Phenotype and homing of CD4 tumor-specific T cells is modulated by tumor bulk

Immune phenotyping of diverse syngeneic murine brain tumors identifies immunologically distinct types

Immunotherapy has emerged as a promising approach to treat cancer, however, its efficacy in highly malignant brain-tumors, glioblastomas (GBM), is limited. Here, we generate distinct imageable syngeneic mouse GBM-tumor models and utilize RNA-sequencing, CyTOF and correlative immunohistochemistry to assess immune-profiles in these models. We identify immunologically-inert and -active syngeneic-tumor types and show that inert tumors have an immune-suppressive phenotype with numerous exhausted CD8 T cells and resident macrophages; fewer eosinophils and SiglecF+ macrophages. To mimic the clinical-settings of first line of GBM-treatment, we show that tumor-resection invigorates an anti-tumor response via increasing T cells, activated microglia and SiglecF+ macrophages and decreasing resident macrophages. A comparative CyTOF analysis of resected-tumor samples from GBM-patients and mouse GBM-tumors show stark similarities in one of the mouse GBM-tumors tested. These findings guide informed choices for use of GBM models for immunotherapeutic interventions and offer a potential to facilitate immune-therapies in GBM patients.

Syngeneic mouse models for glioblastoma (GBM) cannot fully recapitulate clinical findings and response to therapy in patients. Here the authors perform a comprehensive immune profiling of different syngeneic GBM tumour models and compare it with the immune landscape of GBM patients to identify similarities and potential confounding differences.

Bioprofiling TS/A Murine Mammary Cancer for a Functional Precision Experimental Model

The TS/A cell line was established in 1983 from a spontaneous mammary tumor arisen in an inbred BALB/c female mouse. Its features (heterogeneity, low immunogenicity and metastatic ability) rendered the TS/A cell line suitable as a preclinical model for studies on tumor-host interactions and for gene therapy approaches. The integrated biological profile of TS/A resulting from the review of the literature could be a path towards the description of a precision experimental model of mammary cancer.

Osthole promotes anti-tumor immune responses in tumor-bearing mice with hepatocellular carcinoma

Osthole, a natural coumarin derivative, has been shown to have anti-tumor and anti-inflammatory activity. However, the effect of osthole on anti-tumor immune responses in tumor-bearing mice has not yet been reported. In the present study, osthole treatment did not affect the weight and the coefficient of thymus and spleen in tumor-bearing mice with hepatocellular carcinoma (HCC). However, osthole administration significantly elevated the proportion and number of the splenic CD8(+) T cells, the proportion of CD4(+) T and CD8(+) T cells in tumor tissues, and the levels of IL-2 and TNF-α in the serum of HCC tumor-bearing mice. Our results suggested that osthole could promote the activation of the tumor-infiltrating CD4(+) T and CD8(+) T cells, and elevate the proportion of CD4(+) and CD8(+) effector T cells. Osthole treatment also significantly decreased the proportion of CD4(+)CD25(+)Foxp3(+) regulatory T cells in the spleen. Taken together, osthole could enhance the T cell mediated anti-tumor immune responses in the tumor-bearing mice with HCC.

Loss of antigen cross-presentation after complete tumor resection is associated with the generation of protective tumor-specific CD8(+) T-cell immunity

An incomplete understanding on the effect of surgery on tumor-specific immunity continues to hamper efforts to combine surgery with immunotherapy in the clinic. Herein, we describe the impact of tumor resection on the tumor-specific T-cell response, showing that complete tumor resection is associated with (1) a decline in the amount of cross-presented tumor antigens, (2) a decline of cytolytic tumor-specific CD8(+) T cell activity, and (3) the development of systemic CD8(+) T cell-mediated protective immunity. Our findings are consistent with a model whereby tumor resection releases antitumor CD8(+) T cells from chronic antigen exposure, allowing a gradual differentiation toward functional antitumor memory T cells. This process depends on sentinel lymph nodes, as their removal at the time of surgery was associated with a strong negative effect on survival. We conclude that complete tumor resection provides a unique environment that boosts protective immunological memory and might provide a powerful platform for immunotherapy. Our findings also carry important implications for the design and timing of post-surgery immunotherapeutic regimens.

Reduced functional avidity promotes central and effector memory CD4 T cell responses to tumor-associated antigens

The effect of TCR signals on the differentiation of memory T cells is poorly defined. Conventional wisdom suggests that high-avidity interactions are best for the selection of vaccine Ag candidates or T cell specificities for adoptive T cell therapy to stimulate robust responses. However, in conditions of Ag persistence, high-avidity clones might exhaust and fail to form long-lived protective memory. We have manipulated the functional avidity of CD4 T cells by reducing expression of Lck, a key kinase involved in TCR triggering. Using a mouse model, we followed tetramer-positive T cells responding to a tumor Ag expressed by an adenocarcinoma. We show that reducing the functional avidity increased effector-effector memory responses and improved the generation of self-renewing, recirculating, tumor Ag-specific memory phenotype CD4 T cells. Moreover, such cells together with wild type CD8 T cells were better able to control tumor growth. Mechanistically, reducing Lck prolonged IL-2 production and cell turnover in the central memory population while reducing expression of exhaustion markers in the face of chronic Ag. Our data indicate that, in situations of persistent Ag challenge, generating T cells with reduced functional avidity may elicit more effective immune responses.

Redirecting the immune response: role of adoptive T cell therapy

Adoptive T cell therapy is aimed at overcoming constraints of the endogenous immune response. In patients with malignancies, this approach is based on the possibility of administering sufficient numbers of tumor-reactive lymphocytes under conditions in which they will promote a therapeutic response. Although this strategy is potentially applicable to a vast number of malignancies, its efficacy, to date, has been limited. This is likely related to several factors including an insufficient persistence and reactivation of infused cells, insufficient tumor infiltration, and the presence of an immunosuppressive environment. Here, we review the importance of pretransplantation host conditioning and posttransplantation strategies that have been shown to contribute to the therapeutic efficacy of infused T lymphocytes.

Antigen-experienced CD4(+) T cells limit naïve T-cell priming in response to therapeutic vaccination in vivo

CD4(+) T cells play a central role in protective immunity. In a mouse tumor model, we previously found that tumor growth elicits natural CD4(+) T-cell responses, but impedes therapeutic vaccination. We show here that inhibition of vaccine-mediated naïve T-cell priming is due to the presence of a minor but distinct population of tumor-reactive CD4(+) T cells. These cells are generated in the tumor draining lymph nodes (LN), are capable of systemic redistribution, and act to limit the representation of antigen-bearing MHC II(+) antigen-presenting cells (APC) in contralateral LNs or when transferred to tumor-free mice. Surgical tumor resection, which lowers the representation of tumor primed CD4(+) T cells, restored to some extent vaccine-induced CD4(+) T-cell activation. Likewise, vaccination with artificial APCs (latex beads) or higher numbers of dendritic cells allowed comparable CD4(+) T-cell priming in tumor-free and tumor-bearing mice. Together, our results emphasize the ability of antigen-experienced CD4(+) T lymphocytes to interfere with therapeutic vaccination and highlight the need for alternative strategies able to surmount limitations imposed by ongoing immune responses.

IL-7 is superior to IL-2 for ex vivo expansion of tumour-specific CD4(+) T cells

It is well established that tumours hinder both natural and vaccine-induced tumour-specific CD4(+) T-cell responses. Adoptive T-cell therapy has the potential to circumvent functional tolerance and enhance anti-tumour protective responses. While protocols suitable for the expansion of cytotoxic CD8(+) T cells are currently available, data on tumour-specific CD4(+) T cells remain scarce. We report here that CD4(+) T cells sensitized to tumour-associated Ag in vivo, proliferate in vitro in response to IL-7 without the need for exogenous Ag stimulation and accumulate several folds while preserving a memory-like phenotype. Both cell proliferation and survival accounts for the outgrowth of tumour-sensitized T cells among other memory and naive lymphocytes following exposure to IL-7. Also IL-2, previously used to expand anti-tumour CTL, promotes tumour-specific CD4(+) T-cell accumulation. However, IL-7 is superior to IL-2 at preserving lymphocyte viability, in vitro and in vivo, maintaining those properties, that are required by helper CD4(+) T cells to confer therapeutic efficacy upon transplantation in tumour-bearing hosts. Together our data support a unique role for IL-7 in retrieving memory-like CD4(+) T cells suitable for adoptive T-cell therapy.

Antitumor IgE adjuvanticity: key role of Fc epsilon RI

Working with C57BL/6 mouse tumor models, we had previously demonstrated that vaccination with IgE-coated tumor cells can protect against tumor challenge, an observation that supports the involvement of IgE in antitumor immunity. The adjuvant effect of IgE was shown to result from eosinophil-dependent priming of the T cell-mediated adaptive immune response. The protective effect is likely to be mediated by the interaction of tumor cell-bound IgE with receptors, which then trigger the release of mediators, recruitment of effector cells, cell killing and tumor Ag cross-priming. It was therefore of utmost importance to demonstrate the strict dependence of the protective effect on IgE receptor activation. First, the protective effect of IgE was confirmed in a BALB/c tumor model, in which IgE-loaded modified VV Ankara-infected tumor cells proved to be an effective cellular vaccine. However, the protective effect was lost in Fc(epsilon)RIalpha(-/-) (but not in CD23(-/-)) knockout mice, showing the IgE-Fc(epsilo)nRI interaction to be essential. Moreover, human IgE (not effective in BALB/c mice) had a protective effect in the humanized knockin mouse (Fc(epsilon)RIalpha(-/-) hFc(epsilon)RIalpha(+)). This finding suggests that the adjuvant effect of IgE could be exploited for human therapeutics.

T-cell receptor proximal signaling via the Src-family kinases, Lck and Fyn, influences T-cell activation, differentiation, and tolerance

T-cell development in the thymus and activation of mature T cells in secondary lymphoid organs requires the ability of cells to respond appropriately to environmental signals at multiple stages of their development. The process of thymocyte selection insures a functional T-cell repertoire, while activation of naive peripheral T cells induces proliferation, gain of effector function, and, ultimately, long-lived T-cell memory. The T-cell immune response is initiated upon engagement of the T-cell receptor (TCR) and coreceptor, CD4 or CD8, by cognate antigen/major histocompatibility complexes presented by antigen-presenting cells. TCR/coreceptor engagement induces the activation of biochemical signaling pathways that, in combination with signals from costimulator molecules and cytokine receptors, direct the outcome of the response. Activation of the src-family kinases p56(lck) (Lck) and p59(fyn) (Fyn) is central to the initiation of TCR signaling pathways. This review focuses on our current understanding of the mechanisms by which these two proteins orchestrate T-cell function.

Administration of rhIL-7 in humans increases in vivo TCR repertoire diversity by preferential expansion of naive T cell subsets

Interleukin-7 (IL-7) is a homeostatic cytokine for resting T cells with increasing serum and tissue levels during T cell depletion. In preclinical studies, IL-7 therapy exerts marked stimulating effects on T cell immune reconstitution in mice and primates. First-in-human clinical studies of recombinant human IL-7 (rhIL-7) provided the opportunity to investigate the effects of IL-7 therapy on lymphocytes in vivo. rhIL-7 induced in vivo T cell cycling, bcl-2 up-regulation, and a sustained increase in peripheral blood CD4⁺ and CD8⁺ T cells. This T cell expansion caused a significant broadening of circulating T cell receptor (TCR) repertoire diversity independent of the subjects' age as naive T cells, including recent thymic emigrants (RTEs), expanded preferentially, whereas the proportions of regulatory T (T reg) cells and senescent CD8⁺ effectors diminished. The resulting composition of the circulating T cell pool more closely resembled that seen earlier in life. This profile, distinctive among cytokines under clinical development, suggests that rhIL-7 therapy could enhance and broaden immune responses, particularly in individuals with limited naive T cells and diminished TCR repertoire diversity, as occurs after physiological (age), pathological (human immunodeficiency virus), or iatrogenic (chemotherapy) lymphocyte depletion.

Synthetic CD4+ T cell-targeted antigen-presenting cells elicit protective antitumor responses

CD4(+) helper T cells are critical for protective immune responses and yet suboptimally primed in response to tumors. Cell-based vaccination strategies are under evaluation in clinical trials but limited by the need to derive antigen-presenting cells (APC) from patients or compatible healthy donors. To overcome these limitations, we developed CD4(+) T cell-targeted synthetic microbead-based artificial APC (aAPC) and used them to activate CD4(+) T lymphocytes specific for a tumor-associated model antigen (Ag) directly from the naive repertoire. In vitro, aAPC specifically primed Ag-specific CD4(+) T cells that were activated to express high levels of CD44, produced mainly interleukin 2, and could differentiate into Th1-like or Th2-like cells in combination with polarizing cytokines. I.v. administration of aAPC led to Ag-specific CD4(+) T-cell activation and proliferation in secondary lymphoid organs, conferred partial protection against subcutaneous tumors, and prevented the establishment of lung metastasis. Taken together, our data support the use of cell-free, synthetic aAPC as a specific and versatile alternative to expand peptide-specific CD4(+) T cells in adoptive and active immunotherapy.

Tumors Hamper the Immunogenic Competence of CD4+T Cell-Directed Dendritic Cell Vaccination

Dendritic cells loaded with tumor-derived peptides induce protective CTL responses and are under evaluation in clinical trails. We report in this study that prophylactic administration of dendritic cells loaded with a MHC class II-restricted peptide derived from a model tumor Ag (Leishmania receptor for activated C kinase (LACK)) confers protection against LACK-expressing TS/A tumors, whereas therapeutic vaccination fails to cure tumor-bearing mice. Although CD4+ T cell-directed dendritic cell vaccination primed effector-like (CD44(high)CD62L(low), IL-2(+), IFN-gamma(+)) and central memory-like lymphocytes (CD44(high)CD62L(high), only IL-2(+)) in tumor-free mice, this was not the case in tumor-bearing animals in which both priming and persistence of CD4+ T cell memory were suppressed. Suppression was specific for the tumor-associated Ag LACK, and did not depend on CD25+ T cells. Because T cell help is needed for protective immunity, we speculate that the ability of tumors to limit vaccine-induced CD4+ T cell memory could provide a partial explanation for the limited efficacy of current strategies.

Memories are made of this: synergy of T cell receptor and cytokine signals in CD4(+) central memory cell survival

The ability of the immune system to 'remember' a previous encounter with antigen is the hallmark of the adaptive immune response. The signals required for CD4(+) memory T cell survival are not well understood, and a recent paper lends new biochemical insights into how memory T cells might optimally be preserved through the convergence of signals from the engagement of cytokine and antigen-specific T cell receptors.

Dendritic cell targeting of survivin protein in a xenogeneic form elicits strong CD4+ T cell immunity to mouse survivin

To determine whether strong CD4+ T cell immunity could be induced to a nonmutated self protein that is important for tumorigenesis, we selectively targeted the xenogeneic form of survivin, a survival protein overexpressed in tumors, to maturing dendritic cells in lymphoid tissues. Dendritic cell targeting via the DEC205 receptor in the presence of anti-CD40 and poly(I:C) as maturation stimuli, induced strong human and mouse survivin-specific CD4+ T cell responses, as determined by IFN-gamma, TNF-alpha, and IL-2 production, as well as the development of lytic MHC class II-restricted T cells and memory. Immunity was enhanced further by depletion of CD25+foxp3+ cells before vaccination. anti-DEC205-human survivin was superior in inducing CD4+ T cell responses relative to other approaches involving survivin plasmid DNA or survivin peptides with adjuvants. However, we were unable to induce CD8+ T cell immunity to survivin by two doses of DEC205-targeted survivin or the other strategies. Therefore, significant CD4+ T cell immunity to a self protein that is overexpressed in most human cancers can be induced by DEC205 targeting of the Ag in its xenogeneic form to maturing DCs.

Changes in paracrine interleukin-2 requirement, CCR7 expression, frequency, and cytokine secretion of human immunodeficiency virus-specific CD4+ T cells are a consequence of antigen load

Virus-specific CD4+ T-cell responses are thought to be required for the induction and maintenance of many effective CD8+ T-cell and B-cell immune responses in experimental animals and humans. Although the presence of human immunodeficiency virus (HIV)-specific CD4+ T cells has been documented in patients at all stages of HIV infection, many fundamental questions regarding their frequency and function remain. A 10-color, 12-parameter flow cytometric panel was utilized to examine the frequency, memory phenotype (CD27, CCR7, and CD45RA), and cytokine production (interleukin-2 [IL-2], gamma interferon, and tumor necrosis factor alpha) of CD4+ T cells specific for HIV antigens as well as for adenovirus, Epstein-Barr virus (EBV), influenza H1N1 virus, influenza H3N2 virus, cytomegalovirus, varicella-zoster virus (VZV), and tetanus toxoid in normal controls, long-term nonprogressors (LTNP), and HIV-infected patients with progressive disease on or off therapy. The HIV-specific CD4+ T-cell responses in LTNP and patients on therapy were similar in frequency, phenotype, and cytokine production to responses directed against adenovirus, EBV, influenza virus, and VZV. HIV-specific CD4+ T cells from patients off antiretroviral therapy demonstrated a shift towards a CCR7(-) CD45RA(-) phenotype and a reduced percentage of IL-2-producing cells. The alterations in cytokine production during HIV viremia were found to be intrinsic to the HIV-specific CD4+ T cells and caused a requirement for IL-2 supplied exogenously for proliferation to occur. These observations suggest that many previously described changes in HIV-specific CD4+ T-cell function and phenotype are a consequence of high levels of antigen in viremic patients. In addition, defects in function and phenotype of HIV-specific CD4+ T cells are not readily discernible in the context of antiretroviral therapy but rather are similar to responses to other viruses.