On the Other Side: Manipulating the Immune Checkpoint Landscape of Dendritic Cells to Enhance Cancer Immunotherapy

Monoclonal antibodies targeting co-inhibitory immune checkpoint molecules have been successful in clinical trials of both solid and hematological malignancies as acknowledged by the 2018 Nobel Prize in Medicine, however improving clinical response rates is now key to expanding their efficacy in areas of unmet medical need. Antibodies to checkpoint inhibitors target molecules on either T cells or tumor cells to stimulate T cells or remove tumor mediated immunosuppression, respectively. However, many of the well-characterized T cell immune checkpoint receptors have their ligands on antigen presenting cells or exert direct effects on those cells. Dendritic cells are the most powerful antigen presenting cells; they possess the ability to elicit antigen-specific responses and have important roles in regulation of immune tolerance. Despite their theoretical benefits in cancer immunotherapy, the translation of DC therapies into the clinic is yet to be fully realized and combining DC-based immunotherapy with immune checkpoint inhibitors is an attractive strategy. This combination takes advantage of the antigen presenting capability of DC to maximize specific immune responses to tumor antigens whilst removing tumor-associated immune inhibitory mechanisms with immune checkpoint inhibition. Here we review the expression and functional effects of immune checkpoint molecules on DC and identify rational combinations for DC vaccination to enhance antigen-specific T cell responses, cytokine production, and promotion of long-lasting immunological memory

Obesity and the Risk of Cryptogenic Ischemic Stroke in Young Adults

Objectives: We examined the association between obesity and early-onset cryptogenic ischemic stroke (CIS) and whether fat distribution or sex altered this association. Materials and Methods: This prospective, multi-center, case-control study included 345 patients, aged 18-49 years, with first-ever, acute CIS. The control group included 345 age-and sex-matched stroke-free individuals. We measured height, weight, waist circumference, and hip circumference. Obesity metrics analyzed included body mass index (BMI), waist-to-hip ratio (WHR), waist-to-stature ratio (WSR), and a body shape index (ABSI). Models were adjusted for age, level of education, vascular risk factors, and migraine with aura. Results: After adjusting for demographics, vascular risk factors, and migraine with aura, the highest tertile of WHR was associated with CIS (OR for highest versus lowest WHR tertile 2.81, 95%CI 1.43-5.51; P=0.003). In sex-specific analyses, WHR tertiles were not associated with CIS. However, using WHO WHR cutoff values (>0.85 for women, >0.90 for men), abdominally obese women were at increased risk of CIS (OR 2.09, 95%CI 1.02-4.27; P=0.045). After adjusting for confounders, WC, BMI, WSR, or ABSI were not associated with CIS. Conclusions: Abdominal obesity measured with WHR was an independent risk factor for CIS in young adults after rigorous adjustment for concomitant risk factors.Peer reviewe

TOOTH FITNESS: THE RELATIONSHIP BETWEEN EXERCISE AND ORAL HEALTH

Recent studies have shown that over 70 million Americans are obese with 99 million being overweight. In addition to this study, the CDC reported that over half of all Americans age 30 and older have a form of periodontal disease. The purpose of this study is to identify remedies that do not involve medication, such as exercise, that can reduce inflammation and promote good oral hygiene as well as reduce risk factors for related disease. It is an important aspect of modern medicine, for doctors to have the ability to prescribe effective lifestyle changes along with certain antibiotics. The end goal of this study is to encourage dentists to remind their patients to be exercising regularly. In addition to a patient’s oral hygiene routine, exercise will help reduce the risk for periodontal disease. For this reason, I have found it necessary to conduct a literary review that focuses on the effects exercise has on the inflammatory response within the mouth. This will provide crucial evidence for dentists in the Tucson community and further increase the dental education they give to their patients

Dissociation of interferon-gamma production and resistance to leishmaniasis in the absence of tumor necrosis factor

The delineation of T helper 1(Th1) and T helper 2 (Th2) responses in promoting resistance and susceptibility to experimental cutaneous leishmaniasis has provided a substantial contribution to the understanding of the molecular basis of T cell differentiation in the context of infectious disease. Dysregulation of these processes renders the host susceptible to disease pathogenesis or immuno-pathology. Yet, the paradigm of resistance and susceptibility fails if the adaptive immune systems is not coupled adequately to the innate immune system. The pleiotropic cytokine Tumor necrosis factor (TNF) is involved in numerous aspects of homeostatic and inflammatory processes involved with immune cell function. Dysregulation of TNF production is associated with autoimmune diseases such as Rheumatoid Arthritis, or can render the host susceptible to infectious diseases. The mechanisms however, by which the overproduction of, or the lack of TNF promotes these extreme outcomes is still relatively unknown. Here, I analsysed the genetic contribution of the different major components of the TNF signalling family to elucidate how TNF confers protection to infection with the intracellular protozoan parasite Leishmania major. Co-operative induction of inducible nitric oxide synthase (iNOS) in mononuclear phagocytes by Interferon gamma and TNF provides the basis for an effective immune response to L. major. In the absence of TNF the normally resistant C57BL/6 mouse strain develops a fatal visceralising form of leishmaniasis. Protection from this fatal outcome is dependent on the expression of the trans-membrane but not the soluble form of TNF through an interaction with TNFR1, however the mechanism by which this interaction confers protection remains unknown. Here I demonstrate that this susceptibility to infection does not result from altered CD4+ effector T cell differentiation or inpaired induction of iNOS. T cell activation is greatly increased in the absence of TNF, however enhancement of activation as measured by increased CD44 expression does not reflect positively on the clinical outcome. CD44+ CD4+ T cells from L. major infected TNF-deficient mice showed similar transcriptional up-regulation of both Tbx-21 and Ifn-γ compared to WT controls but showed reduced expression of both Gata-3 and Il-10 indicating a more polarized T cell response. This was similarly accompanied by increased levels of IFN-γ that was observed locally and systemically in the absence of either TNF or TNFR1. The up-regulation of IFN-γ in both resistant B6.WT and susceptible B6.TNF-deficient mouse strains correlated with the induction of iNOS that was predominantly expressed by infiltrating CCR2+ inflammatory monocytes. Despite equivalent induction of iNOS in both the lesion and draining lymph node, expression of iNOS and location of L. major amastigotes showed distinct cellular compartmentalization. While iNOS expression was restricted to CCR2+ inflammatory monocytes, a novel CD11b+, iNOS-, Ly6G-, Ly6Clow, CCR2low population was observed that was highly parasitised and accumulated exclusively in the absence of either TNF or TNFR1 in the draining lymph node. The capacity for these CD11b+, iNOS-, ,Ly6G-, Ly6Clow, CCR2low cells to become highly parasitised did not result from any intrinsic deficit of TNFR signalling. Rather, mixed bone marrow chimeras showed that this sensitivity to L. major parasitism results from external cues generated upstream of monocyte and macrophage activation that renders these cells susceptible to infection. These data demonstrate a unique role for TNF in the coupling of innate and adaptive immune responses through modulating the development of infiltrating myeloid cells that have different leishmanicidal potentials and reflect a state of susceptibility to intracellular infection to L. major rather than promoting direct leishmanicidal functions in vivo

Redundancy of interleukin-6 in the differentiation of T cell and monocyte subsets during cutaneous leishmaniasis

Leishmania (L.) major is a protozoan parasite that infects mammalian hosts and causes a spectrum of disease manifestations that is strongly associated with the genetic background of the host. Interleukin (IL)-6 is an acute phase proinflammatory cytokine, known in vitro to be involved in the inhibition of the generation of regulatory T cells. IL-6-deficient mice were infected with L. major, and T cell and monocyte subsets were analyzed with flow cytometry. Our data show that at the site of infection in the footpad and in the draining popliteal lymph node, numbers of regulatory T cells remain unchanged between WT and IL-6-deficient mice. However, the spleens of IL-6−/− mice contained fewer regulatory T cells after infection with L. major. The development of cutaneous lesions is similar between WT and IL-6-deficient mice, while parasite burden in IL-6−/− mice is reduced compared to WT. The development of IFN-γ or IL-10 producing T cells is similar in IL-6−/− mice. Despite a comparable adaptive T cell response, IL-6-deficient mice develop an earlier peak of some inflammatory cytokines than WT mice. This data indicate that the role of IL-6 in the differentiation of regulatory T cells is complex in vivo, and the effect of an absence of this cytokine can be counter-intuitive

The role of TNF in parasitic diseases: still more questions than answers

The inhibition of TNF with therapeutic monoclonal antibodies or antibody/receptor fusion proteins in rheumatoid arthritis still constitutes the benchmark for a successful intervention in an ongoing auto-immune-inflammatory disease and underlines the importance of this cytokine. TNF plays a central role in the defence against intracellular infections and is responsible for the promotion of different aspects of the innate immune response such as inflammatory cell recruitment and cell differentiation. While this cytokine generally displays pro-inflammatory activities supporting the early stages of the inflammatory response, it has been demonstrated to be especially important during infection with intracellular pathogens and, consequently, leishmaniasis of TNF−/− mice ends fatally. However, the specific activities of TNF that confer protection are not yet fully understood. This review will summarize the current understanding of TNF function and signalling, and will discuss recent work in the models of malaria, toxoplasmosis, trypanosomiasis and leishmaniasis with particular emphasis on work with gene-deficient mouse models

Tumor necrosis factor negative bone marrow-derived dendritic cells exhibit deficient IL-10 expression

The effective maturation of dendritic cells (DC) is complex and highly regulated and requires the presence of a variety of signals. Tumor necrosis factor (TNF) and its receptors or innate pattern recognition receptors such as the toll-like receptors have been shown to contribute to this process. DC derived from bone marrow cells in the presence of granulocyte/macrophage colony-stimulating factor can be used as a model to ascertain the contribution of different signals to DC maturation. Analysis of DC activated by addition of the mycobacterial vaccine strain Bacillus Calmette-Guérin showed that of the effector molecules studied only interleukin-10 expression was significantly reduced in TNF-negative (B6.TNF−/−) DC. Another effector molecule produced by DC, inducible nitric oxide synthase, was largely unchanged

Age-dependent, polyclonal hyperactivation of T cells is reduced in TNF-negative gld/gld mice

The generalized lymphoproliferative disorder (gld) mouse strain is characterized by severe splenomegaly/lymphadenopathy, the production of autoimmune antibodies, and the appearance of CD4/CD8-negative T cells. An additional TNF deficiency of gld/gld mice attenuates the course of the disorder through a yet-unknown mechanism. In this study, we could demonstrate that the reduced splenomegaly and lymphadenopathy in B6.gld/gld.TNF–/– mice were correlated with a decreased peripheral T cell proliferation rate and a delayed polyclonal activation. A comparative analysis of naïve T cells and memory/effector T cells showed an age-dependent difference in the T cell activation pattern in the spleen of B6.gld/gld and B6.gld/gld.TNF–/– mice. T cells from B6.gld/gld.TNF–/– spleens and lymph nodes showed significantly higher levels of CCR7 and CD62 ligand on their surface compared with B6.gld/gld mice when mice of the same age were compared. Additionally, we found an increased titer of the Th1 cytokine IFN-{gamma} in the serum of B6.gld/gld mice, whereas the concentration of IFN-{gamma} was markedly reduced in the serum of B6.gld/gld.TNF–/– mice. These findings support the hypothesis that increased T cell activation and proliferation in the presence of TNF contribute to the exacerbation of the gld syndrome

Loss of TNF signaling facilitates the development of a novel Ly-6C(low) macrophage population permissive for Leishmania major infection

In the absence of TNF, the normally resistant C57BL/6 (B6.WT) strain develops a fatal, progressive form of leishmaniasis after infection with Leishmania major. It is not yet understood which TNF activity or the lack thereof is responsible for the dramatic progression of leishmaniasis in TNF-negative (B6.TNF-/-) mice. To elucidate the underlying mechanisms resulting in the fatal outcome of L. major infection in this gene-deficient mouse strain, we analyzed the monocytic component of the inflammatory infiltrate in the draining popliteal lymph node and the site of the infection using multicolor flow cytometry. The leukocytic infiltrate within the draining lymph node and footpad of B6. TNF-/- mice resembled that of B6. WT mice over the first 2 wk of cutaneous L. major infection. Thereafter, the B6. TNF-/- mice showed an increase of CD11c⁺Ly-6C⁺CCR2⁺ monocytic dendritic cells within the popliteal lymph node in comparison with B6.WT mice. This increase of inflammatory dendritic cells was paired with the accumulation of a novel CD11b⁺Ly-6C(low)CCR2(low) population that was not present in B6. WT mice. This B6.TNF-/- and B6.TNFR1(-/-) specific cell population was CD115⁺Ly-6G⁻iNOS⁻, not apoptotic, and harbored large numbers of parasites

A versatile high throughput screening system for the simultaneous identification of anti-inflammatory and neuroprotective compounds

In many chronic neurodegenerative diseases including Frontotemporal Dementia and Alzheimer's disease (AD), microglial activation is suggested to be involved in pathogenesis or disease progression. Activated microglia secrete a variety of cytokines, including interleukin-1β, interleukin-6, and tumor necrosis factor as well as reactive oxygen and nitrogen species (ROS/RNS). ROS and RNS contribute to alterations in neuronal glucose uptake, inhibition of mitochondrial enzymes, a decrease in mitochondrial membrane potential, impaired axonal transport, and synaptic signaling. In addition, ROS act as signaling molecules in pro-inflammatory redox-active signal transduction pathways. To establish a high throughput screening system for anti-inflammatory and neuroprotective compounds, we have constructed an "Enhanced Green Fluorescent protein" (EGFP) expressing neuronal cell line and set up a murine microglia/neuron co-culture system with these EGFP expressing neuronal cells. We show that microglia activation leads to neuronal cell death, which can be conveniently measured by loss of neuronal EGFP fluorescence. Moreover, we used this system to test selected polyphenolic compounds for their ability to downregulate inflammatory markers and to protect neurons against microglial insult. We suggest that this system might allow accelerated drug discovery for the treatment of inflammation-mediated neurodegenerative diseases