Substantially modified ratios of effector to regulatory T cells during chemotherapy in ovarian cancer patients return to pre-treatment levels at completion: implications for immunotherapy

The potential of regulatory T cell-based therapies for alopecia areata

Cytotoxic T lymphocyte has been a concern for the etiopathogenesis of alopecia areata (AA), some recent evidence suggests that the regulatory T (T_reg) cell deficiency is also a contributing factor. In the lesional scalp of AA, T_reg cells residing in the follicles are impaired, leading to dysregulated local immunity and hair follicle (HF) regeneration disorders. New strategies are emerging to modulate T_reg cells' number and function for autoimmune diseases. There is much interest to boost T_reg cells in AA patients to suppress the abnormal autoimmunity of HF and stimulate hair regeneration. With few satisfactory therapeutic regimens available for AA, T_reg cell-based therapies could be the way forward. Specifically, CAR-T_reg cells and novel formulations of low-dose IL-2 are the alternatives.

Conditioning treatment with CD27 Ab enhances expansion and antitumor activity of adoptively transferred T cells in mice

Cyclophosphamide plus fludarabine (C/F) are currently used to improve the expansion and effectiveness of adoptive cell therapy (ACT). However, these chemotherapeutics cause pan-leukopenia and adverse events, suggesting that safer and more effective conditioning treatments are needed to improve ACT outcomes. Previously, we reported that varlilumab, a CD27-targeting antibody, mediates T_reg -preferential T cell depletion, CD8-T cell dominant costimulation, and systemic immune activation in hCD27 transgenic mice and cancer patients. We reasoned that the activities induced by varlilumab may provide an effective conditioning regimen for ACT. Varlilumab pretreatment of hCD27^+/+mCD27 ^{− /−} mice resulted in prominent proliferation of transferred T cells isolated from wild-type mice. These studies uncovered a critical role for CD27 signaling for the expansion of transferred T cells, as transfer of T cells from CD27 deficient mice or treatment with a CD70 blocking antibody greatly reduced their proliferation. In this model, varlilumab depletes endogenous hCD27^+/+ T cells and blocks their subsequent access to CD70, allowing for more CD70 costimulation available to the mCD27^+/+ transferred T cells. CD27-targeted depletion led to a greater expansion of transferred T cells compared to C/F conditioning and resulted in longer median survival and more cures than C/F conditioning in the E.G7 tumor model receiving OT-I cell therapy. We propose that translation of this work could be achieved through engineering of T cells for ACT to abrogate varlilumab binding but preserve CD70 ligation. Thus, varlilumab could be an option to chemotherapy as a conditioning regimen for ACT.

Fluctuation theory of immune response: A statistical mechanical approach to understand pathogen induced T-cell population dynamics

In this period of intense interest in human immunity, we attempt here to quantify the immune response against pathogen invasion through T-cell population dynamics. Borrowing concepts from equilibrium statistical mechanics, we introduce a new description of the immune response function (IMRF) in terms of fluctuations in the population number of relevant biological cells (effector and regulatory T-cells). We use a coarse-grained chemical reaction network model (CG-CRNM) to calculate the number fluctuations and show that the response function derived as such can, indeed, capture the crossover observed in a T-cell driven immune response. We employ the network model to learn the effect of vitamin-D as an immunomodulator. We solve our CG-CRNM using a stochastic Gillespie algorithm. Depending on the effector T-cell concentration, we can classify immune regulation regimes into three categories: weak, strong, and moderate. The IMRF is found to behave differently in these three regimes. A damped cross-regulatory behavior found in the dynamics of effector and regulatory T-cell concentration in the diseased states correlates well with the same found in a cohort of patients with specific malignancies and autoimmune diseases. Importantly, the crossover from the weakly regulated steady state to the other (the strongly regulated) is accompanied by a divergence-like growth in the fluctuation of both the effector and the regulatory T-cell concentration, characteristic of a dynamic phase transition. We believe such steady-state IMRF analyses could help not only to phase-separate different immune stages but also aid in the valuable connection between autoimmunity, optimal vitamin-D, and consequences of immunosuppressive stress and malignancy.

The effect of everolimus and low-dose cyclophosphamide on immune cell subsets in patients with metastatic renal cell carcinoma: results from a phase I clinical trial

For the treatment of metastatic renal cell cancer several strategies are used among which the mTOR inhibitor everolimus. As mTOR plays an important role in the immune system, e.g., by controlling the expression of the transcription factor FoxP3 thereby regulating regulatory T cells (Tregs), it plays a key role in the balance between tolerance and inflammation. Previous reports showed stimulatory effects of mTOR inhibition on the expansion of Tregs, an effect that can be considered detrimental in terms of cancer control. Since metronomic cyclophosphamide (CTX) was shown to selectively deplete Tregs, a phase 1 clinical trial was conducted to comprehensively investigate the immune-modulating effects of several dosages and schedules of CTX in combination with the standard dose of everolimus, with the explicit aim to achieve selective Treg depletion. Our data show that 50 mg of CTX once daily and continuously administered, in combination with the standard dose of 10 mg everolimus once daily, not only results in depletion of Tregs, but also leads to a reduction in MDSC, a sustained level of the CD8⁺ T-cell population accompanied by an increased effector to suppressor ratio, and reversal of negative effects on three peripheral blood DC subsets. These positive effects on the immune response may contribute to improved survival, and therefore this combination therapy is further evaluated in a phase II clinical trial.

Sperm Protein 17 Expression by Murine Epithelial Ovarian Cancer Cells and Its Impact on Tumor Progression

The cancer testis antigen sperm protein 17 (Sp17) is a promising antigenic target in epithelial ovarian cancer (EOC) vaccine development. However, its role in ovarian cancer is unclear. We isolated and expanded Sp17⁺ and Sp17⁻ clones from the murine EOC cell line ID8, and compared their in-vitro cell growth characteristics and in-vivo tumorigenicity. We also examined the potential co-expression of molecules that may influence cancer cell survival and interaction with immune cells. These include stimulatory and immunosuppressive molecules, such as major histocompatibility class I molecules (MHC I), MHC II, cytotoxic T lymphocyte associated antigen-4 (CTLA-4), CD73, CD39, tumor necrosis factor receptor II (TNFRII), signal transducer and activator of transcription 3 (STAT3) and programmed death-ligand 1 (PD-L1). Whilst the presence of Sp17 was not correlated with the ID8 cell proliferation/growth capacity in vitro, it was critical to enable progressive tumor formation in vivo. Flow cytometry revealed that Sp17⁺ ID8 cells displayed higher expression of both STAT3 and PD-L1, whilst MHC II expression was lower. Moreover, Sp17^high (PD-L1⁺MHCII⁻) cell populations showed significantly enhanced resistance to Paclitaxel-induced cell death in vitro compared to Sp17^low (PD-L1⁻MHCII⁺) cells, which was associated in turn with increased STAT3 expression. Together, the data support Sp17 as a factor associated with in-vivo tumor progression and chemo-resistance, validating it as a suitable target for vaccine development.

Remarkable response of nivolumab-refractory lung cancer to salvage chemotherapy

Promising outcomes of salvage chemotherapy after nivolumab therapy have been reported; however, little is known about the detailed clinical and immunologic features in lung cancer patients in whom nivolumab is unsuccessful. We report two cases of nivolumab‐refractory lung cancer, in which chemotherapy resulted in rapid regression of the lung cancer. Upon initial diagnosis, the biopsy specimens showed PD‐ligand 1 (PD‐L1)‐expressing cancer cells, accompanied by tumor‐infiltrating lymphocytes with a favorable CD8/CD4 ratio. Immunosuppressive regulatory T cells and cells positive for TIM‐3 were also observed. Physicians should take caution in treating lung cancer patients after progression on nivolumab. Further studies with a large cohort are warranted to identify the patients that may benefit from salvage chemotherapy.

A flowcytometric analysis to efficiently quantify multiple innate immune cells and T Cell subsets in human blood

The balance of inflammation and immunosuppression driven by changed ratios in diverse myeloid and T cell subsets, as well as their state of activation and ability to migrate to lymphoid compartments or inflammatory sites, has emerged as a highly active area of study across clinical trials of vaccines and therapies against cancer, trauma, as well as autoimmune and infectious diseases. There is a need for effective protocols which maximally use the possibilities offered by modern flow cytometers to characterize such immune cell changes in peripheral blood using small volumes of human blood. Additionally, longitudinal clinical studies often use cryopreserved samples, which can impact flow cytometric results. To efficiently gauge both the innate and the adaptive immune response, two novel 15-color antibody panels to identify key myeloid and T cell subsets and their functional potential were established. This approach was used to compare cellular immune profiles in fresh whole blood and in matched cryopreserved peripheral blood mononuclear cells (PBMCs). Cocktail I was designed to identify and characterize myeloid cell populations including dendritic cells (DCs), monocytic monocyte-derived suppressor cells (MO-MDSC), and monocytes, determining further core aspects of their state of maturity, T cell stimulatory (or inhibitory) potential, and migration capability. Cocktail II was used for phenotyping diverse T cells subsets, and their key migration and functional regulatory capabilities. The two 15-color antibody panels for the evaluation of both immune-stimulating and immunosuppressive processes presented herein allowed for efficient evaluation of the balance of immune activation versus immunosuppression across key blood cells, with good resolution for all 15 markers stained for in each panel. Gating strategies for the myeloid and T cells are presented to further support specific subset identification. This protocol was shown to be reproducible across donors and useful to study both RBC-lysed whole blood and cryopreserved PBMCs. © 2017 International Society for Advancement of Cytometry.

Minireview: Regulatory T Cells and Ovarian Cancer

In the last 15 years, it has become apparent that ovarian cancer is recognized by the immune system, taking into account that T cell infiltration can be associated with increased overall survival. Several studies indicate that a correct combination of cluster of differentiation 8 and cluster of differentiation 4 T cells is key to fight tumor progression and that the presence of regulatory T cells (Tregs) infiltrating ovarian solid tumors (or present in ascites) is deleterious. Several markers that characterize Tregs include glucocorticoid-induced tumor necrosis factor receptor, cytotoxic T lymphocyte antigen-4, and forkhead box protein 3 (Foxp3). Research has shown that Tregs can infiltrate cancerous tissue and contribute to tumor growth by secreting immunosuppressive cytokines such as transforming growth factor beta and interleukin (IL)-10. Importantly, these cells might hamper the efficacy of immunotherapeutic approaches, thus strategies involving depletion or regulation of this population have been proposed and tested in experimental models. In this Minireview, we will discuss the relevance of Tregs in ovarian cancer and the experimental approaches destined to impair their immunosuppressive effects.

Dynamic changes in immune cell profile in head and neck squamous cell carcinoma: Immunomodulatory effects of chemotherapy

Tumor cells have evolved sophisticated means of escape from the host immune system. To date, several important immunological phenomena have been revealed in peripheral blood as well as within tumors. In the present study, we first investigated the proportion and activation status of peripheral immune regulatory cells and CD8(+) T-cell subsets in patients with head and neck squamous cell carcinoma (HNSCC) using a multicolor flow cytometer, and then evaluated how therapy with docetaxel, cisplatin, and 5-fluorouracil modulated the immune cell profile in peripheral blood. The proportion of naïve T cells was lower and that of effector memory T cells (TEM ) was higher in HNSCC patients than in healthy donors. Moreover, the proportions of activated TEM cells and effector T cells (TEFF ) were dramatically increased in patients with advanced stage disease. The proportion of regulatory T cells and CD14(+) HLA-DR(-) myeloid-derived suppressor cells was elevated in HNSCC patients. Of note, after therapy, in addition to the transient reduction in immune regulatory cells, decreases in central memory T cells and increases in TEFF cells were observed among CD8(+) T-cell subsets, suggesting differentiation from central memory T cells into TEFF cells. Our results suggested that, despite the immunosuppressive status in HNSCC patients, tumor-specific immune responses mediated by CD8(+) T cells might be induced and maintained. Moreover, chemotherapy can trigger not only a transient reduction in immune regulatory cells but also further activation of CD8(+) T cells.

Functional Mechanisms of Treg in the Context of HIV Infection and the Janus Face of Immune Suppression

Regulatory T cells (Tregs) play an important role in infections, by modulating host immune responses and avoiding the overreactive immunity that in the case of human immunodeficiency virus (HIV) infection leads to a marked erosion and deregulation of the entire immune system. Therefore, the suppressive function of Treg in HIV-infected patients is critical because of their implication on preventing the immune hyperactivation, even though it could also have a detrimental effect by suppressing HIV-specific immune responses. In recent years, several studies have shown that HIV-1 can directly infect Treg, disturbing their phenotype and suppressive capacity via different mechanisms. These effects include Foxp3 and CD25 downregulation, and the impairment of suppressive capacity. This review describes the functional mechanisms of Treg to modulate immune activation during HIV infection, and how such control is no longer fine-tune orchestrated once Treg itself get infected. We will review the current knowledge about the HIV effects on the Treg cytokine expression, on pathways implying the participation of different ectoenzymes (i.e., CD39/CD73 axis), transcription factors (ICER), and lastly on cyclic adenosine monophosphate (cAMP), one of the keystones in Treg-suppressive function. To define which are the HIV effects upon these regulatory mechanisms is crucial not only for the comprehension of immune deregulation in HIV-infected patients but also for the correct understanding of the role of Tregs in HIV infection.