Epstein-Barr virus strain-specific differences in transformed cell lines demonstrated in growth characteristics, induction of viral antigens and ADCC susceptibility

Characterization of Epstein-Barr virus infection in a human signet ring cell gastric carcinoma cell line, HSC-39

In order to study the mechanism of Epstein-Barr virus (EBV) infection in gastric carcinoma cells, we characterized the EBV infection in signet ring cell line HSC-39, derived from a human gastric carcinoma. HSC-39 cells were highly susceptible to cell-free EBV infection by Akata and P3HR-1 EBV strains. EBV nuclear antigen (EBNA) and EBV-encoded small RNA (EBER) were detected in the infected cells. Akata and P3HR-1 EBV-infected cell clones were isolated by a limiting dilution technique. The Akata and P3HR-1 EBV-infected clones differed from each other in morphology and growth patterns. Akata EBV-infected clones had lower growth rates than did P3HR-1 EBV-infected clones in both liquid and soft agar mediums. Both the infected HSC-39 cells and the clones expressed EBNA1 and EBER, but did not express EBNA2, latent membrane protein (LMP) 1 and LMP2A. The Q promoter (p), but not the Cp/Wp for EBNA transcription, was active in the infected HSC-39 cells and all clones. No lytic infection was observed in either infected parental cells or any clones. Uninfected HSC-39 cells did not express a principal EBV receptor CD21; however, Akata but not P3HR-1 EBV-infected clones expressed low levels of CD21 mRNA. These results demonstrate that the cellular phenotypes of HSC-39 cells are altered by EBV infection in strain-specific manner. We propose the HSC-39 cell line as a model target for the study of the mechanism and significance of EBV infection in gastric carcinoma.

The transforming prototype of Epstein-Barr virus (B95-8) is also a lytic virus

The B95-8 isolate of the Epstein-Barr virus (EBV) has been described as a non-lytic transforming virus. We have performed experiments in order to determine if the B95-8 EBV is capable of super-infecting and replicating in EBV-genome-positive non-producer lymphoblastoid cells. Using concentrates of B95-8 EBV, prepared from 6 different B95-8 cell lines treated with 12-O-tetradecanoylphorbol-13-acetate (TPA), we demonstrated that virus concentrates could transform human or cotton-top tamarin B-lymphocytes and also lytically replicate in Raji cells, inducing EBV antigens and infectious virus. While the virus obtained from B95-8 super-infected Raji cells was able to transform cord-blood lymphocytes (CBLs) and super-infect Raji cells, transformation was abortive, with cell cultures only growing for up to 6 weeks. Transformation titers of the B95-8 virus concentrates ranged from 10(5) to greater than 10(8) transforming units/ml; early antigen (EA) induction ranged from 1% to 50% after superinfection of Raji cells, depending on the virus stock used, as determined by immunofluorescence. Southern blot analysis was carried out on the DNA prepared from B95-8 cells and virion DNA. The results were consistent with the published EcoRI restriction pattern for B95-8 EBV. The issue of whether the B95-8 cells produce virions with a dual biological phenotype or, rather, 2 biologically distinct viruses, is addressed.

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.