TLR Agonist Stimulation Research Articles

Dietary Zinc supplementation impact on relative frequency and innate function of peripheral bovine immune cells

Abstract Zinc (Zn) is an essential micronutrient which is critical for optimum innate and adaptive immune function. While Zn deficiency leads to reduced growth and feed intake, the impact of Zn deficiency and supplementation on immune responses in beef cattle has not been properly addressed. To investigate to impact of dietary Zn supplementation on peripheral immune responses of growing cattle, 27 Angus crossbred steers were stratified by body weight and randomly assigned to three dietary treatments groups: 1) CON, no supplemental Zn, 2) Zn100, 100ppm of Zn or 3) Zn150, 150ppm of Zn delivered in premixes in total mixed rations. Whole blood obtained at 14 (D14) and 58 (D58) days after the start of the treatments was plated and stimulated with TLR agonists LPS (TLR4), PAM3CSK4 (TLR2/1), and Poly-I:C+Imiquimod (TLR3/7) for 48 h, then pro-inflammatory cytokine secretion was measured by ELISA on the supernatants. Additionally, whole blood was stained with surface antibodies to determine relative frequency of peripheral immune cell populations. We observed diminished IL-1ß secretion in response to Poly-I:C+Imiquimod in the CON group when compared to Zn150 (p=0.09) and Zn100 group (p=0.013) at D14 and D58, respectively. We observed no differences in IL-6 secretion upon TLR agonist stimulation between groups at any time point. Further, although no significant changes in CD4+, CD8+, TCRδ+ T cells, or CD21+MHCII+ B cells were observed, CD5+MHCII+ B cells had a higher relative frequency in the CON group when compared to Zn100 (p 0.03) and Zn150 (p 0.10) groups at D58. Future studies will address how Zn supplementation impacts the immune response to infection and disease susceptibility. This project was supported by Agriculture and Food Research Initiative Competitive Grant no. 2020-06540 from the USDA National Institute of Food and Agriculture

Tumor-derived Immunosuppression Inhibits the Efficacy of TLR-agonist Stimulation for Glioblastoma

Tumor-derived Immunosuppression Inhibits the Efficacy of TLR-agonist Stimulation for Glioblastoma

Combined TLR agonist and aeromonas antigens stimulation enhance the immune-related genes in yellowtail leucocytes

The purpose of this study was to characterize the TLR21 gene from yellowtail (Seriola lalandi) and its functional activity using TLR agonist stimulation and Aeromonas antigens. Basal TLR21 gene expression was analyzed in several tissues. Subsequently, the gene expression of TLR21 and IL-1β and TNF-α cytokines was evaluated in head-kidney leucocytes exposed to TLR agonists (CpGODN2006, LPS and Poly I:C) and then subjected to Aeromonas antigen stimulation. The yellowtail full-length cDNA sequence of SlTLR21 was 3615 bp (980 aa). The sequence showed a high degree of similarity with the counterparts of other fish species and shared the common structural architecture of the TLR family, including LRR domains, one C-terminal LRR region and a TIR domain. Gene expression studies revealed the constitutive expression of TLR21 mRNA in all the analyzed tissues, the highest levels being observed in spleen and head-kidney, where they play an important role in the fish immune system. Transcripts of TLR21 and the downstream IL-1β and TNFα cytokine genes were most strongly up-regulated after exposure to the TLR agonists, following Aeromonas antigen stimulation, suggesting they are involved in the immune response. The results indicate that TLR agonists, in combination with Aeromonas antigens in head-kidney leucocytes, synergistically enhance TLR21 and cytokines gene expression in yellowtail.

TLR21's agonists in combination with Aeromonas antigens synergistically up-regulate functional TLR21 and cytokine gene expression in yellowtail leucocytes

The purpose of this study was to characterize the TLR21 gene from yellowtail (Seriola lalandi) and its functional activity using TLR agonist stimulation and Aeromonas antigens. The TLR21 nucleotide sequence from yellowtail was obtained using the whole-genome shotgun sequencing method and bioinformatics tools. Basal TLR21 gene expression was analyzed in several tissues. Subsequently, the gene expression of TLR21 and cytokines IL-1β and TNF-α was evaluated in TLR agonist (CpG-ODN2006, LPS, and Poly I:C) exposing head kidney leucocytes, which were then subjected to Aeromonas antigen stimulation. The yellowtail full-length cDNA sequence of SlTLR21 was 3615 bp (980 aa) showing a high degree of similarity with the counterparts of other fish species and sharing the common structural architecture of the TLR family, including LRR domains, one C-terminal LRR region, and a TIR domain. Gene expression studies revealed the constitutive expression of TLR21 mRNA in all the analyzed tissues; the highest levels were observed in spleen and head kidney where they play an important role in the fish immune system. Transcripts of TLR21 and the downstream IL-1β and TNF-α cytokine genes were most strongly up-regulated after exposure to the TLR agonists following Aeromonas antigen stimulation, suggesting they are involved in immune response. The results indicated that TLR agonists, in combination with Aeromonas antigens in head kidney leucocytes, synergistically enhance TLR21 and cytokines in yellowtail.

Post-Spaceflight (STS-135) Mouse Splenocytes Demonstrate Altered Activation Properties and Surface Molecule Expression.

Alterations in immune function have been documented during or post-spaceflight and in ground based models of microgravity. Identification of immune parameters that are dysregulated during spaceflight is an important step in mitigating crew health risks during deep space missions. The in vitro analysis of leukocyte activity post-spaceflight in both human and animal species is primarily focused on lymphocytic function. This report completes a broader spectrum analysis of mouse lymphocyte and monocyte changes post 13 days orbital flight (mission STS-135). Analysis includes an examination in surface markers for cell activation, and antigen presentation and co-stimulatory molecules. Cytokine production was measured after stimulation with T-cell mitogen or TLR-2, TLR-4, or TLR-5 agonists. Splenocyte surface marker analysis immediate post-spaceflight and after in vitro culture demonstrated unique changes in phenotypic populations between the flight mice and matched treatment ground controls. Post-spaceflight splenocytes (flight splenocytes) had lower expression intensity of CD4+CD25+ and CD8+CD25+ cells, lower percentage of CD11c+MHC II+ cells, and higher percentage of CD11c+MHC I+ populations compared to ground controls. The flight splenocytes demonstrated an increase in phagocytic activity. Stimulation with ConA led to decrease in CD4+ population but increased CD4+CD25+ cells compared to ground controls. Culturing with TLR agonists led to a decrease in CD11c+ population in splenocytes isolated from flight mice compared to ground controls. Consequently, flight splenocytes with or without TLR-agonist stimulation showed a decrease in CD11c+MHC I+, CD11c+MHC II+, and CD11c+CD86+ cells compared to ground controls. Production of IFN-γ was decreased and IL-2 was increased from ConA stimulated flight splenocytes. This study demonstrated that expression of surface molecules can be affected by conditions of spaceflight and impaired responsiveness persists under culture conditions in vitro.

A temporal gate for viral enhancers to co-opt Toll-like-receptor transcriptional activation pathways upon acute infection.

Viral engagement with macrophages activates Toll-Like-Receptors (TLRs) and viruses must contend with the ensuing inflammatory responses to successfully complete their replication cycle. To date, known counter-strategies involve the use of viral-encoded proteins that often employ mimicry mechanisms to block or redirect the host response to benefit the virus. Whether viral regulatory DNA sequences provide an opportunistic strategy by which viral enhancer elements functionally mimic innate immune enhancers is unknown. Here we find that host innate immune genes and the prototypical viral enhancer of cytomegalovirus (CMV) have comparable expression kinetics, and positively respond to common TLR agonists. In macrophages but not fibroblasts we show that activation of NFκB at immediate-early times of infection is independent of virion-associated protein, M45. We find upon virus infection or transfection of viral genomic DNA the TLR-agonist treatment results in significant enhancement of the virus transcription-replication cycle. In macrophage time-course infection experiments we demonstrate that TLR-agonist stimulation of the viral enhancer and replication cycle is strictly delimited by a temporal gate with a determined half-maximal time for enhancer-activation of 6 h; after which TLR-activation blocks the viral transcription-replication cycle. By performing a systematic siRNA screen of 149 innate immune regulatory factors we identify not only anticipated anti-viral and pro-viral contributions but also new factors involved in the CMV transcription-replication cycle. We identify a central convergent NFκB-SP1-RXR-IRF axis downstream of TLR-signalling. Activation of the RXR component potentiated direct and indirect TLR-induced activation of CMV transcription-replication cycle; whereas chromatin binding experiments using wild-type and enhancer-deletion virus revealed IRF3 and 5 as new pro-viral host transcription factor interactions with the CMV enhancer in macrophages. In a series of pharmacologic, siRNA and genetic loss-of-function experiments we determined that signalling mediated by the TLR-adaptor protein MyD88 plays a vital role for governing the inflammatory activation of the CMV enhancer in macrophages. Downstream TLR-regulated transcription factor binding motif disruption for NFκB, AP1 and CREB/ATF in the CMV enhancer demonstrated the requirement of these inflammatory signal-regulated elements in driving viral gene expression and growth in cells as well as in primary infection of neonatal mice. Thus, this study shows that the prototypical CMV enhancer, in a restricted time-gated manner, co-opts through DNA regulatory mimicry elements, innate-immune transcription factors to drive viral expression and replication in the face of on-going pro-inflammatory antiviral responses in vitro and in vivo and; suggests an unexpected role for inflammation in promoting acute infection and has important future implications for regulating latency.

A Novel Gain-of-Function IKBA Mutation Underlies Ectodermal Dysplasia with Immunodeficiency and Polyendocrinopathy

This study reports the identification of a novel heterozygous IKBA missense mutation (p.M37K) in a boy presenting with ectodermal dysplasia with immunodeficiency (EDA-ID) who had wild type IKBKG gene encoding NEMO. Our aim was to characterize the clinical course of this IκB-α gain-of-function mutant and to investigate if the p.M37K substitution affects NF-κB activation by interfering with IκB-α degradation, thus impairing NF-κB signaling and causing the EDA-ID phenotype. NF-κB signaling was evaluated by measuring IκB-α degradation in patient fibroblasts. In addition, transiently transfected HeLa cells expressing either the M37K-mutant IκB-α allele, the previously characterized S36A-mutant IκB-α allele, or wild type IκB-α were evaluated for IκB-α degradation and NF-κB nuclear translocation following stimulation with TNF-α. Clinical findings revealed a classical ectodermal dysplasia phenotype complicated by recurrent mucocutaneous candidiasis, hypothyroidism, hypopituitarism, and profound combined immunodeficiency with decreased numbers of IL-17 T cells. IκB-α degradation after TNF-α and TLR agonist stimulation was abolished in patient fibroblasts as well as in HeLa cells expressing M37K-IκB-α similar to cells expressing S36A-IκB-α resulting in impaired nuclear translocation of NF-κB and reduced NF-κB dependent luciferase activity compared to cells expressing wild type IκB-α. Patient whole blood cells failed to secrete IL-6 in response to IL-1ß, Pam2CSK4, showed reduced responses to LPS and PMA/Ionomycin, and lacked IL-10 production in response to TNF-α. The novel heterozygous mutation p.M37K in IκB-α impairs NF-κB activation causing autosomal dominant EDA-ID with an expanded clinical phenotype.

Cord blood hemopoietic progenitor cell toll like receptor expression and function: a mechanism underlying allergic inflammation in early life?

RATIONALE: Neonatal immune responses to environmental stimuli, mediated via TLR, may determine the development of atopy in childhood. Since hemopoietic mechanisms are involved in development and maintenance of allergic inflammation, we investigated alterations in progenitor expression and differentiation profiles after stimulation with TLR agonists. METHODS: Freshly isolated, CD34-enriched human CB cells were stimulated with 10μg/mL lipopolysaccharide (LPS) or 5μM CpG ODN overnight. Flow cytometric analyses were used to evaluate surface and intracellular expression of TLR-2, TLR-4, TLR-9, as well as the hemopoietic cytokine receptors (HCR) IL-5R, IL-3R and GM-CSFR; methylcellulose cultures were performed to assess CD34+ cell differentiation capacity into Eo/B CFU. RESULTS: After TLR agonist stimulation, CD34+ cell TLR-2, -4 and TLR-9 percentage expression increased significantly (p=0.005), whereas HCR expression decreased (p=0.01); however, mean fluorescence intensity of all receptors was found to be increased. Stimulation with a combination of TLR agonists and hemopoietic cytokines induced increased IL-5- and IL-3-responsive Eo/B CFU (p=0.02), when compared to hemopoietic cytokine stimulation alone. CONCLUSIONS: CB CD34+ progenitor cells significantly express TLR, and TLR ligation directly affects both TLR and HCR expression. These receptor alterations allow modulation of progenitor cell differentiation capacity into eosinophils and basophils, key cells involved in allergic inflammation. These findings may highlight an alternate innate immune pathway of microbial influence on the development of allergic inflammation in early life.

Macrophages of multiple sclerosis patients display deficient SHP-1 expression and enhanced inflammatory phenotype

Recent studies in mice have demonstrated that the protein tyrosine phosphatase SHP-1 is a crucial negative regulator of proinflammatory cytokine signaling, TLR signaling, and inflammatory gene expression. Furthermore, mice genetically lacking SHP-1 (me/me) display a profound susceptibility to inflammatory CNS demyelination relative to wild-type mice. In particular, SHP-1 deficiency may act predominantly in inflammatory macrophages to increase CNS demyelination as SHP-1-deficient macrophages display coexpression of inflammatory effector molecules and increased demyelinating activity in me/me mice. Recently, we reported that PBMCs of multiple sclerosis (MS) patients have a deficiency in SHP-1 expression relative to normal control subjects indicating that SHP-1 deficiency may play a similar role in MS as to that seen in mice. Therefore, it became essential to examine the specific expression and function of SHP-1 in macrophages from MS patients. Herein, we document that macrophages of MS patients have deficient SHP-1 protein and mRNA expression relative to those of normal control subjects. To examine functional consequences of the lower SHP-1, the activation of STAT6, STAT1, and NF-κB was quantified and macrophages of MS patients showed increased activation of these transcription factors. In accordance with this observation, several STAT6-, STAT1-, and NF-κB-responsive genes that mediate inflammatory demyelination were increased in macrophages of MS patients following cytokine and TLR agonist stimulation. Supporting a direct role of SHP-1 deficiency in altered macrophage function, experimental depletion of SHP-1 in normal subject macrophages resulted in an increased STAT/NF-κB activation and increased inflammatory gene expression to levels seen in macrophages of MS patients. In conclusion, macrophages of MS patients display a deficiency of SHP-1 expression, heightened activation of STAT6, STAT1, and NF-κB and a corresponding inflammatory profile that may be important in controlling macrophage-mediated demyelination in MS.

Purified Neonatal Plasmacytoid Dendritic Cells Overcome Intrinsic Maturation Defect with TLR Agonist Stimulation

Neonates are more susceptible than adults to viral and bacterial diseases. We hypothesized that plasmacytoid dendritic cells, the cells that provide large amounts of IFN-alpha in response to Toll-like receptor 9 (TLR9) agonists, are defective in neonates. To assess the intrinsic functionality of plasmacytoid dendritic cells from neonates we compared IFN-alpha production by plasmacytoid dendritic cells derived from neonates versus adults in both whole blood and in purified plasmacytoid dendritic cells. TLR9-stimulation of whole blood from adults and neonates resulted in comparable amounts of IFN-alpha production. However, we observed small but significant differences in IFN-alpha production from purified CD123+ plasmacytoid dendritic cells from neonates after stimulation with the TLR9 ligand CpG-DNA. Furthermore, we assessed surface expression of co-stimulatory molecules on plasmacytoid dendritic cells after stimulation. While purified CD123+ plasmacytoid dendritic cells from adults up-regulated co-stimulatory molecules CD80 and CD86 with IL-3 alone those from neonates required the addition of CpG-DNA to reach adult levels. Therefore, the intrinsic deficiencies of neonatal plasmacytoid dendritic cells can be mitigated by TLR9 agonists. These results are consistent with the observation that vaccines that effect strong adjuvant activity on dendritic cells can induce protective responses in neonates.

TLRs Mediate IFN-γ Production by Human Uterine NK Cells in Endometrium

The human endometrium (EM) contains macrophages, NK cells, T cells, B cells, and neutrophils in contact with a variety of stromal and epithelial cells. The interplay between these different cell types and their roles in defense against pathogen invasion in this specialized tissue are important for controlling infection and reproduction. TLRs are a family of receptors able to recognize conserved pathogen-associated molecular patterns. In this study, we determined the expression of TLRs on uterine NK (uNK) cells from the human EM and the extent to which uNK cells responded to TLR agonist stimulation. uNK cells expressed TLRs 2, 3, and 4, and produced IFN-gamma when total human endometrial cells were stimulated with agonists to TLR2 or TLR3 (peptidoglycan or poly(I:C), respectively). Activated uNK cell clones produced IFN-gamma upon stimulation with peptidoglycan or poly(I:C). However, purified uNK cells did not respond directly to TLR agonists, but IFN-gamma was produced by uNK cells in response to TLR stimulation when cocultured with APCs. These data indicate that uNK cells express TLRs and that they can respond to TLR agonists within EM by producing IFN-gamma. These data also indicate that the uNK cells do not respond directly to TLR stimulation, but rather their production of IFN-gamma is dependent upon interactions with other cells within EM.