Comprehensive analyses of therapeutic strategy against chronic active Epstein-Barr virus(EBV) infection

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The aim of this study was to identify the cellular genes associated with or responsible for the oncogenesisi of Epstein-Barr virus (EBV) in EBV-positive T, MC and epithelial tumor cells, by utilizing dominant-negative EBNA1 (DNE1; Mal. Ther., 11(4): 578-90, 2005)that can eradicate EBV episomes from cells. We prepared isogenic pairs of EBV-positive and -negative NK- and T-cell lines by DNE1 transduction and compared their malignant grade. Concomitantly alterations of cellular gene expression in those cell pairs were comprehensively assessed with the multi-cytokine assay system, thereby elucidating the role(s)of EBV in malignant conversion. Further, we analysed EBV-specific cytotoxic T-cells (EBV-CTL) by a tetramer assay using 3 EBV-antigens, i.e., BRLF1, BMLF1 and EBNA3. The results obtained are as follows.1. Adenovirus vector-mediated transduction of our DNE1 successfully eradicated EBV episomes from the majority of naturally EBV-positive T-cell and NK-cell lymphoma and epithelial tumo … More r cell lines in a few days.2. The DNE1-induced EBV-lost T-cells and NK-cells showed a striking suppression of their malignant phenotypes, such as prolongation of doubling time and loss of anchorage-independent growth potential, compared with parental EBV-positive T-cell and NK-cell tumors. In a part of the EBV-lost T-cells and NK-cells, loss of viral genome also brought about cell death.3. The EBV-lost T-cells and NK-cells showed significantly decreased production of some cytokines, such as interleukin-9, compared with the parental EBV-positive T-cell and NK-cell tumors. Conversely, the production levels of another cytokine was also found to be upregulated in the EBV-lost T-cells.These results indicate that the EBV-dependent malignant phenotypes in T- and NK-cells and perhaps also in epithelial cells, as in B-cell lymphomas, are associated, at least partly, with upregulation (i.e., the autocrine mechanism) and/or down regulation of certain cytokines. We are planning to explore precisely the mechanisms of cytokine gene control and specific effects on EBV oncogenesis. Less