Effect Of Toll-like Receptor Ligands Research Articles

Immunostimulatory effects of Toll-like receptor ligands as adjuvants in establishing a novel mouse model for pemphigus vulgaris.

The meticulous selection of appropriate vaccine adjuvants is crucial for optimizing immune responses. Traditionally, pemphigus vulgaris (PV), an autoimmune disorder, has been modelled using complete Freund's adjuvant (CFA). In this study, we aimed to discern potential variations in immune responses elicited by Toll-like receptor (TLR) ligands as compared to CFA. A comprehensive investigation was conducted, comparing the effects of these adjuvants in conjunction with ovalbumin or desmoglein-3. Flow cytometry was employed to analyse distinct cell subsets, while enzyme-linked immunosorbent assay quantified antigen-specific antibodies and cytokine levels. Histological examination of harvested skin tissues and transcriptome analysis of skin lesions were performed to identify differentially expressed genes. TLR ligands demonstrated efficacy in inducing PV-like symptoms in wild-type mice, in contrast to CFA. This underscored the substantial impact of the adjuvant on self-antigen tolerance. Furthermore, we proposed an enhanced method for establishing a PV model through adoptive transfer, substituting CFA with TLR ligands. Our results revealed that in contrast to the perception that CFA being the most potent immunopotentiator reported, CFA promoted regulatory T cells (Treg), follicular regulatory T cells and IL-10-producing neutrophils, whereas TLR ligands downregulated CCL17 and IL-10. This suggested potential implications for the recruitment and activation of Treg subsets. While B cell and CD8+ T cell responses exhibited similarity, CFA induced less activation in dendritic cell subsets. A novel mouse model of PV and systemic comparison of immunostimulatory effects of adjuvants were provided by this study. The systematic comparison of CFA and TLR ligands shed light on the distinctive properties of these adjuvants, presenting innovative mouse models for the investigation of pemphigus. This study significantly contributes to adjuvant research and advances our understanding of PV pathogenesis. Immunization with desmoglein 3 and Toll-like receptor (TLR) ligands effectively induces pemphigus symptoms in wild-type mice, whereas complete Freund's adjuvant (CFA) fails. TLR ligands heightened the autoreactivity of donor cells in the adoptive transfer pemphigus model. CFA promoted regulatory T cells and IL-10-producing neutrophils, whereas TLR ligands downregulated CCL17 and IL-10, leading to more effective immune responses.

The effect of toll-like receptor ligands on energy metabolism and myokine expression and secretion in cultured human skeletal muscle cells

Skeletal muscle plays an important role in glycaemic control and metabolic homeostasis, making it a tissue of interest with respect to type 2 diabetes mellitus. The aim of the present study was to determine if ligands of Toll-like receptors (TLRs) could have an impact on energy metabolism and myokine expression and secretion in cultured human skeletal muscle cells. The myotubes expressed mRNA for TLRs 1–6. TLR3, TLR4, TLR5 and TLR6 ligands (TLRLs) increased glucose metabolism. Furthermore, TLR4L and TLR5L increased oleic acid metabolism. The metabolic effects of TLRLs were not evident until after at least 24 h pre-incubation of the cells and here the metabolic effects were more evident for the metabolism of glucose than oleic acid, with a shift towards effects on oleic acid metabolism after chronic exposure (168 h). However, the stimulatory effect of TLRLs on myokine expression and secretion was detected after only 6 h, where TLR3-6L stimulated secretion of interleukin-6 (IL-6). TLR5L also increased secretion of interleukin-8 (IL-8), while TLR6L also increased secretion of granulocyte–macrophage colony stimulating factor (GM-CSF). Pre-incubation of the myotubes with IL-6 for 24 h increased oleic acid oxidation but had no effect on glucose metabolism. Thus IL-6 did not mimic all the metabolic effects of the TLRLs, implying metabolic effects beyond the actions of this myokine.

Effects of Toll-like Receptor Ligands on the Expression of Proinflammatory Cytokines and Avian β-defensins in Cultured Chick Intestine.

Few studies have focused on the regulation of cytokine and avian β-defensin (AvBDs) expression for promoting immune defense in the avian intestine. The aim of this study was to investigate the effects of different Toll-like receptor (TLR) ligands (bacterial patterns) on the expression of proinflammatory cytokines (IL-1β and IL-6) and AvBDs (AvBD1, AvBD4, and AvBD7) in the chick intestine. The ileum and cecum of 3-day-old chicks were collected and examined histologically to identity the cells present in the intestinal mucosa. Other tissues were cultured with or without the TLR2, TLR4, and TLR21 ligands—Pam3CSK4, LPS, and CpG-ODN—for 1 or 3 h. The gene expression profiles of proinflammatory cytokines and AvBDs were determined in these tissues using real-time polymerase chain reaction (PCR). The mucosa of the ileum and cecum contained leukocytes, luminal and crypt epithelial cells, and other enterocytes. Pam3CSK4 tended to downregulate the expression of IL-1β, AvBD1, and AvBD7 in the ileum but upregulated their expression in the cecum. LPS downregulated the expression of IL-1β and IL-6 in both the ileum and the cecum, whereas it upregulated the expression of AvBD1, AvBD4, and AvBD7 in the cecum. CpG-ODN upregulated the expression of IL-6 and AvBD7 in the ileum and IL-1β in the cecum, and downregulated the expression of IL-1β and AvBDs in the ileum. We suggested that the expression levels of proinflammatory cytokines and AvBDs in the chick intestine are affected by TLR2, TLR4, and TLR21 ligands. Thus, these innate immune factors may be modulated by the luminal microbe complex in the intestine.

Abstract A81: Early TLR-mediated killing of leukemia in bone marrow is correlated with durable protection against B cell precursor acute lymphoblastic leukemia

Abstract The ability of Toll-like receptor (TLR)-induced innate immune responses to activate adaptive immune responses offers considerable therapeutic potential for cancer treatment, most likely as part of combination therapies. The potent immunostimulatory capacity of TLR agonists provides means to generate antigen-specific antitumor T cell responses from antigen-nonspecific innate immune stimulation. B cell precursor (BCP) acute lymphoblastic leukemia (ALL) exhibits the very low mutational burden common to other pediatric cancers. Despite this limited neo-antigenicity, we previously reported the ability of CpG oligodioxynucleotides (ODN), a ligand for TLR9, to mediate anti-leukemia activities that establish long-term protection against ALL outgrowth in a transplantable syngeneic model using cell lines. CpG ODN also reduced the burden of primary human ALL in mouse xenografts, primarily via induction of NK cell-mediated cytotoxicity. However, our recent demonstration that endosomal TLR agonists generated distinct effects on pre-leukemic BCP cells, coupled with the divergent effects of TLR ligands on the immunogenicity of primary human ALL cells suggest that there are significant variables that contribute to the overall outcome of TLR stimulation in the context of BCP cell malignancy. In this study, we compared the ligands for TLR3 (polyI:C), TLR7/8(R848) and TLR9 (CpG ODN) for their ability to elicit control of primary ALL cells and correlated protection with early innate immune activation to identify the necessary component of a long-term protective anti-leukemic response. We adoptively transferred syngeneic primary ALL cells to wild-type mice then administered TLR ligands starting at day 7 for 3 doses every 4 days. 21 days after leukemia challenge, we evaluated the disease burden in the peripheral blood, spleen, and bone marrow of recipients. While a significantly lower disease burden was observed in all three anatomical compartments of mice treated with polyI:C, CpG ODN- and R848-treated mice failed to control the early outgrowth of transferred cells in the spleen and bone marrow, respectively. While R848-treated mice had a slightly delayed disease progression with median survival (MS) of 40 days compared to that of 28 days of PBS-treated control group, CpG ODN treatment conferred a significant survival advantage where over 57% of treated mice achieved a prolonged disease-free status. Despite successfully inducing systemic anti-ALL responses, poly I:C treatment failed to confer durable protection, achieving only a modest increase in disease-free survival in treated mice (MS=42 days). Moreover, CpG ODN-induced long-term survival in the absence of effective early immune-mediated control of ALL in spleen implies that bone marrow is not only an important homing niche supporting the survival and proliferation of leukemia blasts prior to migration into the circulation, but a critical target site for controlling disease progression. Furthermore, to investigate the early innate immune responses associated with the differential overall effects induced by TLR agonists, we evaluated the activation status of innate immune system using RAG-knockout mice. A single administration of CpG ODN, but not polyI:C nor R848, was sufficient to rapidly induce anti-ALL immune responses involving activated natural killer and antigen-presenting cells in the bone marrow of the mice bearing ALL in 4 days. This suggests that CpG ODN has superior capacity to initiate innate immune-mediated anti-ALL immune responses and activate subsequent antigen-specific T cell responses. TLR-mediate innate immune responses induced early in life are distinct from that induced in adult life. Given the peak incidence of pediatric ALL between 3-5 years of age, we are currently examining the influence of age on the TLR-induced anti-ALL immune responses to further evaluate the therapeutic benefits of TLR ligands. Our results demonstrate the differential magnitude of tissue-specific innate immune-mediated control of leukemia outgrowth induced by TLR stimulations correlating with durable disease-free survival. These findings provide mechanistic explanation for TLR-mediated protective immune responses and highlight the potential target site necessary for effective elimination of leukemia cells. Citation Format: Sumin Jo, Peter van den Elzen, Gregor S.D Reid. Early TLR-mediated killing of leukemia in bone marrow is correlated with durable protection against B cell precursor acute lymphoblastic leukemia [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2017 Oct 1-4; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2018;6(9 Suppl):Abstract nr A81.

Effects of TLR Ligands on the Expression of Cytokines and Possible Role of NFκB in its Process in the Theca of Chicken Follicles.

The aim of this study was to determine the effects of Toll-like receptor (TLR) ligands on the expression of cytokines in chicken follicular theca and to investigate whether nuclear factor-κB (NFκB) was involved in their expression. The follicular theca was collected from the largest follicle of laying hens. In experiment 1, the expression of TLRs in the theca interna and externa was confirmed using RT-PCR. The theca tissues were then incubated with or without Pam3CSK4 (TLR2 ligand), poly I:C (TLR3 ligand), LPS (TLR4 ligand), flagellin (TLR5 ligand), R837 (TLR7 ligand), and CpG-ODN (TLR21 ligand) for 3 h, after which cytokine expression (IL-1β, IL-6, TNFSF15, CXCLi2, IFN-α, and IFN-β) was analyzed by real-time PCR. In experiment 2, the theca tissues were incubated in a medium containing Pam3CSK4, poly I:C, LPS, or CpG-ODN with or without BAY 11-7085 (an inhibitor of NFκB) for 3 h. The results of experiment 1 revealed that all TLRs, namely TLR1 (type 1 and 2), TLR2 (type 1 and 2), 3–5, 7, 15, and 21, were expressed in the follicular theca, although the PCR products of TLR1 (type 2) and TLR21 were faint. Moreover, Pam3CSK4 and LPS upregulated the expression of all detected cytokines, except for IFN-α, whose expression was not upregulated by LPS. Poly I:C upregulated the expression of IL-6, CXCLi2, and IFN-β, while CpG-ODN upregulated IL-1β. Flagellin and R837 did not significantly affect cytokine expression. In experiment 2, the expression of IL-1β, IL-6, CXCLi2 and IFN-β in tissues incubated with LPS was downregulated by BAY 11-7085. These results suggest that the innate immune system, including pattern recognition by TLRs and cytokine synthesis, occur in the theca; whereas, functions for recognition of bacterial patterns is more developed than that of viral ones.

Opposing Effects of Toll-Like Receptor Ligands and Ascorbic Acid On T and Natural Killer Cell Development From Lymphoid Progenitor Cells.

Abstract 1491Poster Board I-514 Introduction:A complete understanding of lymphocyte development, particularly factors driving T and natural killer (NK) cell differentiation from progenitor cells, remains an elusive goal in medicine. T and NK cells are key regulators in the defense against infections and malignancies and play a direct causative role in autoimmune diseases and graft-versus-host disease. The OP9-DL1 stromal line is an important tool in the in vitro study of lymphocyte development. Lymphocyte progenitors (KLS,Thy1.1-) harvested from adult murine bone marrow and seeded on this stromal line can be followed through stages of maturation by immunophenotyping. We observed that addition of stem cell factor (SCF), contaminated with lipopolysaccharide (LPS) through its production in E. coli, was particularly effective at promoting NK cell development in the OP9-DL1 culture system. Toll-like receptors, an important component of anti-microbial defense by the innate immune response, recognize LPS and other microbial products. Toll-like receptor ligands (TLR-L) have been shown to enhance NK cell proliferation, however an effect on NK cell differentiation from progenitor cells has not been established. A separate set of experiments led us to hypothesize that ascorbic acid (vitamin C) promotes T cell differentiation. We therefore designed experiments to evaluate the differential effects of TLR-L and ascorbic acid on NK and T cell development from lymphoid progenitors co-cultured with OP9-DL1 stromal cells. Methods:Lymphocyte progenitor cells (KLS,Thy1.1-) were sorted from adult mouse bone marrow and 1000-2000 progenitor cells were seeded per well in a 24 well plate coated with OP9-DL1 stroma. Cultures were supplemented with IL-7 (5 ng/ml), Flt3 ligand (5 ng/ml), and SCF (100 ng/ml) plus one of 5 different TLR-L (TLR1/2, TLR3, TLR4, TLR5, and a crude LPS preparation that likely contains a number of TLR-L), with or without addition of a stabilized form of ascorbic acid. Cells were passaged, counted and re-seeded with fresh media and supplements twice a week over a 30-day period. Immunophenotype and viability were evaluated by flow cytometry. Markers for T cell development included CD44, CD25, CD3, CD4, CD8, T cell receptor beta chain and T cell receptor gamma-delta chains. NK cells were evaluated for the presence of NKp46, NK1.1, and DX5. Results:We observed robust cell expansion, inhibited somewhat by addition of ascorbic acid. The inhibitory effect of ascorbate on expansion was most pronounced in the culture condition lacking TLR-L. T cell differentiation was markedly advanced by the addition of ascorbic acid in the absence of TLR-L, with the majority of cells co-expressing CD4/CD8 and TCRB/CD3. The addition of different TLR-Ls inhibited T cell differentiation, and this inhibition was partially rescued by addition of ascorbic acid. NK cell differentiation, defined as co-expression of NKp46 and NK1.1, was two to three-fold greater with the addition of TLR1/2, TLR4, TLR5, and crude LPS compared to cultures lacking TLR-L addition. In each of these conditions, NK cell differentiation was markedly inhibited by addition of ascorbic acid. Conclusions:Our data supports the hypothesis that both T and NK cell progenitors require Notch signaling for differentiation. In our in vitro model, differentiation of one lineage at the expense of the other can be manipulated with addition of TLR-L or ascorbic acid. Addition of bacterial TLR-L promotes NK cell differentiation at the expense of T cell differentiation; an effect that is partially overcome with the addition of ascorbic acid. The addition of ascorbic acid promotes robust T cell differentiation, and inhibits significant NK cell differentiation in all conditions. The ability of ascorbic acid to promote T cell differentiation appears to dominate over TLR-L promotion of NK lineage differentiation. Further work will include microarray to evaluate these effects at a genetic level. These findings will contribute to our understanding of the immune response under normal and pathologic conditions, and further a model both for study and ex vivo expansion of immune cells for therapeutic use. Disclosures:No relevant conflicts of interest to declare.

Novel adjuvants for B cell immune responses

To summarize recent progress in the development of adjuvants with a special focus on adjuvants that enhance B-cell responses to protein-based vaccines. Both established and new experimental approaches are described and also briefly we discuss how adjuvants and virus-based vaccines interact with the immune system. Two new adjuvants were recently approved for human applications and many others are in preclinical or clinical testing. Significant advances were made to describe the mechanism of action of adjuvants. For example, aluminum hydroxide salts were shown to engage Nalp3, a member of the cytosolic NOD-like receptors and activation of B cells via invariant natural killer cell presentation of alpha-galactosylceramide was described. The effects of Toll-like receptor ligands on B-cell differentiation were further characterized and a peptide derived from IPS-1, a cytosolic signaling molecule, was shown to provide adjuvant effect. Stimulation of protective antibodies against HIV-1 may require extensive antibody affinity maturation, thus long-term exposure or repeated administration of antigen may be needed to induce effective B-cell responses. Advances in our understanding of how specific signaling pathways link innate and adaptive immunity provides a basis for the design of improved adjuvants to promote broad and potent B-cell responses.

TLR2 Stimulates Th1 Effector Functions

Toll-like receptors (TLRs) are pattern-recognition receptors that recognize microbial products and are crucial components of the innate immune system. TLR ligands have costimulatory roles with stimulation of the T cell antigen receptor (TCR) of naïve CD4 + T cells (although TLR ligands alone cannot stimulate naïve cells), but the actions of TLR ligands on established effector (memory) T cells are poorly understood. T helper (Th) cells are distinct lineages of memory CD4 + T cells. Th1 cells secrete the effector cytokine interferon-γ (IFN-γ) and are important in the immune response to intracellular pathogens, whereas Th2 cells secrete interleukin-4 (IL-4) and protect against infection by extracellular pathogens. Imanishi et al . investigated the effects of TLR ligands on mouse Th1 and Th2 cell cultures established after TCR stimulation of naïve CD4 + T cells under the appropriate conditions. When Th1 cells were restimulated with various TLR ligands, only the TLR2 ligands MALP-2 (macrophage-activating lipopeptide 2) and Pam3 [ N -palmitoyl- S -(2,3-bis(palmitoyloxy)-(2 RS )-propyl)-Cys-Ser-Lys 4 ] stimulated the secretion of IFN-γ, as measured by enzyme-linked immunosorbant assay. TLR2 stimulation also resulted in the activation and proliferation of Th1 cells. In contrast, TLR2 stimulation of Th2 cells did not increase IL-4 secretion or cause cellular activation. TLR2-mediated production of IFN-γ also occurred in Th1 cells that were treated with the TCR inhibitor cyclosporine A, indicating that TCR signaling was not necessary for IFN-γ production. Western blot analyses demonstrated that Pam3 treatment of Th1 cells, but not Th2 cells, resulted in strong and sustained activation of nuclear factor-κB (NF-κB) and mitogen-activated protein kinases (MAPKs). Activation of these pathways by TLR2 requires the adaptor molecule MyD88 and IRAK4 (IL-1 receptor-associated kinase 4). Th1 cells from mice deficient in either MyD88 or IRAK4 did not secrete IFN-γ after TLR2 stimulation. The secretion of IFN-γ by Th1 cells after stimulation with Pam3 was enhanced by either IL-2 or IL-12, and these effects were mediated by enhanced MAPK activation. Together, these data establish TLR2 as a direct stimulator of Th1 functions and suggest that TLR2 signaling differs in naïve and memory CD4 + T cells. T. Imanishi, H. Hara, S. Suzuki, N. Suzuki, S. Akira, T. Saito, Cutting Edge: TLR2 directly triggers Th1 effector functions. J. Immunol. 178 , 6715-6719 (2007). [PubMed]

The direct effects of Toll-like receptor ligands on human NK cell cytokine production and cytotoxicity

Toll-like receptor (TLR) ligands are potent inducers of the innate immune system, of which NK and NKT cells play an important role. We examined the direct activation of highly purified human NK and/or NKT cells with known TLR ligands. NK/NKT cells were positive for all known TLR mRNA (TLR1–10). Ligands for TLR2–5 induced production of significant amounts of IFN-γ by purified NK cells. However, a TLR9 ligand failed to induce significant levels of the cytokine. NK cells were depleted from PBMCs to confirm that they were the main source of IFN-γ following treatment with TLR ligands, which resulted in a significant decrease in cytokines. The direct effects of TLR ligands on NK cytotoxicity were determined using 51Cr-labeled K562 target cells. Ligands for TLR2–5 were potent inducers of NK cell cytotoxicity, a TLR9 ligand was not. Our results suggest that TLR ligands can directly stimulate and enhance NK cell cytokine production and induce cytotoxic activities.

Differential liver sensitization to Toll-like receptor pathways in mice with alcoholic fatty liver

Gut-derived, endotoxin-mediated hepatocellular damage has been postulated to play a crucial role in the pathogenesis of alcohol-induced liver injury in rodents. Endotoxins induce production of tumor necrosis factor alpha (TNF-alpha) by Kupffer cells via Toll-like receptor (TLR) 4 and contribute to liver injury. This study addressed the contribution of other TLRs and ligands to alcoholic fatty liver. C57Bl6/J mice were fed a modified Lieber-DeCarli diet. Serum aminotransferase measurements, histological analysis, and quantification of liver TNF-alpha and TLR1-9 messenger RNA (mRNA) were performed. The effect of TLR ligands on liver injury was assessed in vivo. Neomycin and metronidazole or diphenyleneiodonium sulfate (DPI) were administered to evaluate the role of gut bacteria and NADPH oxidase activity, respectively, in hepatic TLR expression. Enteral ethanol (EtOH) exposure induced steatosis and increased liver weight, aminotransferase levels, and expression of TLR1, 2, 4, 6, 7, 8, and 9 liver mRNA. Injection of lipoteichoic acid, peptidoglycan (PGN), lipopolysaccharide (LPS), loxoribine, and oligonudeotide containing CpG (ISS-ODN) increased TNF-alpha mRNA expression more in the livers of EtOH-fed mice than in control mice. PGN, LPS, flagellin, and ISS-ODN induced liver inflammatory infiltrate in EtOH-fed mice but not control mice. Addition of antibiotics reduced the severity of alcoholic fatty liver without affecting TLR expression, whereas daily DPI injections reduced the EtOH-mediated upregulation of TLR2, 4, 6, and 9 mRNA. In conclusion, EtOH-fed mice exhibited an oxidative stress dependent on upregulation of multiple TLRs in the liver and are sensitive to liver inflammation induced by multiple bacterial products recognized by TLRs.

Effect of Toll-like receptor ligands on survival of human bronchial epithelial cells

Effect of Toll-like receptor ligands on survival of human bronchial epithelial cells