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Epstein-Barr virus (EBV) has been found in most cases of rare gastric lymphoepithelioma-like carcinomas and a small but significant proportion of common gastric adenocarcinomas. The presence of EBV in gastric cancer has been detected by polymerase chain reaction and in-situ hybridization, the latter technique demonstrating EBV in every malignant epithelial cell. The carcinoma cells express EBNA1 but not the other EBNAs or LMP1. A single fused terminal fragment of the EBV genome was detected in each of the EBNA1-expressing tumours suggesting that the virus-positive gastric carcinomas represent a clonal proliferation of EBV-infected cells. EBV antibody titres were elevated in patients with virus-positive carcinomas and also in those destined to develop EBV-positive carcinomas. EBV-specific cytotoxic T-lymphocyte activity was retained in patients with EBV-positive carcinomas suggesting that the tumours can evade immunosurveillance possibly by only expressing the EBNA1 protein which is not able to be processed and presented. These results implicate EBV as one of the factors contributing to the development of gastric cancer.

Epstein-Barr virus (EBV), a ubiquitous human B-lymphotropic virus, is associated with certain lymphoproliferative diseases of T-cell lineage. To understand the mechanism by which EBV infects T cells, we have tested the susceptibility of various human T-cell lines to the virus. We report here that the HTLV-I-harbouring T-lymphoblastoid line MT-2 carries a high level of CD21/EBV receptors on their surface, adsorbs fluorescein isothiocyanate-labeled EBV, and synthesizes virus latent antigens (EBNA-1 and LMP) following EBV infection. Pretreatment of MT-2 cells with anti-CD21 monoclonal antibody OKB7 inhibited the virus binding as well as the synthesis of virus latent antigen. These data suggest that human T-cells can be infected with EBV via functionally active virus receptors.

The distribution of Epstein-Barr virus receptor (EBVR) among the different B-cell subpopulations was analyzed by flow cytometry, using simultaneous two-color immunofluorescence of EBVR and cell-surface markers. The expression of EBVR was established by the binding of fluorescein isothiocyanate (FITC)-labeled EBV to the cells, while surface markers were stained by phycoerythrin (PE)-indirect immunofluorescence, using monoclonal antibodies. All cells of both the resting B-cell subpopulation defined by L30 and the B-cell subpopulations expressing surface IgM, IgD, IgA, and IgG were EBVR-positive. In contrast, EBVR was absent from about 10% cells of the activated B-cell subpopulation recognized by OKT9, as well as from about 10% cells of the highly differentiated B-cell subpopulation which reacted with OKT10. These results suggest that the expression of EBVR on the B-cell lineage varies with the maturation stage and with the state of activation. This postulation was further supported by analyses based on in vitro B-cell activation.

A quantitative analysis of Epstein-Barr virus (EBV)-induced early antigen (EA) and viral capsid antigen (VCA) syntheses was carried out in Raji cells superinfected with purified, concentrated P3HR-1 EBV. When the cells were exposed to the virus and assessed by immunofluorescence and immunoprecipitation, EA induction occurred significantly (17%) but not VCA (less than 1%), at a low-input multiplicity of infection (MOI) of 10 EBV DNA copies/cell. In contrast, at a high MOI of 500 EBV DNA copies/cell, the majority of cells were positive for both EA (82%) and VCA (61%). The latter VCA synthesis was accompanied by the replication of EBV DNA. Kinetic studies showed that EA induction was directly proportional to the dilution of the infecting virus, while VCA was made following three-hit kinetics. The implications of these results are discussed in relation to the heterogeneous nature of P3HR-1 EBV and a possible role of EA in VCA synthesis.

The possible production of human monoclonal antibodies against Epstein-Barr virus (EBV) was assessed through the EBV immortalization technique. When individual lymphocyte samples from 50 clinical patients and healthy donors were immortalized by EBV, 4 lymphoblastoid lines yielded antibodies to EBV antigens. These positive lines were cloned and each line yielded cultures that secreted monoclonal antibodies against either viral capsid antigen (VCA) or membrane antigen (MA) component. Above all, a clonal line TAKA-SP-8 produced 5 micrograms MA antibody/10(6) cells/ml for more than 12 months. The culture fluid specifically immunoprecipitated a single polypeptide with a size of 93K from both P3HR-1 and B95-8 cell extracts. FUKA-SP-3, on the other hand, secreted 5 micrograms VCA antibody/10(6) cells/ml for at least 8 months. This antibody recognized two polypeptides with sizes of 123K and 120K, from P3HR-1 and B95-8 cell extracts, respectively. When B95-8 and P3HR-1 EBV were treated with the human MA monoclonal, both nuclear antigen (EBNA) synthesis and early antigen (EA) induction were strongly inhibited. All EBV antibody-producing cultures were exclusively achieved from splenic lymphocytes of patients with autoimmune diseases, but not from other donors.