Pattern Recognition Receptor Signaling Research Articles

Intimate Association of PRR- and NLR-Mediated Signaling in Plant Immunity.

This article is part of the Top 10 Unanswered Questions in MPMI invited review series.Plants recognize the presence or invasion of microbes through cell surface-localized pattern recognition receptors (PRRs) and intracellular nucleotide-binding domain leucine-rich repeat receptors (NLRs). Although PRRs and NLRs are activated by ligands located in different subcellular compartments through distinct mechanisms, signals initiated from PRRs and NLRs converge into several common signaling pathways with different dynamics. Increasing evidence suggests that PRR- and NLR-mediated signaling extensively crosstalk and such interaction can greatly influence immune response outcomes. Sophisticated experimental setups enabled dissection of the signaling events downstream of PRRs and NLRs with fine temporal and spatial resolution; however, the molecular links underlying the observed interactions in PRR and NLR signaling remain to be elucidated. In this review, we summarize the latest knowledge about activation and signaling mediated by PRRs and NLRs, deconvolute the intimate association between PRR- and NLR-mediated signaling, and propose hypotheses to guide further research on key topics.[Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Vitamin D-regulated Gene Expression Profiles: Species-specificity and Cell-specific Effects on Metabolism and Immunity.

Vitamin D has pleiotropic physiological actions including immune system regulation, in addition to its classical role in calcium homeostasis. Hormonal 1,25-dihydroxyvitamin D (1,25D) signals through the nuclear vitamin D receptor, and large-scale expression profiling has provided numerous insights into its diverse physiological roles. To obtain a comprehensive picture of vitamin D signaling, we analyzed raw data from 94 (80 human, 14 mouse) expression profiles of genes regulated by 1,25D or its analogs. This identified several thousand distinct genes directly or indirectly up- or downregulated in a highly cell-specific manner in human cells using a 1.5-fold cut-off. There was significant overlap of biological processes regulated in human and mouse but minimal intersection between genes regulated in each species. Disease ontology clustering confirmed roles for 1,25D in immune homeostasis in several human cell types, and analysis of canonical pathways revealed novel and cell-specific roles of vitamin D in innate immunity. This included cell-specific regulation of several components of Nucleotide-binding Oligomerization Domain-like (NOD-like) pattern recognition receptor signaling, and metabolic events controlling innate immune responses. Notably, 1,25D selectively enhanced catabolism of branched-chain amino acids (BCAAs) in monocytic cells. BCAA levels regulate the major metabolic kinase mammalian Target of Rapamycin (mTOR), and pretreatment with 1,25D suppressed BCAA-dependent activation of mTOR signaling. Furthermore, ablation of BCAT1 expression in monocytic cells blocked 1,25D-induced increases in autophagy marker LAMP1. In conclusion, the data generated represents a powerful tool to further understand the diverse physiological roles of vitamin D signaling and provides multiple insights into mechanisms of innate immune regulation by 1,25D.

Blockade of T cell activation induced by the simultaneous absence of Nod1 and Nod2 is bypassed by TLR2 signals

Pattern recognition receptors (PRRs) trigger adaptive inflammatory responses and as such are attractive targets for therapeutic manipulation of inflammation. In order to develop effective therapies however we need to understand the complexities of PRR signaling and clarify how individual PRRs contribute to an inflammatory response in a given cell type.Data from our lab and others have shown that cross-talk occurs between different PRR family members that directs T cell responses to a particular stimuli. It is well-established that the cell surface toll-like receptor 2 (TLR2) provides a potent costimulatory signal for TCR-stimulated T cell activation. We have shown that signaling through the intracellular nucleotide-binding oligomerization domain-containing proteins 1 and 2 (Nod1 and Nod2) also provides important signals for T cell activation, and that when both Nod1 and Nod 2 are deleted stimulated T cells undergo activation-induced cell death.This study found that TLR2 costimulation could bypass the defect induced by the simultaneous absence of Nods1 and 2 in both antibody- and antigen-stimulated T cells. Since blocking one set of PRR-mediated responses can be overcome by signaling through another PRR family member, then effective therapeutic immune blockade strategies will likely require a multi-pronged approach in order to be effective.

The Dichotomous Role of Inflammation in the CNS: A Mitochondrial Point of View.

Innate immune response is one of our primary defenses against pathogens infection, although, if dysregulated, it represents the leading cause of chronic tissue inflammation. This dualism is even more present in the central nervous system, where neuroinflammation is both important for the activation of reparatory mechanisms and, at the same time, leads to the release of detrimental factors that induce neurons loss. Key players in modulating the neuroinflammatory response are mitochondria. Indeed, they are responsible for a variety of cell mechanisms that control tissue homeostasis, such as autophagy, apoptosis, energy production, and also inflammation. Accordingly, it is widely recognized that mitochondria exert a pivotal role in the development of neurodegenerative diseases, such as multiple sclerosis, Parkinson’s and Alzheimer’s diseases, as well as in acute brain damage, such in ischemic stroke and epileptic seizures. In this review, we will describe the role of mitochondria molecular signaling in regulating neuroinflammation in central nervous system (CNS) diseases, by focusing on pattern recognition receptors (PRRs) signaling, reactive oxygen species (ROS) production, and mitophagy, giving a hint on the possible therapeutic approaches targeting mitochondrial pathways involved in inflammation.

Lipopolysaccharide-induced DC-SIGN/TLR4 crosstalk activates NLRP3 inflammasomes via MyD88-independent signaling in gastric epithelial cells

Abnormal pattern recognition receptor (PRR) signaling plays an important role in gastric mucosal damage caused by stomach microbiota; however, the underlying molecular mechanisms remain obscure. Here, we show that DC-SIGN, a surface phenotype marker of dendritic cells, is overexpressed in gastric epithelial cells facing LPS stimulation. NLRP3 expression in gastric epithelial cells are significantly increased and related to the degree of LPS stimulation. Furthermore, DC-SIGN could interact with TLR4, promote NLRP3 and related genes expression via MyD88-independent signaling pathway and regulate the secretion of IL-1β and IL-18 in gastric epithelial cells. The results of flow cytometry analysis show that DC-SIGN primarily mediates Th1 differentiation when co-cultured with gastric epithelial cells. These results reveal that LPS-induced DC-SIGN expression modulates NLRP3 inflammasomes formation via MyD88-independent TLR4 signaling in gastric epithelial cell, and induces a Th1-predominant host immune response,these findings may indicate a new function of DC-SIGN in non-immune cells, and elucidate the diversity role of gastric epithelial cells in mechanism of immune damage caused by microbial flora.

Systems pharmacological study illustrates the immune regulation, anti-infection, anti-inflammation, and multi-organ protection mechanism of Qing-Fei-Pai-Du decoction in the treatment of COVID-19

BackgroundThe traditional Chinese medicine (TCM) formula Qing-Fei-Pai-Du decoction (QFPDD) was the most widely used prescription in China's campaign to contain COVID-19, which has exhibited positive effects. However, the underlying mode of action is largely unknown. PurposeA systems pharmacology strategy was proposed to investigate the mechanisms of QFPDD against COVID-19 from molecule, pathway and network levels. Study design and methodsThe systems pharmacological approach consisted of text mining, target prediction, data integration, network study, bioinformatics analysis, molecular docking, and pharmacological validation. Especially, we proposed a scoring method to measure the confidence of targets identified by prediction and text mining, while a novel scheme was used to identify important targets from 4 aspects. Results623 high-confidence targets of QFPDD's 12 active compounds were identified, 88 of which were overlapped with genes affected by SARS-CoV-2 infection. These targets were found to be involved in biological processes related with the development of COVID-19, such as pattern recognition receptor signaling, interleukin signaling, cell growth and death, hemostasis, and injuries of the nervous, sensory, circulatory, and digestive systems. Comprehensive network and pathway analysis were used to identify 55 important targets, which regulated 5 functional modules corresponding to QFPDD's effects in immune regulation, anti-infection, anti-inflammation, and multi-organ protection, respectively. Four compounds (baicalin, glycyrrhizic acid, hesperidin, and hyperoside) and 7 targets (AKT1, TNF-α, IL6, PTGS2, HMOX1, IL10, and TP53) were key molecules related to QFPDD's effects. Molecular docking verified that QFPDD's compounds may bind to 6 host proteins that interact with SARS-CoV-2 proteins, further supported the anti-virus effect of QFPDD. At last, in intro experiments validated QFPDD's important effects, including the inhibition of IL6, CCL2, TNF-α, NF-κB, PTGS1/2, CYP1A1, CYP3A4 activity, the up-regulation of IL10 expression, and repressing platelet aggregation. ConclusionThis work illustrated that QFPDD could exhibit immune regulation, anti-infection, anti-inflammation, and multi-organ protection. It may strengthen the understanding of QFPDD and facilitate more application of this formula in the campaign to SARS-CoV-2.

Plants take the splice to the fight

Signal Transduction Plants transiently activate immune responses using layers of diverse regulatory mechanisms. This strategy minimizes any potential damage from an overly active protective response. Dressano et al. discovered in the model plant Arabidopsis that when an immune response was activated, the plant's immunoregulatory RNA binding protein (IRR) became dephosphorylated. Dephosphorylation altered IRR's interaction with messenger RNA transcripts, including that of calcium-dependent protein kinase 28 (CPK28), a key negative regulator of pattern recognition receptor signaling complexes. CPK28 is acutely regulated by changes in calcium concentration and its own phosphorylation state. However, altered splicing results in the expression of a truncated CPK28 protein that cannot bind calcium, and thus an enhanced immune response can be triggered. Nat. Plants 6 , 1008 (2020).

The antiviral protein viperin interacts with the viral N protein to inhibit proliferation of porcine epidemic diarrhea virus.

In the early stage of virus infection, the pattern recognition receptor (PRR) signaling pathway of the host cell is activated to induce interferon production, activating interferon-stimulated genes (ISGs) that encode antiviral proteins that exert antiviral effects. Viperin is one of the innate antiviral proteins that exert broad-spectrum antiviral effects by various mechanisms. Porcine epidemic diarrhea virus (PEDV) is a coronavirus that causes huge losses to the pig industry. Research on early antiviral responses in the gastrointestinal tract is essential for developing strategies to prevent the spread of PEDV. In this study, we investigated the mechanisms of viperin in PEDV-infected IPEJ-C2 cells. Increased expression of interferon and viperin and decreased replication of PEDV with a clear reduction in the viral load were observed in PEDV-infected IPEC-J2 cells. Amino acids 1–50 of porcine viperin contain an endoplasmic reticulum signal sequence that allows viperin to be anchored to the endoplasmic reticulum and are necessary for its function in inhibiting PEDV proliferation. The interaction of the viperin S-adenosylmethionine domain with the N protein of PEDV was confirmed via confocal laser scanning microscopy and co-immunoprecipitation. This interaction might interfere with viral replication or assembly to reduce virus proliferation. Our results highlight a potential mechanism whereby viperin is able to inhibit PEDV replication and play an antiviral role in innate immunity.

Dynamic regulation of Pep-induced immunity through post-translational control of defence transcript splicing.

The survival of all living organisms requires the ability to detect attacks and swiftly counter them with protective immune responses. Despite considerable mechanistic advances, the interconnectivity of signalling modules often remains unclear. A newly characterized protein, IMMUNOREGULATORY RNA-BINDING PROTEIN (IRR), negatively regulates immune responses in both maize and Arabidopsis, with disrupted function resulting in enhanced disease resistance. IRR associates with and promotes canonical splicing of transcripts encoding defence signalling proteins, including the key negative regulator of pattern-recognition receptor signalling complexes, CALCIUM-DEPENDENT PROTEIN KINASE 28 (CPK28). On immune activation by Plant Elicitor Peptides (Peps), IRR is dephosphorylated, disrupting interaction with CPK28 transcripts and resulting in the accumulation of an alternative splice variant encoding a truncated CPK28 protein with impaired kinase activity and diminished function as a negative regulator. We demonstrate a new mechanism linking Pep-induced post-translational modification of IRR with post-transcriptionally mediated attenuation of CPK28 function to dynamically amplify Pep signalling and immune output.

Filtered Kombucha Tea Rings the Bell for TLR2, TLR4, MYD88, and Dectin-1 in Mice Model of Colitis

Background and objectivesTLR2, TLR4, and Dectin-1 (Clec7) are pattern recognition receptors (PRRs) expressed by intestinal epithelia cells and MYD88 is a signaling molecule of TLR2 and TLR4. They warn immune system about the presence of invading pathogens promoting initiation of inflammatory response. Because of colonic cancer risk, therapy of intestinal inflammation is of high importance. Natural products are suitable candidates among which Kombucha tea has shown healing effect on mice model of colitis.MethodsFiltered Kombucha tea was prepared from black tea and sucrose plus tea fungus and previously fermented Kombucha tea. The collection was fermented by incubation at 28 °C for 14 days and filtered. Colitis was induced in young and old mice by administration of 3.5% (w/v) dextran sodium sulfate in drinking water during 7 days; filtrated Kombucha tea was given orally to animals with colitis, at a dose volume of 10 mL/kg daily for 21 days. Dectin-1, f toll-like receptor (TLR)-2, 4, as PRRs, and MyD88, as PRR signaling molecule were measured and compared with the age-matched normal and colitis model.ResultsTreatment with filtrated Kombucha tea significantly affected TLR2/TLR4 pathway and its downstream signaling molecules, MYD88 & dectin-1expression and subsequently inflammatory condition in dextran sodium sulfate-induced colitis.Conclusion The results of the present study may indicate possible implication of Kombucha tea with TLRS which consequently produces the anti-colitis effects.

Upregulation of CD47 Is a Host Checkpoint Response to Pathogen Recognition.

It is well understood that the adaptive immune response to infectious agents includes a modulating suppressive component as well as an activating component. We now show that the very early innate response also has an immunosuppressive component. Infected cells upregulate the CD47 "don't eat me" signal, which slows the phagocytic uptake of dying and viable cells as well as downstream antigen-presenting cell (APC) functions. A CD47 mimic that acts as an essential virulence factor is encoded by all poxviruses, but CD47 expression on infected cells was found to be upregulated even by pathogens, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), that encode no mimic. CD47 upregulation was revealed to be a host response induced by the stimulation of both endosomal and cytosolic pathogen recognition receptors (PRRs). Furthermore, proinflammatory cytokines, including those found in the plasma of hepatitis C patients, upregulated CD47 on uninfected dendritic cells, thereby linking innate modulation with downstream adaptive immune responses. Indeed, results from antibody-mediated CD47 blockade experiments as well as CD47 knockout mice revealed an immunosuppressive role for CD47 during infections with lymphocytic choriomeningitis virus and Mycobacterium tuberculosis Since CD47 blockade operates at the level of pattern recognition receptors rather than at a pathogen or antigen-specific level, these findings identify CD47 as a novel potential immunotherapeutic target for the enhancement of immune responses to a broad range of infectious agents.IMPORTANCE Immune responses to infectious agents are initiated when a pathogen or its components bind to pattern recognition receptors (PRRs). PRR binding sets off a cascade of events that activates immune responses. We now show that, in addition to activating immune responses, PRR signaling also initiates an immunosuppressive response, probably to limit inflammation. The importance of the current findings is that blockade of immunomodulatory signaling, which is mediated by the upregulation of the CD47 molecule, can lead to enhanced immune responses to any pathogen that triggers PRR signaling. Since most or all pathogens trigger PRRs, CD47 blockade could be used to speed up and strengthen both innate and adaptive immune responses when medically indicated. Such immunotherapy could be done without a requirement for knowing the HLA type of the individual, the specific antigens of the pathogen, or, in the case of bacterial infections, the antimicrobial resistance profile.

Balancing selection in Pattern Recognition Receptor signalling pathways is associated with gene function and pleiotropy in a wild rodent.

Pathogen-mediated balancing selection is commonly considered to play an important role in the maintenance of genetic diversity, in particular in immune genes. However, the factors that may influence which immune genes are the targets of such selection are largely unknown. To address this, here we focus on Pattern Recognition Receptor (PRR) signalling pathways, which play a key role in innate immunity. We used whole-genome resequencing data from a population of bank voles (Myodes glareolus) to test for associations between balancing selection, pleiotropy and gene function in a set of 123 PRR signalling pathway genes. To investigate the effect of gene function, we compared genes encoding (a) receptors for microbial ligands versus downstream signalling proteins, and (b) receptors recognizing components of microbial cell walls, flagella and capsids versus receptors recognizing features of microbial nucleic acids. Analyses based on the nucleotide diversity of full coding sequences showed that balancing selection primarily targeted receptor genes with a low degree of pleiotropy. Moreover, genes encoding receptors recognizing components of microbial cell walls etc. were more important targets of balancing selection than receptors recognizing nucleic acids. Tests for localized signatures of balancing selection in coding and noncoding sequences showed that such signatures were mostly located in introns, and more evenly distributed among different functional categories of PRR pathway genes. The finding that signatures of balancing selection in full coding sequences primarily occur in receptor genes, in particular those encoding receptors for components of microbial cell walls etc., is consistent with the idea that coevolution between hosts and pathogens is an important cause of balancing selection on immune genes.

The Cytomegalovirus Tegument Protein UL35 Antagonizes Pattern Recognition Receptor-Mediated Type I IFN Transcription.

The rapid activation of pattern recognition receptor (PRR)-mediated type I interferon (IFN) signaling is crucial for the host response to infection. In turn, human cytomegalovirus (HCMV) must evade this potent response to establish life-long infection. Here, we reveal that the HCMV tegument protein UL35 antagonizes the activation of type I IFN transcription downstream of the DNA and RNA sensors cGAS and RIG-I, respectively. We show that ectopic expression of UL35 diminishes the type I IFN response, while infection with a recombinant HCMV lacking UL35 induces an elevated type I IFN response compared to wildtype HCMV. With a series of luciferase reporter assays and the analysis of signaling kinetics upon HCMV infection, we observed that UL35 downmodulates PRR signaling at the level of the key signaling factor TANK-binding kinase 1 (TBK1). Finally, we demonstrate that UL35 and TBK1 co-immunoprecipitate when co-expressed in HEK293T cells. In addition, we show that a previously reported cellular binding partner of UL35, O-GlcNAc transferase (OGT), post-translationally GlcNAcylates UL35, but that this modification is not required for the antagonizing effect of UL35 on PRR signaling. In summary, we have identified UL35 as the first HCMV protein to antagonize the type I IFN response at the level of TBK1, thereby enriching our understanding of how this important herpesvirus escapes host immune responses.

Pattern Recognition Receptor Signaling and Innate Responses to Influenza A Viruses in the Mallard Duck, Compared to Humans and Chickens.

Mallard ducks are a natural host and reservoir of avian Influenza A viruses. While most influenza strains can replicate in mallards, the virus typically does not cause substantial disease in this host. Mallards are often resistant to disease caused by highly pathogenic avian influenza viruses, while the same strains can cause severe infection in humans, chickens, and even other species of ducks, resulting in systemic spread of the virus and even death. The differences in influenza detection and antiviral effectors responsible for limiting damage in the mallards are largely unknown. Domestic mallards have an early and robust innate response to infection that seems to limit replication and clear highly pathogenic strains. The regulation and timing of the response to influenza also seems to circumvent damage done by a prolonged or dysregulated immune response. Rapid initiation of innate immune responses depends on viral recognition by pattern recognition receptors (PRRs) expressed in tissues where the virus replicates. RIG-like receptors (RLRs), Toll-like receptors (TLRs), and Nod-like receptors (NLRs) are all important influenza sensors in mammals during infection. Ducks utilize many of the same PRRs to detect influenza, namely RIG-I, TLR7, and TLR3 and their downstream adaptors. Ducks also express many of the same signal transduction proteins including TBK1, TRIF, and TRAF3. Some antiviral effectors expressed downstream of these signaling pathways inhibit influenza replication in ducks. In this review, we summarize the recent advances in our understanding of influenza recognition and response through duck PRRs and their adaptors. We compare basal tissue expression and regulation of these signaling components in birds, to better understand what contributes to influenza resistance in the duck.

Vps33B is a crucial regulator of Type I Interferon response downstream of the cGAS-STING pathway

Abstract Vacuolar protein sorting-associated protein 33B (Vps33B) plays a critical role in the trafficking of endosomal contents to lysosomes in macrophages, particularly following Toll-like receptor (TLR) activation. Upon activation by microbial ligands, TLRs are internalized into endosomes, then trafficked to lysosomes for degradation. We have previously shown that endosomal to lysosomal trafficking, and subsequent degradation of TLR4, is mediated by Vps33B. Without this crucial degradation step, TLRs remain trapped within altered endosomes, leading to an enhanced inflammatory response. Since Vps33B is critical for termination of signaling following TLR ligation, we wanted to determine if it had a conserved role in regulating other pattern recognition receptor (PRR) signaling pathways. Specifically, we investigated the role of Vps33B in regulating cytosolic DNA sensing by the cGAS-STING pathway. Absence of Vps33B in macrophages and mouse embryonic fibroblasts resulted in an exaggerated type 1 interferon and interferon-stimulated gene response after stimulation with dsDNA and other STING ligands. Our findings suggest that Vps33B has a conserved role as a regulator of innate inflammatory responses downstream of both plasma membrane as well as cytosolic PRRs. Mechanistically, we hypothesize that Vps33B plays a role in STING degradation, similarly to how it permits TLR4 degradation, through mediating endo-lysosomal trafficking. This would suggest a broad and critical role for Vps33B in PRR-induced vesicular transportation and receptor degradation. Future work will investigate the mechanisms by which Vps33B regulates STING-mediated signaling as well as its importance for anti-viral immunity.

Ligand-induced monoubiquitination of BIK1 regulates plant immunity.

Recognition of microbe-associated molecular patterns (MAMPs) via plasma membrane (PM)-resident pattern recognition receptors (PRRs) triggers the first line of inducible defense against invading pathogens1–3. Receptor-like cytoplasmic kinases (RLCKs) are convergent regulators that associate with multiple PRRs in plants4. The mechanisms underlying PM-tethered RLCK activation remain elusive. We report here that, upon MAMP perception, RLCK BOTRYTIS-INDUCED KINASE 1 (BIK1) is monoubiquitinated following phosphorylation, then released from the flagellin receptor FLAGELLIN SENSING 2 (FLS2)-BRASSINOSTEROID INSENSITIVE 1-ASSOCIATED KINASE 1 (BAK1) complex, and internalized dynamically into endocytic compartments. Arabidopsis E3 ubiquitin ligases RING-H2 FINGER A3A (RHA3A) and RHA3B mediate the monoubiquitination of BIK1, which is essential for the subsequent BIK1 release from the FLS2-BAK1 complex and immune signaling activation. Ligand-induced monoubiquitination and endosomal puncta of BIK1 exhibit spatial and temporal dynamics distinct from those of PRR FLS2. Our study reveals the intertwined regulation of PRR-RLCK complex activation by protein phosphorylation and ubiquitination, and elucidates that ligand-induced monoubiquitination contributes to the release of BIK1 family RLCKs from the PRR complex and activation of PRR signaling.

Abstract P3-01-03: Modulating inflammation with nucleic acid scavengers to prevent breast cancer metastasis

Abstract Rationale: Chronic inflammation is a hallmark of cancer. Inflammation, whether it is an underlying baseline condition or induced/exacerbated due to treatment, is a major hurdle that ultimately impacts the efficacy of standard of care therapy. However, no strategy exists to effectively control endogenous or therapy-induced inflammation in women with breast cancer. Moreover, there is limited information on how endogenous or therapy-induced inflammation modulates immune cells in women with breast cancer. Nucleic acid-containing pro-inflammatory complexes, termed Nucleic Acid-containing Damage Associated Molecular Patterns (NA-DAMPs), are released from dead or dying cancer cells or activated immune cells. NA-DAMPs activate nucleic acid sensing toll-like receptors (TLR) and other pattern recognition receptors (PRR). NA-DAMPs promote tumor progression and metastasis by inducing pro-tumorigenic signaling in cancer cells. Excessive and persistent NA-DAMP-mediated PRR signaling in immune cells is associated with immune dysfunction. Nucleic acid binding polymers have been used as vehicles for DNA/RNA delivery. We have discovered that a subset of nucleic acid binding polymers, termed nucleic acid scavengers (NAS), act as anti-inflammatory agents by capturing cancer-promoting pro-inflammatory NA-DAMPs. Therefore, we investigated if a NAS could limit cancer progression and metastasis by capturing and mitigating the effects of NA-DAMPs in immunocompetent murine models of breast cancer. Methods: We tested the use of the NAS PAMAM-G3 in the 1] orthotopic surgical resection 4T1 breast cancer model; 2] intravenous experimental metastasis 4T1 breast cancer model; 3] MMTV-PyMT spontaneous breast cancer model. We also measured changes in inflammation/inflammatory cell profile in tumor and in blood. Next, we investigated the relationship between therapy, NA-DAMPs and immune cell profile in blood from women with breast cancer. We also examined if NA-DAMPs in patient serum induces tumor invasion and if the NAS PAMAM-G3 prevents tumor invasion using an in vitro assay. Results: We have determined that the NAS PAMAM-G3 controls lung metastasis in immunocompetent murine models of breast cancer and our data indicate that: 1] chronic inflammation and inflammatory cells in the tumor and periphery promote cancer invasion and metastasis; 2] modulating inflammation by removing excessive NA-DAMPs using the NAS PAMAM-G3 limits cancer metastasis; 3] scavenging inflammation-associated NA-DAMPs significantly alters immune cell and cytokine/chemokine profile in the tumor and periphery, promotes T cell infiltration in the tumor and induces antitumor CD8+ T cell responses. In experiments conducted using blood collected longitudinally from women undergoing standard of care therapy, we observed that: 1] NA-DAMPs and inflammatory monocytes are elevated in women undergoing standard of care therapy; 2] Post-chemotherapy breast cancer patient serum increases invasion/migration of human breast cancer cells in vitro; 3] PAMAM-G3 abrogates increase in invasion/migration of human breast cancer cells in vitro in response to post-chemotherapy breast cancer patient serum. Conclusions: These results highlight the potential utility of NAS to treat cancer associated inflammation and thereby inhibit cancer metastasis by 1) limiting extracellular NA-DAMP-induced persistent activation of pro-inflammatory signaling, and 2) promoting full engagement of both the innate and adaptive immune systems. These principles will aid in the development of a novel anti-metastatic therapy for women with breast cancer. This work is supported by Department of Defense Breast Cancer Research Program Awards W81XWH-16-1-0512 (Nair) and W81XWH-16-1-0513 (Sullenger). Citation Format: Smita Nair, Eda Holl, Karenia Landa, Victoria Frazier, Elias Eteshola, David Boczkowski, Rachel Rempel, Shelley Hwang, Bruce Sullenger. Modulating inflammation with nucleic acid scavengers to prevent breast cancer metastasis [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P3-01-03.

Pectin Interaction with Immune Receptors is Modulated by Ripening Process in Papayas

Dietary fibers have been shown to exert immune effects via interaction with pattern recognition receptors (PRR) such as toll-like receptors (TLR) and nucleotide-binding oligomerization domain (NOD)-like receptors. Pectin is a dietary fiber that interacts with PRR depending on its chemical structure. Papaya pectin retains different chemical structures at different ripening stages. How this influence PRR signaling is unknown. The aim of this work was to determine how ripening influences pectin structures and their ability to interact with TLR2, 3, 4, 5 and 9, and NOD1 and 2. It was evaluated the interaction of the water-soluble fractions rich in pectin extracted from unripe to ripe papayas. The pectin extracted from ripe papayas activated all the TLR and, to a lesser extent, the NOD receptors. The pectin extracted from unripe papayas also activated TLR2, 4 and 5 but inhibited the activation of TLR3 and 9. The differences in pectin structures are the higher methyl esterification and smaller galacturonan chains of pectin from ripe papayas. Our finding might lead to selection of ripening stages for tailored modulation of PRR to support or attenuate immunity.

Immunomodulation of intracranial melanoma in response to blood-tumor barrier opening with focused ultrasound.

Background: Focused ultrasound (FUS) activation of microbubbles (MBs) for blood-brain (BBB) and blood-tumor barrier (BTB) opening permits targeted therapeutic delivery. While the effects of FUS+MBs mediated BBB opening have been investigated for normal brain tissue, no such studies exist for intracranial tumors. As this technology advances into clinical immunotherapy trials, it will be crucial to understand how FUS+MBs modulates the tumor immune microenvironment.Methods and Results: Bulk RNA sequencing revealed that FUS+MBs BTB/BBB opening (1 MHz, 0.5 MPa peak-negative pressure) of intracranial B16F1cOVA tumors increases the expression of genes related to proinflammatory cytokine and chemokine signaling, pattern recognition receptor signaling, and antigen processing and presentation. Flow cytometry revealed increased maturation (i.e. CD86) of dendritic cells (DCs) in the meninges and altered antigen loading of DCs in both the tumor and meninges. For DCs in tumor draining lymph nodes, FUS+MBs had no effect on maturation and elicited only a trend towards increased presentation of tumor-derived peptide by MHC. Neither tumor endothelial cell adhesion molecule expression nor homing of activated T cells was affected by FUS+MBs.Conclusion: FUS+MBs-mediated BTB/BBB opening elicits signatures of inflammation; however, the response is mild, transient, and unlikely to elicit a systemic response independent of administration of immune adjuvants.

Plant immune signaling: Advancing on two frontiers.

Plants have evolved multiple defense strategies to cope with pathogens, among which plant immune signaling that relies on cell-surface localized and intracellular receptors takes fundamental roles. Exciting breakthroughs were made recently on the signaling mechanisms of pattern recognition receptors (PRRs) and intracellular nucleotide-binding site (NBS) and leucine-rich repeat (LRR) domain receptors (NLRs). This review summarizes the current view of PRRs activation, emphasizing the most recent discoveries about PRRs' dynamic regulation and signaling mechanisms directly leading to downstream molecular events including mitogen-activated protein kinase (MAPK) activation and calcium (Ca2+ ) burst. Plants also have evolved intracellular NLRs to perceive the presence of specific pathogen effectors and trigger more robust immune responses. We also discuss the current understanding of the mechanisms of NLR activation, which has been greatly advanced by recent breakthroughs including structures of the first full-length plant NLR complex, findings of NLR sensor-helper pairs and novel biochemical activity of Toll/interleukin-1 receptor (TIR) domain.