.

Antibodies, Viral↗
PubMed1977

Differential induction of Epstein-Barr virus-related antigens in heterokaryon cultures.

Different paterns of induction of Epstein-Barr virus (EBV)-related antigens were observed in heterokaryons produced by Sendai virus-mediated fusion of producer and non-producer human lymphoblastoid cells with various other cell types. EBV-related early antigens (EA) and viral capsid antigen (VCA) could obviously be induced in heterokaryons between producer cells (P3HR-1 and QIMR-WIL), normally expressing these natigens at very low frequency, and human FL or HeLa cells. Positive cells were detected as early as 3 h after fusion and there often followed a rapid increase in positive cells. In contrast, in heterokaryons between non-producer cells (Raji and NC-37) and FL or HeLa cells, only EA but not VCA was induced. EA induction was also evident in fusion of human lymphoblastoid cells with monkey cells (Vero) but with mouse cells (L-M(TK-) C11D and MCB-2) no EBV induction occurred. The EBV induction in heterokaryons was significantly enhanced by 5-iododeoxyuridine treatment.

Animals↗
PubMed1977

Studies on Epstein-Barr virus-related antigens. II. Biochemical properties of soluble antigen in Raji Burkitt lymphoma cells.

Biochemical properties of Epstein-Barr virus (EBV)-related soluble antigen in non-producer Raji Burkitt lymphoblastoid cells, assayed by the indirect single radial immunodiffusion (ISRD) test, were investigated. The soluble ISRD antigen retained activity even after exposure to a temperature of 80 degrees C. The antigen was precipitated in 40% saturated ammonium sulfate and ISRD activity was recovered from the precipitate when reconstituted into a solution. Isoelectric focusing and crossed immunoelectrophoretic analyses revealed that the esoelectric point of the ISRD antigen is pH 4.8 with an electrophoretic mobility similar to that of serum alpha-globulin. With Sephadex G-200 or Sepharose 6B gel filtration, ISRD activity was obtained as a single peak which corresponded to the activity absorbing anti-complement immunofluorescence. The molecular weight of the present EBV-related soluble antigen was estimated to be 220,000-2408000 daltons.

Antigens, Viral↗
PubMed1976

Studies on Epstein-Barr virus-related antigens. I. Indirect single radial immunodiffusion as a useful method for detection and assay of soluble antigen.

A useful method for the detection and assay of Epstein-Barr virus (EBV)-related soluble antigen has been developed by the application of the indirect single radial immunodiffusion technique which is frequently used for quantitative measurements of immunoglobulins and other soluble proteins. When the extracts of EBV-determined nuclear antigen (EBNA)-positive non-producer cells (Raji and NC-37) were applied to agar plates containing seropositive human serum, followed by overlay with anti-human IgG serum, ring-shaped precipitates with high specificity were clearly evident. The size of such precipitin rings was proportional to the amount of the antigen. This method is simple and applicable for a quantitative assay of a particular EBV-related soluble antigen and antibody and the sensitivity is equivalent to that seen with the complement fixation test.

Antibodies, Viral↗
PubMed1976

Differential induction of Epstein-Barr virus-related antigens in human lymphoblastoid cells by virus-mediated cell-to-cell contact.

Differential induction of Epstein-Barr virus (EBV)-related antigens was observed after Sendai virus-medicated fusion of producer and non-producer cells with various human and mouse cells. The EBV-determined early nuclear antigen (ENA), early antigen (EA) and viral capsid antigen (VCA) could be induced at a high rate in producer cells (P3HR-1 and B95-8), normally expressing these antigens at very low frequency, as early as 12-24 h after fusion with each other or with human amnion FL cells. In contrast, only one antigen, ENA, was induced in producer cells following fusion with non-producer cells. This limited induction occurred also in non-producer cells fused with FL cells, but not after fusion with each other. EBV induction did not result from fusion of either producer or non-producer cells with mouse cells (L-M (TK-) Cl1D and MCB-L). The differential induction was not the result of heterokaryon formation as determined by autoradiography. The implications of these findings are discussed.

Antigens, Viral↗
PubMed1976

Growth in semisolid agar medium of human cord leukocytes freshly transformed by Epstein-Barr virus.

The semisolid agar method for the selective growth of transformed cells was applied to investigations of Epstein-Barr virus (EBV) transformation. When 1 X 10(5) HUMAn umbilical-cord blood leukocytes were seeded in agar medium immediately after EBV exposure, about 100 colonies developed in each dish. The occurrence of colonies correlated well with dilutions of EBV inoculum. These colonies were composed of lymphoblasts, were positive for EBV-determined nuclear antigen immunofluorescence, and consistently resulted in the establishment of cell lines. In cord leukocyte cultures exposed to EBV, cells capable of growing in semisolid agar medium appeared early and increased rapidly, though the total numbers of leukocytes and control cultures decreased during the first several days.

Cell Line↗
PubMed1975

Alteration in Epstein-Barr virus-human lymphoid cell interactions caused by the presence of type-C viral genome.

We have recently established a cell line, designated FVNC, by infection of non-EBV-productive human lymphoid NC-37 cells with the type-C virus FLV. The FVNC cell line has been maintained free of detectable EBV- and FLV-related immunofluorescent antigens for three years but both viral genomes exist in the cells in a repressed form. The FVNC cells were morphologically similar to the uninfected NC-37 cells but a D-group chromosome change was consistently seen. The colony-forming capacity of FVNC cells in semi-solid agar medium was about 1/10 of that of NC-37, although the former grew rather faster than the latter in fluid culture. FVNC cells were three times more sensitive to EBV superinfection than NC-37, as shown by immunofluorescence. In addition, an obvious induction of FLV antigenic markers occurred in FVNC cells on exposure to EBV. Nucleic acid hybridization experiments showed a striking decrease in the number of EBV genomes in FVNC cells. The number of genomes was too small to be measured, but EBNA was clearly present in all FVNC cells as well as in NC-37 cells. The implications of these findings were discussed from the point of view of a possible co-carcinogenesis in man by EBV and the type-C virus.

Antigens, Viral↗