Toll-like receptor 8-mediated reversal of CD4+ regulatory T cell function

Vaccine Strategy in Melanoma

The incidence of melanoma continues to increase even as advances in immunotherapy have led to survival benefits in advanced stages. Vaccines are capable of inducing strong, antitumor immune responses with limited toxicity. Some vaccines have demonstrated clinical benefit in clinical trials alone; however, others have not despite inducing strong immune responses. Recent advancements have improved vaccine design, and combining vaccines with other immunotherapies offers promise. This review highlights the underlying principles of vaccine development, common components of vaccines, and the remaining challenges and future directions of vaccine therapy in melanoma.

Toll-Like Receptors as Therapeutic Targets in Central Nervous System Tumors

In recent years, progress has been made in understanding the pathological, genetic, and molecular heterogeneity of central nervous system (CNS) tumors. However, improvements in risk classification, prognosis, and treatment have not been sufficient. Currently, great importance has been placed to the tumor microenvironment and the immune system, which are very important components that influence the establishment and development of tumors. Toll-like receptors (TLRs) are innate immunite system sensors of a wide variety of molecules, such as those associated with microorganisms and danger signals. TLRs are expressed on many cells, including immune cells and nonimmune cells such as neurons and cancer cells. In the tumor microenvironment, activation of TLRs plays dual antitumoral (dendritic cells, cytotoxic T cells, and natural killer cells activation) and protumoral effects (tumor cell proliferation, survival, and resistance to chemotherapy) and constitutes an area of opportunities and challenges in the development of new therapeutic strategies. Several clinical trials have been carried out, and others are currently in process; however, the results obtained to date have been contradictory and have not led to a definitive position about the use of TLR agonists in adjuvant therapy during the treatment of central nervous system (CNS) tumors. In this review, we focus on recent advances in TLR agonists as immunotherapies for treatment of CNS tumors.

Turning the Tide Against Regulatory T Cells

Regulatory T (Treg) cells play crucial roles in health and disease through their immunosuppressive properties against various immune cells. In this review we will focus on the inhibitory role of Treg cells in anti-tumor immunity. We outline how Treg cells restrict T cell function based on our understanding of T cell biology, and how we can shift the equilibrium against regulatory T cells. To date, numerous strategies have been proposed to limit the suppressive effects of Treg cells, including Treg cell neutralization, destabilizing Treg cells and rendering T cells resistant to Treg cells. Here, we focus on key mechanisms which render T cells resistant to the suppressive effects of Treg cells. Lastly, we also examine current limitations and caveats of overcoming the inhibitory activity of Treg cells, and briefly discuss the potential to target Treg cell resistance in the context of anti-tumor immunity.

Innate sensors that regulate vaccine responses

Pattern recognition receptors (PRRs) control elemental functions of antigen presenting cells (APCs) and critically shape adaptive immune responses. Wielding a natural adjuvanticity, live attenuated vaccines elicit exceptionally efficient and durable immunity. Commonly used vaccine adjuvants target individual PRRs or bolster the immunogenicity of vaccines via indirect mechanisms of inflammation. Here, we review the impact of innate sensors on immune responses to live attenuated vaccines and commonly used vaccine adjuvants, with a focus on human vaccine responses. We discuss the unique potential of microbial nucleic acids and their corresponding sensing receptors to mimic live attenuated vaccines and promote protective immunity.

The Relationship between Toll-like Receptors and Helicobacter pylori-Related Gastropathies: Still a Controversial Topic

Innate immunity represents the first barrier against bacterial invasion. Toll-like receptors (TLRs) belong to the large family of pattern recognition receptors (PRRs), and their activation leads to the induction of inflammatory cytokines, chemokines, antigen-presenting molecules, and costimulatory molecules. Recent studies have focused on identifying the association between TLRs and Helicobacter pylori- (H. pylori-) related diseases. Therefore, this minireview focuses on assessing the role of these TLRs in the development of H. pylori-related gastropathies. Both TLR2 and TLR were found to be involved in H. pylori LPS recognition, with contradictory results most likely due to both the inability to obtain pure LPS in experimental studies and the heterogeneity of the bacterial LPS. In addition, TLR2 was found to be the most extensively expressed gene among all the TLRs in gastric tumors. High levels of TLR4 were also associated with a higher risk of gastric cancer. TLR5 was initially associated with the recognition of H. pylori flagellin, but it seems that this bacterium has developed mechanisms to escape this recognition representing an important factor involved in the persistence of this infection and subsequent carcinogenesis. TLR9, the only TLR with both anti- and proinflammatory roles, was involved in the recognition of H. pylori DNA. The dichotomous role of TLR9, promoting or suppressing the infection, depends on the gastric environment. Recently, TLR7 and TLR8 were shown to recognize purified H. pylori RNA, thereby inducing proinflammatory cytokines. TLR1 and TLR10 gene polymorphisms were associated with a higher risk for gastric cancer in H. pylori-infected individuals. Different gene polymorphisms of these TLRs were found to be associated with gastric cancer depending mostly on ethnicity. Further studies are required in order to develop preventive and therapeutic strategies against H. pylori infections based on the functions of TLRs.

TLR8-Mediated Metabolic Control of Human Treg Function: A Mechanistic Target for Cancer Immunotherapy

Regulatory T (Treg) cells induce an immunosuppressive microenvironment that is a major obstacle for successful tumor immunotherapy. Dissecting the regulatory mechanisms between energy metabolism and functionality in Treg cells will provide insight toward developing novel immunotherapies against cancer. Here we report that human naturally occurring and tumor-associated Treg cells exhibit distinct metabolic profiles with selectivity for glucose metabolism compared with effector T cells. Treg-mediated accelerated glucose consumption induces cellular senescence and suppression of responder T cells through cross-talk. TLR8 signaling selectively inhibits glucose uptake and glycolysis in human Treg cells, resulting in reversal of Treg suppression. Importantly, TLR8 signaling-mediated reprogramming of glucose metabolism and function in human Treg cells can enhance anti-tumor immunity in vivo in a melanoma adoptive transfer T cell therapy model. Our studies identify mechanistic links between innate signaling and metabolic regulation of human Treg suppression, which may be used as a strategy to advance tumor immunotherapy.

Nucleic Acid Sensing in Allergic Disorders

Recent advances indicate that there is crosstalk between allergic disorders and nucleic acid sensing. Triggers that activate inflammatory mechanisms via nucleic acid sensors affect both allergic phenotypes and anti-viral responses, depending on the timing and the order of exposure. Viral respiratory infections, such as those caused by the rhinovirus, influenza, and respiratory syncytial virus, are the most frequent cause of significant asthma exacerbations through effects mediated predominantly by TLR3. However, agonists of other nucleic acid sensors, such as TLR7/8 and TLR9 agonists, may inhibit allergic inflammation and reduce clinical manifestations of disease. The allergic state can predispose the immune system to both exaggerated responses to viral infections or protection from anti-viral inflammatory responses. T_H2 cytokines appear to alter the epithelium, leading to defective viral clearance or exaggerated responses to viral infections. However, a T_H2 skewed allergic response may be protective against a T_H1-dependent inflammatory anti-viral response. This review briefly introduces the receptors involved in nucleic acid sensing, addresses mechanisms by which nucleic acid sensing and allergic responses can counteract one another, and discusses the strategies in experimental settings, both in animal and human studies, to harness the nucleic acid sensing machinery for the intervention of allergic disorders.

Cancer Stem Cells and Immunosuppressive Microenvironment in Glioma

Glioma is one of the most common malignant tumors of the central nervous system and is characterized by extensive infiltrative growth, neovascularization, and resistance to various combined therapies. In addition to heterogenous populations of tumor cells, the glioma stem cells (GSCs) and other nontumor cells present in the glioma microenvironment serve as critical regulators of tumor progression and recurrence. In this review, we discuss the role of several resident or peripheral factors with distinct tumor-promoting features and their dynamic interactions in the development of glioma. Localized antitumor factors could be silenced or even converted to suppressive phenotypes, due to stemness-related cell reprogramming and immunosuppressive mediators in glioma-derived microenvironment. Furthermore, we summarize the latest knowledge on GSCs and key microenvironment components, and discuss the emerging immunotherapeutic strategies to cure this disease.

IL-33 increases ST2+ Tregs and promotes metastatic tumour growth in the lungs in an amphiregulin-dependent manner

Regulatory T cells (Tregs) facilitate primary and metastatic tumour growth through the suppression of anti-tumour immunity. Emerging evidence suggests a distinct role for Tregs in mediating tissue repair and barrier integrity in the lungs by IL-33 mediated production of the growth factor amphiregulin (AREG). Dependent on the type of cancer and local microenvironment, AREG may induce tumour cell proliferation, invasion, migration or resistance to apoptosis by signaling through the epidermal growth factor receptor (EGFR). We have found that IL-33 is dramatically increased in and around metastatic tumour foci in the lungs of mice bearing orthotopic murine mammary tumours. We observed that Tregs express significantly more of the IL-33 receptor, ST2, relative to conventional T cells, that ST2⁺ Tregs accumulate in the lungs of metastatic tumour-bearing mice, and that ST2⁺ Tregs produce significantly more AREG than ST2^- Tregs. The intranasal administration of recombinant IL-33 increased the proportion of AREG producing ST2⁺ Tregs and enhanced the level of phosphorylated EGFR in the metastatic lungs. While recombinant AREG did not impact mammary tumour cell proliferation in vitro despite inducing a dose-dependent increase in phosphorylated EGFR, intranasal administration of AREG resulted in a ten-fold increase in pulmonary metastatic tumour burden in vivo. Further, the intranasal administration of recombinant IL-33 significantly increased metastatic tumour burden in the lungs in an amphiregulin-dependent manner. These data identify ST2⁺ Tregs as a microenvironmental source of AREG in the lungs of mice with orthotopic metastatic mammary tumours and highlight an important role for AREG in promoting metastatic tumour growth in the lungs.

The choice of linker for conjugating R848 to inactivated influenza virus determines the stimulatory capacity for innate immune cells

Inactivated influenza vaccines are not approved for use in infants less than 6 months of age due to poor immunogenicity in that population. While the live attenuated influenza vaccine has the potential to be more immunogenic, it is not an option for infants and other vulnerable populations, including the elderly and immunocompromised individuals due to safety concerns. In an effort to improve the immunogenicity of the inactivated vaccine for use in vulnerable populations, we have used an approach of chemically crosslinking the Toll-like receptor (TLR) 7/8 agonist R848 directly to virus particles. We have reported previously that an R848-conjugated, inactivated vaccine is more effective at inducing adaptive immune responses and protecting against lung pathology in influenza challenged neonatal African green monkeys than is the unmodified counterpart. In the current study, we describe a second generation vaccine that utilizes an amide-sulfhydryl crosslinker with different spacer chemistry and length to couple R848 to virions. The new vaccine has significantly enhanced immunostimulatory activity for murine macrophages and importantly for monocyte derived human dendritic cells. Demonstration of the significant differences in stimulatory activity afforded by modest changes in linker impacts our fundamental view of the design of TLR agonist-antigen vaccines.

Establishment of a novel safety assessment method for vaccine adjuvant development

Vaccines effectively prevent infectious diseases. Many types of vaccines against various pathogens that threaten humans are currently in widespread use. Recently, adjuvant adaptation has been attempted to activate innate immunity to enhance the effectiveness of vaccines. The effectiveness of adjuvants for vaccinations has been demonstrated in many animal models and clinical trials. Although a highly potent adjuvant tends to have high effectiveness, it also has the potential to increase the risk of side effects such as pain, edema, and fever. Indeed, highly effective adjuvants, such as poly(I:C), have not been clinically applied due to their high risks of toxicity in humans. Therefore, the task in the field of adjuvant development is to clinically apply highly effective and non- or low-toxic adjuvant-containing vaccines. To resolve this issue, it is essential to ensure a low risk of side effects and the high efficacy of an adjuvant in the early developmental phases. This review summarizes the theory and history of the current safety assessment methods for adjuvants, using the inactivated influenza vaccine as a model. Our novel method was developed as a system to judge the safety of a candidate compound using biomarkers identified by genomic technology and statistical tools. A systematic safety assessment tool for adjuvants would be of great use for predicting toxicity during novel adjuvant development, screening, and quality control.

Photochemical Treatment of Drosophila APCs Can Eliminate Associated Viruses and Maintain the APC Function for Generating Antigen-Specific CTLs Ex Vivo

Drosophila cells transfected with MHC class I and a number of costimulation molecules including B7.1, ICAM, LFA-3, and CD70 are potent antigen-presenting cells (APCs) for the generation of antigen-specific cytotoxic T cells (CTLs) in vitro. Using Drosophila APCs, CTLs specific for melanoma antigens have been generated in vitro and adoptively transferred to melanoma patients. However, the recent discovery that Drosophila cells can carry insect viruses raises the potential risk of Drosophila APCs transmitting xenogenic viruses to patient CTLs. In this study, we have investigated photoreactive methods to inactivate insect viruses in APC. A clinical grade psoralen compound, 8-MOP (UVADEX) in combination with UVA treatment (5 joules/cm²) can be used to inactivate Drosophila cell viruses. UVADEX treatment is sufficient to inactivate insect viruses but does not affect the expression of MHC class I molecules and costimulation molecules on Drosophila APCs. In fact, UVADEX treatment prevents Drosophila APC growth while maintaining APC function. Furthermore, UVADEX-treated Drosophila APCs maintain or have enhanced APC function as determined by enhanced T cell activation, proliferation, and CTL generation. Thus, the use of UVADEX-treated Drosophila APCs may provide a valuable tool for immunotherapy to generate tumor antigen-specific CTLs.

Diminished TLR2-TLR9 mediated CD4+ T cell responses are associated with increased inflammation in intraocular tuberculosis

Intraocular tuberculosis (IOTB) is amongst the leading causes of uveitis in tropical countries. Despite reports on involvement of proinflammatory cytokines, studies on innate immune responses in disease pathogenesis are lacking. Reports from animal models and patients with pulmonary tuberculosis indicate that defects in toll like receptor (TLR)2 and TLR9 signalling predispose them to tuberculosis. In this context, we investigated the role of TLR2, TLR4 and TLR9 in generation of CD4+ T effector (Teff) cell responses during IOTB. Firstly, the cells in vitreous fluids showed lower expression of TLR2 and TLR9 in IOTB as compared to non-uveitis and non-TB uveitis groups. Next, peripheral CD4+ Teff cells of subjects with IOTB showed decreased proliferative responses and lower induction of Tregs following TLR2 and TLR9 stimulation. Further, TLR9 ligation resulted in increased IFN-γ and IL-17a but decreased expression of IL-10 and TGF-β. Lastly, lower expression of genes involved in TLR9 signalling after direct TLR9 ligation was observed in IOTB. Collectively, our results show that a subdued response to direct TLR2 and TLR9 stimulation in CD4+ T cells is associated with increased proinflammatory responses in IOTB. These findings reveal an important link between innate immune signalling and ensuing adaptive immune responses in IOTB with implications in other forms of extrapulmonary tuberculosis.

Vaccine-induced antigen-specific regulatory T cells attenuate the antiviral immunity against acute influenza virus infection

Peptide-based T cell vaccines targeting the conserved epitopes of influenza virus can provide cross-protection against distantly related strains, but they are generally not immunogenic. Foreign antigen-specific regulatory T (Treg) cells are induced under subimmunogenic conditions peripherally, although their development and role in vaccine-mediated antiviral immunity is unclear. Here, we demonstrated primary vaccination with peptides alone significantly induced antigen-specific Foxp3⁺ Treg cells, which were further expanded by repeated vaccination with unadjuvanted peptides. Certain adjuvants, including CpG, suppressed the induction and expansion of antigen-specific Treg cells by peptide vaccination. Interestingly, secondary influenza virus infection significantly increased the frequency of preexisting antigen-specific Treg cells, although primary infection barely induced them. Importantly, specific depletion of vaccine-induced antigen-specific Treg cells promoted influenza viral clearance, indicating their inhibitory role in vivo. Immunization with CpG-adjuvanted peptides by the subcutaneous prime-intranasal-boost strategy restricted the recruitment and accumulation of antigen-specific Treg cells in lung, and stimulated robust T cell immunity. Finally, subcutaneous prime-intranasal-boost immunization with CpG-adjuvanted peptides or whole-inactivated influenza vaccines protected mice from heterosubtypic influenza virus infection. In conclusion, antigen-specific Treg cells induced by peptide vaccines attenuate the antiviral immunity against influenza virus infection. CpG-adjuvanted peptide vaccines provide heterosubtypic influenza protection probably by inhibiting Treg development and enhancing T cell immunity.

Immunological Mechanisms in Allergic Diseases and Allergen Tolerance: The Role of Treg Cells

The immune system regulates itself to establish an appropriate immune response to potentially harmful pathogens while tolerating harmless environmental antigens and self-antigens. A central role in this balance is played by regulatory T cells (Tregs) through various ways of actions. By means of molecule secretion and cell-cell contact mechanisms, Tregs may have the capacity to modulate effector T cells and suppress the action of proinflammatory cytokines across a broad range of cell types. As a result, abnormal regulatory T cell function has been pointed as a main cause in the development of allergic diseases, a major public health problem in industrialized countries, with a high socioeconomic impact. This prevalence and impact have created an international interest in improving the allergy diagnosis and therapy. Additionally, research has sought to gain a better understanding of the molecular mechanisms underlining this kind of disease, in order to a better management. At this respect, the role of Treg cells is one of the most promising areas of research, mainly because of their potential use as new immunotherapeutical approaches. Therefore, the aim of this review is to update the existing knowledge of the role of Tregs in this pathology deepening in their implication in allergen-specific therapy (AIT).

Regulatory functions of γδ T cells

γδ T cells share characteristics of innate and adaptive immune cells and are involved in a broad spectrum of pro-inflammatory functions. Nonetheless, there is accumulating evidence that γδ T cells also exhibit regulatory functions. In this review, we describe the different phenotypes of regulatory γδ T cells in correlation with the identified mechanisms of suppression.

Toll-like receptors in immunity and inflammatory diseases: Past, present, and future

The immune system is a very diverse system of the host that evolved during evolution to cope with various pathogens present in the vicinity of environmental surroundings inhabited by multicellular organisms ranging from achordates to chordates (including humans). For example, cells of immune system express various pattern recognition receptors (PRRs) that detect danger via recognizing specific pathogen-associated molecular patterns (PAMPs) and mount a specific immune response. Toll-like receptors (TLRs) are one of these PRRs expressed by various immune cells. However, they were first discovered in the Drosophila melanogaster (common fruit fly) as genes/proteins important in embryonic development and dorso-ventral body patterning/polarity. Till date, 13 different types of TLRs (TLR1-TLR13) have been discovered and described in mammals since the first discovery of TLR4 in humans in late 1997. This discovery of TLR4 in humans revolutionized the field of innate immunity and thus the immunology and host-pathogen interaction. Since then TLRs are found to be expressed on various immune cells and have been targeted for therapeutic drug development for various infectious and inflammatory diseases including cancer. Even, Single nucleotide polymorphisms (SNPs) among various TLR genes have been identified among the different human population and their association with susceptibility/resistance to certain infections and other inflammatory diseases. Thus, in the present review the current and future importance of TLRs in immunity, their pattern of expression among various immune cells along with TLR based therapeutic approach is reviewed.

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TLRs are first described PRRs that revolutionized the biology of host-pathogen interaction and immune response

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The discovery of different TLRs in humans proved milestone in the field of innate immunity and inflammation

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The pattern of expression of all the TLRs expressed by human immune cells

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An association of various TLR SNPs with different inflammatory diseases

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Currently available drugs or vaccines based on TLRs and their future in drug targeting along with the role in reproduction, and regeneration

TLR Agonists as Adjuvants for Cancer Vaccines

Toll-like receptors (TLRs) are one of the best characterised families of pattern recognition receptors (PRRs) and play a critical role in the host defence to infection. Accumulating evidence indicates that TLRs also participate in maintaining tissue homeostasis by controlling inflammation and tissue repair, as well as promoting antitumour effects via activation and modulation of adaptive immune responses. TLR agonists have successfully been exploited to ameliorate the efficacy of various cancer therapies. In this chapter, we will discuss the rationales of using TLR agonists as adjuvants to cancer treatments and summarise the recent findings of preclinical and clinical studies of TLR agonist-based cancer therapies.

SALL1 functions as a tumor suppressor in breast cancer by regulating cancer cell senescence and metastasis through the NuRD complex

Background

SALL1 is a multi-zinc finger transcription factor that regulates organogenesis and stem cell development, but the role of SALL1 in tumor biology and tumorigenesis remains largely unknown.

Methods

We analyzed SALL1 expression levels in human and murine breast cancer cells as well as cancer tissues from different types of breast cancer patients. Using both in vitro co-culture system and in vivo breast tumor models, we investigated how SALL1 expression in breast cancer cells affects tumor cell growth and proliferation, metastasis, and cell fate. Using the gain-of function and loss-of-function strategies, we dissected the molecular mechanism responsible for SALL1 tumor suppressor functions.

Results

We demonstrated that SALL1 functions as a tumor suppressor in breast cancer, which is significantly down-regulated in the basal like breast cancer and in estrogen receptor (ER), progesterone receptor (PR) and epidermal growth factor receptor 2 (HER2) triple negative breast cancer patients. SALL1 expression in human and murine breast cancer cells inhibited cancer cell growth and proliferation, metastasis, and promoted cell cycle arrest. Knockdown of SALL1 in breast cancer cells promoted cancer cell growth, proliferation, and colony formation. Our studies revealed that tumor suppression was mediated by recruitment of the Nucleosome Remodeling and Deacetylase (NuRD) complex by SALL1, which promoted cancer cell senescence. We further demonstrated that the mechanism of inhibition of breast cancer cell growth and invasion by SALL1-NuRD depends on the p38 MAPK, ERK1/2, and mTOR signaling pathways.

Conclusion

Our studies indicate that the developmental control gene SALL1 plays a critical role in tumor suppression by recruiting the NuRD complex and thereby inducing cell senescence in breast cancer cells.

Electronic supplementary material

The online version of this article (10.1186/s12943-018-0824-y) contains supplementary material, which is available to authorized users.

TLR-mediated metabolic reprogramming in the tumor microenvironment: potential novel strategies for cancer immunotherapy

Cellular energy metabolism not only promotes tumor cell growth and metastasis but also directs immune cell survival, proliferation and the ability to perform specific and functional immune responses within the tumor microenvironment. A better understanding of the molecular regulation of metabolism in different cell components in the tumor-suppressive microenvironment is critical for the development of effective strategies for human cancer treatments. Toll-like receptors (TLRs) have recently been recognized as critical factors involved in tumor pathogenesis, regulating both tumor cells and tumor-infiltrating innate and adaptive immune cells. However, little is known about the molecular crosstalk between TLR signaling and tumor or/and immune cell metabolism, although there is abundant expression of TLRs in these cells. In this review, we explore the functional role of TLR signaling in reprogramming cell metabolism in the tumor microenvironment. In particular, we discuss how malignant tumors regulate metabolism to support their growth and survival, summarize more recently identified metabolic profiles of different immune cell subsets and TLR-mediated regulation of cellular metabolism in both tumor and immune cells, and further explore potential strategies targeting cell metabolism for TLR-based cancer therapy. An improved understanding of these issues should open new avenues for the development of novel strategies via TLR-mediated metabolic reprogramming of the tumor microenvironment for cancer immunotherapy.

Role of toll-like receptors in inflammatory bowel disease

Inflammatory bowel disease (IBD) is the chronic inflammation of the gastrointestinal tract. Recently, studies of the interplay between the adaptive and innate immune responses have provided a better understanding of the immunopathogenesis of inflammatory disorders such as IBD, as well as identification of novel targets for more potent interventions. Toll-like receptors (TLRs) are a class of proteins that play a significant role in the innate immune system and are involved in inflammatory processes. Activation of TLR signal transduction pathways lead to the induction of numerous genes that function in host defense, including those for inflammatory cytokines, chemokines, and antigen presenting molecules. It was proposed that TLR mutations and dysregulation are major contributing factors to the predisposition and susceptibility to IBD. Thus, modulating TLRs represent an innovative immunotherapeutic approach in IBD therapy. This article outlines the role of TLRs in IBD, focusing on both animal and human studies; the role of TLR-targeted agonists or antagonists as potential therapeutic agents in the different stages of the disease is discussed.

Regulatory T cells trigger effector T cell DNA damage and senescence caused by metabolic competition

Defining the suppressive mechanisms used by regulatory T (Treg) cells is critical for the development of effective strategies for treating tumors and chronic infections. The molecular processes that occur in responder T cells that are suppressed by Treg cells are unclear. Here we show that human Treg cells initiate DNA damage in effector T cells caused by metabolic competition during cross-talk, resulting in senescence and functional changes that are molecularly distinct from anergy and exhaustion. ERK1/2 and p38 signaling cooperate with STAT1 and STAT3 to control Treg-induced effector T-cell senescence. Human Treg-induced T-cell senescence can be prevented via inhibition of the DNA damage response and/or STAT signaling in T-cell adoptive transfer mouse models. These studies identify molecular mechanisms of human Treg cell suppression and indicate that targeting Treg-induced T-cell senescence is a checkpoint for immunotherapy against cancer and other diseases associated with Treg cells.

Regulatory T (Treg) cells can induce senescence of tumour-associated effector T cells, but it is not clear how. Here the authors show that Treg cells outcompete effector T cells for glucose uptake, resulting in activation of the DNA damage response in effector T cells.

Baicalein and baicalin inhibit colon cancer using two distinct fashions of apoptosis and senescence

Baicalein and baicalin are active components of the Scutellaria baicalensis Georgi and both have broad anti-tumor activity. However, how and whether baicalein and baicalin inhibit colon cancer is unclear. Here we demonstrate that baicalein and baicalin can significantly inhibit human colon cancer cell growth and proliferation. Furthermore, both can induce cell cycle arrest, and suppress cancer cell colony formation and migration. The suppressive effects are mechanistically due to the induction of colon cancer cell apoptosis and senescence mediated by baicalein and baicalin, respectively. Furthermore, we revealed that baicalin-induced senescence in tumor cells is due to its inhibition of telomerase reverse transcriptase expression in tumor cells, and that MAPK ERK and p38 signaling pathways are causatively involved in the regulation of colon cancer cell apoptosis and senescence mediated by baicalein and baicalin. In addition, our in vivo studies using human colon cancer cells in humanized mouse xenograft models, further demonstrated that baicalein and baicalin can induce tumor cell apoptosis and senescence, resulting in inhibition of tumorigenesis and growth of colon cancer in vivo. These data clearly suggest that baicalein and baicalin have potent anti-cancer effects against human colon cancer and could be potential novel and effective target drugs for cancer therapy.

TLRs/NLRs: Shaping the landscape of host immunity

Innate immune system provides the first line of defense against pathogenic organisms. It has a varied and large collection of molecules known as pattern recognition receptors (PRRs) which can tackle the pathogens promptly and effectively. Toll-like receptors (TLRs) and NOD-like receptors (NLRs) are members of the PRR family that recognize pathogen associated molecular patterns (PAMPs) and play pivotal roles to mediate defense against infections from bacteria, fungi, virus and various other pathogens. In this review, we discuss the critical roles of TLRs and NLRs in the regulation of host immune-effector functions such as cytokine production, phagosome-lysosome fusion, inflammasome activation, autophagy, antigen presentation, and B and T cell immune responses that are known to be essential for mounting a protective immune response against the pathogens. This review may be helpful to design TLRs/NLRs based immunotherapeutics to control various infections and pathophysiological disorders.

Molecular adjuvants that modulate regulatory T cell function in vaccination: A critical appraisal

Adjuvants are substances used to enhance the efficacy of vaccines. They influence the magnitude and alter the quality of the adaptive immune response to vaccine antigens by amplifying or modulating different signals involved in the innate immune response. The majority of known adjuvants have been empirically identified. The limited immunogenicity of new vaccine antigens and the need for safer vaccines have increased the importance of identifying single, well-defined adjuvants with known cellular and molecular mechanisms for rational vaccine design. Depletion or functional inhibition of CD4⁺CD25⁺FoxP3⁺ regulatory T cells (Tregs) by molecular adjuvants has become an emergent approach in this field. Different successful results have been obtained for specific vaccines, but there are still unresolved issues such as the risk of autoimmune disease induction, the involvement of cells other than Tregs and optimization for different conditions. This work provides a comprehensive analysis of current approaches to inhibit Tregs with molecular adjuvants for vaccine improvement, highlights the progress being made, and describes ongoing challenges.

Vaccine responses in newborns

Immunisation of the newborn represents a key global strategy in overcoming morbidity and mortality due to infection in early life. Potential limitations, however, include poor immunogenicity, safety concerns and the development of tolerogenicity or hypo-responsiveness to either the same antigen and/or concomitant antigens administered at birth or in the subsequent months. Furthermore, the neonatal immunological milieu is polarised towards Th2-type immunity with dampening of Th1-type responses and impaired humoral immunity, resulting in qualitatively and quantitatively poorer antibody responses compared to older infants. Innate immunity also shows functional deficiency in antigen-presenting cells: the expression and signalling of Toll-like receptors undergo maturational changes associated with distinct functional responses. Nevertheless, the effectiveness of BCG, hepatitis B and oral polio vaccines, the only immunisations currently in use in the neonatal period, is proof of concept that vaccines can be successfully administered to the newborn via different routes of delivery to induce a range of protective mechanisms for three different diseases. In this review paper, we discuss the rationale for and challenges to neonatal immunisation, summarising progress made in the field, including lessons learnt from newborn vaccines in the pipeline. Furthermore, we explore important maternal, infant and environmental co-factors that may impede the success of current and future neonatal immunisation strategies. A variety of approaches have been proposed to overcome the inherent regulatory constraints of the newborn innate and adaptive immune system, including alternative routes of delivery, novel vaccine configurations, improved innate receptor agonists and optimised antigen-adjuvant combinations. Crucially, a dual strategy may be employed whereby immunisation at birth is used to prime the immune system in order to improve immunogenicity to subsequent homologous or heterologous boosters in later infancy. Similarly, potent non-specific immunomodulatory effects may be elicited when challenged with unrelated antigens, with the potential to reduce the overall risk of infection and allergic disease in early life.

The Role of Toll-Like Receptors and Vitamin D in Cardiovascular Diseases-A Review

Cardiovascular diseases are the leading cause of mortality worldwide. Therefore, a better understanding of their pathomechanisms and the subsequent implementation of optimal prophylactic and therapeutic strategies are of utmost importance. A growing body of evidence states that low-grade inflammation is a common feature for most of the cardiovascular diseases in which the contributing factors are the activation of toll-like receptors (TLRs) and vitamin D deficiency. In this article, available data concerning the association of cardiovascular diseases with TLRs and vitamin D status are reviewed, followed by a discussion of new possible approaches to cardiovascular disease management.

An R848 adjuvanted influenza vaccine promotes early activation of B cells in the draining lymph nodes of non-human primate neonates

Impaired immune responsiveness is a significant barrier to vaccination of neonates. By way of example, the low seroconversion observed following influenza vaccination has led to restriction of its use to infants over 6 months of age, leaving younger infants vulnerable to infection. Our previous studies using a non-human primate neonate model demonstrated that the immune response elicited following vaccination with inactivated influenza virus could be robustly increased by inclusion of the Toll-like receptor agonist flagellin or R848, either delivered individually or in combination. When delivered individually, R848 was found to be the more effective of the two. To gain insights into the mechanism through which these adjuvants functioned in vivo, we assessed the initiation of the immune response, i.e. at 24 hr, in the draining lymph node of neonate non-human primates. Significant up-regulation of co-stimulatory molecules on dendritic cells could be detected, but only when both adjuvants were present. In contrast, R848 alone could increase the number of cells in the lymph node, presumably through enhanced recruitment, as well as B-cell activation at this early time-point. These changes were not observed with flagellin and the dual adjuvanted vaccine did not promote increases beyond those observed with R848 alone. In vitro studies showed that R848 could promote B-cell activation, supporting a model wherein a direct effect on neonate B-cell activation is an important component of the in vivo potency of R848 in neonates.

IFN-γ alters the expression of diverse immunity related genes in a cell culture model designed to represent maturing neutrophils

The cytokine interferon-γ (IFN-γ) is approved as a drug to treat chronic granulomatous disease (CGD) and osteopetrosis and is also used in hyperimmunoglobulin E syndromes. Patients with CGD have defects in proteins of the NOX2 NADPH oxidase system. This leads to reduced production of microbicidal ROS by PMNs and recurrent life threatening infections. The goal of this study was to better understand how IFN-γ might support phagocyte function in these diseases, and to obtain information that might expand potential uses for IFN-γ. Neutrophils mature in the bone marrow and then enter the blood where they quickly undergo apoptotic cell death with a half-life of only 5–10 hours. Therefore we reasoned that IFN-γ might exert its effects on neutrophils via prolonged exposure to cells undergoing maturation in the marrow rather than by its brief exposure to short-lived circulating cells. To explore this possibility we made use of PLB-985 cells, a myeloblast-like myeloid cell line that can be differentiated into a mature, neutrophil-like state by treatment with various agents including DMSO. In initial studies we investigated transcription and protein expression in PLB-985 cells undergoing maturation in the presence or absence of IFN-γ. We observed IFN-γ induced differences in expression of genes known to be involved in classical aspects of neutrophil function (transmigration, chemotaxis, phagocytosis, killing and pattern recognition) as well as genes involved in apoptosis and other mechanisms that regulating neutrophil number. We also observed differences for genes involved in the major histocompatibility complex I (MHCI) and MHCII systems whose involvement in neutrophil function is controversial and not well defined. Finally, we observed significant changes in expression of genes encoding guanylate binding proteins (Gbps) that are known to have roles in immunity but which have not as yet been linked to neutrophil function. We propose that changes in the expression within these classes of genes could help explain the immune supportive effects of IFN-γ. Next we explored if the effect of IFN-γ on expression of these genes is dependent on whether the cells are undergoing maturation; to do this we compared the effects of IFN-γ on cells cultured with and without DMSO. For a subset of genes the expression level changes caused by IFN-γ were much greater in maturing cells than non-maturing cells. These findings indicate that developmental changes associated with cell maturation can modulate the effects of IFN-γ but that this is gene specific. Since the effects of IFN-γ depend on whether cells are maturing, the gene expression changes observed in this study must be due to more than just prolonged application of IFN-γ and are instead the result of interplay between cell maturation and changes caused by the chemokine. This supports our hypothesis that the effects of IFN-γ on developing neutrophils in the bone marrow may be very different from its effects on mature cells in the blood. Collectively the findings in this study enhance our understanding of the effects of IFN-γ on maturing myeloid cells and indicate possible mechanisms by which this cytokine could support immune function.

Toll-like receptor pathways and innate responses to allografts

PURPOSE OF REVIEW

There is an increasing appreciation of the role of the innate immune system in modulating alloimmunity following organ transplantation. This review will outline the studies that have investigated the role of the Toll-like receptors in allograft rejection.

RECENT FINDINGS

Evidence indicates that Toll like receptors are involved in acute allograft rejection by inducing dendritic cells to mature and migrate to the draining lymph nodes and initiate Th1 alloimmune responses. Within the last year the impact of Toll-like receptor activation on transplantation tolerance has been investigated. Two studies have shown that Toll-like receptor activation can prevent the induction of transplantation tolerance whereas our own study has shown that deficiency in Toll-like receptor signaling facilitates transplantation tolerance. Finally, a recent study indicated that fragmented hyaluronan, part of the extracellular matrix, might be one of the endogenous Toll-like receptor activators in the setting of alloimmunty.

SUMMARY

Toll-like receptors play an important role in modulating the alloimmune response. Their manipulation may have profound effects on the induction of transplantation tolerance. Future investigation into other aspects of innate immunity and their influence on solid organ transplantation will likely yield important insights to the field.

The Yin and Yang of regulatory T cell and therapy progress in autoimmune disease

Autoimmune diseases (ADs) are primarily mediated by the failure of immunological self-tolerance. Regulatory T cells (Tregs) play a critical role in the maintenance of induced tolerance to peripheral self-antigens, suppressing immoderate immune responses deleterious to the host and preventing the AD development. Tregs and suppressive cytokines are homeostatic with effective cells plus pro-inflammatory cytokines in healthy hosts which is defined as "Yang", and ADs are usually induced in case of disturbed homeostasis, which is defined as "Yin". Indeed, the Yin-Yang balance could explain the pathogenic mechanism of ADs. Tregs not only suppress CD4⁺ and CD8⁺ T cells but also can suppress other immune cells such as B cell, natural killer cell, DC and other antigen-presenting cell through cell-cell contact or secreting suppressive cytokines. In Tregs, Foxp3 as an intracellular protein displays a more specific marker than currently used other cell-surface markers (such as CD25, CD40L, CTLA-4, ICOS and GITR) in defining the naturally occurring CD4⁺ Tregs. Though the precise mechanism for the opposite effects of Tregs has not been fully elucidated, the importance of Tregs in ADs has been proved to be associated with kinds of immunocytes. At present, the surface marker, frequency and function of Tregs existed conflicts and hence the Tregs therapy in ADs faces challenges. Though some success has been achieved with Tregs therapy in few ADs both in murine models and humans, more effort should paid to meet the future challenges. This review summarizes the progress and discusses the phenotypic, numeric and functional abnormalities of Tregs and is the first time to systematically review the progress of Tregs therapy in kinds of ADs.

Metabolism-associated danger signal-induced immune response and reverse immune checkpoint-activated CD40+ monocyte differentiation

Adaptive immunity is critical for disease progression and modulates T cell (TC) and antigen-presenting cell (APC) functions. Three signals were initially proposed for adaptive immune activation: signal 1 antigen recognition, signal 2 co-stimulation or co-inhibition, and signal 3 cytokine stimulation. In this article, we propose to term signal 2 as an immune checkpoint, which describes interactions of paired molecules leading to stimulation (stimulatory immune checkpoint) or inhibition (inhibitory immune checkpoint) of an immune response. We classify immune checkpoint into two categories: one-way immune checkpoint for forward signaling towards TC only, and two-way immune checkpoint for both forward and reverse signaling towards TC and APC, respectively. Recently, we and others provided evidence suggesting that metabolic risk factors (RF) activate innate and adaptive immunity, involving the induction of immune checkpoint molecules. We summarize these findings and suggest a novel theory, metabolism-associated danger signal (MADS) recognition, by which metabolic RF activate innate and adaptive immunity. We emphasize that MADS activates the reverse immune checkpoint which leads to APC inflammation in innate and adaptive immunity. Our recent evidence is shown that metabolic RF, such as uremic toxin or hyperhomocysteinemia, induced immune checkpoint molecule CD40 expression in monocytes (MC) and elevated serum soluble CD40 ligand (sCD40L) resulting in CD40⁺ MC differentiation. We propose that CD40⁺ MC is a novel pro-inflammatory MC subset and a reliable biomarker for chronic kidney disease severity. We summarize that CD40:CD40L immune checkpoint can induce TC and APC activation via forward stimulatory, reverse stimulatory, and TC contact-independent immune checkpoints. Finally, we modeled metabolic RF-induced two-way stimulatory immune checkpoint amplification and discussed potential signaling pathways including AP-1, NF-κB, NFAT, STAT, and DNA methylation and their contribution to systemic and tissue inflammation.

TLR7 Signaling Regulates Th17 Cells and Autoimmunity: Novel Potential for Autoimmune Therapy

Innate regulation through TLR signaling has been shown to be important for promoting T cell subset development and function. However, limited information is known about whether differential TLR signaling can selectively inhibit Th17 and/or Th1 cells, which are important for controlling excessive inflammation and autoimmune responses. In this article, we demonstrate that activation of TLR7 signaling in T cells can inhibit Th17 cell differentiation from naive T cells and IL-17 production in established Th17 cells. We further report that downregulation of STAT3 signaling is responsible for TLR7-mediated inhibition of Th17 cells due to induction of suppressor of cytokine signaling 3 and 5. TLR7-mediated suppression of Th17 cells does not require dendritic cell involvement. In addition, we show that TLR7 signaling can suppress Th1 cell development and function through a mechanism different from Th17 cell suppression. Importantly, our complementary in vivo studies demonstrate that treatment with the TLR7 ligand imiquimod can inhibit Th1 and Th17 cells, resulting in the prevention of, and an immunotherapeutic reduction in, experimental autoimmune encephalomyelitis. These studies identify a new strategy to manipulate Th17/Th1 cells through TLR7 signaling, with important implications for successful immunotherapy against autoimmune and inflammatory diseases.

Microbiota, Inflammation and Colorectal Cancer

Colorectal cancer, the fourth leading cause of cancer-related death worldwide, is a multifactorial disease involving genetic, environmental and lifestyle risk factors. In addition, increased evidence has established a role for the intestinal microbiota in the development of colorectal cancer. Indeed, changes in the intestinal microbiota composition in colorectal cancer patients compared to control subjects have been reported. Several bacterial species have been shown to exhibit the pro-inflammatory and pro-carcinogenic properties, which could consequently have an impact on colorectal carcinogenesis. This review will summarize the current knowledge about the potential links between the intestinal microbiota and colorectal cancer, with a focus on the pro-carcinogenic properties of bacterial microbiota such as induction of inflammation, the biosynthesis of genotoxins that interfere with cell cycle regulation and the production of toxic metabolites. Finally, we will describe the potential therapeutic strategies based on intestinal microbiota manipulation for colorectal cancer treatment.

Viral RNA-Unprimed Rig-I Restrains Stat3 Activation in the Modulation of Regulatory T Cell/Th17 Cell Balance

Innate immunity activation by viral RNA-primed retinoid acid inducible gene-I (Rig-I) in CD4⁺ T cells antagonizes TGFβ signaling to suppress the differentiation of regulatory T cells (Tregs). However, how viral RNA-unliganded Rig-I (apo-Rig-I) modulates Treg generation remains unclear. In this article, we show that, in the absence of viral infection, Treg differentiation of Rig-I^-/- CD4⁺ T cells was compromised, in the presence of increased generation of Th17 cells and overactivation of Stat3, a critical regulator tilting the Treg/Th17 cell balance. Mechanistically, apo-Rig-I physically associates with Stat3, thereby inhibiting Jak1's association with Stat3 while facilitating Shp2's association to inhibit p-Stat3 levels. Interestingly, inhibition of Stat3 ameliorates the Treg/Th17 imbalance and the colitis observed in Rig-I^-/- mice. Collectively, these results uncover an independent functional contribution of the apo-Rig-I/Stat3 interaction in the maintenance of Treg/Th17 cell balance.

Controlled release of antigen and Toll-like receptor ligands from PLGA nanoparticles enhances immunogenicity

AIM

Dendritic cells rapidly capture nanoparticles and induce a potent cellular immune response. It is yet unknown whether the immunological response induced by slow release of encapsulated versus soluble antigen and adjuvant is superior.

MATERIALS & METHODS

The kinetics of poly(lactic-co-glycolic acid) PLGA nanoparticles antigen release was studied by the DQ-bovine serum albumin (BSA) self-quenching antigen model. The immunological response induced was evaluated by means of dendritic cell activation/maturation markers, cytokine production and their ability to drive antigen-specific T-cell proliferation.

RESULTS & CONCLUSION

PLGA-encapsulated antigen and adjuvant showed an enhanced T-cell response when compared with soluble vaccine components by increasing antigenicity and adjuvanticity. Although the kinetic profile followed the same pattern, encapsulation increased strength and duration of the response.

Extrinsic MAVS signaling is critical for Treg maintenance of Foxp3 expression following acute flavivirus infection

Given the rapid spread of flaviviruses such as West Nile virus (WNV) and Zika virus, it is critical that we develop a complete understanding of the key mediators of an effective anti-viral response. We previously demonstrated that WNV infection of mice deficient in mitochondrial antiviral-signaling protein (MAVS), the signaling adaptor for RNA helicases such as RIG-I, resulted in increased death and dysregulated immunity, which correlated with a failure of Treg expansion following infection. Thus, we sought to determine if intrinsic MAVS signaling is required for participation of Tregs in anti-WNV immunity. Despite evidence of increased Treg cell division, Foxp3 expression was not stably maintained after WNV infection in MAVS-deficient mice. However, intrinsic MAVS signaling was dispensable for Treg proliferation and suppressive capacity. Further, we observed generation of an effective anti-WNV immune response when Tregs lacked MAVS, thereby demonstrating that Treg detection of the presence of WNV through the MAVS signaling pathway is not required for generation of effective immunity. Together, these data suggest that while MAVS signaling has a considerable impact on Treg identity, this effect is not mediated by intrinsic MAVS signaling but rather is likely an effect of the overproduction of pro-inflammatory cytokines generated in MAVS-deficient mice after WNV infection.

Expression of C-type lectin receptors and Toll-like receptors in decidua of patients with unexplained recurrent spontaneous abortion

In the present study, the mechanisms underlying the pathogenesis of unexplained recurrent spontaneous abortion (URSA) were explored. The protein and mRNA expression of two C-type lectin-like receptors (CLRs), namely dendritic cell-specific intercellular adhesion molecule-3-grabbing non-integrin (DC-SIGN) and mannose receptor (MR), and two Toll-like receptors (TLRs), namely TLR2 and TLR4, in the decidua and dendritic cells (DCs) was compared between URSA patients and normal controls. URSA patients had significantly lower protein and mRNA expression of DC-SIGN and significantly higher expression of TLR2 and TLR4 in decidual tissues compared with normal controls. In addition, URSA patients had significantly higher levels of the T helper (Th) 1 cytokines interleukin (IL)-2 and interferon-γ, and significantly lower levels of the Th2 cytokines IL-10 and transforming growth factor β1 in decidual tissues compared with the control group. The TLR2 agonist synthetic triacylated lipoprotein (Pam3CSK4) and the TLR4 agonist lipopolysaccharide were used to demonstrate that TLR2 and TLR4 modulate Th1/Th2 cytokine imbalance in DC–T cell cocultures. The results suggest that the balance between CLRs and TLRs was tilted towards a TLR-dominant response in URSA patients, which may disrupt maternal–fetal immune tolerance, resulting in spontaneous abortion.

Foxp3 and Toll-like receptor signaling balance Treg cell anabolic metabolism for suppression

CD4⁺ effector T cells (T_eff cells) and regulatory T cells (T_reg cells) undergo metabolic reprogramming to support proliferation and immunological function. Although signaling via the lipid kinase PI(3)K (phosphatidylinositol-3-OH kinase), the serine-threonine kinase Akt and the metabolic checkpoint kinase complex mTORC1 induces both expression of the glucose transporter Glut1 and aerobic glycolysis for T_eff cell proliferation and inflammatory function, the mechanisms that regulate T_reg cell metabolism and function remain unclear. We found that Toll-like receptor (TLR) signals that promote T_reg cell proliferation increased PI(3)K-Akt-mTORC1 signaling, glycolysis and expression of Glut1. However, TLR-induced mTORC1 signaling also impaired T_reg cell suppressive capacity. Conversely, the transcription factor Foxp3 opposed PI(3)K-Akt-mTORC1 signaling to diminish glycolysis and anabolic metabolism while increasing oxidative and catabolic metabolism. Notably, Glut1 expression was sufficient to increase the number of T_reg cells, but it reduced their suppressive capacity and Foxp3 expression. Thus, inflammatory signals and Foxp3 balance mTORC1 signaling and glucose metabolism to control the proliferation and suppressive function of T_reg cells.

Costimulatory and coinhibitory immune checkpoint receptors in head and neck cancer: unleashing immune responses through therapeutic combinations

Head and neck squamous cell carcinoma (HNSCC) represents a model of escape from anti-tumor immunity. The high frequency of p53 tumor suppressor loss in HNSCC leads to genomic instability and immune stimulation through the generation of neoantigens. However, the aggressive nature of HNSCC tumors and significant rates of resistance to conventional therapies highlights the ability of HNSCC to evade this immune response. Advances in understanding the role of co-stimulatory and immune checkpoint receptors in HNSCC-mediated immunosuppression lay the foundation for development of novel therapeutic approaches. This article provides an overview of these co-stimulatory and immune checkpoint pathways, as well as a review of preclinical and clinical evidence supporting the modulation of these pathways in HNSCC. Finally, the synergistic potential of combining these approaches is discussed, along with an update of current clinical trials evaluating combinations of immune-based therapies in HNSCC patients.

T-Regulatory Cells as Part of Strategy of Immune Evasion by Pathogens

Under physiological conditions, regulatory processes can suppress the immune response after elimination of a pathogen and restore homeostasis through the destruction and suppression of obsolete effector cells of the immune system. The main players in this process are T-regulatory cells (Tregs) and immature dendritic cells, which suppress the immune response by their own products and/or by inducing synthesis of immunosuppressive interleukins IL-10, IL-35, and transforming growth factor (TGF-β) by other cells. This mechanism is also used by widespread "successful" pathogens that are capable of chronically persisting in the human body - herpes virus, hepatitis viruses, human immunodeficiency virus, Mycobacterium tuberculosis, Helicobacter pylori, and others. During coevolution of microbial pathogens and the host immune system, the pathogens developed sophisticated strategies for evading the host defense, so-called immune evasion. In particular, molecular structures of pathogens during the interaction with dendritic cells via activating and inhibitory receptors can change intracellular signal transduction, resulting in block of maturation of dendritic cells. Immature dendritic cells become tolerogenic and cause differentiation of Tregs from the conventional T-cell CD4+. Microbial molecules can also react directly with Tregs through innate immune receptors. Costimulation of Toll-like receptor 5 (TLR5) by flagellin increases the expression of the transcription factor Foxp3, which increases the suppressive activity of Treg cells. From all evasion mechanisms, the induction of immunosuppression by Treg through IL-10, IL-35, and TGF-β appears most effective. This results in the suppression of inflammation and of adaptive immune responses against pathogens, optimizing the conditions for the survival of bacteria and viruses.

A Novel R848-Conjugated Inactivated Influenza Virus Vaccine Is Efficacious and Safe in a Neonate Nonhuman Primate Model

Influenza virus infection of neonates poses a major health concern, often resulting in severe disease and hospitalization. At present, vaccines for this at-risk population are lacking. Thus, development of an effective vaccine is an urgent need. In this study, we have used an innovative nonhuman primate neonate challenge model to test the efficacy of a novel TLR 7/8 agonist R848-conjugated influenza virus vaccine. The use of the intact virus represents a step forward in conjugate vaccine design because it provides multiple antigenic targets allowing for elicitation of a broad immune response. Our results show that this vaccine induces high-level virus-specific Ab- and cell-mediated responses in neonates that result in increased virus clearance and reduced lung pathology postchallenge compared with the nonadjuvanted virus vaccine. Surprisingly, the addition of a second TLR agonist (flagellin) did not enhance vaccine protection, suggesting that combinations of TLR that provide increased efficacy must be determined empirically. These data support further exploration of this new conjugate influenza vaccine approach as a platform for use in the at-risk neonate population.

Low expression of Toll-like receptors in peripheral blood mononuclear cells of pediatric patients with acute lymphoblastic leukemia

Cancer is the second most common cause of death among children aged 1-14 years. Leukemia accounts for one-third of all childhood cancers, 78% of which is acute lymphoblastic leukemia (ALL). The development of cancer has been associated with malignant cells that express low levels of immunogenic molecules, which facilitates their escape from the antineoplastic immune response. It is thought that it may be possible to rescue the antineoplastic immune response through the activation of recognition receptors, such as Toll-like receptors (TLRs), which activate the innate immune system. TLRs are type I membrane glycoproteins expressed mainly in immune system cells such as monocytes, neutrophils, macrophages, dendritic cells, T, B and natural killer cells. The aim of the present study was to evaluate the expression of TLR1, TLR3, TLR4, TLR7 and TLR9 in peripheral blood mononuclear cells (PBMCs) in patients with ALL and prior to any treatment. PBMCs were obtained from 50 pediatric patients diagnosed with ALL and from 20 children attending the ophthalmology and orthopedics services. The mean fluorescence intensity was obtained by analysis of immunofluorescence. We found lower expression levels of TLR1, TLR3, TLR4, TLR7 and TLR9 in PBMCs from patients with ALL compared with those from control patients. We also observed that the PBMCs from patients with Pre-B and B ALL had lower TLR4 expression than controls and patients with Pro-B, Pre-B, B and T ALL had lower TLR7 expression than controls. The present study is the first to demonstrate reduced expression of TLRs in PBMCs from pediatric patients with ALL. This finding is of great relevance and may partly explain the reduction in the antineoplastic immune response in patients with ALL.

Vasohibin-1 suppresses colon cancer

Vasohibin-1 (VASH1) is an endogenous angiogenesis inhibitor.However, the clinical relevance of VASH1 in colon cancer and its regulations on cancer angiogenesis and cancer cell biological characteristics are still unknown. Here we showed that stromal VASH1 levels were negatively correlated with tumor size, advanced clinical stage and distant metastases in colon cancer patients. Overexpression of VASH1 in colon cancer cells induced apoptosis and senescence, inhibiting cancer cell growth and colony formation in vitro and tumor growth in vivo. In addition, knockdown of VASH1 in cancer cells promoted cell growth, adhesion and migration in vitro, and enhanced tumorigenesis and metastasis in vivo.

CD4+ and CD8+ T cells have opposing roles in breast cancer progression and outcome

The Cancer Immunoediting concept has provided critical insights suggesting dual functions of immune system during the cancer initiation and development. However, the dynamics and roles of CD4⁺ and CD8⁺ T cells in the pathogenesis of breast cancer remain unclear. Here we utilized two murine breast cancer models (4T1 and E0771) and demonstrated that both CD4⁺ and CD8⁺ T cells were increased and involved in immune responses, but with distinct dynamic trends in breast cancer development. In addition to cell number increases, CD4⁺ T cells changed their dominant subsets from Th1 in the early stages to Treg and Th17 cells in the late stages of the cancer progression. We also analyzed CD4⁺ and CD8⁺ T cell infiltration in primary breast cancer tissues from cancer patients. We observed that CD8⁺ T cells are the key effector cell population mediating effective anti-tumor immunity resulting in better clinical outcomes. In contrast, intra-tumoral CD4⁺ T cells have negative prognostic effects on breast cancer patient outcomes. These studies indicate that CD4⁺ and CD8⁺ T cells have opposing roles in breast cancer progression and outcomes, which provides new insights relevant for the development of effective cancer immunotherapeutic approaches.

Breaking Free of Control: How Conventional T Cells Overcome Regulatory T Cell Suppression

Conventional T (Tcon) cells are crucial in shaping the immune response, whether it is protection against a pathogen, a cytotoxic attack on tumor cells, or an unwanted response to self-antigens in the context of autoimmunity. In each of these immune settings, regulatory T cells (Tregs) can potentially exert control over the Tcon cell response, resulting in either suppression or activation of the Tcon cells. Under physiological conditions, Tcon cells are able to transiently overcome Treg-imposed restraints to mount a protective response against an infectious threat, achieving clonal expansion, differentiation, and effector function. However, evidence has accumulated in recent years to suggest that Tcon cell resistance to Treg-mediated suppression centrally contributes to the pathogenesis of autoimmune disease. Tipping the balance too far in the other direction, cancerous tumors utilize Tregs to establish an overly suppressive microenvironment, preventing antitumor Tcon cell responses. Given the wide-ranging clinical importance of the Tcon/Treg interaction, this review aims to provide a better understanding of what determines whether a Tcon cell is susceptible to Treg-mediated suppression and how perturbations to this finely tuned balance play a role in pathological conditions. Here, we focus in detail on the complex array of factors that confer Tcon cells with resistance to Treg suppression, which we have divided into two categories: (1) extracellular factor-mediated signaling and (2) intracellular signaling molecules. Further, we explore the therapeutic implications of manipulating the phosphatidylinositol-3 kinase (PI3K)/Akt signaling pathway, which is proposed to be the convergence point of signaling pathways that mediate Tcon resistance to suppression. Finally, we address important unresolved questions on the timing and location of acquisition of resistance, and the stability of the “Treg-resistant” phenotype.