Non-conventional Inhibitory CD4Foxp3PD-1 T Cells as a Biomarker of Immune Checkpoint Blockade Activity.

A significant proportion of cancer patients do not respond to immune checkpoint blockade. To better understand the molecular mechanisms underlying these treatments, we explored the role of CD4Foxp3 T cells expressing PD-1 (4PD1) and observed that 4PD1 accumulate intratumorally as a function of tumor burden. Interestingly, CTLA-4 blockade promotes intratumoral and peripheral 4PD1 increases in a dose-dependent manner, while combination with PD-1 blockade mitigates this effect and improves anti-tumor activity.

Overcoming resistance to checkpoint blockade therapy by targeting PI3Kγ in myeloid cells.

Recent clinical trials using immunotherapy have demonstrated its potential to control cancer by disinhibiting the immune system. Immune checkpoint blocking (ICB) antibodies against cytotoxic-T-lymphocyte-associated protein 4 or programmed cell death protein 1/programmed death-ligand 1 have displayed durable clinical responses in various cancers. Although these new immunotherapies have had a notable effect on cancer treatment, multiple mechanisms of immune resistance exist in tumours.

The New Era of Cancer Immunotherapy: Manipulating T-Cell Activity to Overcome Malignancy.

Using the immune system to control cancer has been investigated for over a century. Yet it is only over the last several years that therapeutic agents acting directly on the immune system have demonstrated improved overall survival for cancer patients in phase III clinical trials. Furthermore, it appears that some patients treated with such agents have been cured of metastatic cancer.

Targeting tumor-necrosis factor receptor pathways for tumor immunotherapy.

With the success of ipilimumab and promise of programmed death-1 pathway-targeted agents, the field of tumor immunotherapy is expanding rapidly. Newer targets for clinical development include select members of the tumor necrosis factor receptor (TNFR) family. Agonist antibodies to these co-stimulatory molecules target both T and B cells, modulating T-cell activation and enhancing immune responses.

Combination of alphavirus replicon particle-based vaccination with immunomodulatory antibodies: therapeutic activity in the B16 melanoma mouse model and immune correlates.

Induction of potent immune responses to self-antigens remains a major challenge in tumor immunology. We have shown that a vaccine based on alphavirus replicon particles (VRP) activates strong cellular and humoral immunity to tyrosinase-related protein-2 (TRP2) melanoma antigen, providing prophylactic and therapeutic effects in stringent mouse models. Here, we report that the immunogenicity and efficacy of this vaccine is increased in combination with either antagonist anti-CTL antigen-4 (CTLA-4) or agonist anti-glucocorticoid-induced TNF family-related gene (GITR) immunomodulatory monoclonal antibodies (mAb).

Enhancement of tumor-reactive cytotoxic CD4+ T cell responses after ipilimumab treatment in four advanced melanoma patients.

CD4(+) T cells provide help to enhance and sustain cytotoxic CD8(+) T cell responses. A direct lytic role for this cell population in mouse models further supports the use of tumor-reactive CD4(+) T cells for cancer immunotherapy. CTLA-4 blockade has been shown to expand antigen-specific cytotoxic CD4(+) T cells in mouse models.

Agonist antibodies to TNFR molecules that costimulate T and NK cells.

Therapy for cancer can be achieved by artificially stimulating antitumor T and natural killer (NK) lymphocytes with agonist monoclonal antibodies (mAb). T and NK cells express several members of the TNF receptor (TNFR) family specialized in delivering a costimulatory signal on their surface. Engagement of these receptors is typically associated with proliferation, elevated effector functions, resistance to apoptosis, and differentiation into memory cells.

Induction of tumoricidal function in CD4+ T cells is associated with concomitant memory and terminally differentiated phenotype.

Harnessing the adaptive immune response to treat malignancy is now a clinical reality. Several strategies are used to treat melanoma; however, very few result in a complete response. CD4(+) T cells are important and potent mediators of anti-tumor immunity and adoptive transfer of specific CD4(+) T cells can promote tumor regression in mice and patients.

Monocytic CCR2(+) myeloid-derived suppressor cells promote immune escape by limiting activated CD8 T-cell infiltration into the tumor microenvironment.

Myeloid-derived suppressor cells (MDSC) are a heterogeneous population of cells that accumulate during tumor formation, facilitate immune escape, and enable tumor progression. MDSCs are important contributors to the development of an immunosuppressive tumor microenvironment that blocks the action of cytotoxic antitumor T effector cells. Heterogeneity in these cells poses a significant barrier to studying the in vivo contributions of individual MDSC subtypes.

Alphavirus replicon particles expressing TRP-2 provide potent therapeutic effect on melanoma through activation of humoral and cellular immunity.

Background: Malignant melanoma is the deadliest form of skin cancer and is refractory to conventional chemotherapy and radiotherapy. Therefore alternative approaches to treat this disease, such as immunotherapy, are needed. Melanoma vaccine design has mainly focused on targeting CD8+ T cells.

Cytokine-FC fusion genes as molecular adjuvants for DNA vaccines.

The use of gene constructs for DNA immunization offers several potential advantages over other commonly used vaccine approaches: (1) full-length cDNA provides multiple potential class I and class II epitopes, thus bypassing limitations of MHC restriction; (2) bacterial plasmid DNA contains immunogenic unmethylated CpG motifs (immunostimulatory sequences) that may act as a potent immunological adjuvant; and (3) DNA is relatively simple to purify in large quantities. The cDNA encoding the antigen of interest is cloned into a bacterial expression plasmid with a constitutively active promoter and this plasmid is injected into the skin or muscle where it is taken up by professional antigen-presenting cells, particularly dendritic cells, either through direct transfection or cross-priming. One can further enhance or modulate the immune response through co-delivery of DNA encoding cytokines or chemokines, including cytokine-Fc fusion molecules.

Cyclophosphamide enhances immunity by modulating the balance of dendritic cell subsets in lymphoid organs.

Cyclophosphamide (CTX), a commonly used chemotherapeutic agent can enhance immune responses. The ability of CTX to promote the proliferation of effector T cells and abrogate the function of regulatory T cells (Tregs) has been described. In this study, we examined the effects of CTX treatment on dendritic cell (DC) subsets and the subsequent outcome on the effector and suppressive arms of adaptive immunity.

The cytolytic molecules Fas ligand and TRAIL are required for murine thymic graft-versus-host disease.

Thymic graft-versus-host disease (tGVHD) can contribute to profound T cell deficiency and repertoire restriction after allogeneic BM transplantation (allo-BMT). However, the cellular mechanisms of tGVHD and interactions between donor alloreactive T cells and thymic tissues remain poorly defined. Using clinically relevant murine allo-BMT models, we show here that even minimal numbers of donor alloreactive T cells, which caused mild nonlethal systemic graft-versus-host disease, were sufficient to damage the thymus, delay T lineage reconstitution, and compromise donor peripheral T cell function.

Cutting Edge: OX40 agonists can drive regulatory T cell expansion if the cytokine milieu is right.

We report that OX40 stimulation drives all lineages of CD4 T cell development, including regulatory T cells (Tregs), and the plasticity of the response is dependant on local cytokines. In TGF-beta1-treated cultures, an OX40 agonist increased IFN-gamma and IL-4 production and diverted T cells from the Treg lineage. However, cytokine blockade in the context of OX40 stimulation promoted enhanced Treg accumulation.

OX40 engagement and chemotherapy combination provides potent antitumor immunity with concomitant regulatory T cell apoptosis.

Expansion and recruitment of CD4(+) Foxp3(+) regulatory T (T reg) cells are mechanisms used by growing tumors to evade immune elimination. In addition to expansion of effector T cells, successful therapeutic interventions may require reduction of T reg cells within the tumor microenvironment. We report that the combined use of the alkylating agent cyclophosphamide (CTX) and an agonist antibody targeting the co-stimulatory receptor OX40 (OX86) provides potent antitumor immunity capable of regressing established, poorly immunogenic B16 melanoma tumors.

Self-antigen-specific CD8+ T cell precursor frequency determines the quality of the antitumor immune response.

A primary goal of cancer immunotherapy is to improve the naturally occurring, but weak, immune response to tumors. Ineffective responses to cancer vaccines may be caused, in part, by low numbers of self-reactive lymphocytes surviving negative selection. Here, we estimated the frequency of CD8(+) T cells recognizing a self-antigen to be <0.

Adjuvanticity of plasmid DNA encoding cytokines fused to immunoglobulin Fc domains.

Purpose: Plasmid DNAs encoding cytokines enhance immune responses to vaccination in models of infectious diseases and cancer. We compared DNA adjuvants for their ability to enhance immunity against a poorly immunogenic self-antigen expressed by cancer.

Experimental Design: DNAs encoding cytokines that affect T cells [interleukin (IL)-2, IL-12, IL-15, IL-18, IL-21, and the chemokine CCL21] and antigen-presenting cells [granulocyte macrophage colony-stimulating factor (GM-CSF)] were compared in mouse models as adjuvants to enhance CD8+ T-cell responses and tumor immunity.

Glucocorticoid-induced TNF receptor family related gene activation overcomes tolerance/ignorance to melanoma differentiation antigens and enhances antitumor immunity.

Glucocorticoid-induced TNF receptor family related protein (GITR) is present on many different cell types. Previous studies have shown that in vivo administration of an anti-GITR agonist mAb (DTA-1) inhibits regulatory T cells (Treg)-dependent suppression and enhances T cell responses. In this study, we show that administration of DTA-1 induces >85% tumor rejection in mice challenged with B16 melanoma.