The roles of V[gamma]9Vδ2-T cells in Epstein-Barr virus-induced B cell lymphoproliferative disease

Abstract

Epstein-Barr virus (EBV) infects over 95% of the population worldwide, and is associated with several human malignancies, such as Hodgkin’s disease, Burkitt lymphoma, and especially the nasopharyngeal carcinoma which is a common cancer in southern China including Hong Kong. Epstein-Barr virus-induced lymphoproliferative disease (EBV-LPD) in the immunosuppressed patients after transplantation or at late stage of HIV infection remains as a serious and life-threatening complication. Current treatments for EBV-LPD include restoring the cellular immune responses to EBV and targeting EBV-infected B cells with monoclonal antibodies or chemotherapy. Restoring the cellular immune responses by adoptive transfer of ex vivo-generated EBV-specific cytotoxic T lymphocytes (CTL) has been shown as a promising treatment against EBV-LPD. However, the application of this treatment is limited by the difficulties in generating enough EBV-specific CTL in vitro and lack of in vivo expansion of infused CTL. Targeting EBV-infected B cells also has unwanted side-effects as anti-CD20 antibody would deplete normal B cells, and chemotherapy can cause general immunosuppression.

Vγ9Vδ2-T cells share many characteristics of T cells, NK cells and antigen presenting cells (APC). They are unique in fast and potent antiviral activities, suggesting that they may be developed as novel antiviral therapies against EBV and its associated diseases. Here, we show that human Vγ9Vδ2-T cells expanded by the aminobisphosphonate pamidronate efficiently killed EBV-transformed autologous lymphoblastoid B cell lines and inhibited EBV replication in vitro. The cytotoxicity of Vγ9Vδ2-T cells against EBV-LCL was required cell-cell contact and was triggered by γ/δ-TCR and NKG2D. Engagement of Fas and TRAIL, and release of cytotoxic effectors (perforin and granzyme) and antiviral cytokine IFN-γ are involved in their antitumor and antiviral activities. By inoculation of EBV-LCL in Rag2-/-γc-/- mice and humanized mice reconstituted with autologous EBV-seropositive human peripheral blood mononuclear cells, we establish lethal EBV-LPD with characteristics similar to those in humans. Adoptive transfer of pamidronate-expanded Vγ9Vδ2-T cells alone effectively prevented EBV-LPD in Rag2-/-γc-/- mice and induced the regression of EBV-LPD in EBV+ tumor-bearing Rag2-/-γc-/- mice. Pamidronate exerted therapeutic efficacy in controlling the development of EBV-LPD in humanized mice through selective activation and expansion of Vγ9Vδ2-T cells in vivo. This study provides proof-of-principle for a novel therapeutic approach by targeting Vγ9Vδ2-T cells to control EBV-LPD.