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T Osato

Publications and source records attributed to T Osato.

At least 91 records · Page 5Linked to original sources
PubMed1983

Monoclonal antibody specific for capsid antigen of Epstein-Barr virus.

A hybrid cell line (Cl-51) producing an anti-capsid antibody was obtained by fusion of mouse myeloma cells with spleen cells from mice immunized with purified P3HR-1 Epstein-Barr virus (EBV). Immunofluorescence showed that the Cl-51 antibody reacted with the cytoplasm and the nucleus of P3HR-1 and B95-8 cells, but not with Raji, BJAB, Molt-4, and superinfected Raji cells in the presence of cytosine arabinoside (Ara-C). The viable P3HR-1 and B95-8 cells were not stained nor was the viral infectivity neutralized. The Cl-51 antibody immunoprecipitated 123,000 and 120,000 dalton polypeptides of P3HR-1 and B95-8 cells, respectively, and both were sensitive to phosphonoacetic acid. Specific reactions were not evident with extracts of Raji cells and superinfected Raji cells in the presence of Ara-C. An analysis of the purified virus particles showed that this antibody recognized a capsid component of EBV.

Animals↗
PubMed1983

Chinese and African Euphorbiaceae plant extracts: markedly enhancing effect on Epstein-Barr virus-induced transformation.

Chinese and African Euphorbiaceae plant extracts were shown to have a markedly enhancing effect on Epstein-Barr virus (EBV)-induced transformation of human lymphocytes. When 5 X 10(5) cord blood lymphocytes were seeded into the semisolid agar medium immediately after EBV exposure, 3-10 times more colonies developed in the presence of the plant extracts at their optimal doses. When a smaller number of 5 X 10(4) cells were seeded, transformed colonies were also observed in the presence of the plant extracts but not in their absence. All of the colonies picked up from the agar medium were EBV-determined nuclear antigen (EBNA)-positive and showed the typical blastoid morphology. There were no colonies detected in the EBV-uninfected cultures with the extracts, indicating that the virus was required for the promotion by these plant extracts of this lymphocyte transformation. Euphorbiaceae plants are known to be employed as local herbal drugs in southern China and tropical Africa, and the possible role as a co-factor of the plant extracts in the development of nasopharyngeal carcinoma (NPC) and African Burkitt's lymphoma (BL) is discussed.

Africa↗
PubMed1982

Evolution of infectious mononucleosis into Epstein-Barr virus carrying monoclonal malignant lymphoma.

A monoclonal malignant lymphoma was diagnosed in a 30-month-old Japanese boy, who, since the age of 12 months, had had chronic, recurrent infectious mononucleosis manifested by repeated episodes of severe cough and high fever accompanied by marked lymphadenopathy and hepatosplenomegaly and high serum Epstein-Barr virus (EBV) antibody titres. The diagnosis of Burkitt's lymphoma was made when a cervical lymph-node biopsy specimen revealed massive proliferation of immature B-cells with starry-sky histiocytes. These lymph-node cells were characterised by a translocation between chromosomes 10 and 17. There were approximately 9 EBV genome-equivalents per cell. Most cells were positive for nuclear antigen (EBNA); early antigen (EA) and viral capsid antigen (VCA) were also detected. The presence of EBV was supported by finding that the cell-free lymph-node extract transformed cord-blood lymphocytes into EBNA-positive blast cells. The proportion of EA-positive and VCA-positive cells increased rapidly in culture for 24 h, then the positive cells degenerated rapidly and completely. The cells also contained numerous herpes-type virus particles. The child improved considerably with cytostatic treatment and has been in remission for 2 years.

Antibodies, Viral↗
PubMed1982

Simple assay method for susceptibility of human lymphocytes to Epstein-Barr virus infection.

On the basis of the sequential early events induced by Epstein-Barr virus (EBV), the infectivity of human lymphocytes to EBV was quantified as a plateau value of the maximum nuclear antigen (EBNA) synthesis preceding cellular DNA synthesis. The frequency of EBV-infectible cells was an average of 7.6% of unfractionated umbilical cord lymphocytes and was 4.9% in the counterparts from human adults. In the B-cell-enriched populations, the average plateau values were 29.2% in umbilical cord and 15.5% in adult samples. This method is simple and applicable for quantitative assay of the sensitivity to EBV infection of a given lymphocyte preparation.

Adult↗
PubMed1981

Analysis of the transformation of human lymphocytes by Epstein-Barr virus III. Induction of early events by P3HR-1 strain without subsequent immortalization.

T-cell depleted human cord blood lymphocytes were exposed to P3HR-1 strain of Epstein-Barr virus (EBV) and simultaneous observations of immunofluorescence, cellular morphology, and autoradiography were carried out in individual cells. Soon after infection, nuclear antigen (EBNA) synthesis, blastogenesis, and DNA synthesis occurred, as was previously observed B95-8 strain EBV infection. Although mitosis followed with characteristic cell aggregate formation, the cell proliferation was temporary and death followed in about 2 weeks. The synthesis of the early antigens (EA) and the viral capsid antigen (VCA) were not significant. These findings seem to indicate that the strain P3HR-1 EBV is capable of inducing early events of transformation in primary human B-lymphocytes, but the cells infected in this way have a short life span.

Antigens, Viral↗
PubMed1981

Epstein-Barr virus susceptibility of B cells correlates to the presence of complement receptors but not surface immunoglobulins.

Nuclear antigen (EBNA) inducibility by Epstein-Barr virus (EBV) was assessed in relation to the presence of complement (C3) receptors and surface immunoglobulins (SIg) on leukemic lymphocytes. When erythrocyte-antibody-complement complex(EAC)-positive, SIg-negative B cells were exposed to EBV, EBNA synthesis occurred with a high frequency. In contrast, no significant EBNA induction was evident in SIg-positive, EAC-negative B cells. Cells possessing both markers were EBV-infectable, in proportion to the frequency of EAC-rosette formation. These data seem to indicate that EBV susceptibility of human B cells is closely related to the presence of C3 receptors but not SIg. Leukemic T cells and myelogenous leukemia cells were not EBV-susceptible, although some cells were significantly positive for C3 receptors.

Antigens, Viral↗
PubMed1980

Chromosomal alterations of rat cell lines transformed by human adenovirus type-12 virion, whole DNA and left-end DNA fragments.

A normal rat cell line, 3Y1-B clone 1-6 (3Y1) and its adenovirus (Ad) type-12-transformed derivatives, W4 (transformed by Ad12 Virion), WY3 (transformed by Ad12 whole DNA), CY1-1 (transformed by the Ad12 EcoRI-C fragment, left 16.5%), GY1-1 (transformed by the Ad12 HindIII-G fragment, left 6.8%) and HY1 (transformed by the Ad12 Acd-H fragment, left 4.7%) were studied cytogenetically. 3Y1 and some of the transformed cell lines (W4, WY3 and GY1-1) were diploid or pseudodiploid, while others (CY1-1 and HY1) were hypotetraploid. A metacentric marker M1 was detected in GY1-1 cells and another marker M2 in W4 and CY1-1 cells at a high frequency. By the Giemsa banding technique, the metacentric markers M1 and M2 from these fully transformed cell lines were identified as isochromosomes derived from 1q (M1) and 3q (M2), respectively. On the other hand, the markers were detected only at a low frequency in incompletely transformed HY1 cells. However, hypersomy in chromosome No. 1 was observed at a high frequency in this cell line. It can be concluded that hypersomy of chromosomes No. 1 or 3 found in transformants and metacentric markers found in complete transformants are characteristic features in rat cells transformed by Ad12.

Adenoviruses, Human↗
PubMed1980

Analysis of the transformation of human lymphocytes by Epstein-Barr virus. II. Abortive response of leukemic cells to the transforming virus.

Leukemic lymphocytes with B-cell markers were obtained from the peripheral blood of 4 patients with chronic lymphocytic leukemia (CLL) or acute lymphocytic leukemia (ALL); a significant number of T cells was not involved. The lymphocytes were inoculated with the transforming B95-8 Epstein-Barr virus (EBV). Synthesis of EBV-determined nuclear antigen (EBNA) occurred in three CLL preparations: 15.1--25.4% of cells expressed maximum EBNA 24--48 h after viral exposure. A characteristic immunofluorescence pattern similar to a coarsely clumped chromatin structure was observed. In contrast to EBV infection of normal lymphocytes, EBNA synthesis in CLL cells (morphologically similar to normal lymphocytes) was not followed by either blastogenesis or DNA synthesis. EBNA-positive cells, which usually degenerate within 1--2 weeks, could be maintained for more than 30 days on feeder human embryo fibroblasts pretreated with mitomycin C. DNA synthesis and mitosis occurred, but unlimited cell growth did not. 41.9% of ALL cells were EBNA-positive at 36 h prior to DNA synthesis, and they subsequently grew rapidly for up to 9 days. The cell proliferation, however, was temporary, and death resulted in about 2 weeks. No significant synthesis of EBV-related early antigens and viral capsid antigen was noted in any of the infected cultures throughout the incubation period. These results indicate that certain intracellular restrictions may have exceeded the potent transforming capacity of EBV in these target leukemic cells.

Antigens, Viral↗
PubMed1980

Immunologic cytotoxicity against autologous human lymphocytes transformed or infected by Epstein-Bar virus: role of antibody-dependent cellular cytotoxicity in health individuals.

Immunologic cytotoxicity against lymphocytes transformed or infected by Epstein-Barr virus (EBV) was mainly studied in an autologous in vitro system by 51Cr release assay and EBV-determined nuclear antigen (EBNA)-specific trypan blue exclusion method. When the cells of newly established EBV-transformed or spontaneously transformed lines were incubated with unfractionated autologous healthy donor lymphocytes or T-cell-depleted lymphocytes in the presence of EBV-positive autologous or allogeneic serum, the transformed cells were killed with high frequency. Exposure to lymphocytes alone or to EBV-positive serum alone was not effective. The cytotoxic reaction was directed against cells positive for EBV-induced membrane antigens (MA) but not against MA-negative transformed cells. A very small fraction (1 of 200) of healthy donor lymp]hocytes exposed to EBV converted into EBNA-positive and MA-positive cells, and these were also killed by the remaining autologous lymphocytes in the presence of EBV-positive serum. These results indicated that the present cytotoxic reaction represents antibody-dependent cellular cytotoxicity (ADCC), and this particular mechanism probably plays an important role in the immunologic surveillance in the protection against EBV-induced oncogenesis in seropositive individuals. Such ADCC, however, does not seem to function effectively in patients with systemic lupus erythematosus.

Antibodies, Viral↗
PubMed1979

Analysis of the transformation of human lymphocytes by Epstein-Barr virus. I. Sequential occurrence from the virus-determined nuclear antigen synthesis, to blastogenesis, to DNA synthesis.

A B-cell population of human cord blood lymphocytes was exposed to the B95-8 strain of Epstein-Barr virus (EBV), and simultaneous observations of immunofluorescence, cellular morphology and autoradiography were carried out in each individual cell. It was evident that EBV-determined nuclear antigen (EBNA) synthesis occurred prior to blastogenic response and DNA synthesis. EBNA-positive cells could be observed as early as 12 h after infection and reached a maximum of 17% at 24 h, followed by a plateau for a subsequent 12 h. The positive cells were seen exclusively as morphologically normal lymphocytes until 18 h; at 24 h, blastogenesis became evident, without cell division. DNA synthesis was detected at 36 h in EBNA-positive blast cells, after which these cells increased rapidly. EBNA synthesis was similarly evident in the presence of cytosine arabinoside, but was significantly inhibited by a short-term exposure to cycloheximide immediately after infection. These findings suggest that the early events in EBV-induced transformation of human lymphocytes occur sequentially from EBNA synthesis, to blastogenesis, to DNA synthesis and that the crucial step of such transformation is probably involved in protein synthesis occurring in the very early stage of EBV infection.

Antigens, Viral↗
PubMed1978

Studies on Epstein-Barr virus-related antigens. III. Purification of the virus-determined nuclear antigen (EBNA) from non-producer Raji cells.

The purification of Epstein-Barr virus-determined nuclear antigen (EBNA) was attempted on the basis of its biochemical and physicochemical properties and its immunological specificity, assayed by the indirect single radial immunodiffusion test and anti-complement immunofluorescence absorption test. When non-producer Raji cell extract was subjected to 20--60% saturated ammonium sulfate fractionation, followed by DNA-cellulose chromatography and immunoadsorbent chromatography, EBNA was purified more than 3,000 times with a 8% yield. Such purified protein was composed of three polypeptides with molecular weights of 100,000 +/- 5,000, 70,000 +/- 5,000 and 50,000 daltons, respectively, on SDS-polyacrylamide gel electrophoresis. Similar purification was achieved by heating the extract at 70 degrees C for 10 min, instead of ammonium sulfate fractionation, followed by DNA-cellulose chromatography and immunoadsorbent chromatography. This final preparation consisted almost exclusively of 100,000 +/- 5,000 daltons polypeptide, 50,000 polypeptide, and the 70,000 +/- 5,000 polypeptide passing through the adsorbent column. These findings suggest that EBNA is probably a molecular complex of three smaller subunits of heat-stable 100,000 +/- 5,000 and 50,000 daltons and heat-labile 70,000 +/- 5,000 daltons polypeptides, respectively.

Ammonium Sulfate↗
PubMed1978

The simultaneous observations of immunofluorescence and cellular morphology in viral infections: a new procedure.

A simple method for comparative observations of immunofluorescence and cellular morphology has been developed in the investigation of Epstein-Barr virus (EBV) infection and oncogenesis. When cells were stained for immunofluorescence of EBV-determined nuclear antigen, early antigens, or the viral capsid antigen, followed by treatment with hematoxylin, viral marker expression and cellular morphology could be simultaneously observed in individual cells by simply changing ultraviolet illumination to visible light. In our double-staining method, hematoxylin was not counteractive to specific immunofluorescence, and pretreatment of cells with antibodies did not affect hematoxylin staining. This method may possibly be more widely applied in virology and other fields.

Fluorescent Antibody Technique↗
PubMed1978

Abortive growth of human lymphocytes carrying a dormant Epstein-Barr viral genome.

When P3HR-1 lymphoblastoid cells expressing Epstein-Barr virus (EBV)-related antigens at very low frequency were cocultivated with human umbilical cord blood lymphocytes and the cell-free mixed culture fluid was applied to fresh cord lymphocytes, cells morphologically distinct from normal lymphocytes became evident after one to two weeks' exposure. The abnormal cells became abundant after one month and were easily identified by B-cell markers and a variety of morphologic abnormalities. Such abnormal B-lymphocytes appeared to be negative for EBV-determined nuclear antigen (EBNA), but when the immunofluorescence-negative cells were exposed to pokeweed mitogen and 5-iododeoxyuridine, a striking EBNA induction occurred. The growth of these abnormal cells was limited and they could be maintained for no more than three months. The implications of these findings are discussed in relation to the biological activity of EBV.

B-Lymphocytes↗