T-cell modulation was accomplished by systemic administration of monoclonal antibodies (mAb) against both effector and CD4+CD25+regulatory T-cell (Treg) populations. T-cell modulation aimed at enhancing antitumor immunity can be accomplished in 3 ways: (1) by stimulating antitumor T cells directly, (2) by blocking intrinsic unfavorable T-cell signals, or (3) by eliminating Treg cells that typically dampen antitumor immune responses. CpG, it induced antitumor CD4 and CD8 T-cell immunity, cured large and systemic lymphoma tumors without chemotherapy, and provided long-lasting immunity against tumor rechallenge. Our results show that this combination of intratumoral CpG and immunomodulatory T-cell antibodies has promise for therapeutic vaccination against lymphoma. These reagents are becoming available CNQX disodium salt for human clinical trials. == Introduction == Lymphoma is usually a malignancy which is usually responsive to immunotherapy.1Despite the success of passive immunotherapy with monoclonal antibodies (eg anti-CD20, rituximab), many patients with lymphoma remain incurable. Therapeutic vaccines against lymphoma might elicit long-lasting antitumor immune responses and prevent or prolong the time to recurrence. Most recently, our group has shown that intratumoral injection of CpG, in combination with systemic chemotherapy, can serve as a therapeutic vaccine to eradicate large and metastatic lymphoma tumors.2CpG oligodeoxynucleotides (ODNs) are ssDNA fragments containing immune stimulatory unmethylated C-G sequence motifs similar to those found in microbes, capable of activating dendritic cells (DCs) and B cells by engaging Toll-like receptor 9.3In our model, intratumoral injection of CpG can directly activate tumor-infiltrating DCs as well as tumor B cells to force tumor-antigen presentation in situ.2In addition, CpG can directly inhibit proliferation of tumor cells in contrast to their proliferative and antiapoptotic effects on normal B cells.2 This vaccine strategy has several advantages. First, it does not require in vitro manipulation and can thus be made available to large numbers of patients. Second, the therapy is usually personalized since CNQX disodium salt the patients will be immunized against their own tumor antigens (Ag). Third, this therapy does not hinge on a single tumor antigen, thus, multiple tumor antigens may be targeted, reducing the risk that this tumor will be able to evade the immune response. In this study, we hypothesized that antibody-mediated modulation of T-cell populations would increase the efficacy of CpG vaccination, thereby eliminating the need for chemotherapy. Indeed, we have previously shown that this antitumor effect of CpG vaccination is usually T-cell mediated.2Moreover, antitumor T cells may be rendered inefficient due to tumor-induced immunosuppression.4We postulated that T-cell modulation would amplify the antitumor response and overcome these immunosuppressive mechanisms, leading to enhanced efficacy of CpG vaccination. T-cell modulation was accomplished by systemic administration of monoclonal antibodies (mAb) against both effector and CD4+CD25+regulatory T-cell (Treg) populations. T-cell modulation aimed at enhancing antitumor immunity can be accomplished in 3 ways: (1) by stimulating antitumor T cells directly, (2) by blocking intrinsic unfavorable T-cell signals, CNQX disodium salt or (3) by eliminating Treg cells that typically dampen antitumor immune responses. Following MHC-TCR engagement (signal 1), additional signals Rabbit Polyclonal to FBLN2 from costimulatory receptors (signal 2) are required for T-cell activation.5One of these receptors, OX40 (CD134) is expressed on activated but not resting T cells and its engagement leads to increased proliferation and survival of these cells.6Conversely, cytotoxic T-lymphocyteassociated CNQX disodium salt antigen (CTLA4, also known as CD152)7,8is a cell intrinsic unfavorable regulator of activated T cells which suppresses T-cell activity by binding to the B7 molecules, CD80 and 86. Therefore, enhancing activation of effector T cells can be achieved by stimulating OX40 with an agonist mAb or by blocking CTLA4 with an antagonist mAb. Treg cells are another target for antibody-mediated T-cell modulation. Folate-receptor 4 (FR4) is usually constitutively and preferentially expressed by Treg cells and mAb directed against this receptor can be used to specifically deplete Treg cells while sparing effector T cells.9Glucocorticoid-induced TNF-related protein (GITR) is another potential Treg target. This receptor is usually constitutively expressed on Treg cells and is up-regulated following T-cell activation.10Signaling through GITR has been shown to both abrogate the suppressive functions of Treg cells and also serve as a costimulatory molecule for effector T cells.11Therefore, Treg cells can be effectively depleted with anti-FR4 mAb9or can be functionally inhibited with anti-GITR mAb.12In addition to its effect on effector.