ABSTRACT
EBV infection causes mononucleosis and is associated with specific subsets of B cell lymphomas. Immunosuppressed patients such as organ transplant recipients are particularly susceptible to EBV-induced lymphoproliferative disease (LPD), which can be fatal. Leflunomide (a drug used to treat rheumatoid arthritis) and its active metabolite teriflunomide (used to treat multiple sclerosis) inhibit de novo pyrimidine synthesis by targeting the cellular dihydroorotate dehydrogenase, thereby decreasing T cell proliferation. Leflunomide also inhibits the replication of cytomegalovirus and BK virus via both "on target" and "off target" mechanisms and is increasingly used to treat these viruses in organ transplant recipients. However, whether leflunomide/teriflunomide block EBV replication or inhibit EBV-mediated B cell transformation is currently unknown. We show that teriflunomide inhibits cellular proliferation, and promotes apoptosis, in EBV-transformed B cells in vitro at a clinically relevant dose. In addition, teriflunomide prevents the development of EBV-induced lymphomas in both a humanized mouse model and a xenograft model. Furthermore, teriflunomide inhibits lytic EBV infection in vitro both by preventing the initial steps of lytic viral reactivation, and by blocking lytic viral DNA replication. Leflunomide/teriflunomide might therefore be clinically useful for preventing EBV-induced LPD in patients who have high EBV loads yet require continued immunosuppression.
Subject(s)
Crotonates/pharmacology , Epstein-Barr Virus Infections/complications , Epstein-Barr Virus Infections/virology , Herpesvirus 4, Human/drug effects , Herpesvirus 4, Human/physiology , Isoxazoles/pharmacology , Lymphoproliferative Disorders/etiology , Lymphoproliferative Disorders/pathology , Toluidines/pharmacology , Virus Replication/drug effects , Animals , Apoptosis/drug effects , Apoptosis/genetics , B-Lymphocytes/drug effects , B-Lymphocytes/metabolism , B-Lymphocytes/virology , Cell Line, Transformed , Cell Proliferation/drug effects , Cyclin E/genetics , Disease Models, Animal , Epstein-Barr Virus Infections/drug therapy , Gene Expression Regulation/drug effects , Gene Expression Regulation, Viral/drug effects , Genes, myc , Humans , Hydroxybutyrates , Leflunomide , Lymphoproliferative Disorders/drug therapy , Mice , NF-kappa B/metabolism , Nitriles , Virus Activation/drug effects , Virus Latency/drug effects , Virus Latency/genetics , Xenograft Model Antitumor AssaysABSTRACT
Epstein-Barr virus (EBV) infection transforms B cells in vitro and is associated with human B cell lymphomas. The major EBV oncoprotein, latent membrane protein 1 (LMP1), mimics constitutively active CD40 and is essential for outgrowth of EBV-transformed B cells in vitro; however, EBV-positive diffuse large B cell lymphomas and Burkitt lymphomas often express little or no LMP1. Thus, EBV may contribute to the development and maintenance of human lymphomas even in the absence of LMP1. Here, we found that i.p. injection of human cord blood mononuclear cells infected with a LMP1-deficient EBV into immunodeficient mice induces B cell lymphomas. In this model, lymphoma development required the presence of CD4+ T cells in cord blood and was inhibited by CD40-blocking Abs. In contrast, LMP1-deficient EBV established persistent latency but did not induce lymphomas when directly injected into mice engrafted with human fetal CD34+ cells and human thymus. WT EBV induced lymphomas in both mouse models and did not require coinjected T cells in the cord blood model. Together, these results demonstrate that LMP1 is not essential for EBV-induced lymphomas in vivo and suggest that T cells supply signals that substitute for LMP1 in EBV-positive B cell lymphomagenesis.
