Function Of Toll-like Receptors Research Articles

Motor, Cognitive, and Behavioral Impairment in TLR3 and TLR9 Deficient Male Mice: Insights into the Non-Immunological Roles of Toll-Like Receptors

Toll-like receptors (TLRs) play a critical role in initiating the innate immune response to infection or injury. Recent studies have uncovered their intriguing functions as moonlighting proteins involved in various biological processes, including development, learning, and memory. However, the specific functions of individual TLRs are still largely unknown. We investigated the effects of TLR3 and TLR9 receptor deficiency on motor, cognitive, and behavioral functions during development using genetically modified male mice of different ages. We evaluated the motor coordination, anxiety-like behavior, spatial learning, and working memory of male mice lacking the TLR3 and TLR9 genes at different ages (two, four, six, and eight months) using the rotarod, open field, water maze, and T-maze tests. We observed that the deletion of either TLR3 or TLR9 resulted in impaired motor performance. Furthermore, young TLR3-deficient mice exhibited reduced anxiety-like behavior and spatial learning deficits; however, their working memory was unaffected. In contrast, young TLR9-knockout mice showed hyperactivity and a tendency toward decreased working memory. These findings provide valuable insights into the broader roles of the TLR system beyond the innate immune response, revealing its involvement in pathways associated with the central nervous system. Importantly, our results establish a strong association between the endosomal receptors TLR3 and TLR9 and the performance of motor, cognitive, and behavioral tasks that change over time. This study contributes to the growing body of research on the multifaceted functions of TLRs and enhances our understanding of their participation in non-immune-related processes.

TRAF3 regulation of proximal TLR signaling in B cells.

Toll-like receptors are pattern recognition receptors that bridge the innate and adaptive immune responses and are critical for host defense. Most studies of Toll-like receptors have focused upon their roles in myeloid cells. B lymphocytes express most Toll-like receptors and are responsive to Toll-like receptor ligands, yet Toll-like receptor-mediated signaling in B cells is relatively understudied. This is an important knowledge gap, as Toll-like receptor functions can be cell type specific. In striking contrast to myeloid cells, TRAF3 inhibits TLR-mediated functions in B cells. TRAF3-deficient B cells display enhanced IRF3 and NFκB activation, cytokine production, immunoglobulin isotype switching, and antibody production in response to Toll-like receptors 3, 4, 7, and 9. Here, we address the question of how TRAF3 impacts initial B-cell Toll-like receptor signals to regulate downstream activation. We found that TRAF3 in B cells associated with proximal Toll-like receptor 4 and 7 signaling proteins, including MyD88, TRAF6, and the tyrosine kinase Syk. In the absence of TRAF3, TRAF6 showed a greater association with several Toll-like receptor signaling proteins, suggesting that TRAF3 may inhibit TRAF6 access to Toll-like receptor signaling complexes and thus early Toll-like receptor signaling. In addition, our results highlight a key role for Syk in Toll-like receptor signaling in B cells. In the absence of TRAF3, Syk activation was enhanced in response to ligands for Toll-like receptors 4 and 7, and Syk inhibition reduced downstream Toll-like receptor-mediated NFκB activation and proinflammatory cytokine production. This study reveals multiple mechanisms by which TRAF3 serves as a key negative regulator of early Toll-like receptor signaling events in B cells.

UNC93B1 variants underlie TLR7-dependent autoimmunity.

UNC93B1 is critical for trafficking and function of nucleic acid-sensing Toll-like receptors (TLRs) TLR3, TLR7, TLR8, and TLR9, which are essential for antiviral immunity. Overactive TLR7 signaling induced by recognition of self-nucleic acids has been implicated in systemic lupus erythematosus (SLE). Here, we report UNC93B1 variants (E92G and R336L) in four patients with early-onset SLE. Patient cells or mouse macrophages carrying the UNC93B1 variants produced high amounts of TNF-α and IL-6 and upon stimulation with TLR7/TLR8 agonist, but not with TLR3 or TLR9 agonists. E92G causes UNC93B1 protein instability and reduced interaction with TLR7, leading to selective TLR7 hyperactivation with constitutive type I IFN signaling. Thus, UNC93B1 regulates TLR subtype-specific mechanisms of ligand recognition. Our findings establish a pivotal role for UNC93B1 in TLR7-dependent autoimmunity and highlight the therapeutic potential of targeting TLR7 in SLE.

Effects of histone acetyltransferase (HAT) and histone deacetylase (HDAC) inhibitors on proliferative, differentiative, and regenerative functions of Toll-like receptor 2 (TLR-2)-stimulated human dental pulp cells (hDPCs).

This in vitro study aimed to modify TLR-2-mediated effects on the paracrine, proliferative, and differentiation potentials of human dental pulp-derived cells using histone acetyltransferase (HAT) and histone deacetylase (HDAC) inhibitors. Cell viability was assessed using the XTT assay. Cells were either treated with 10μg/ml Pam3CSK4 only, or pre-treated with valproic acid (VPA) (3mM), trichostatin A (TSA) (3μM), and MG-149 (3μM) for a total of 4h and 24h. Control groups included unstimulated cells and cells incubated with inhibitors solvents only. Transcript levels for NANOG, OCT3-4, FGF-1 and 2, NGF, VEGF, COL-1A1, TLR-2, hβD-2 and 3, BMP-2, DSPP, and ALP were assessed through qPCR. After 24h, TSA pre-treatment significantly upregulated the defensins and maintained the elevated pro-inflammatory cytokines, but significantly reduced healing and differentiation genes. VPA significantly upregulated the pro-inflammatory cytokine levels, while MG-149 significantly downregulated them. Pluripotency genes were not significantly affected by any regimen. At the attempted concentrations, TSA upregulated the defensins gene expression levels, and MG-149 exerted a remarkable anti-inflammatory effect; therefore, they could favorably impact the immunological profile of hDPCs. Targeting hDPC nuclear function could be a promising option in the scope of the biological management of inflammatory pulp diseases.

Toll-like receptor expression and functional behavior in platelets from patients with systemic lupus erythematosus

BackgroundMultiple blood cell abnormalities participate in the development of inflammation in systemic lupus erythematosus (SLE). Although platelets have been suggested as one of these contributors through the release of their content during activation, there are limited specific data about their role as immune players in SLE. Materials and MethodsThirteen SLE patients were included. Flow cytometry was used to measure Toll-like receptors (TLR) 2, 4, and 9 in resting platelets, platelet-activation markers (PAC-1 binding, P-selectin, CD63, and CD40 ligand -L) and platelet-leukocyte aggregates before and after specific TLR stimulation. Soluble CD40L and von Willebrand factor (vWf) release from stimulated platelets was measured using ELISA. ResultsIn resting conditions, SLE platelets showed normal expression levels of TLR 2, 4 and 9. Platelet surface activation markers, soluble CD40L, and vWf release were normal at baseline and after TLR stimulation. Platelet-monocyte aggregates were elevated in resting conditions in SLE samples and showed only a marginal increase after TLR stimulation, while baseline and stimulated platelet-neutrophil and platelet-lymphocyte aggregates were normal. C-reactive protein levels positively correlated with platelet-monocyte aggregates both at baseline and after stimulation with the TLR-2 agonist PAM3CSK4, suggesting these complexes could reflect the inflammatory activity in SLE. In our cohort, 12 of 13 patients received treatment with hydroxychloroquine (HCQ), a known inhibitor of endosomal activity and a potential inhibitor of platelet activation. The fact that SLE platelets showed an adequate response to TLR agonists suggests that, despite this treatment, they retain the ability to respond to the increased levels of damage-associated molecular patterns (DAMPs), which represent known TLR ligands, present in the circulation of SLE patients. Interestingly, elevated plasma levels of high mobility group box 1 (HMGB1), a classical DAMP, correlated with vWf release from TLR-stimulated platelets, suggesting that HMGB1 may also be released by platelets, thereby creating a positive feedback loop for platelet activation that contributes to inflammation. ConclusionOur study demonstrates normal platelet TLR expression and function together with increased circulating platelet-monocyte aggregates. In addition, a direct correlation was observed between plasma HMGB1 levels and platelet vWf release following TLR2 stimulation. This platelet behavior in a group of patients undergoing HCQ treatment suggests that platelets could play a role in the inflammatory state of SLE.

Inhibition of Toll-like Receptor 4 (TLR4) Promotes Erythroid and Myeloid Differentiation in Myelodysplastic Syndrome (MDS) and Acute Myeloid Leukemia (AML)

Introduction: The hallmark of Myelodysplastic Syndrome (MDS) is a block in differentiation of hematopoietic precursors resulting in single or multilineage cytopenias. Evaluation of regulatory pathways that are inappropriately overactive and lead to a blockade in erythroid and myeloid differentiation is an important process in determining future therapeutic targets for the treatment of MDS. The Toll-like receptor (TLR) pathways play an important role in the innate immune response and are also highly expressed on hematopoietic stem cells. Aberrant overactivation of these pathways can stimulate inflammation and cytokine production in the marrow microenvironment. Also, while the overactivation of interleukin-1 receptor-associated kinase 4 (IRAK4), tumor necrosis factor receptor associated factor 6 (TRAF6) and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) pathways has been seen in Myelodysplastic Syndrome and Acute Myeloid Leukemia (AML), the upstream signals that drive their activation are not fully identified. Results: We investigated the expression of all TLRs in a large database of MDS CD34+ marrow samples and age-matched controls. Our findings revealed that TLR6 and TLR4 were the most significantly overexpressed receptors in MDS samples (FDR<0.001). Furthermore, we observed that the TLR4 cofactor lymphocyte antigen 96 (LY96), also known as myeloid differentiation factor 2 (MD-2), was also overexpressed in MDS samples when compared to controls. Furthermore, the S100A8 and S100A9 proteins are ligands for TLR4 and were found to be positively associated with severity of anemia in the cohort of MDS samples. These data provided the rationale for determining the functional role of the TLR4 pathway in MDS/AML models. To obtain a potent and specific antibody against TLR4, we inoculated rabbits with recombinant human TLR4 and obtained high affinity antibodies that neutralized TLR4 function at low nano-molar range of doses. The TLR4 polyclonal antibody was able to inhibit lipopolysaccharide (LPS)-induced NF-κb activation in leukemic THP-1 cells. The TLR4 antibody also led to a decrease in proliferative phosphorylated extracellular signal-regulated kinase (ERK) mitogen-activated protein (MAP) kinase in leukemic cells. We then treated samples from MDS/AML patients (n=14) with the TLR4 antibody (1 nM dosing) and assessed for erythroid and myeloid growth and differentiation. Fluorescence activated cell sorting (FACS) analysis for erythroid differentiation showed increased expression of either CD71, CD235a or both after treatment with the TLR4 antibody. FACS analysis for myeloid differentiation showed increased expression of either CD11b, CD14 or both after treatment with the TLR4 antibody. This effect was more pronounced in the intermediate/high risk group than in the low-risk group of patients. Conclusion: Inhibition of the TLR4 pathway with a potent TLR4 antibody promotes erythroid and myeloid maturation and relieves the differentiation block on these lineages in MDS patient samples in the in vitro setting. Our preclinical data supports further evaluation of TLR4 inhibition as a therapeutic target in patients with MDS, as anemia and neutropenia are hallmarks of the disease.

Molecular characteristics and therapeutic implications of Toll-like receptor signaling pathway in melanoma

Melanoma is a malignant tumor of melanocytes and is often considered immunogenic cancer. Toll-like receptor-related genes are expressed differently in most types of cancer, depending on the immune microenvironment inside cancer, and the key function of Toll-like receptors (TLRs) for melanoma has not been fully elucidated. Based on multi-omics data from TCGA and GEO databases, we first performed pan-cancer analysis on TLR, including CNV, SNV, and mRNA changes in TLR-related genes in multiple human cancers, as well as patient prognosis characterization. Then, we divided melanoma patients into three subgroups (clusters 1, 2, and 3) according to the expression of the TLR pathway, and explored the correlation between TLR pathway and melanoma prognosis, immune infiltration, metabolic reprogramming, and oncogene expression characteristics. Finally, through univariate Cox regression analysis and LASSO algorithm, we selected six TLR-related genes to construct a survival prognostic model, divided melanoma patients into the training set, internal validation set 1, internal validation set 2, and external validation set for multiple validations, and discussed the correlation between model genes and clinical features of melanoma patients. In conclusion, we constructed a prognostic survival model based on TLR-related genes that precisely and independently demonstrated the potential to assess the prognosis and immune traits of melanoma patients, which is critical for patients’ survival.

The Protective Role of TLR4 in Intestinal Epithelial Cells through the Regulation of the Gut Microbiota in DSS-Induced Colitis in Mice.

The cause of ulcerative colitis (UC) is not yet fully understood. Previous research has pointed towards a potential role for mutations in nucleotide-binding oligomerization domain-containing protein 2 (NOD2) in promoting the onset and progression of inflammatory bowel disease (IBD) by altering the microbiota of the gut. However, the relationship between toll-like receptor 4 (TLR4) and gut microbiota in IBD is not well understood. To shed light on this, the interaction between TLR4 and gut microbiota was studied using a mouse model of IBD. To examine the function of TLR4 signaling in intestinal injury repair, researchers developed Dextran Sulfate Sodium Salt (DSS)-induced colitis and injury models in both wild-type (WT) mice and TLR4 knockout (TLR4-KO) mice. To assess changes in the gut microbiota, 16S rRNA sequencing was conducted on fecal samples from both the TLR4-KO and WT enteritis mouse models. The data obtained depicted a protective function of TLR4 against DSS-induced colitis. The gut microbiota composition was found to vary considerably between the WT and TLR4-KO mice groups as indicated by β-diversity analysis and operational taxonomic units (OTUs) cluster. Statistical analysis of microbial multivariate variables depicted an elevated abundance of Escherichia coli/Shigella, Gammaproteobacteria, Tenerlcutes, Deferribacteres, Enterobacteria, Rikenellaceae, and Proteobacteria in the gut microbiota of TLR4-KO mice, whereas there was a considerable reduction in Bacteroidetes at five different levels of the phylogenetic hierarchy including phylum, class, order, family, and genus in comparison with the WT control. TLR4 may protect intestinal epithelial cells from damage in response to DSS-induced injury by controlling the microbiota in the gut.

How Toll-like receptors influence Parkinson's disease in the microbiome-gut-brain axis.

Recently, a large number of experimenters have found that the pathogenesis of Parkinson's disease may be related to the gut microbiome and proposed the microbiome-gut-brain axis. Studies have shown that Toll-like receptors, especially Toll-like receptor 2 (TLR2) and Toll-like receptor 4 (TLR4), are key mediators of gut homeostasis. In addition to their established role in innate immunity throughout the body, research is increasingly showing that the Toll-like receptor 2 and Toll-like receptor 4 signaling pathways shape the development and function of the gut and enteric nervous system. Notably, Toll-like receptor 2 and Toll-like receptor 4 are dysregulated in Parkinson's disease patients and may therefore be identified as the core of early gut dysfunction in Parkinson's disease. To better understand the contribution of Toll-like receptor 2 and Toll-like receptor 4 dysfunction in the gut to early α-synuclein aggregation, we discussed the structural function of Toll-like receptor 2 and Toll-like receptor 4 and signal transduction of Toll-like receptor 2 and Toll-like receptor 4 in Parkinson's disease by reviewing clinical, animal models, and in vitro studies. We also present a conceptual model of the pathogenesis of Parkinson's disease, in which microbial dysbiosis alters the gut barrier as well as the Toll-like receptor 2 and Toll-like receptor 4 signaling pathways, ultimately leading to a positive feedback loop for chronic gut dysfunction, promoting α-synuclein aggregation in the gut and vagus nerve.

Abstract 554: Monocyte Toll-like Receptor 4 (tlr4) Signaling Is Essential For Post Thrombotic Upa Expression

Background: Leukocyte expression of Toll-like receptor 4 (TLR4) increases with transformation to chronic deep venous thrombosis (DVT) & in non-resolving thrombi, but TLR4 function during thrombus clearance is unclear. We hypothesized TLR4 signaling to regulate expression of fibrinolytic factors in monocytes & macrophages (MO/MFs) for VT resolution. Methods: Small interfering RNA (siRNA) knockdown (KD) of TLR4 & disruption of Myd88-dependent/independent pathways occurred in immortalized MFs (RAW264.7), with quantitative real-time PCR (qRT-PCR) for a panel of fibrinolytic factors & immunoblotting for urokinase (uPA). Tlr4-/- mice & wild-type controls underwent IVC stasis/ligation, yielding VT at 2h, 2d, & 8d. Murine/chronic human thrombi underwent immunofluorescent staining for indicated targets & murine thrombi weight-length ratios were found. Splenic & Bone marrow-derived MFs from Tlr4 Cre mice were immunoblotted for uPA. Results: TLR4 silencing in RAW264.7 cells yielded suppression of uPA mRNA (Fig 1B) & protein levels (not shown). TRIF KD yielded decreased uPA mRNA (Fig 1C) & protein levels (not shown), implicating Myd88-independent signaling in MO/MF uPA production. Human (not shown) & murine chronic thrombi staining saw TLR4 co-localization with MF marker CCR2 (Fig 1D). Global knockout (KO) of murine TLR4 did not affect early thrombogenesis (Fig 1E left), with delayed VT resolution seen from 2d (Fig 1E right). Decreased uPA protein levels were observed in Tlr4 KO mice (Fig 1F). Conclusions: TLR4 signaling stimulates in vivo VT resolution. Expression of fibrinolytic factor uPA is enforced in MO/MFs by TLR4-Myd88-independent signaling, a potential target for VT resolution.

Immunodeficiency in a female patient with Incontinentia Pigmenti

Incontinentia pigmenti (IP) is a rare X-linked dominant neuroectodermal disorder characterized by ocular, dermatologic, and neurological abnormalities. It is caused by heterozygous mutations in IKBKG (NEMO), which encodes a regulatory factor involved in NF-kB activation. Random and skewed X-inactivation allows for female survival and determines extent of disease. Although immune function is typically normal in IP patients, hypomorphic IKBKG mutations are known to cause immunodeficiency, as occurs in X-linked NEMO deficiency. A female newborn presented with bullous vesicles, peeling skin, alopecia, hearing loss, and tonic-clonic seizures with MRI demonstrating evidence of in utero stroke. She developed intermittent fevers and cellulitis and was diagnosed with IP based on clinical findings. Following discharge, she was readmitted at 1 month of age due to bronchiolitis complicated by pulmonary abscess. Labs demonstrated hyperleukocytosis with hypereosinophilia, normal T, B, and NK lymphocyte enumeration, abnormal lymphocyte proliferation to phytohemagglutinin (PHA) and anti-CD3, and abnormal toll-like receptor (TLR) function. Genetic analysis revealed a heterozygous deletion of exons 4–10 in IKBKG. Labs at 1 year follow up showed normal lymphocyte (T, B, and NK) enumeration and mitogen responses, normal immunoglobulin levels, and normal responses to pneumococcal and tetanus vaccines. While about 70% of IP patients harbor a deletion of exons 4–10 in IKBKG. unlike other hypomorphic NEMO mutations, this mutation is not typically associated with altered immune function. This case highlights that immunodeficiency may be an early clinical manifestation in female patients with IP.

Effects of TcpC’s NADase Activity on Inhibition of Innate Immune Signaling

Abstract The innate immune system is activated by pattern recognition receptors such as Toll-like receptors (TLRs), which differentiate between self and non-self by recognizing distinct molecular structures on pathogens. As this process threatens pathogen survival in the host, bacteria have developed mechanisms to combat this. Uropathogenic Escherichia coli (UPEC) express the Toll/Interleukin-1 Receptor (TIR) domain-containing protein TcpC, which inhibits the function of TLRs by binding to the signaling adapter protein myeloid differentiation factor 88 (MyD88). Bacterial TIR proteins, including TcpC, recently have been found to also exhibit NADase activity. We hypothesize that the ability of TcpC to block TLR signaling and its NADase function are interrelated and that the TcpC EA mutant, which has been shown to have diminished NADase activity will not bind efficiently to MyD88. We performed in vitro translation assays to first produce both WT and EA mutant versions of TcpC that contain both a streptavidin and histidine tag. Then we conducted pull-down experiments to determine if the TcpC EA mutant could successfully bind to streptavidin beads, as well as MyD88, potentially resulting in clustering with the TIR signaling protein and blocking the signaling pathway entirely. While we have successfully produced tagged WT and EA TcpC proteins and pulled down the proteins using streptavidin beads, we are working to optimize conditions to determine if the NADase-deficient TcpC EA mutant is able to bind MyD88, as has been shown previously for WT TcpC. The resulting information will give us a closer look into TcpC’s effect on virulence and the suppression of the innate immune response via TLR and MyD88 related signaling pathways. This research was partially funded by the USM LSAMP program, supported by NSF LSAMP Award #1619676, the Towson OSPR Seed Funding for Grant Seekers, and the Bridges to Doctorate Scholars Program, NIH-R25GM119970 04.

Upregulation of TLR5 indicates a favorable prognosis in prostate cancer.

Toll-like receptors (TLRs) are the key sensors of innate immunity for triggering immune responses against infections. TLRs are well known to be expressed and activated in innate immune cells, such as macrophage and dendritic cells, but we and others have found that some TLRs are also functional in epithelial cells. However, the role of an epithelial TLR in prostate cancer remains elusive. TLR5 expression in messenger RNA and protein level in prostate cancer was determined by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and immunohistochemistry (IHC). The activation of TLR5 signaling in epithelial cells was detected upon nuclear factor-κB activation by luciferase assay and western blot analysis, and proinflammatory cytokine activation by RT-qPCR. Distinguishing between the TLR5 and NLRC4 pathways, both recognizing flagellin, is determined by small interfering RNA and proinflammatory cytokine activation. The role of TLR5 in prostate cancer was analyzed by IHC and bioinformatics using a general and single-cell database. In the present study, we show that TLR5, among other TLRs, is exceedingly expressed in human prostate cancer cells. This cancer epithelial cell TLR5 functions to activate the TLR5 signaling pathway in human prostate cancer cells, as it does with innate immune cell TLR5. The bacterial protein flagellin induces a robust immune response in prostate cancer cells in a TLR5-dependent but NLRC4-independent manner. TLR5 is highly expressed in prostate cancer patient specimens, and high TLR5 expression in prostate cancer patients indicates a favorable prognosis. TLR5, as an innate immunity receptor, is a functional TLR in human prostate cancer epithelial cells. TLR5 plays an important role in prostate cancer development and is a new potential prognosis biomarker. TLR5 may represent a novel immunotherapy target against prostate cancer.

Histochemical assessment on osteoclasts in long bones of toll-like receptor 2 (TLR2) deficient mice

ObjectiveToll-like receptor 2 (TLR2), recognizes a wide variety of pathogen-associated molecular patterns such as lipopolysaccharides, peptidoglycans, and lipopeptides, and is generally believed to be present in monocytes, macrophages, dendritic cells, and vascular endothelial cells. However, no histological examination of osteoclasts, which differentiate from precursors common to macrophages/monocytes, has been performed in a non-infected state of TLR2 deficiency. The objective of this study was to examine the histological properties and function of osteoclasts in the long bones of 8-week-old male TLR2 deficient (TLR2−/−) mice to gain insight into TLR2 function in biological circumstances without microbial infection. MethodsEight-week-old male wild-type and TLR2−/− mice were fixed with paraformaldehyde solution, and their tibiae and femora were used for micro-CT analysis, immunohistochemistry, transmission electron microscopy, and real-time PCR analysis. ResultsTLR2−/− tibiae and femora exhibited increased bone volume of metaphyseal trabeculae and elevated numbers of TRAP-positive osteoclasts. However, the number of multinucleated TRAP-positive osteoclasts was reduced, whereas mononuclear TRAP-positive cells increased, despite the high expression levels of Dc-Stamp and Oc-Stamp. Although TRAP-positive multinucleated and mononuclear osteoclasts showed the immunoreactivity and elevated expression of RANK and siglec-15, they revealed weak cathepsin K-positivity and less incorporation of the mineralized bone matrix, and often missing ruffled borders. It seemed likely that, despite the increased numbers, TLR2−/− osteoclasts reduced cell fusion and bone resorption activity. ConclusionIt seems likely that even without bacterial infection, TLR2 might participate in cell fusion and subsequent bone resorption of osteoclasts.

Prospects of toll-like receptors in dairy cattle breeding.

Toll-like receptors (TLRs) play an important role in mediating the immune response against various microbes, such as bacteria, viruses, parasites, and fungi, in innate and adaptive immunity. Ten functional TLRs (TLR1 to TLR10) have been identified and mapped in cattle, with each TLR recognising specific pathogen-associated molecular patterns. The variation in genes controlling the immune response contributes to susceptibility or resistance to various infectious diseases such as mastitis, bovine tuberculosis, and paratuberculosis. Identifying TLR SNPs shows promising results for future marker-assisted breeding strategies, screening for disease risks, and improving the genetic resistance of dairy cattle. This article aims not only to review the research into susceptibility or resistance to infectious diseases and milk production traits in dairy cattle but also to discuss the limitations in current studies and the prospects in dairy cattle breeding.

Toll-like receptors in cardiac hypertrophy.

Toll-like receptors (TLRs) are a family of pattern recognition receptors (PRRs) that can identify pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs). TLRs play an important role in the innate immune response, leading to acute and chronic inflammation. Cardiac hypertrophy, an important cardiac remodeling phenotype during cardiovascular disease, contributes to the development of heart failure. In previous decades, many studies have reported that TLR-mediated inflammation was involved in the induction of myocardium hypertrophic remodeling, suggesting that targeting TLR signaling might be an effective strategy against pathological cardiac hypertrophy. Thus, it is necessary to study the mechanisms underlying TLR functions in cardiac hypertrophy. In this review, we summarized key findings of TLR signaling in cardiac hypertrophy.

Abstract 835: Translational nanotechnology-based cancer vaccine to re-educate host immune response against metastatic cancers

Abstract Sixty percent of melanoma patients present brain metastases, having low response rates to current systemic therapies, which do not prolong survival. New therapeutic options to address this clinical need are urgent. Here, we report the development of a polymeric nanoparticle as a cancer nanovaccine capable of selectively co-targeting toll-like receptor function and PD-L1 expression to improve antigen presentation and subsequent effector immune cell function within brain microenvironment. Mannose-poly(lactic-co-glycolic acid)/poly(lactic acid) (man-PLGA/PLA) nanoparticles (NP) were prepared by a modified double emulsion solvent evaporation method, to deliver combinations of melanoma neoantigens, toll-like receptor ligands and regulators of the PD-1/PD-L1 axis. NP physicochemical properties were fully characterized, including size, surface charge and morphology. The amount of melanoma neoantigens and immune regulators entrapped within NP was determined by HPLC. Immature dendritic cells (DC) were used to evaluate the impact of NP on cell viability, and to assess NP uptake kinetics by flow cytometry. NP ability to target and trigger the activation of DC and T cells, was assessed in the lymph nodes and spleen of immunized mice. The NP anti-tumor immune-mediated effect was evaluated in vivo in two primary melanoma-bearing immunocompetent mouse models (B16F10 and B16MO5), and in a melanoma brain metastasis (MBM) mouse model (B16F10), which also included the immune profiling within tumor site by flow cytometry, before and after treatment.NP presented an average diameter of 180 nm, narrow polydispersity index, surface charge close to neutrality, spherical morphology, and high loadings of the neoantigens and immunoregulators. NP did not affect DC viability and were extensively internalized by immature DC. NP were preferentially taken-up in vivo by DC, increasing the expression of activation/maturation markers at DC surface, such as CD80 and CD86. NP elicited antigen-specific T-cell responses, by the significant increase in the expression of TNF-alpha and IFN-gamma (TH1-guided response). In vivo combination of NP with anti-PD-L1 induced a potent immune-mediated anti-tumor response in both primary and preclinical models of MBM, overcoming tumor development with an increased overall survival. This combination re-shaped immune and stroma cell populations in primary tumor and MBM microenvironment, which presented a marked infiltration of cytotoxic T cells that correlated with a decreased expression of PD-1 and PD-L1 within the TME. The synergy between our nanovaccine and anti-PD-L1 provide essential insights to devise alternative combinations regiments to improve the efficacy of immune checkpoint inhibitors in metastatic melanoma, thus opening new line for this unmet medical need. Citation Format: Barbara Carreira, Rita A. Acúrcio, Sabina Pozzi, Ron Kleiner, Liane I. Moura, Ana I. Matos, Daniela vaskovich, Carina Peres, Adelaide Fernandes, Sara Xapelli, Ronit Satchi-Fainaro, Helena F. Florindo. Translational nanotechnology-based cancer vaccine to re-educate host immune response against metastatic cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 835.

TIRAP, TRAM, and Toll-Like Receptors: The Untold Story.

Toll-like receptors (TLRs) are the most studied receptors among the pattern recognition receptors (PRRs). They act as microbial sensors, playing major roles in the regulation of the innate immune system. TLRs mediate their cellular functions through the activation of MyD88-dependent or MyD88-independent signaling pathways. Myd88, or myeloid differentiation primary response 88, is a cytosolic adaptor protein essential for the induction of proinflammatory cytokines by all TLRs except TLR3. While the crucial role of Myd88 is well described, the contribution of other adaptors in mediating TLR signaling and function has been underestimated. In this review, we highlight important results demonstrating that TIRAP and TRAM adaptors are also required for full signaling activity and responses induced by most TLRs.

Use of Fluorescent Chemical Probes in the Study of Toll-like Receptors (TLRs) Trafficking.

Fluorescent chemical probes are used nowadays as a chemical resource to study the physiology and pharmacology of several important endogenous receptors. Different fluorescent groups have been coupled with known ligands of these receptors, allowing the visualization of their localization and trafficking. One of the most important molecular players of innate immunity and inflammation are the Toll-Like Receptors (TLRs). These Pattern-Recognition Receptors (PRR) have as natural ligands microbial-derived pathogen-associated molecular patterns (PAMPs) and also endogenous molecules called danger-associated molecular patterns (DAMPs). These ligands activate TLRs to start a response that will determine the host's protection and overall cell survival but can also lead to chronic inflammation and autoimmune syndromes. TLRs action is tightly related to their subcellular localization and trafficking. Understanding this trafficking phenomenon can enlighten critical molecularpathways that might allow to decipher the causes of different diseases. In this chapter, the study of function, localization and trafficking of TLRs through the use of chemical probes will be discussed. Furthermore, an example protocol of the use of fluorescent chemical probes to study TLR4 trafficking using high-content analysis will be described.

Autophagy Induced by Toll-like Receptor Ligands Regulates Antigen Extraction and Presentation by B Cells.

The engagement of B cells with surface-tethered antigens triggers the formation of an immune synapse (IS), where the local secretion of lysosomes can facilitate antigen uptake. Lysosomes intersect with other intracellular processes, such as Toll-like Receptor (TLR) signaling and autophagy coordinating immune responses. However, the crosstalk between these processes and antigen presentation remains unclear. Here, we show that TLR stimulation induces autophagy in B cells and decreases their capacity to extract and present immobilized antigens. We reveal that TLR stimulation restricts lysosome repositioning to the IS by triggering autophagy-dependent degradation of GEF-H1, a Rho GTP exchange factor required for stable lysosome recruitment at the synaptic membrane. GEF-H1 degradation is not observed in B cells that lack αV integrins and are deficient in TLR-induced autophagy. Accordingly, these cells show efficient antigen extraction in the presence of TLR stimulation, confirming the role of TLR-induced autophagy in limiting antigen extraction. Overall, our results suggest that resources associated with autophagy regulate TLR and BCR-dependent functions, which can finetune antigen uptake by B cells. This work helps to understand the mechanisms by which B cells are activated by surface-tethered antigens in contexts of subjacent inflammation before antigen recognition, such as sepsis.