Functional association of class II antigens with cell surface binding of Epstein-Barr virus

A functional role of class II antigen in the binding of Epstein-Barr virus (EBV) was deduced from the study of membrane proteins on Jijoye, an EBV receptor (EBVR)-positive B cell line, and its mutant, EBVR-negative daughter cell line, P3HR-1. From gel electrophoresis of radiolabeled microsomal membrane proteins and immunoprecipitates, we identified class II antigen on Jijoye but not on P3HR-1 cells and the presence of Ii on both cell lines. The role of these molecules in EBVR function was tested by antibody blocking of virus adsorption. Anti-p23,30 serum (to class II antigen) was found to block binding of EBV to B lymphoblasts under conditions in which normal rabbit serum, rabbit antiserum to butyrate-treated P3HR-1 cells (with ample anti-Ii antibodies), and rabbit anti-p44,12 (to class I antigen and beta 2-microglobulin) serum did not block virus binding. Only one of four commercial monoclonal antibodies (MoAb) to framework epitopes on class II antigens blocked binding of EBV, whereas all four MoAb demonstrated immunofluorescent reactivity with the EBVR+ Raji cells. In previous studies of binding of EBV to hairy leukemic cells, a substantial subpopulation of HLA-DR+, EBVR- cells was identified, in addition to HLA-DR+, EBVR+ cells. These findings were consistent with the view that the HLA-DR complex has a role in the binding of EBV but that other components are also needed for the expression of EBVR function.

Functional association of class II antigens with cell surface binding of Epstein-Barr virus

A functional role of class II antigen in the binding of Epstein-Barr virus (EBV) was deduced from the study of membrane proteins on Jijoye, an EBV receptor (EBVR)-positive B cell line, and its mutant, EBVR-negative daughter cell line, P3HR-1. From gel electrophoresis of radiolabeled microsomal membrane proteins and immunoprecipitates, we identified class II antigen on Jijoye but not on P3HR-1 cells and the presence of Ii on both cell lines. The role of these molecules in EBVR function was tested by antibody blocking of virus adsorption. Anti-p23,30 serum (to class II antigen) was found to block binding of EBV to B lymphoblasts under conditions in which normal rabbit serum, rabbit antiserum to butyrate-treated P3HR-1 cells (with ample anti-Ii antibodies), and rabbit anti-p44,12 (to class I antigen and beta 2-microglobulin) serum did not block virus binding. Only one of four commercial monoclonal antibodies (MoAb) to framework epitopes on class II antigens blocked binding of EBV, whereas all four MoAb demonstrated immunofluorescent reactivity with the EBVR+ Raji cells. In previous studies of binding of EBV to hairy leukemic cells, a substantial subpopulation of HLA-DR+, EBVR- cells was identified, in addition to HLA-DR+, EBVR+ cells. These findings were consistent with the view that the HLA-DR complex has a role in the binding of EBV but that other components are also needed for the expression of EBVR function.

Kinetics of Ii synthesis, processing, and turnover in n-butyrate-treated Burkitt's lymphoma cell lines which express or do not express class II antigens and in hairy leukemic cells

We have sought to understand the role of the electrophoretically invariant chain (Ii) in class II antigen functions, particularly in certain transformed cells in which we have previously demonstrated hyperexpression of Ii. Molecular structures and relative kinetics of Ii synthesis, processing and turnover were compared in paired, Ia+ and Ia- Burkitt's lymphoma (BL) cell lines and in hairy cell leukemia (HCL) cells. Cells were metabolically labeled with [35S] methionine for 15 min (with or without a cold methionine chase to 3 hr) or were continuously labeled for 3 hr. One- and two-dimensional gel electrophoresis resolved immunoprecipitates formed with a) a heteroantiserum to purified class II antigen (demonstrating alpha and beta chains and Ii associated with that complex), b) a heteroantiserum to hairy cell leukemia (HCL) membranes (demonstrating principally the dominant, basic form of Ii molecules, class I antigens, and some additional proteins), and c) a monoclonal antibody to human Ii. Treatment of Ia+ Jijoye and its daughter, Ia- P3HR-1, BL cells with 4 mM butyrate for 48 hr enhanced the synthesis of the dominant, basic form of Ii but did not affect apparent turnover rates of that pool of Ii chains in either cell line. In Ia+ Jijoye cells but not in Ia- P3HR-1 cells Ii was terminally processed to more acidic, sialic acid-derivatized forms. Butyrate treatment did not alter the relative turnover rate of terminally processed Ii in Jijoye cells. The level of the dominant, basic form of Ii in HCL cells equaled that in butyrate-treated Jijoye cells, and relative turnover rates of this terminally unprocessed Ii pool were similar in HCL and Jijoye cells. However, HCL Ia-associated Ii was not terminally processed, as was Ia-associated Ii in Jijoye cells. The expression of Ia auxiliary proteins, p41 and p25, was also enhanced in Jijoye cells by butyrate treatment and was prominent in HCL cells. From these experiments, we may hypothesize the following. In lymphoblastoid cells, two pathways for Ii turnover could exist. One is through association with Ia complexes and progressive terminal processing of carbohydrate side chains and a second is not associated with Ia or, apparently, with such processing. Because Ii is not found to be terminally processed in the absence of class II antigen, Ia might be considered to direct the processing of a subset of Ii towards some function (rather than vice versa).(ABSTRACT TRUNCATED AT 400 WORDS)

Kinetics of Ii synthesis, processing, and turnover in n-butyrate-treated Burkitt's lymphoma cell lines which express or do not express class II antigens and in hairy leukemic cells

We have sought to understand the role of the electrophoretically invariant chain (Ii) in class II antigen functions, particularly in certain transformed cells in which we have previously demonstrated hyperexpression of Ii. Molecular structures and relative kinetics of Ii synthesis, processing and turnover were compared in paired, Ia+ and Ia- Burkitt's lymphoma (BL) cell lines and in hairy cell leukemia (HCL) cells. Cells were metabolically labeled with [35S] methionine for 15 min (with or without a cold methionine chase to 3 hr) or were continuously labeled for 3 hr. One- and two-dimensional gel electrophoresis resolved immunoprecipitates formed with a) a heteroantiserum to purified class II antigen (demonstrating alpha and beta chains and Ii associated with that complex), b) a heteroantiserum to hairy cell leukemia (HCL) membranes (demonstrating principally the dominant, basic form of Ii molecules, class I antigens, and some additional proteins), and c) a monoclonal antibody to human Ii. Treatment of Ia+ Jijoye and its daughter, Ia- P3HR-1, BL cells with 4 mM butyrate for 48 hr enhanced the synthesis of the dominant, basic form of Ii but did not affect apparent turnover rates of that pool of Ii chains in either cell line. In Ia+ Jijoye cells but not in Ia- P3HR-1 cells Ii was terminally processed to more acidic, sialic acid-derivatized forms. Butyrate treatment did not alter the relative turnover rate of terminally processed Ii in Jijoye cells. The level of the dominant, basic form of Ii in HCL cells equaled that in butyrate-treated Jijoye cells, and relative turnover rates of this terminally unprocessed Ii pool were similar in HCL and Jijoye cells. However, HCL Ia-associated Ii was not terminally processed, as was Ia-associated Ii in Jijoye cells. The expression of Ia auxiliary proteins, p41 and p25, was also enhanced in Jijoye cells by butyrate treatment and was prominent in HCL cells. From these experiments, we may hypothesize the following. In lymphoblastoid cells, two pathways for Ii turnover could exist. One is through association with Ia complexes and progressive terminal processing of carbohydrate side chains and a second is not associated with Ia or, apparently, with such processing. Because Ii is not found to be terminally processed in the absence of class II antigen, Ia might be considered to direct the processing of a subset of Ii towards some function (rather than vice versa).(ABSTRACT TRUNCATED AT 400 WORDS)

Inhibition of Epstein-Barr virus (EBV) release from the P3HR-1 Burkitt's lymphoma cell line by a monoclonal antibody against a 200,000 dalton EBV membrane antigen

In raising murine hybridoma antibodies against Epstein-Barr virus (EBV)-induced membrane antigens (MA), we found one antibody that blocked the release of infectious EBV from cultured P3HR-1 cells. This monoclonal antibody (mAb) recognized a 200 kD, phosphonoacetic acid-sensitive (late) MA, and did not directly neutralize virus without complement. When this mAb was added to 33 degrees C-cultured, spontaneously EBV-producing P3HR-1 cells, the intracellular expression of viral capsid antigen and infectious virus was not inhibited, but the appearance of infectious virus in the culture medium was significantly reduced. The duration of this suppression was dependent upon the concentration of the mAb, an effect being observed to a 1:4 X 10(5) titer of the ascites mAb preparation. A more acute effect of suppression of EBV release was observed in a second model of 12-o-tetradecanoyl phorbol-13-acetate and n-butyrate induction of EBV in 37 degrees C-cultured P3HR-1 cells. Again, intracellular infectious virus production was not inhibited, but the level of infectious virus in the culture medium was significantly reduced as early as 1 and 2 d of culture with antibody. This effect was reversed within 31 h after replacement of mAb-containing medium with fresh medium. This description of antibody-mediated inhibition of EBV release might lead to the characterization of another form of immune defense for the control of EBV infections.

Epstein-Barr virus infections in hairy cell leukemia patients in the presence of complement-dependent neutralizing antibody

Immune system status was characterized in patients with hairy cell leukemia (HCL) with respect to explaining their chronic or recurrent infections with Epstein-Barr virus. Measures of cellular immune responsiveness for a group of 11 HCL patients were, in general, decreased when expressed as the proportion of tested patients with values less than 2 S.D. below mean values for a group of 17 healthy adults: T-cell enumeration, seven of 13; mitogen responsiveness of phytohemagglutinin, 10 of 11; concanavalin A, 10 of 11; pokeweed mitogen, 10 of 11; B-cell responsiveness by anti-immunoglobulin immunobead stimulation, two of six; responsiveness to streptolysin O antigen, four of seven; mixed-lymphocyte reaction, six of seven; natural killer cell activity, six of eight. Specific immunity to Epstein-Barr virus was measured by complement-independent, antibody-mediated virus neutralization (mean index for HCL patients being 56% of control value) and complement-dependent virus neutralization (98% of control value). We concluded that, in spite of depressed levels of immune responses measured with general, cellular assays, functional levels of complement-dependent virus-neutralizing antibody were present in these HCL patients.

Differential effect of TPA and n-butyrate on induction of Ii and EBV antigens in the P3HR-1 lymphoblastoid cell line

The aim of this study was to test whether EBV induction by TPA or n-butyrate was related directly to hyperexpression of Ii, an electrophoretically invariant, 35 000 dalton, HLA-DR antigen-associated glycoprotein which is abundantly detected in EBV freshly transformed cells and is enhanced by EBV superinfection of lymphoblastoid cell lines. P3HR-1 lymphoblasts were treated with n-butyrate or TPA in variable doses and durations. The augmented expression of Ii, EBV antigens (EA and VCA), DNA synthesis, and cell growth and viability were monitored. n-Butyrate induced hyperexpression of Ii at 2 days with a maximal effective dose of 4 mM, induced EBV antigens (EA and VCA) in 36 per cent of the cells at 2 days, inhibited DNA synthesis and cell growth, and was not cytolytic at 48 h when Ii induction was maximal. TPA did not induce hyperexpression of Ii, induced EBV antigens (EA) in 30 per cent of the cells at 4 days, did not inhibit DNA synthesis and cell growth, and was not cytolytic in the time course and doses studied. Ii expression, therefore, did not appear to be an obligatory consequence of EBV antigen induction. Ii induction might be related to an effect of EBV inducers on cellular DNA synthesis, or on control of the cell cycle, or directly upon Ii gene regulation.

Enhanced Ii expression after n-butyrate treatment of a P3HR-1 Burkitt's lymphoma subline which does not express HLA-D

Treatment of P3HR-1 Burkitt's lymphoma cultured cells with 4 mM n-butyrate for 48 h induced the abundant expression of a 35 000 dalton, microsomal membrane protein which was demonstrated to be the electrophoretically invariant Ii molecule. To prove this point, [35S]methionine-labelled, microsomal membrane proteins or immunoprecipitates of such detergent-solubilized proteins were subjected to electrophoresis either in SDS gels or in two-dimensional, nonequilibrium pH gradient gels. The induced p35 molecule was judged to be Ii by molecular weight and isoelectric characteristics and by immune complex associations. The abundant expression of Ii on butyrate-treated P3HR-1 cells mimicked the high level of expression of p35 or Ii on leukemic cells of a subset of patients with hairy cell leukemia. Alpha and beta chains of the HLA-D complex were absent from the P3HR-1 cell line and present in the Jijoye parent from which mutant P3HR-1 was derived. This relatively simple model can lead to the study of inducible synthesis, processing and expression of Ii, with or without HLA-D alpha and beta chains.

Complement-dependent, Epstein-Barr virus-neutralizing antibody appearing early in the sera of patients with infectious mononucleosis

The first serum specimens obtained after onset of illness and those obtained later from patients with infectious mononucleosis were examined for neutralization of P3HR-1-derived Epstein-Barr virus (EBV). Without complement, viral neutralization indices of sera obtained soon after onset were all less than 0.2, and those of sera obtained later were less than 0.5. In contrast, sera from EBV-seropositive, healthy adults had neutralization indices of 0.45-1.0. Sera from EBV-seronegative adults showed no evidence of viral neutralization. The addition of complement from EBV antibody-negative human serum to 31 early and 34 late serum samples from 34 patients with infectious mononucleosis yielded neutralization indices of greater than or equal to 0.95. Complement-dependent neutralizing antibodies were also demonstrated in sera from EBV-seropositive, healthy adults. In contrast, sera from EBV-seronegative adults failed to neutralize EBV after the addition of complement. Heat inactivation destroyed the capacity of complement to induce additional neutralization of EBV by sera from patients with mononucleosis. The early appearance of complement-dependent neutralizing antibodies in the course of mononucleosis is consistent with a role in recovery from acute EBV infection.

Detection of circular and linear herpesvirus DNA molecules in mammalian cells by gel electrophoresis

A simple gel technique is described for the detection of large, covalently closed, circular DNA molecules in eucaryotic cells. The procedure is based on the electrophoretic technique of Eckhardt (T. Eckhardt, Plasmid 1:584-588, 1978) for detecting bacterial plasmids and has been modified for the detection of circular and linear extrachromosomal herpesvirus genomes in mammalian cells. Gentle lysis of suspended cells in the well of an agarose gel followed by high-voltage electrophoresis allows separation of extrachromosomal DNA from the bulk of cellular DNA. Circular viral DNA from cells which carry the genomes of Epstein-Barr virus, Herpesvirus saimiri, and Herpesvirus ateles can be detected in these gels as sharp bands which comigrate with bacterial plasmid DNA of 208 kilobases. Epstein-Barr virus producer cell lines also show a sharp band of linear 160-kilobase DNA. The kinetics of the appearance of this linear band after induction of viral replication after temperature shift parallels the known kinetics of Epstein-Barr virus production in these cell lines. Hybridization of DNA after transfer to filters shows that the circular and linear DNA bands are virus specific and that as little as 0.25 Epstein-Barr virus genome per cell can be detected. The technique is simple, rapid, and sensitive and requires relatively low amounts of cells (0.5 X 10(6) to 2.5 X 10(6)).

Isolation and characterization of an EBV superinfection-enhanced, host-cell-coded, 53,000-dalton protein

Microsomal membrane fraction proteins with enhanced synthesis after P3HR-1 Epstein-Barr virus (EBV) superinfection of Raji cells were identified with [35S]-methionine labeling and SDS-PAGE. One 53,000-dalton protein, which was found in both the microsomal membrane and cytosol fractions, was purified by ion-exchange chromatography, and specific rabbit antisera were prepared to it. This protein was found to be present in Raji cells, but its expression was enhanced after P3HR-1 EBV superinfection. It was more abundant in the cytosol than in the microsomal membrane fraction of the cell, and its synthesis was not affected by treatment of the cells with phosphonoacetic acid. It was present in several EBV-genome-negative cell lines and in activated B lymphocytes and consequently represents a host-cell-coded protein which is enhanced by EBV superinfection or by lymphocyte activation.

Identification of hairy cell leukemia subset defining p35 as the human homologue of Ii

A molecule defining a subset of patients with hairy cell leukemia (HCL) on the basis of being abundantly labeled with [35S]methionine, was demonstrated to be the human homologue of murine Ii, a glycoprotein which lacks alloantigenic variation and is associated non-covalently with Ia antigens. In one-dimensional SDS-polyacrylamide gradient gel electrophoresis, the HCL-subset-defining molecule migrated with HLA-DR molecules which were immunoprecipitated with a specific heteroantiserum. These molecules were further defined in two-dimensional, SDS and non-equilibrium pH gradient electrophoresis of either membrane preparations or immunoprecipitates formed with various antibodies. [35S]methionine-labeling of the HCL-subset-defining molecule was greater in hairy leukemic cells than in lymphoblastoid cell lines. The subset-defining species was associated non-covalently with HLA-DR alpha and beta chains and ran electrophoretically at a position described for murine and human Ii molecules (in terms of pI and weight). Metabolic labeling of HLA-A,-B and -DR was also increased in HCL cells relative to lymphoblastoid cell lines. A separate protein, of 41,000 mol. wt and pI of 7-8, resembled another Ii-associated molecule which has been described in murine and human studies.

Analysis of transformation with Epstein-Barr virus and phenotypic characteristics of lymphoblastoid cell lines established from patients with hairy cell leukemia

In order to assess the role of Epstein-Barr virus (EBV) in patients with hairy cell leukemia (HCL), we have sought to characterize 1) the ability of EBV to infect and transform hairy leukemic cells in vitro and 2) the phenotypes of cell lines putatively derived from those leukemic cells. Analysis of EBV-induced transformation and the kinetics of Epstein-Barr nuclear antigen (EBNA) induction in leukemic preparations indicated that most leukemic cells were not susceptible to EBV infection but that at least a small subpopulation of leukemic cells could be infected with EBV. Lymphoblastoid cells lines were established after exposure of peripheral blood or splenic cells from HCL patients to B95-8 or QIMR-WIL EBV. Splenic leukemic cell preparations were more sensitive targets for EBV transformation than were peripheral blood cell samples. The newly established cell lines, but not long-established B lines such as Raji, demonstrated high levels of synthesis of p35, (a protein complex expressed abundantly by cells of a subset of HCL patients) and high levels of tartrate-resistant acid phosphatase (an enzyme relatively diagnostic for HCL). Lymphoblastoid lines from one patient with HCL expressed lambda light chains and no kappa chains as did the patient's leukemic cells. Virus expression in these lines showed that HCL-derived lines had spontaneous early antigen (EA) and viral capsid antigen (VCA) expression. Transforming EBV could be rescued from HCL-derived cell lines but not from cord blood-derived lines.

Restrictions upon Epstein-Barr virus infection of the leukemic cell are demonstrated in patients with hairy cell leukemia

We tested the hypothesis that Epstein-Barr virus (EBV) might actually infect leukemic hairy cells in vivo by examining those cells for the EBV-receptor, EBV nuclear antigen (EBNA) and membrane antigen (MA), for spontaneous transformation and rescue of infectious virus and for presence of EBV genome. EBV-receptors were found on subpopulations of leukemic cells from each of 7 patients with hairy cell leukemia (HCL) tested. MA was present on low numbers (1-5 per cent) of fresh leukemic cells of 7 patients and in some instances occurred with a greater frequency after 3 to 5 days in culture, with or without 12-O-tetradecanoylphorbol-13-acetate. In 11 fresh leukemic cell preparations from 8 HCL patients, no EBNA was demonstrated. However, 2 samples after 4 days in culture expressed low frequencies of EBNA-positive cells. Spontaneous, EBV-positive cell lines were established with a high transformation efficiency from 3 HCL blood samples but not from 8 other specimens. Infectious EBV could be rescued from some hairy leukemic cell preparations by co-cultivation with cord blood lymphocytes. These results demonstrated that leukemic cell populations harbored infectious EBV, that the leukemic cells expressed virus receptors and suggested that a small subpopulation of leukemic cells might become infected in vivo at least transiently and possibly transformed in vitro by EBV. To test for the extent of occult in vivo infection of leukemic cells with EBV, Southern type hybridization studies were performed with a probe for EBV genome (Bam HI W). At a sensitivity level of 0.1 genome per cell, EBV genome was not detected in the leukemic cell populations of 7 patients. We conclude that host defence mechanisms protecting these individuals from EBV also prevent infections of the leukemic cell and/or most hairy leukemic cells are not suitable targets for both infection and transformation.

p105, an Epstein-Barr virus-induced, phosphonoacetic acid-insensitive glycoprotein target of the anti-Epstein-Barr virus immune response

To describe structures and biological functions of targets for antibody-mediated immune responses to Epstein-Barr virus (EBV)-infected lymphoid cells, we have characterized a membrane-associated protein of 105,000 daltons, p105, which was prominently recognized in immunoprecipitates with some EBV antigen-reactive patients' sera. A rabbit antiserum to immunopurified p105 was developed. [35S]methionine-labeled p105 was specific to EBV-superinfected Raji cells, and its synthesis was not blocked with phosphonoacetic acid, indicating that it is an "early" viral antigen. Phosphonoacetic acid treatment of EBV-superinfected Raji cells was associated with the accumulation, mainly in the cytosol, of an 88,000-dalton protein, p88, which was also recognized with anti-p105 serum, but was not detected in superinfected cells which had not been treated with phosphonoacetic acid. Although anti-p105 serum immunoprecipitated a membrane fraction protein, it did not neutralize P3HR-1 virus and was not considered to be an exposed virion component. We conclude that p105 is an early, EBV-induced, membrane fraction antigen to which EBV-infected patients generate a substantial antibody response.

Interferon production potentials of various human lymphoblastoid cell lines

A number of human lymphoblastoid cells were examined concerning their ability to produce spontaneously liberated and virus-induced interferon (IFN). It was found that, in addition to B cells, various T and nonT-nonB lymphoblastoid cells responded well to Sendai virus infection to form IFN, the characterization of which has been recently reported (20). One B lymphoblastoid cell line from an infectious mononucleosis (IM) patient produced a large amount of IFN-alpha and might become an alternative source of IFN production. Among 68 cell lines examined, 35 cell lines liberated 10 U/ml or more of IFN spontaneously in culture fluid. The presence of Epstein-Barr virus (EBV) genome or its activation appears to have no correlation with the spontaneous liberation of IFN. Spontaneously produced IFN from three cell lines was characterized as IFN-alpha. Comparatively higher amounts of IFN were produced in cells from IM patients than those from Burkitt's lymphoma cases or healthy adults. Spontaneously produced IFN was detected more easily in cells transformed by EBV alone than in those transformed by EBV and a tumor promoter, TPA.

Inhibitory effect of 1-beta-D-arabinofuranosylthymine on synthesis of Epstein-Barr virus

The effect of 1-beta-D-arabinofuranosylthymine (ara-T) on cell growth and synthesis of Epstein-Barr virus (EBV) in human lymphoblastoid cell lines was determined. The growth of P3HR-1 cells was not inhibited by 1 microgram of the drug per ml; however, infectious virus production was strongly inhibited and was accompanied by decreased expression of early antigen (EA) and viral capsid antigen (VCA). The ability of 12-O-tetradecanoylphorbol-13-acetate or n-butyric acid to induce synthesis of VCA, but not EA, in P3HR-1 cells was inhibited by ara-T. Similarly, VCA synthesis but not EA synthesis was inhibited by ara-T in Jijoye cells superinfected with the P3HR-1 strain of EBV. The results suggest that ara-T has a specific inhibitory action against EBV replication.

Identification of target antigen for antibody-dependent cellular cytotoxicity on cells carrying Epstein-Barr virus genome

The target antigen for antibody-dependent-cellular cytotoxicity (ADCC) on Epstein-Barr virus-(EBV) carrying lymphoblastoid cells expressing EBV-specific membrane antigen (MA) were examined with human serum antibody and adult human peripheral lymphocytes as effector cells. These studies confirmed that anti-MA-positive but not MA-negative sera were reactive in the ADCC. The ADCC reaction was positive with cells in which the MA consisted of late (LMA) and early (EMA) components. These included 1) MA-positive cells prepared by EBV antigen-adsorption, 2) cells carrying de novo-synthesized MA without adsorbed MA, and 3) EBV-producer cells expressing MA spontaneously. In all these preparations, the target cells were lysed roughly in parallel with the frequency of MA-positive cells. Inhibition of LMA synthesis in EBV-superinfected cells by phosphonoacetate (PA) reduced ADCC sensitivity significantly and to a far greater extent than MA synthesis as measured by immunofluorescence. This suggests that a target for ADCC is the PA-sensitive LMA. No ADCC reaction occurred with the cell preparation comprised of a high percentage of MA-positive cells induced by 5-iodo-2'-deoxyuridine, which is believed to be EMA only. These results strongly suggest that the target antigen for ADCC in EBV-positive cells is a late MA but not early MA.

Identification of target antigen for antibody-dependent cellular cytotoxicity on cells carrying Epstein-Barr virus genome

The target antigen for antibody-dependent-cellular cytotoxicity (ADCC) on Epstein-Barr virus-(EBV) carrying lymphoblastoid cells expressing EBV-specific membrane antigen (MA) were examined with human serum antibody and adult human peripheral lymphocytes as effector cells. These studies confirmed that anti-MA-positive but not MA-negative sera were reactive in the ADCC. The ADCC reaction was positive with cells in which the MA consisted of late (LMA) and early (EMA) components. These included 1) MA-positive cells prepared by EBV antigen-adsorption, 2) cells carrying de novo-synthesized MA without adsorbed MA, and 3) EBV-producer cells expressing MA spontaneously. In all these preparations, the target cells were lysed roughly in parallel with the frequency of MA-positive cells. Inhibition of LMA synthesis in EBV-superinfected cells by phosphonoacetate (PA) reduced ADCC sensitivity significantly and to a far greater extent than MA synthesis as measured by immunofluorescence. This suggests that a target for ADCC is the PA-sensitive LMA. No ADCC reaction occurred with the cell preparation comprised of a high percentage of MA-positive cells induced by 5-iodo-2'-deoxyuridine, which is believed to be EMA only. These results strongly suggest that the target antigen for ADCC in EBV-positive cells is a late MA but not early MA.

Re-evaluation of a transforming strain of Epstein-Barr virus from the Burkitt lymphoma cell line, Jijoye

The biological properties of Epstein-Barr virus (EBV) from a Burkitt lymphoma cell line, Jijoye, were examined. the synthesis of virus capsid antigen (VCA) and early antigen (EA) in Jijoye cells was markedly enhanced by shift-down of the temperature of incubation from 37 degrees C to 33 degrees C. Cultures of Jijoye cells at 33 degrees C released a large amount of transforming EBV (10(5.2) of 50% transforming doses/ml) into the culture fluid. However, no infectious virus was produced in all cultures at 37 degrees C during the course of this study. The EBV (Jijoye EBV) from Jijoye line was found to possess only transforming activity, but not EA-inducing activity. Jijoye EBV lacks adsorbing capacity to Jijoye cells, in contrast to P3HR-I EBV which can adsorb to Jijoye cells. The Jijoye cells were highly susceptible to superinfection with P3HR-I EBV as demonstrated by the induction of EA, VCA and infectious EBV. The EBV induced by the P3HR-I EBV superinfection of Jijoye cells has also transforming activity but neither EA-inducing activity nor adsorbing capacity to Jijoye cells.

Modulation of Epstein-Barr virus release from cells by components of normal human serum

By filtration of normal human serum through a Sephadex G-200 column, an anti-virus release factor (AVRF), which is capable of inhibiting the release of Epstein-Barr virus (EBV) from cells cultured in vitro, was found in the fractions corresponding to IgM. Another component, antagonistic to the activity of AVRF, was found in the fractions close to those of albumin. Both AVRF and anti-AVRF were found in all sera from four EBV seropositive and three sero-negative adults tested. EBV-release inhibition by AVRF was reversible. AVRF did not neutralize virus infectivity or inhibit intracellular virus growth. Virus adsorption on to cells was not prevented by AVRF but cap formation of EBV antigens on cells was augmented by it.