T-cell analysis on chronic active Epstein-Barr virus (EBV) infection and EBV-associated lymphoproliferative diseases

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Epstein-Barr virus (EBV), the causative agent of acute infectious mononucleosis (IM) leads to the persistent reactivation and the subsequent development of B-cell lymphoma/lymphoproliferative disease (LPD) in immunodeficient patients. This γ-herpes virus can infect T/NK cells and thus be associated with lymphoreticular diseases including chronic active EBV infection (CAEBV) and hemophagocytic lymphohistiocytosis (HLH). These conditions have now been classified into EBV^+T-cell LPD.The present study on CAEBV revealed the followings ; 1) T-cells are activated and expanded ologoclonally, 2) The activated T-cells carried increased copy number of EBV genome, 3) and expressed unbalanced high expression of cytokines. These results suggest that activated T-cells of CAEBV may represent the clonal evolution of malignancy, rather than the reactive condition against EBV infection. We also demonstrated the usefulness of quantitative monitoring of EBV-DNA in predicting the development of posttransplant LPD.1) EBV load and cytokine expression in CAEBV T-cellsThe inverse PCR methods using T-cell antigen receptor (TCR) Vβ/Jβ region genes revealed oligoclonal expansion of T-cells in CAEBV patients. T cells were fractionated into HLA-DR^+ or HLA-DR^-CD3^+ cells by a cell sorter (EPICS-XL), and DNA and cDNA were constructed from each population, respectively. EBV-DNA and cytokine mRNA were quantified by real-time PCR (TaqMan). CD3^+HLA-DR^+ cells contained higher copy numbers of virus than CD3^+HLA-DR^- cells. Quantitative PCR for cytokines indicated high expressions of Th1 (IFNγ, IL-2) and Th2 (IL-10, TGF-β) cytokines in activated T-cells.2) Clinical usefulness of posttransplant EBV-DNA monitoringEBV-DNA was sequentially quantified by real-time PCR in 12 patients after hematopoietic stem cell transplantation. Progressive increase of EBV-DNA indicated the development of posttransplant LPD.