TLR ligand suppression or enhancement of Treg cells? A double-edged sword in immunity to tumours

A Marek's Disease Virus Messenger RNA-Based Vaccine Modulates Local and Systemic Immune Responses in Chickens

Marek's disease (MD), caused by the Marek's disease virus, is a lymphoproliferative disease in chickens that can be controlled by vaccination. However, the current vaccines can limit tumor growth and death but not virus replication and transmission. The present study aimed to evaluate host responses following intramuscular injection of an mRNA vaccine encoding gB and pp38 proteins of the MDV within the first 36 h. The vaccine was injected in low and high doses using prime and prime-boost strategies. The expression of type I and II interferons (IFNs), a panel of interferon-stimulated genes, and two key antiviral cytokines, IL-1β and IL-2, were measured in spleen and lungs after vaccination. The transcriptional analysis of the above genes showed significant increases in the expression of MDA5, Myd88, IFN-α, IFN-β, IFN-γ, IRF7, OAS, Mx1, and IL-2 in both the spleen and lungs within the first 36 h of immunization. Secondary immunization increased expression of all the above genes in the lungs. In contrast, only IFN-γ, MDA5, MyD88, Mx1, and OAS showed significant upregulation in the spleen after the secondary immunization. This study shows that two doses of the MDV mRNA vaccine encoding gB and pp38 antigens activate innate and adaptive responses and induce an antiviral state in chickens.

Depletion of regulatory T cells enhancing the anti-tumor effect of in situ vaccination in solid tumors

The emergence of immune checkpoint inhibitors (ICIs) has revolutionized the clinical treatment for tumor. However, the low response rate of ICIs remains the major obstacle for curing patients and effective approaches for patients with primary or secondary resistance to ICIs remain lacking. In this study, immune stimulating agent unmethylated CG-enriched (CpG) oligodeoxynucleotide (ODN) was locally injected into the tumor to trigger a robust immune response to eradicate cancer cells, while anti-CD25 antibody was applied to remove immunosuppressive regulatory T cells, which further enhanced the host immune activity to attack tumor systematically. The combination of CpG and anti-CD25 antibody obtained notable regression in mouse melanoma model. Furthermore, rechallenge of tumor cells in the xenograft model has resulted in smaller tumor volume, which demonstrated that the combinational treatment enhanced the activity of memory T cells. Remarkably, this combinational therapy presented significant efficacy on multiple types of tumors as well and was able to prevent relapse of tumor partially. Taken together, our combinational immunotherapy provides a new avenue to enhance the clinical outcomes of patients who are insensitive or resistant to ICIs treatments.

Immunotherapy for lung cancer

Immune checkpoint blockers have transformed non-small-cell lung cancer treatment, but they can lead to autoimmune and inflammatory side effects, leading to the concurrent use of immunosuppressive treatments. In this analysis, we delve into the potential of antibodies checkpoint blockade, focusing on CTLA-4 inhibition using ipilimumab, as a groundbreaking cancer immunotherapy. We also concentrate on the role of biomarkers, particularly PD-L1 activity and mutation significance, in predicting the response to programmed cell death protein 1 blockage and the prevalence of side effects associated with immune-related side effects. In describing the patterns of cancer response to immunotherapy, we underline the limitations of response assessment criteria like RECIST and World Health Organization. We also stress the necessity of ongoing studies and clinical trials, standardized guidelines, and additional research to improve response assessment in the era of immunotherapy.

Toll-like receptor-targeted anti-tumor therapies: Advances and challenges

Toll-like receptors (TLRs) are pattern recognition receptors, originally discovered to stimulate innate immune reactions against microbial infection. TLRs also play essential roles in bridging the innate and adaptive immune system, playing multiple roles in inflammation, autoimmune diseases, and cancer. Thanks to the immune stimulatory potential of TLRs, TLR-targeted strategies in cancer treatment have proved to be able to regulate the tumor microenvironment towards tumoricidal phenotypes. Quantities of pre-clinical studies and clinical trials using TLR-targeted strategies in treating cancer have been initiated, with some drugs already becoming part of standard care. Here we review the structure, ligand, signaling pathways, and expression of TLRs; we then provide an overview of the pre-clinical studies and an updated clinical trial watch targeting each TLR in cancer treatment; and finally, we discuss the challenges and prospects of TLR-targeted therapy.

Protein-Based Adjuvants for Vaccines as Immunomodulators of the Innate and Adaptive Immune Response: Current Knowledge, Challenges, and Future Opportunities

New-generation vaccines, formulated with subunits or nucleic acids, are less immunogenic than classical vaccines formulated with live-attenuated or inactivated pathogens. This difference has led to an intensified search for additional potent vaccine adjuvants that meet safety and efficacy criteria and confer long-term protection. This review provides an overview of protein-based adjuvants (PBAs) obtained from different organisms, including bacteria, mollusks, plants, and humans. Notably, despite structural differences, all PBAs show significant immunostimulatory properties, eliciting B-cell- and T-cell-mediated immune responses to administered antigens, providing advantages over many currently adopted adjuvant approaches. Furthermore, PBAs are natural biocompatible and biodegradable substances that induce minimal reactogenicity and toxicity and interact with innate immune receptors, enhancing their endocytosis and modulating subsequent adaptive immune responses. We propose that PBAs can contribute to the development of vaccines against complex pathogens, including intracellular pathogens such as Mycobacterium tuberculosis, those with complex life cycles such as Plasmodium falciparum, those that induce host immune dysfunction such as HIV, those that target immunocompromised individuals such as fungi, those with a latent disease phase such as Herpes, those that are antigenically variable such as SARS-CoV-2 and those that undergo continuous evolution, to reduce the likelihood of outbreaks.

A Novel Design of Multi-epitope Peptide Vaccine Against Pseudomonas aeruginosa

Background:

As an opportunistic pathogen, Pseudomonas aeruginosa causes many different hazardous infections. The high mortality rate resulting from infection with this antibiotic-resistant pathogen has made it a major challenge in clinical treatment; it has been listed as the most harmful bacterium to humans by the WHO. So far, no vaccine has been approved for P. aeruginosa.

Objective:

Infections performed by bacterial attachment and colonization with type IV pili (T4P), known as the most essential adhesive vital for adhesion, while pilQ is necessary for the biogenesis of T4P, also outer membrane proteins of a pathogen is also effective in stimulating the immune system; in this regard, pilQ, OprF, and OprI, are excellent candidate antigens for production of an effective vaccine against P. aeruginosa.

Methods:

In this research, various bioinformatics methods were employed in order to design a new multiepitope peptide vaccine versus P. aeruginosa. Since T CD4+ cell immunity is important in eradicating P. aeruginosa, OprF, OprI, and pilQ antigens were analyzed to determine Helper T cell Lymphocyte (HTL) epitopes by many different immunoinformatics servers. One of the receptor agonists 2 (TLR2), a segment of the Por B protein from Neisseria meningitides was used as an adjuvant in order to stimulate an effective cellular immune response, and suitable linkers were used to connect all the above mentioned parts. In the vaccine construct, linear B cell epitopes were also identified.

Results:

Conforming the bioinformatics forecasts, the designed vaccine possesses high antigenicity and is not allergen.

Conclusion:

In this regard, the designed vaccine candidate is strongly believed to possess the potential of inducing cellular and humoral immunity against P. aeruginosa.

The interactions of paclitaxel with tumour microenvironment

Today, it is well-known that the interactions and secretion within the tumour are crucial to consider for cancer therapy. Some novel cancer therapy modalities such as immunotherapy or tumour vaccination therapy work based on the control of interactions within the tumour microenvironment (TME). It has been revealed that anti-cancer drugs or radiotherapy can modulate some interactions in favour of cancer therapy. However, they may induce some mechanisms to increase the resistance of cancer cells to therapy. Paclitaxel is known as the first approved herbal derived chemotherapy drug. Although the main known anti-cancer effect of paclitaxel is the inhibition of the cell cycle, today, it has been well known that paclitaxel may suppress the tumour via modulating several interactions in TME. Furthermore, paclitaxel may increase the expression of some tumour resistance drivers. This review aims to discuss the interactions within TME following treatment with paclitaxel. The effects of paclitaxel on the anti-tumour immunity, immunosuppressive cells, hypoxia, and also angiogenesis will be discussed. The targeting of these interactions may be interesting to increase therapy efficiency using the combination modalities.

Antioxidants Present in Reproductive Tract Fluids and Their Relevance for Fertility

Nowadays, infertility is classified as a disease of the reproductive system. Although it does not compromise the life of the individual, it can have detrimental effects on the physiological and psychological health of the couple. Male fertility evaluation is mainly focused on the analysis of sperm parameters. However, the ejaculated fluid is also composed of seminal plasma, and the study of this fluid can provide crucial information to help in the assessment of male fertility status. Total antioxidant capacity of the seminal plasma has been positively correlated with the fertility of men. Moreover, evidence highlights to a similar importance as that of female reproductive tract fluid antioxidant capabilities and female fertility. Herein, we describe the functions of seminal plasma and female reproductive tract fluids, as well as their main antioxidant components and their relationships with fertility outcomes. Additionally, this review contains the most up to date information regarding the mechanisms of the interaction between the male and the female reproductive fluids and the importance of proper antioxidant capacity for fertilization.

Engineering Therapeutic Strategies in Cancer Immunotherapy via Exogenous Delivery of Toll-like Receptor Agonists

As a currently spotlighted method for cancer treatment, cancer immunotherapy has made a lot of progress in recent years. Among tremendous cancer immunotherapy boosters available nowadays, Toll-like receptor (TLR) agonists were specifically selected, because of their effective activation of innate and adaptive immune cells, such as dendritic cells (DCs), T cells, and macrophages. TLR agonists can activate signaling pathways of DCs to express CD80 and CD86 molecules, and secrete various cytokines and chemokines. The maturation of DCs stimulates naïve T cells to differentiate into functional cells, and induces B cell activation. Although TLR agonists have anti-tumor ability by activating the immune system of the host, their drawbacks, which include poor efficiency and remarkably short retention time in the body, must be overcome. In this review, we classify and summarize the recently reported delivery strategies using (1) exogenous TLR agonists to maintain the biological and physiological signaling activities of cargo agonists, (2) usage of multiple TLR agonists for synergistic immune responses, and (3) co-delivery using the combination with other immunomodulators or stimulants. In contrast to naked TLR agonists, these exogenous TLR delivery strategies successfully facilitated immune responses and subsequently mediated anti-tumor efficacy.

Intra-Tumoral Activation of Endosomal TLR Pathways Reveals a Distinct Role for TLR3 Agonist Dependent Type-1 Interferons in Shaping the Tumor Immune Microenvironment

Toll-like receptor (TLR) agonists have received considerable attention as therapeutic targets for cancer immunotherapy owing to their ability to convert immunosuppressive tumor microenvironments towards a more T-cell inflamed phenotype. However, TLRs differ in their cell expression profiles and intracellular signaling pathways, raising the possibility that distinct TLRs differentially influence the tumor immune microenvironment. Using single-cell RNA-sequencing, we address this by comparing the tumor immune composition of B16F10 melanoma following treatment with agonists of TLR3, TLR7, and TLR9. Marked differences are observed between treatments, including decreased tumor-associated macrophages upon TLR7 agonist treatment. A biased type-1 interferon signature is elicited upon TLR3 agonist treatment as opposed to a type-2 interferon signature with TLR9 agonists. TLR3 stimulation was associated with increased macrophage antigen presentation gene expression and decreased expression of PD-L1 and the inhibitory receptors Pirb and Pilra on infiltrating monocytes. Furthermore, in contrast to TLR7 and TLR9 agonists, TLR3 stimulation ablated FoxP3 positive CD4 T cells and elicited a distinct CD8 T cell activation phenotype highlighting the potential for distinct synergies between TLR agonists and combination therapy agents.

Realgar increases defenses against infection by Enterococcus faecalis in Caenorhabditis elegans

ETHNOPHARMACOLOGICAL RELEVANCE

Realgar has been used in traditional remedies for a long history in China and India. It is clinically used to treat diverse cancers, especially acute promyelocytic leukemia (APL), chronic myelogenous leukemia (CML) in China. However, paradoxic roles of realgar to increase or decrease immunity are reported. It is urgent to address this question, due to immune depression can be strongly benefit to cancer development, but detrimental to patients.

AIM OF THE STUDY

This present work is to explore whether realgar promote or suppress immune responses, and shed light on its mode of action. Our results should provide cues for rational strategy to explore realgar for clinical use.

MATERIAL AND METHODS

Infection model in vivo was established by using Enterococcus faecalis to attack Caenorhabditis elegans, then realgar was used to treat the infected worms to investigate its effects on infectivity and the underlying mechanism. Killing analysis was carried out to test whether realgar can mitigate worm infection. Thermotolerance resistance analysis was used to evaluate if realgar functions hormetic effect. Quantification of live E. faecalis in nematode intestine was employed to ascertain if realgar alleviate the bacterial load in worm gut. Quantitative real-time PCR (qRT-PCR) was used to test the expression of antibacterial effectors. Western blot was used to test the effect of realgar on the expressions of p38 and phospho-p38 in worms infected by E. faecalis.

RESULTS

Realgar alleviated the infected worms in strains of N2, glp-4, and daf-2, but failed in sek-1, glp-4; sek-1, and daf-2; daf-16 when p38 MAPK or daf-16 was blocked or inactivated. Western blot assay demonstrated that realgar increased the expression of phosph-p38. Thermotolerance assay showed that realgar played a hormetic role on nemtodes, triggered protective response and reduced bacterial load after realgar treatment for 120 h qRT-PCR demonstrated that realgar significantly increased antibacterial effectors, thus leading to pathogen elimination.

CONCLUSION

Realgar increased defenses against E. faecalis in C. elegans by inducing both immune responses and protective responses. It was regulated by p38 MAPK pathway and DAF-16.

Comprehensive analysis of current approaches to inhibit regulatory T cells in cancer

CD4⁺CD25⁺Foxp3⁺ regulatory T cells (Treg) have emerged as a dominant T cell population inhibiting anti-tumor effector T cells. Initial strategies used for Treg-depletion (cyclophosphamide, anti-CD25 mAb…) also targeted activated T cells, as they share many phenotypic markers. Current, ameliorated approaches to inhibit Treg aim to either block their function or their migration to lymph nodes and the tumor microenvironment. Various drugs originally developed for other therapeutic indications (anti-angiogenic molecules, tyrosine kinase inhibitors,etc) have recently been discovered to inhibit Treg. These approaches are expected to be rapidly translated to clinical applications for therapeutic use in combination with immunomodulators.

A TLR2-Activating Fraction From Mycobacterium abscessus Rough Variant Demonstrates Vaccine and Diagnostic Potential

Mycobacterium abscessus is a prevalent pathogenic mycobacterium in cystic fibrosis (CF) patients and one of the most highly drug resistant mycobacterial species to antimicrobial agents. It possesses the property to transition from a smooth (S) to a rough (R) morphotype, thereby influencing the host innate immune response. This transition from the S to the R morphotype takes place in patients with an exacerbation of the disease and a persistence of M. abscessus. We have previously shown that the exacerbation of the Toll-like receptor 2 (TLR2)-mediated inflammatory response, following this S to R transition, is essentially due to overproduction of bacilli cell envelope surface compounds, which we were able to extract by mechanical treatment and isolation by solvent partition in a fraction called interphase. Here, we set up a purification procedure guided by bioactivity to isolate a fraction from the R variant of M. abscessus cells which exhibits a high TLR2 stimulating activity, referred to as TLR2-enriched fraction (TLR2eF). As expected, TLR2eF was found to contain several lipoproteins and proteins known to be stimuli for TLR2. Vaccination with TLR2eF showed no protection toward an M. abscessus aerosol challenge, but provided mild protection in ΔF508 mice and their FVB littermates when intravenously challenged by M. abscessus. Interestingly however, antibodies against TLR2eF compounds were detected during disease in CF patients. In conclusion, we show the potential for compounds in TLR2eF as vaccine and diagnostic candidates, in order to enhance diagnosis, prevent and/or treat M. abscessus-related infections.

OMV Vaccines and the Role of TLR Agonists in Immune Response

Outer Membrane Vesicles (OMVs) are bacterial nanoparticles that are spontaneously released during growth both in vitro and in vivo by Gram-negative bacteria. They are spherical, bilayered membrane nanostructures that contain many components found within the external surface of the parent bacterium. Naturally, OMVs serve the bacteria as a mechanism to deliver DNA, RNA, proteins, and toxins, as well as to promote biofilm formation and remodel the outer membrane during growth. On the other hand, as OMVs possess the optimal size to be uptaken by immune cells, and present a range of surface-exposed antigens in native conformation and Toll-like receptor (TLR) activating components, they represent an attractive and powerful vaccine platform able to induce both humoral and cell-mediated immune responses. This work reviews the TLR-agonists expressed on OMVs and their capability to trigger individual TLRs expressed on different cell types of the immune system, and then focuses on their impact on the immune responses elicited by OMVs compared to traditional vaccines.

FOXP3 and CTLA-4 genetic variants' influence on the susceptibility and clinical course of basal cell carcinoma

Introduction

The pathogenesis of basal cell carcinoma (BCC) is multifactorial and not fully elucidated. Previous studies showed that behaviour of the tumour may be influenced by the immune system and identified CD4⁺CD25⁺FoxP3⁺ regulatory T cells (T_regs) as dominant immune cells in BCC microenvironment. The function and development of Tregs is regulated by FOXP3, encoding transcription factor Forkhead box P3. FOXP3 regulates transcription of many genes, including up-regulation of cytotoxic lymphocyte-associated antigen-4 gene (CTLA-4). Expressed on Tregs, CTLA-4 interacts with antigen-presenting cells to inhibit T-cell activation.

Aim

To investigate the role of two polymorphisms (rs3761548 and rs2232365) of FOXP3 and CTLA-4 polymorphism (rs5742909) in BCC patients from northern Poland.

Material and methods

We analysed 280 unrelated patients with BCC of mean age 70.93 ±11.53 (70.54 ±12.55 women, 71.38 ±10.26 men) and 200 healthy, unrelated age- and sex-matched volunteers.

Results

The differences in the occurrence of BCC between genotypes and alleles of the analysed polymorphisms were not statistically significant. In the studied group, the presence of the CC genotype in CTLA-4 rs5742909 polymorphism was statistically more frequent in patients with multiple BCCs.

Conclusions

It seems that the analysed FOXP3 and CTLA-4 polymorphisms do not influence the BCC susceptibility. CTLA-4 rs5742909 polymorphism may influence the susceptibility to multiple BCCs.

The Female Response to Seminal Fluid

Seminal fluid is often assumed to have just one function in mammalian reproduction, delivering sperm to fertilize oocytes. But seminal fluid also transmits signaling agents that interact with female reproductive tissues to facilitate conception and .pregnancy. Upon seminal fluid contact, female tissues initiate a controlled inflammatory response that affects several aspects of reproductive function to ultimately maximize the chances of a male producing healthy offspring. This effect is best characterized in mice, where the female response involves several steps. Initially, seminal fluid factors cause leukocytes to infiltrate the female reproductive tract, and to selectively target and eliminate excess sperm. Other signals stimulate ovulation, induce an altered transcriptional program in female tract tissues that modulates embryo developmental programming, and initiate immune adaptations to promote receptivity to implantation and placental development. A key result is expansion of the pool of regulatory T cells that assist implantation by suppressing inflammation, mediating tolerance to male transplantation antigens, and promoting uterine vascular adaptation and placental development. Principal signaling agents in seminal fluid include prostaglandins and transforming growth factor-β. The balance of male signals affects the nature of the female response, providing a mechanism of ‟cryptic female choiceˮ that influences female reproductive investment. Male-female seminal fluid signaling is evident in all mammalian species investigated including human, and effects of seminal fluid in invertebrates indicate evolutionarily conserved mechanisms. Understanding the female response to seminal fluid will shed new light on infertility and pregnancy disorders and is critical to defining how events at conception influence offspring health.

Immunometabolic modulation of retinal inflammation by CD36 ligand

In subretinal inflammation, activated mononuclear phagocytes (MP) play a key role in the progression of retinopathies. Little is known about the mechanism involved in the loss of photoreceptors leading to vision impairment. Studying retinal damage induced by photo-oxidative stress, we observed that cluster of differentiation 36 (CD36)-deficient mice featured less subretinal MP accumulation and attenuated photoreceptor degeneration. Moreover, treatment with a CD36-selective azapeptide ligand (MPE-001) reduced subretinal activated MP accumulation in wild type mice and preserved photoreceptor layers and function as assessed by electroretinography in a CD36-dependent manner. The azapeptide modulated the transcriptome of subretinal activated MP by reducing pro-inflammatory markers. In isolated MP, MPE-001 induced dissociation of the CD36-Toll-like receptor 2 (TLR2) oligomeric complex, decreasing nuclear factor-kappa B (NF-κB) and NLR family pyrin domain containing 3 (NLRP3) inflammasome activation. In addition, MPE-001 caused an aerobic metabolic shift in activated MP, involving peroxisome proliferator-activated receptor-γ (PPAR-γ) activation, which in turn mitigated inflammation. Accordingly, PPAR-γ inhibition blocked the cytoprotective effect of MPE-001 on photoreceptor apoptosis elicited by activated MP. By altering activated MP metabolism, MPE-001 decreased immune responses to alleviate subsequent inflammation-dependent neuronal injury characteristic of various vision-threatening retinal disorders.

Papillomavirus Immune Evasion Strategies Target the Infected Cell and the Local Immune System

Persistent infection with human papillomavirus (HPV) initiates ~5% of all human cancers, and particularly cervical and oropharyngeal cancers. HPV vaccines prevent HPV infection, but do not eliminate existing HPV infections. Papillomaviruses induce hyperproliferation of epithelial cells. In this review we discuss how hyperproliferation renders epithelial cells less sensitive to immune attack, and impacts upon the efficiency of the local immune system. These observations have significance for the design of therapeutic HPV cancer immunotherapies.

IFN-γ: A cytokine at the right time, is in the right place

Interferon gamma has long been studied as a critical mediator of tumor immunity. In recent years, the complexity of cellular interactions that take place in the tumor microenvironment has become better appreciated in the context of immunotherapy. While checkpoint inhibitors have dramatically improved remission rates in cancer treatment, IFN-γ and related effectors continue to be identified as strong predictors of treatment success. In this review, we provide an overview of the multiple immunosuppressive barriers that IFN-γ has to overcome to eliminate tumors, and potential avenues for modulating the immune response in favor of tumor rejection.

Alterations in the inflammatory cells infiltrating basal cell carcinomas during immunocryosurgery

Immunocryosurgery, the combination modality of a cryosurgery session at day 14 of a 5-week daily imiquimod treatment cycle, has shown remarkable efficacy in the treatment of basal cell carcinoma (BCC). The modality was designed to exploit synergy of antitumor effects, including the induction of immune responses, elicited by imiquimod and cryosurgery. Herein, we report on the infiltration of the BCC by selected inflammatory cell species during an immunocryosurgery treatment cycle. The density of tissue infiltrating CD68⁺, CD3⁺ and Foxp3⁺ cells was studied by immunohistochemistry in 56 BCC biopsies from 28 treated sites (26 patients) at baseline and at days 12, 16 or 28 during treatment. Immunocryosurgery induces statistically significant alterations in all three cell species (p < 0.003): The density of CD68⁺ increased already by day 12 and remained at a higher level during the treatment thereafter. The density of CD3⁺ cells increased significantly between days 12 and 16 of treatment. The density of T_reg (Foxp3⁺) cells increased in the early phase of treatment (highest at day 12) to decrease significantly already 2 days after the cryosurgery session (day 16) and thereafter up to day 28 of the treatment cycle (p = 0.033). Within the tumor tissue, these alterations result in an abrupt increase in the CD3⁺/Foxp3⁺ ratio, a finding suggesting that the cryosurgical perturbation may probably play a decisive modulating role in the cellular composition of the inflammatory infiltrate during immunocryosurgery, eventually heralding the induction of an effective tumor-destructing immune response.

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.

A Chromatin-Mimetic Nanomedicine for Therapeutic Tolerance Induction

The undesirable immune response poses a life-threatening challenge to human health. It not only deteriorates the therapeutic performance of biologic drugs but also contributes to various diseases such as allergies and autoimmune diseases. Inspired by the role of chromatin in the maintenance of natural immune tolerance, here we report a DNA-protein polymeric nanocomplex that can mimic the tolerogenic function of chromatin and induce an immune tolerance to its protein cargos. We first proved that the chromatin-mimetic nanomedicine loaded with keyhole limpet hemocyanin (KLH), a highly immunogenic model protein, could elicit a durable antigen-specific immune tolerance to KLH lasting for at least five weeks in mice. Following the proof-of-concept study, we demonstrated that this nanomedicine could be applied to improve the safety and efficacy of a biologic drug, PEGylated uricase, by attenuating the relevant antibody (Ab) responses. Moreover, we also demonstrated that prophylactic treatments with this nanomedicine could tolerize the immune system with the allergen of ovalbumin (OVA) and thus inhibit the occurrence of airway inflammation in an OVA-induced allergic asthma murine model. Collectively, our work illustrates a nature-inspired concept of immune tolerance induction and establishes a useful tool to specifically suppress unwanted immune responses for therapeutic purposes.

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.

In ovo administration of Toll-like receptor ligands encapsulated in PLGA nanoparticles impede tumor development in chickens infected with Marek's disease virus

One of the economically important diseases in the poultry industry is Marek's disease (MD) which is caused by Marek's disease virus (MDV). The use of current vaccines provides protection against clinical signs of MD in chickens. However, these vaccines do not prevent the transmission of MDV to susceptible hosts, hence they may promote the development of new virulent strains of MDV. This issue persuaded us to explore alternative approaches to control MD in chickens. Induction of innate responses at the early stage of life in the chicken may help to prevent or reduce MDV infection. Further, prophylactic use of Toll-like receptor ligands (TLR-Ls) has been shown to generate host immunity against infectious diseases. In this regard, encapsulation of TLR-Ls in Poly(d, l-lactic-co-glycolic acid) (PLGA) may further enhance host responses by controlled release of TLR-Ls for an extended period. Hence, in the current study, protective effects of encapsulated TLR4 and TLR21 ligands, LPS and CpG, respectively, were investigated against MD. Results indicated that administration of encapsulated CpG and LPS first at embryonic day (ED) 18, followed by post-hatch at 14 days-post infection (dpi) intramuscularly, diminished tumor incidence by 60% and 42.8%, respectively at 21dpi compared to the MDV only group. In addition, analysis of cytokine gene profiles of interferon (IFN)-α, IFN-β, IFN-γ, inducible nitric oxide synthase (iNOS), interleukin (IL)-1β, IL-18 and IL-10 in spleen and bursa of Fabricius at different time points suggests that TLR-Ls possibly triggered host responses through the expression of IL-1β and IL-18 to reduce tumor formation. However, further studies are needed to explore the role of these pro-inflammatory cytokines and other influencing elements like lymphocytes in the hindrance of tumor development by TLR-Ls treatment in chickens.

Role of Pattern Recognition Receptors in KSHV Infection

Kaposi’s sarcoma-associated herpesvirus or Human herpesvirus-8 (KSHV/HHV-8), an oncogenic human herpesvirus and the leading cause of cancer in HIV-infected individuals, is a major public health concern with recurring reports of epidemics on a global level. The early detection of KSHV virus and subsequent activation of the antiviral immune response by the host’s immune system are crucial to prevent KSHV infection. The host’s immune system is an evolutionary conserved system that provides the most important line of defense against invading microbial pathogens, including viruses. Viruses are initially detected by the cells of the host innate immune system, which evoke concerted antiviral responses via the secretion of interferons (IFNs) and inflammatory cytokines/chemokines for elimination of the invaders. Type I IFN and cytokine gene expression are regulated by multiple intracellular signaling pathways that are activated by germline-encoded host sensors, i.e., pattern recognition receptors (PRRs) that recognize a conserved set of ligands, known as ‘pathogen-associated molecular patterns (PAMPs)’. On the contrary, persistent and dysregulated signaling of PRRs promotes numerous tumor-causing inflammatory events in various human cancers. Being an integral component of the mammalian innate immune response and due to their constitutive activation in tumor cells, targeting PRRs appears to be an effective strategy for tumor prevention and/or treatment. Cellular PRRs are known to respond to KSHV infection, and KSHV has been shown to be armed with an array of strategies to selectively inhibit cellular PRR-based immune sensing to its benefit. In particular, KSHV has acquired specific immunomodulatory genes to effectively subvert PRR responses during the early stages of primary infection, lytic reactivation and latency, for a successful establishment of a life-long persistent infection. The current review aims to comprehensively summarize the latest advances in our knowledge of role of PRRs in KSHV infections.

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.

IL-33/ST2 pathway drives regulatory T cell dependent suppression of liver damage upon cytomegalovirus infection

Regulatory T (Treg) cells dampen an exaggerated immune response to viral infections in order to avoid immunopathology. Cytomegaloviruses (CMVs) are herpesviruses usually causing asymptomatic infection in immunocompetent hosts and induce strong cellular immunity which provides protection against CMV disease. It remains unclear how these persistent viruses manage to avoid induction of immunopathology not only during the acute infection but also during life-long persistence and virus reactivation. This may be due to numerous viral immunoevasion strategies used to specifically modulate immune responses but also induction of Treg cells by CMV infection. Here we demonstrate that liver Treg cells are strongly induced in mice infected with murine CMV (MCMV). The depletion of Treg cells results in severe hepatitis and liver damage without alterations in the virus load. Moreover, liver Treg cells show a high expression of ST2, a cellular receptor for tissue alarmin IL-33, which is strongly upregulated in the liver of infected mice. We demonstrated that IL-33 signaling is crucial for Treg cell accumulation after MCMV infection and ST2-deficient mice show a more pronounced liver pathology and higher mortality compared to infected control mice. These results illustrate the importance of IL-33 in the suppressive function of liver Treg cells during CMV infection.

Treg cells are crucial for immune homeostasis and for dampening immune response to several diseased conditions, including viral infections. Murine cytomegalovirus (MCMV) is a herpesvirus with pathogenic potential, so that early immune mechanisms are essential in controlling virus and protecting from virus-induced pathology. Studies on Foxp3⁺ Treg cells have revealed their inhibitory role on the early T cell response to MCMV infection and have suggested Treg cells as a target of MCMV’s immunoevasion mechanisms. Here we demonstrate that the number and activation status of liver Treg cells is strongly induced upon MCMV infection in order to protect the host from severe liver damage. They constitutively express high amounts of IL-33 receptor ST2 and their accumulation depends on IL-33, which is released as a tissue alarmin after the cell damage. For the first time, we show an immunoregulatory role of IL-33-dependent Treg cells in the liver of MCMV infected mice and their suppression of MCMV-induced immunopathology.

Forkhead box-P3+ regulatory T cells and toll-like receptor 2 co-expression in oral squamous cell carcinoma

BACKGROUND

The function of forkhead box-P3 (FoxP3) regulatory T cells (Treg) and toll-like receptor (TLR)2 protein in the oral cancer microenvironment is not fully understood, but evidence from other malignancies suggests it is likely they are involved with tumour development and progression. The aim of this study was to investigate the distribution of FoxP3⁺cells, TLR2⁺ cells and double-labelled FoxP3⁺TLR2⁺ immune cells in oral squamous cell carcinoma (OSCC), using immunohistochemistry (IHC) and immunofluorescence (IF).

METHODS

25 archival cases of OSCC were immunostained with anti-FoxP3 and anti-TLR2 antibodies. Inflamed hyperplastic oral mucosal tissues were used as controls. The proportion of single-labelled, double-labelled and negative cells was determined.

RESULTS

A higher frequency of double-labelled FoxP3⁺TLR2⁺ Tregs was observed within the immune cells of OSCC compared to inflamed controls using IHC (p<0.05). Cell-to-cell contact between single-stained TLR2⁺ cells and FoxP3⁺ cells was noted. Double IF studies validated demonstration of co-expression of FoxP3⁺/TLR2⁺ immune cells in OSCC.

CONCLUSION

The presence of FoxP3⁺TLR2⁺ cells within the OSCC microenvironment may represent a dendritic cell-dependent pathway capable of inhibiting Treg suppressive activity, potentially enhancing the anti-tumour response. Modulation of TLR2-Treg interactions should be further explored to determine if they have a role in the therapeutic management of OSCC.

Heterogeneity of Toll-like receptor 9 signaling in B cell malignancies and its potential therapeutic application

Toll-like receptor 9 (TLR9) is expressed in a variety of B-cell malignancies and works as a bridge between innate and adaptive immunity. CpG oligodeoxynucleotides (CpG ODNs), TLR9 agonists, are able to induce anticancer immune responses and exert direct effects against cancer cells, serving as cancer therapeutic agents. Therefore, TLR9 might be a potential therapeutic target for drug development. However, several new evidences have revealed that direct effects of TLR9 agonists on B-cell malignancies is controversial. For example, CpG ODNs can induce apoptosis in certain type of chronic lymphocytic leukemia and lymphoma cells, while induce proliferation in multiple myeloma and other types of lymphoma cells. In this review, we summarize current understanding of the heterogeneity in responses of normal and malignant B cells to TLR9 agonists, due to differences in TLR9 expression levels, genetic alterations (such as MyD88 mutation), and signaling pathway activation. Especially, the downstream molecules of NF-κB signaling pathway play an important role in the heterogeneous response. In order to provide possibilities for therapeutic manipulation of TLR9 agonists in the treatment of these disorders, the preclinical and clinical advances in using CpG ODNs alone and in combination therapies are also summarized in this review.

CD4+ regulatory T cells in gastric cancer mucosa are proliferating and express high levels of IL-10 but little TGF-β

BACKGROUND

An increase of regulatory T cells, defined as CD25^high- and/or FOXP3⁺-expressing CD4⁺ T cells, within tumors has been reported in several studies. Tregs promote tumor growth by modulating the antitumor immune response, mainly through inhibition of T-cell-mediated tumor cell killing: this has been suggested to be dependent on IL-10 and/or TGF-β. In stomach cancer, the mechanisms behind the accumulation of Tregs in tumor tissue has not been fully elucidated, and neither has Treg gene expression in situ.

MATERIALS AND METHODS

Stomach tissue from gastric cancer patients undergoing gastric resection was analyzed using flow cytometry and cell sorting, followed by RT-PCR.

RESULTS

We observed that stomach CD4⁺ FOXP3⁺ T cells proliferated to a higher degree than CD4⁺ FOXP3^- T cells, which may contribute to Treg accumulation in the mucosa. By analyzing DNA methylation, we demonstrated that both proliferating and nonproliferating FOXP3⁺ T cells exhibited complete demethylation of the FOXP3 gene, indicating a stable FOXP3 expression in both cell populations. Furthermore, analysis of T-cell populations isolated directly from the tumor and tumor-free mucosa demonstrated that CD4⁺ CD25^high T cells have a higher IL-10/IFN-γ gene expression ratio but express lower levels of TGF-β than CD4⁺ CD25^low/- T cells.

CONCLUSION

We demonstrate strong proliferation among regulatory CD4⁺ FOXP3⁺ CD25^high T cells in the gastric cancer mucosa. These local Treg express a suppressive cytokine profile characterized by high IL-10 and low TGF-β and IFN-γ production.

Regulatory T Cells Suppress Natural Killer Cell Immunity in Patients With Human Cervical Carcinoma

OBJECTIVE

To determine the functional attributes of CD4 CD25 regulatory T (Treg) cells by suppressing natural killer (NK) cell activity in human cervical cancer (CC).

METHODS

Triple-color flow cytometry was used to study the phenotypic expression of CD4 CD25 Treg cells and NK cells in the peripheral blood lymphocytes (PBLs) and tumor-infiltrating lymphocytes (TILs). In vitro coculture assays were performed to illustrate the cytokine immunoregulations between Treg cells and NK cells.

RESULTS

Significantly lower expression ratio of NK cells and higher expression ratio of Treg cells in TILs than PBLs were found. The NK cells displayed significantly higher expression ratio of inhibitory NK receptors (CD158a, CD158b, and NKG2A) and lower expression ratio of activating NK receptors (NKG2D, NKp46, and NKp30) as well as perforin in TILs than PBLs, suggesting the suppressed cytotoxicity of the NK cells in the CC tumor milieu. The expression ratio of transforming growth factor-β1 (TGF-β1) on Treg cells as well as TGF-βRII on Treg cells and NK cells was significantly higher in TILs than PBLs. Further functional in vitro assays demonstrated that NK cell function was suppressed by Treg cells, mimicking the inhibition of TGF-β on NK cells, and interleukin-2/interleukin-15 stimulation was able to restore the NK cell activity.

CONCLUSIONS

These findings indicate that Treg cells in TILs may abrogate NK cell cytotoxicity through TGF-β pathway, and therefore, Treg cell elimination may enhance NK cell activity and be a novel therapeutic strategy for CC.

Prevention of allograft rejection in heart transplantation through concurrent gene silencing of TLR and Kinase signaling pathways

Toll-like receptors (TLRs) act as initiators and conductors responsible for both innate and adaptive immune responses in organ transplantation. The mammalian target of rapamycin (mTOR) is one of the most critical signaling kinases that affects broad aspects of cellular functions including metabolism, growth, and survival. Recipients (BALB/c) were treated with MyD88, TRIF and mTOR siRNA vectors, 3 and 7 days prior to heart transplantation and 7, 14 and 21 days after transplantation. After siRNA treatment, recipients received a fully MHC-mismatched C57BL/6 heart. Treatment with mTOR siRNA significantly prolonged allograft survival in heart transplantation. Moreover, the combination of mTOR siRNA with MyD88 and TRIF siRNA further extended the allograft survival; Flow cytometric analysis showed an upregulation of FoxP3 expression in spleen lymphocytes and a concurrent downregulation of CD40, CD86 expression, upregulation of PD-L1 expression in splenic dendritic cells in MyD88, TRIF and mTOR treated mice. There is significantly upregulated T cell exhaustion in T cells isolated from tolerant recipients. This study is the first demonstration of preventing immune rejection of allogeneic heart grafts through concurrent gene silencing of TLR and kinase signaling pathways, highlighting the therapeutic potential of siRNA in clinical transplantation.

The role of Toll-like receptors in retinal ischemic diseases

Toll-like receptors (TLRs) are commonly referred to a series of evolutionary conserved receptors which recognize and respond to various microbes and endogenous ligands. Growing evidence has demonstrated that the expression of TLRs in the retina is regulated during retinal ischemic diseases, including ischemia-reperfusion injury, glaucoma, diabetic retinopathy (DR) and retinopathy of prematurity (ROP). TLRs can be expressed in multiple cells in the retina, such as glial cells, retinal pigment epithelium (RPE), as well as photoreceptor cells and endothelium cells. Activation of TLRs in retina could initiate a complex signal transduction cascade, induce the production of inflammatory cytokines and regulate the level of co-stimulatory molecules, which play prominent roles in the pathogenesis of retinal ischemic diseases. In this review, we summarized current studies about the relationship between TLRs and ischemic retinopathy. A greater understanding of the effect of TLRs on ischemic injuries may contribute to the development of specific TLR targeted therapeutic strategies in these conditions.

TLR2, TLR4 AND MyD88 Mediate Allergic Airway Disease (AAD) and Streptococcus pneumoniae-Induced Suppression of AAD

Background

Exposure to non-pathogenic Streptococcus pneumoniae and vaccination are inversely associated with asthma. Studies in animal models demonstrate that airway administration of S. pneumoniae (live or killed), or its vaccines or components, suppresses the characteristic features of asthma in mouse models of allergic airway disease (AAD). These components could be developed into immunoregulatory therapies. S. pneumoniae components are recognized by Toll-like receptors (TLR) 2 and TLR4, and both induce inflammatory cell responses through the adaptor protein myeloid differentiation primary response gene 88 (MyD88). The involvement of TLR2, TLR4 and MyD88 in the pathogenesis of AAD and asthma is incompletely understood, and has not been studied in S. pneumoniae-mediated suppression of AAD. We investigated the role of TLR2, TLR4 and MyD88 in the development of AAD and S. pneumoniae-mediated suppression of AAD.

Methods and Findings

OVA-induced AAD and killed S. pneumoniae-mediated suppression of AAD were assessed in wild-type, TLR2^-/-, TLR4^-/-, TLR2/4^-/- and MyD88^-/- BALB/c mice. During OVA-induced AAD, TLR2, TLR4 and MyD88 were variously involved in promoting eosinophil accumulation in bronchoalveolar lavage fluid and blood, and T-helper type (Th)2 cytokine release from mediastinal lymph node T cells and splenocytes. However, all were required for the induction of airways hyperresponsiveness (AHR). In S. pneumoniae-mediated suppression of AAD, TLR2, TLR4 and MyD88 were variously involved in the suppression of eosinophilic and splenocyte Th2 responses but all were required for the reduction in AHR.

Conclusions

These results highlight important but complex roles for TLR2, TLR4 and MyD88 in promoting the development of OVA-induced AAD, but conversely in the S. pneumoniae-mediated suppression of AAD, with consistent and major contributions in both the induction and suppression of AHR. Thus, TLR signaling is likely required for both the development of asthma and the suppression of asthma by S. pneumoniae, and potentially other immunoregulatory therapies.

Conditioning of naive CD4(+) T cells for enhanced peripheral Foxp3 induction by nonspecific bystander inflammation

Inflammation induced during infection can both promote and suppress immunity. This contradiction suggests that inflammatory cytokines impact the immune system in a context-dependent manner. Here we show that non-specific bystander inflammation conditioned naïve CD4⁺ T cells for enhanced peripheral Foxp3 induction and reduced effector differentiation. This resulted in inhibition of immune responses in vivo via Foxp3-dependent effect on antigen-specific naïve CD4⁺ T cell precursors. Such conditioning may have evolved to allow immunity to infection while limiting subsequent autoimmunity caused by release of self-antigens in the wake of infection. Furthermore, this phenomenon suggests a mechanistic explanation for the concept that early tuning of the immune system by infection impacts the long-term quality of immune regulation.

TLR Function in Murine CD4(+) T Lymphocytes and Their Role in Inflammation

Toll-like receptor (TLR) signaling represents an evolutionary-conserved mechanism allowing for the rapid detection of broad molecular patterns that are common to different groups of pathogens. TLRs are traditionally associated with cells of the innate immune response where ligation of a TLR alone can lead to cellular activation and the initialization of an immune response. Cells of adaptive immunity, namely different classes of T and B lymphocytes, are also known to express a variety of TLRs. Conversely, the functional and signaling outcomes of TLRs are decidedly different in cells of the adaptive immune response. T lymphocytes generally have substantially lower TLR expression compared to innate cells, suggesting that TLRs function in a highly specialized capacity in this cell type. Certain TLRs act in a co-stimulatory capacity on T cells, amplifying activation only in the presence of simultaneous T-cell receptor engagement. However, the full array of TLR signaling events and outcomes in T lymphocytes remains poorly understood. Here, we describe a few methods for investigating the general function of TLRs on T lymphocytes in vitro and in vivo with an emphasis on the study of CD4(+) T cells. Most of these procedures can be adapted for the study of TLR signaling on other classes of lymphocytes as well.

Differential induction of inflammatory cytokines and reactive oxygen species in murine peritoneal macrophages and resident fresh bone marrow cells by acute staphylococcus aureus infection: contribution of toll-like receptor 2 (TLR2)

Among the known Toll-like receptors (TLRs), Toll-like receptor 2 (TLR2) is a key sensor for detecting Staphylococcus aureus invasion. But the function of TLR2 during S. aureus infection in different cell populations is unclear. Two different cell subtypes were chosen to study the interaction of S. aureus with TLR2 because macrophages are extremely different from one compartment to another and their capacity to respond to live bacteria or bacterial products differs from one site to another. The contribution of TLR2 to the host innate response against acute live S. aureus infection and heat-killed S. aureus (HKSA) using anti-TLR2 antibody in murine peritoneal macrophages and resident fresh bone marrow cells has been investigated here. TLR2 blocking before infection induces the release of interleukin (IL)-10 by macrophages thereby inhibiting excessive production of oxidants by activating antioxidant enzymes. TLR2-blocked peritoneal macrophages showed impaired release of tumor necrosis factor-alpha (TNF-α), interferon-gamma (IFN-γ) and IL-6 in response to both live and heat-killed S. aureus infection except bone marrow cells. TLR2-mediated free radical production and killing of S. aureus were modulated by TLR2 blocking in peritoneal macrophages and resident bone marrow cells. This study supported that S. aureus persists in resident bone marrow cells in a state of quiescence.

Soluble β-glucan from Grifola frondosa induces tumor regression in synergy with TLR9 agonist via dendritic cell-mediated immunity

The maturation of dendritic cells into more-immunostimulatory dendritic cells by stimulation with different combinations of immunologic agents is expected to provide efficient, adoptive immunotherapy against cancer. Soluble β-glucan maitake D-fraction, extracted from the maitake mushroom Grifola frondosa, acts as a potent immunotherapeutic agent, eliciting innate and adoptive immune responses, thereby contributing to its antitumor activity. Here, we evaluated the efficacy of maitake D-fraction, in combination with a Toll-like receptor agonist, to treat tumors in a murine model. Our results showed that maitake D-fraction, in combination with the Toll-like receptor 9 agonist, cytosine-phosphate-guanine oligodeoxynucleotide, synergistically increased the expression of dendritic cell maturation markers and interleukin-12 production in dendritic cells, but it did not increase interleukin-10 production, generating strong effector dendritic cells with an augmented capacity for efficiently priming an antigen-specific, T helper 1-type T cell response. Maitake D-fraction enhances cytosine-phosphate-guanine oligodeoxynucleotide-induced dendritic cell maturation and cytokine responses in a dectin-1-dependent pathway. We further showed that a combination therapy using cytosine-phosphate-guanine oligodeoxynucleotide and maitake D-fraction was highly effective, either as adjuvants for dendritic cell vaccination or by direct administration against murine tumor. Therapeutic responses to direct administration were associated with increased CD11c(+) dendritic cells in the tumor site and the induction of interferon-γ-producing CD4(+) and CD8(+) T cells. Our results indicate that maitake D-fraction and cytosine-phosphate-guanine oligodeoxynucleotide synergistically activated dendritic cells, resulting in tumor regression via an antitumor T helper cell 1-type response. Our findings provide the basis for a potent antitumor therapy using a novel combination of immunologic agents for future clinical immunotherapy studies in patients.

Pattern Recognition Receptors in Cancer Progression and Metastasis

The innate immune system is an integral component of the inflammatory response to pathophysiological stimuli. Toll-like receptors (TLRs) and inflammasomes are the major sensors and pattern recognition receptors (PRRs) of the innate immune system that activate stimulus (signal)-specific pro-inflammatory responses. Chronic activation of PRRs has been found to be associated with the aggressiveness of various cancers and poor prognosis. Involvement of PRRs was earlier considered to be limited to infection- and injury-driven carcinogenesis, where they are activated by pathogenic ligands. With the recognition of damage-associated molecular patterns (DAMPs) as ligands of PRRs, the role of PRRs in carcinogenesis has also been implicated in other non-pathogen-driven neoplasms. Dying (apoptotic or necrotic) cells shed a plethora of DAMPs causing persistent activation of PRRs, leading to chronic inflammation and carcinogenesis. Such chronic activation of TLRs promotes tumor cell proliferation and enhances tumor cell invasion and metastasis by regulating pro-inflammatory cytokines, metalloproteinases, and integrins. Due to the decisive role of PRRs in carcinogenesis, targeting PRRs appears to be an effective cancer-preventive strategy. This review provides a brief account on the association of PRRs with various cancers and their role in carcinogenesis.

TLR4 Signaling Is a Major Mediator of the Female Tract Response to Seminal Fluid in Mice

Seminal fluid interacts with epithelial cells lining the female reproductive tract to induce expression of proinflammatory cytokines and chemokines, initiating immune tolerance mechanisms to facilitate pregnancy. TGFB cytokines are key signaling agents in seminal plasma but do not fully account for the female response to seminal fluid. We hypothesized that additional molecular pathways are utilized in seminal fluid signaling. Affymetrix microarray was employed to compare gene expression in the endometrium of mice 8 h after mating with either intact males or seminal fluid deficient (SVX/VAS) males. Bioinformatics analysis revealed TLR4 signaling as a strongly predicted upstream regulator activated by the differentially expressed genes and implicated TGFB signaling as a second key pathway. Quantitative PCR and microbead data confirmed that seminal fluid induces endometrial synthesis of several TLR4-regulated cytokines and chemokines, including CSF3, CXCL1, CXCL2, IL1A, IL6, LIF, and TNF. In primary uterine epithelial cells, CSF3, CXCL1, and CXCL2 were strongly induced by the TLR4 ligand LPS but suppressed by TGFB, while IL1A, TNF, and CSF2 were induced by both ligands. TLR4 was confirmed as essential for the full endometrial cytokine response using mice with a null mutation in Tlr4, where seminal fluid failed to induce endometrial Csf3, Cxcl2, Il6, and Tnf expression. This study provides evidence that TLR4 contributes to seminal fluid modulation of the periconception immune environment. Activation of TLR4 signaling by microbial or endogenous components of seminal fluid is thus implicated as a key element of the female tract response to seminal fluid at the outset of pregnancy in mice.

Inhibition of indoleamine 2,3-dioxygenase activity enhances the anti-tumour effects of a Toll-like receptor 7 agonist in an established cancer model

Toll-like receptor (TLR) agonists have been shown to have anti-tumour activity in basic research and clinical studies. However, TLR agonist monotherapy does not sufficiently eliminate tumours. Activation of the innate immune response by TLR agonists is effective at driving adaptive immunity via interleukin-12 (IL-12) or IL-1, but is counteracted by the simultaneous induction of immunosuppressive cytokines and other molecules, including IL-10, transforming growth factor-β, and indoleamine 2,3-dioxygenase (IDO). In the present study, we evaluated the anti-cancer effect of the TLR7 agonist, imiquimod (IMQ), in the absence of IDO activity. The administration of IMQ in IDO knockout (KO) mice inoculated with tumour cells significantly suppressed tumour progression compared with that in wild-type (WT) mice, and improved the survival rate. Moreover, injection with IMQ enhanced the tumour antigen-specific T helper type 1 response in IDO-KO mice with tumours. Combination therapy with IMQ and an IDO inhibitor also significantly inhibited tumour growth. Our results indicated that the enhancement of IDO expression with TLR agonists in cancer treatment might impair host anti-tumour immunity while the inhibition of IDO could enhance the therapeutic efficacy of TLR agonists via the increase of T helper type 1 immune response.

Inhibition of induced nitric oxide synthase enhances the anti-tumor effects on cancer immunotherapy using TLR7 agonist in mice

Toll-like receptor (TLR) agonists have been shown to have anti-tumor activity in basic research and clinical studies. However, TLR agonist monotherapy in cancer treatment dose not sufficiently eliminate tumors. Activation of the innate immune response by TLR agonists and other pathogen-associated molecular patterns is effective for driving adaptive immunity via interleukin (IL)-12 or IL-1, but is counteracted by the simultaneous induction of immunosuppressive cytokines and other molecules, including IL-10, tumor growth factor-β, and induced nitric oxide synthase (iNOS). In the present study, we evaluated the anticancer effect of the TLR7 agonist, imiquimod (IMQ), in the absence of iNOS. The administration of IMQ in iNOS-knockout (KO) mice implanted with tumor cells significantly suppressed tumor progression as compared to that in wild-type mice and improved the survival rate. Moreover, injection with IMQ enhanced the tumor antigen-specific Th1 response in iNOS-KO mice with tumors. The enhancement of the antigen-specific Th1 response was associated with an increase in IL-2 and IL-12b expressions in the tumor-draining lymph nodes. Combination therapy with IMQ and an iNOS inhibitor also significantly inhibited tumor growth in the established tumor model. Finally, our results indicated that the enhancement of iNOS expression through the administration with TLR agonists impairs host anti-tumor immunity, while the inhibition of iNOS could enhance the therapeutic efficacy of TLR agonists via the increase in Th1 immune response.

Seminal Fluid Signalling in the Female Reproductive Tract: Implications for Reproductive Success and Offspring Health

Carriage of sperm is not the only function of seminal fluid in mammals. Studies in mice show that at conception, seminal fluid interacts with the female reproductive tract to induce responses which influence whether or not pregnancy will occur, and to set in train effects that help shape subsequent fetal development. In particular, seminal fluid initiates female immune adaptation processes required to tolerate male transplantation antigens present in seminal fluid and inherited by the conceptus. A tolerogenic immune environment to facilitate pregnancy depends on regulatory T cells (Treg cells), which recognise male antigens and function to suppress inflammation and immune rejection responses. The female response to seminal fluid stimulates the generation of Treg cells that protect the conceptus from inflammatory damage, to support implantation and placental development. Seminal fluid also elicits molecular and cellular changes in the oviduct and endometrium that directly promote embryo development and implantation competence. The plasma fraction of seminal fluid plays a key role in this process with soluble factors, including TGFB, prostaglandin-E, and TLR4 ligands, demonstrated to contribute to the peri-conception immune environment. Recent studies show that conception in the absence of seminal plasma in mice impairs embryo development and alters fetal development to impact the phenotype of offspring, with adverse effects on adult metabolic function particularly in males. This review summarises our current understanding of the molecular responses to seminal fluid and how this contributes to the establishment of pregnancy, generation of an immune-regulatory environment and programming long-term offspring health.

Intratumoral immunization: a new paradigm for cancer therapy

Immune cell infiltration in the tumor microenvironment is of prognostic and therapeutic import. These immune cell subsets can be heterogeneous and are composed of mature antigen-presenting cells, helper and effector cytotoxic T cells, toleragenic dendritic cells, tumor-associated macrophages, and regulatory T cells, among other cell types. With the development of novel drugs that target the immune system rather than the cancer cells, the tumor immune microenvironment is not only prognostic for overall patient outcome, but also predictive for likelihood of response to these immune-targeted therapies. Such therapies aim to reverse the cancer immunotolerance and trigger an effective antitumor immune response. Two major families of immunostimulatory drugs are currently in clinical development: pattern recognition receptor agonists (PRRago) and immunostimulatory monoclonal antibodies (ISmAb). Despite their immune-targeted design, these agents have so far been developed clinically as if they were typical anticancer drugs. Here, we review the limitations of this conventional approach, specifically addressing the shortcomings of the usual schedules of intravenous infusions every 2 or 3 weeks. If the new modalities of immunotherapy target specific immune cells within the tumor microenvironment, it might be preferable to deliver them locally into the tumor rather than systemically. There is preclinical and clinical evidence that a therapeutic systemic antitumor immune response can be generated upon intratumoral immunomodulation. Moreover, preclinical results have shown that therapeutic synergy can be obtained by combining PRRagos and ISmAbs to the local tumor site.