TLR activation triggers the rapid differentiation of monocytes into macrophages and dendritic cells

Non-coding RNA LINC01010 regulates macrophage polarization and innate immune functions by modulating NFκB signaling pathway

Innate immune response is regulated by tissue resident or infiltrating immune cells such as macrophages (Mφ) that play critical role in tissue development, homeostasis, and repair of damaged tissue. However, the epigenetic mechanisms that regulate Mφ plasticity and innate immune functions are not well understood. Long non-coding RNA (lncRNA) are among the most abundant class of transcriptome but their function in myeloid cell biology is less explored. In this study, we deciphered the regulatory role of previously uncharacterized lncRNAs in Mφ polarization and innate immune responses. Two lncRNAs showed notable changes in their levels during M1 and M2 Mφ differentiation. Our findings indicate that LINC01010 expression increased and AC007032 expression decreased significantly. LINC01010 exhibit myeloid cell-specificity, while AC007032.1 is ubiquitous and expressed in both myeloid and lymphoid (T cells, B cells and NK cells) cells. Expression of these lncRNAs is dysregulated in periodontal disease (PD), a microbial biofilm-induced immune disease, and responsive to lipopolysaccharide (LPS) from different oral and non-oral bacteria. Knockdown of LINC01010 but not AC007032.1 reduced the surface expression of Mφ differentiation markers CD206 and CD68, and M1Mφ polarization markers MHCII and CD32. Furthermore, LINC01010 RNAi attenuated bacterial phagocytosis, antigen processing and cytokine secretion suggesting its key function in innate immunity. Mechanistically, LINC01010 knockdown Mφ treated with Escherichia coli LPS exhibit significantly reduced expression of multiple nuclear factor kappa B pathway genes. Together, our data highlight functional role of a PD-associated lncRNA LINC01010 in shaping macrophage differentiation, polarization, and innate immune activation.

Association of CC-chemokine ligand-2 gene polymorphisms with leprosy reactions

BACKGROUND

C-C motif chemokine ligand 2, a gene that codes for a protein involved in inflammation. Certain SNPs in the CCL2 gene have been studied for their potential associations with susceptibility to various diseases. These SNPs may affect the production and function of the CCL2 protein, which is involved in the recruitment of immune cells to the site of inflammation. Variations in CCL2 may influence the immune response to Mycobacterium leprae infection.

OBJECTIVE

To investigate the association of the C-C motif chemokine ligand-2 single nucleotide polymorphisms with leprosy.

METHODS

CCL2 single nucleotide polymorphisms were analyzed in a total of 975 leprosy patients and 357 healthy controls. Of those, 577 leprosy and 288 healthy controls were analyzed by PCR-RFLP for CCL2 -2518 A>G, 535 leprosy and 290 controls for CCL2 -362 G>C, 295 leprosy and 240 controls for CCL2 -2134 T>G, 325 leprosy and 288 controls for CCL2 -1549 A>T SNPs by melting curve analysis using hybridization probe chemistry and detection by fluorescence resonance energy transfer (FRET) technique in Realtime PCR. The levels of CCL2, IL-12p70, IFN-γ, TNF-α, and TGF-β were estimated in sera samples and correlated with CCL2 genotypes.

RESULTS

The frequency of the GCT (-2518 A>G, -362 G>C, -2134 T>G) haplotype is observed to be higher in leprosy patients compared to healthy controls (P = 0.04). There was no significant difference observed in genotypic frequencies between leprosy patients and healthy controls {(-2518A>G, p = 0.53), (-362 G>C, p = 0.01), (-2134 T>G, p = 0.10)}. G allele at the -2134 site is predominant in leprosy (borderline) without any reaction (8 %) compared to borderline patients with RR reactions (2.1 %) (P = 0.03). GG genotype (p = 0.008) and G allele at -2518 (p = 0.030) of the CCL 2 gene were found to be associated with patients with ENL reaction. An elevated level of serum CCL2 was observed in leprosy patients with the -2518 AA and AG genotypes (p = 0.0001).

CONCLUSIONS

G allele and GG genotype at the CCL2 -2518 site are associated with a risk of ENL reactions.

MicroRNAs correlate with bacillary index and genes associated to cell death processes in leprosy

Mycobacterium leprae infects skin and peripheral nerves causing a broad of clinical forms. MicroRNAs (miRNAs) control immune mechanisms such as apoptosis, autophagy as well as to target genes leading to abnormal proliferation, metastasis, and invasion of cells. Herein we evaluated miRNAs expression for leprosy phenotypes in biopsies obtained from patients with and without reactions. We also correlated those miRNAs with both, bacillary index (BI) and genes involved in the micobacteria elimination process. Our results show a significant increase in the miR-125a-3p expression in paucibacillary (PB) patients vs multibacillary (MB) subjects (p = 0.007) and vs reversal reactions (RR) (p = 0.005), respectively. Likewise, there was a higher expression of miR-125a-3p in patients with erythema nodosum leprosum (ENL) vs MB without reactions (p = 0.002). Furthermore, there was a positive correlation between miR-125a-3p, miR-146b-5p and miR-132-5p expression and BI in patients with RR and ENL. These miRNAS were also correlated with genes such as ATG12 (miR-125a-3p), TNFRSF10A (miR-146b-5p), PARK2, CFLAR and STX7 (miR-132-5p). All together we underpin a role for these miRNAs in leprosy pathogenesis, implicating mechanisms such as apoptosis and autophagy in skin. The miR-125a-3p might have a distinct role associated with PB phenotype and ENL in MB patients.

Blood and guts: how the intestinal microbiome shapes hematopoiesis and treatment of hematologic disease

ABSTRACT

Over the past 10 years, there has been a marked increase in recognition of the interplay between the intestinal microbiome and the hematopoietic system. Despite their apparent distance in the body, a large literature now supports the relevance of the normal intestinal microbiota to steady-state blood production, affecting both hematopoietic stem and progenitor cells as well as differentiated immune cells. Microbial metabolites enter the circulation where they can trigger cytokine signaling that influences hematopoiesis. Furthermore, the state of the microbiome is now recognized to affect outcomes from hematopoietic stem cell transplant, immunotherapy, and cellular therapies for hematologic malignancies. Here we review the mechanisms by which microbiotas influence hematopoiesis in development and adulthood as well as the avenues by which microbiotas are thought to impact stem cell transplant engraftment, graft-versus-host disease, and efficacy of cell and immunotherapies. We highlight areas of future research that may lead to reduced adverse effects of antibiotic use and improved outcomes for patients with hematologic conditions.

Leprosy: treatment, prevention, immune response and gene function

Since the leprosy cases have fallen dramatically, the incidence of leprosy has remained stable over the past years, indicating that multidrug therapy seems unable to eradicate leprosy. More seriously, the emergence of rifampicin-resistant strains also affects the effectiveness of treatment. Immunoprophylaxis was mainly carried out through vaccination with the BCG but also included vaccines such as LepVax and MiP. Meanwhile, it is well known that the infection and pathogenesis largely depend on the host's genetic background and immunity, with the onset of the disease being genetically regulated. The immune process heavily influences the clinical course of the disease. However, the impact of immune processes and genetic regulation of leprosy on pathogenesis and immunological levels is largely unknown. Therefore, we summarize the latest research progress in leprosy treatment, prevention, immunity and gene function. The comprehensive research in these areas will help elucidate the pathogenesis of leprosy and provide a basis for developing leprosy elimination strategies.

A novel polysaccharide isolated from Coriolus versicolor polarizes M2 macrophages into an M1 phenotype and reversesits immunosuppressive effect on tumor microenvironment

Converting M2 macrophages into an M1 phenotype in the tumor microenvironment, provides a new direction for tumor treatment. Here, we further report CVPW-1, a new polysaccharide of 1.03 × 106 Da that was isolated from Coriolus versicolor. Its monosaccharide was composed of mannose, glucose, and galactose at a ratio of 1.00:8.73:1.68. The backbone of CVPW-1 was composed of (1 → 3)-linked α-D-Glcp residues and (1 → 3,6)-linked α-D-Glcp residues that branched at O-6. The branch consisted of (1 → 6)-linked α-D-Glcp residues and (1 → 4)-linked α-D-Glap, and some branches were terminated with (1→)-linked β-D-Manp residues according to the results of HPLC, FT-IR, GC-MS, 1D and 2D NMR. Meanwhile, CVPW-1 could polarize M2 macrophages to M1 phenotypein vitro by binding to TLR4 and inducing the activation of Akt, JNK and NF-κB. This process involved reversing the functional inhibition of CD8+ T lymphocytes by inhibiting the expression of TREM2 in M2 macrophages. The in vivo experiments showed that oral administration of CVPW-1 could inhibit the growth of tumor in mice and polarize TAMs to M1 phenotype. Thus, the novel polysaccharide CVPW-1 from Coriolus versicolor might activate a variety of immune cells and then play an anti-tumor role. These results demonstrated that CVPW-1 could be developed as a potential immuno-oncology treatment reagent.

Monocyte regulation by gut microbial signals

Monocytes are innate immune cells that sense environmental changes and participate in the immunoregulation of autoimmune, neurologic, cardiovascular, and metabolic diseases as well as cancer. Recent studies have suggested that the gut microbiome shapes the biology of monocytes via microbial signals at extraintestinal sites. Interestingly, in chronic diseases, communication between microbial signals and monocytes can either promote or inhibit disease activity, suggesting that some of these pathways can be harnessed for clinical therapies. In this review, we discuss the newer concepts of regulation of monocyte homeostasis and function by gut microbial signals during steady state and inflammation. We also highlight the therapeutic potential of microbial signal-based approaches for modulation in the context of various diseases.

CD1-mediated immune responses in mucosal tissues: molecular mechanisms underlying lipid antigen presentation system

The cluster of differentiation 1 (CD1) molecule differs from major histocompatibility complex class I and II because it presents glycolipid/lipid antigens. Moreover, the CD1-restricted T cells that recognize these self and foreign antigens participate in both innate and adaptive immune responses. CD1s are constitutively expressed by professional and nonprofessional antigen-presenting cells in mucosal tissues, namely, the skin, lung, and intestine. This suggests that CD1-reactive T cells are involved in the immune responses of these tissues. Indeed, evidence suggests that these cells play important roles in diverse diseases, such as inflammation, autoimmune disease, and infection. Recent studies elucidating the molecular mechanisms by which CD1 presents lipid antigens suggest that defects in these mechanisms could contribute to the activities of CD1-reactive T cells. Thus, improving our understanding of these mechanisms could lead to new and effective therapeutic approaches to CD1-associated diseases. In this review, we discuss the CD1-mediated antigen presentation system and its roles in mucosal tissue immunity.

Peptide-based vaccine for cancer therapies

Different strategies based on peptides are available for cancer treatment, in particular to counter-act the progression of tumor growth and disease relapse. In the last decade, in the context of therapeutic strategies against cancer, peptide-based vaccines have been evaluated in different tumor models. The peptides selected for cancer vaccine development can be classified in two main type: tumor-associated antigens (TAAs) and tumor-specific antigens (TSAs), which are captured, internalized, processed and presented by antigen-presenting cells (APCs) to cell-mediated immunity. Peptides loaded onto MHC class I are recognized by a specific TCR of CD8+ T cells, which are activated to exert their cytotoxic activity against tumor cells presenting the same peptide-MHC-I complex. This process is defined as active immunotherapy as the host's immune system is either de novo activated or restimulated to mount an effective, tumor-specific immune reaction that may ultimately lead to tu-mor regression. However, while the preclinical data have frequently shown encouraging results, therapeutic cancer vaccines clinical trials, including those based on peptides have not provided satisfactory data to date. The limited efficacy of peptide-based cancer vaccines is the consequence of several factors, including the identification of specific target tumor antigens, the limited immunogenicity of peptides and the highly immunosuppressive tumor microenvironment (TME). An effective cancer vaccine can be developed only by addressing all such different aspects. The present review describes the state of the art for each of such factors.

Cigarette Smoke-Induced Respiratory Response: Insights into Cellular Processes and Biomarkers

Cigarette smoke (CS) poses a significant risk factor for respiratory, vascular, and organ diseases owing to its high content of harmful chemicals and reactive oxygen species (ROS). These substances are known to induce oxidative stress, inflammation, apoptosis, and senescence due to their exposure to environmental pollutants and the presence of oxidative enzymes. The lung is particularly susceptible to oxidative stress. Persistent oxidative stress caused by chronic exposure to CS can lead to respiratory diseases such as chronic obstructive pulmonary disease (COPD), pulmonary fibrosis (PF), and lung cancer. Avoiding exposure to environmental pollutants, like cigarette smoke and air pollution, can help mitigate oxidative stress. A comprehensive understanding of oxidative stress and its impact on the lungs requires future research. This includes identifying strategies for preventing and treating lung diseases as well as investigating the underlying mechanisms behind oxidative stress. Thus, this review aims to investigate the cellular processes induced by CS, specifically inflammation, apoptosis, senescence, and their associated biomarkers. Furthermore, this review will delve into the alveolar response provoked by CS, emphasizing the roles of potential therapeutic target markers and strategies in inflammation and oxidative stress.

Role of UPRmt and mitochondrial dynamics in host immunity: it takes two to tango

The immune system of a host contains a group of heterogeneous cells with the prime aim of restraining pathogenic infection and maintaining homeostasis. Recent reports have proved that the various subtypes of immune cells exploit distinct metabolic programs for their functioning. Mitochondria are central signaling organelles regulating a range of cellular activities including metabolic reprogramming and immune homeostasis which eventually decree the immunological fate of the host under pathogenic stress. Emerging evidence suggests that following bacterial infection, innate immune cells undergo profound metabolic switching to restrain and countervail the bacterial pathogens, promote inflammation and restore tissue homeostasis. On the other hand, bacterial pathogens affect mitochondrial structure and functions to evade host immunity and influence their intracellular survival. Mitochondria employ several mechanisms to overcome bacterial stress of which mitochondrial UPR (UPR^mt) and mitochondrial dynamics are critical. This review discusses the latest advances in our understanding of the immune functions of mitochondria against bacterial infection, particularly the mechanisms of mitochondrial UPR^mt and mitochondrial dynamics and their involvement in host immunity.

Interleukin-2 family cytokines: An overview of genes, expression, signaling and functional roles in teleost

The interleukin-2 (IL-2) family cytokines include IL-2, IL-4, IL-7, IL-9, IL-15, and IL-21, which share γ chain (γc) subunit in receptors. The IL-2 family cytokines have unique biological effects that regulate differentiation, survival and activation of multiple lymphocyte lineages. Deficiency of IL-2 family signaling pathway in mammals prevents CD4⁺ T cells from developing effector functions and CD8⁺ T cells from developing immunological memory. In the present review, we addressed available information from teleost IL-2 family cytokines and discussed implications in teleost immunity. Also, we described and discussed their expression profiles, receptors, signaling transductions and functions. In teleost, IL-2 family has 5 members (IL-2, IL-4/13, IL-7, IL-15, IL-21) without IL-9, and their receptors share a common γc subunit and include other 6 subunits (IL-2Rβ1/2, IL-4Rα1/2, IL-13Rα1/2, IL-7Rα, IL-15Rα, and IL-21Rα1/2). Some paralogues have changes in domain structure and show differential expression, modulation, functions. IL-2 family cytokines constitutively express in many immune associated tissues and are largely induced after pathogenic microbial stimulation. In general, there are relatively conserved functions in the IL-2 family throughout vertebrates, and many of the key IL-2 family members are important in lymphocyte proliferation and differentiation, development, inflammation from fishes to mammals. This review will give an update on the effective information of teleost IL-2 family cytokines. Thus, it will provide a source of reference for other researchers/readers and inspire further interest.

Dendritic Cells or Macrophages? The Microenvironment of Human Clear Cell Renal Cell Carcinoma Imprints a Mosaic Myeloid Subtype Associated with Patient Survival

Since their initial description by Elie Metchnikoff, phagocytes have sparked interest in a variety of biologic disciplines. These important cells perform central functions in tissue repair and immune activation as well as tolerance. Myeloid cells can be immunoinhibitory, particularly in the tumor microenvironment, where their presence is generally associated with poor patient prognosis. These cells are highly adaptable and plastic, and can be modulated to perform desired functions such as antitumor activity, if key programming molecules can be identified. Human clear cell renal cell carcinoma (ccRCC) is considered immunogenic; yet checkpoint blockades that target T cell dysfunction have shown limited clinical efficacy, suggesting additional layers of immunoinhibition. We previously described "enriched-in-renal cell carcinoma" (erc) DCs that were often found in tight contact with dysfunctional T cells. Using transcriptional profiling and flow cytometry, we describe here that ercDCs represent a mosaic cell type within the macrophage continuum co-expressing M1 and M2 markers. The polarization state reflects tissue-specific signals that are characteristic of RCC and renal tissue homeostasis. ErcDCs are tissue-resident with increasing prevalence related to tumor grade. Accordingly, a high ercDC score predicted poor patient survival. Within the profile, therapeutic targets (VSIG4, NRP1, GPNMB) were identified with promise to improve immunotherapy.

Lipopolysaccharide from Porphyromonas gingivalis, but Not from Porphyromonas endodontalis, Induces Macrophage M1 Profile

Apical Lesions of Endodontic Origin (ALEO) are initiated by polymicrobial endodontic canal infection. Porphyromonas gingivalis (Pg) and Porphyromonas endodontalis (Pe) lipopolysaccharides (LPS) can induce a pro-inflammatory macrophage response through their recognition by TLR2 and TLR4. However, polarization responses induced by Pg and/or Pe LPS in macrophages are not fully understood. We aimed to characterize the polarization profiles of macrophages differentiated from THP-1 cells following Pg and/or Pe LPS stimulation from reference strain and clinical isolates. A modified LPS purification protocol was implemented and the electrophoretic LPS profiles were characterized. THP-1 human monocytes differentiated to macrophages were stimulated with Pg and Pe LPS. Polarization profiles were characterized through cell surface markers and secreted cytokines levels after 24 h of stimulation. TLR2 and TLR4 cell surfaces and transcriptional levels were determined after 24 or 2 h of LPS stimulation, respectively. LPS from Pg induced a predominant M1 profile in macrophages evidenced by changes in the expression of the surface marker CD64 and pro-inflammatory cytokine profiles, TNF-α, IL-1β, IL-6, and IL-12. Pe LPS was unable to induce a significant response. TLR2 and TLR4 expressions were neither modified by Pg or Pe LPS. Pg LPS, but not Pe LPS, induced a macrophage M1 Profile.

TLR2 and TLR4 activity in monocytes and macrophages after exposure to amoxicillin, ciprofloxacin, doxycycline and erythromycin

BACKGROUND

Antibiotics are used to treat bacterial infections but also impact immunity. This is usually attributed to antibiotic-induced dysbiosis of the microbiota, but antibiotics may have a direct effect on immune cells and immunity-associated receptors, such as Toll-like receptors (TLRs).

OBJECTIVES

To investigate whether antibiotics alter TLR2/1, TLR2/6 and TLR4 activity in immune cells.

METHODS

We evaluated the effects of amoxicillin, ciprofloxacin, doxycycline and erythromycin on TLR2/1-, TLR2/6- and TLR4-induced NF-κB activation in THP1-XBlue™-MD2-CD14 cells. Furthermore, we studied TNF-α and IL-6 levels in THP-1-derived macrophages after exposure to these antibiotics and TLR ligands.

RESULTS

Amoxicillin had no effect on any of the TLRs studied. However, ciprofloxacin reduced TLR2/1, TLR2/6 and TLR4 activity in THP1-XBlue™-MD2-CD14 cells and decreased TLR2/1-induced TNF-α and IL-6 in macrophages. Doxycycline reduced TLR2/6 and TLR4 activity in THP1-XBlue™-MD2-CD14 cells and TNF-α and IL-6 levels in response to TLR2/6 stimulation in macrophages. Erythromycin decreased TLR2/1 and TLR4 activity in THP1-XBlue™-MD2-CD14 cells without changes in TNF-α and IL-6 levels in macrophages. In addition, ciprofloxacin decreased the expression of TLR2 mRNA.

CONCLUSIONS

These results suggest that some antibiotics may attenuate TLR-dependent monocyte/macrophage responses and likely reduce bacterial clearance. The latter is particularly important in infections with AMR bacteria, where misprescribed antibiotics not only fail in control of AMR infections but might also weaken host defence mechanisms by limiting innate immune responses. Our data suggest that efforts should be made to prevent the deterioration of the immune response during and after antibiotic treatment.

MicroRNA-22 represses glioma development via activation of macrophage-mediated innate and adaptive immune responses

Macrophage-mediated tumor cell phagocytosis and subsequent neoantigen presentation are critical for generating anti-tumor immunity. This study aimed to uncover the potential clinical value and molecular mechanisms of miRNA-22 (miR-22) in tumor cell phagocytosis via macrophages and more efficient T cell priming. We found that miR-22 expression was markedly downregulated in primary macrophages from glioma tissue samples compared to adjacent tissues. miR-22-overexpressing macrophages inhibited glioma cell proliferation and migration, respectively. miR-22 upregulation stimulated the phagocytic ability of macrophages, enhanced tumor cell phagocytosis, antigen presentation, and efficient T cell priming. Additionally, our data revealed that miR-22-overexpressing macrophages inhibited glioma formation in vivo, HDAC6 was a target, and NF-κB signaling was a pathway closely associated with miR-22 in tumor-associated macrophages (TAMs) of glioma. Our findings revealed the essential roles of miR-22 in tumor cell phagocytosis by macrophages and more efficient T cell priming, facilitating further research on phagocytic regulation to enhance the response to tumor immunotherapy.

Skin immunity: dissecting the complex biology of our body's outer barrier

Our skin contributes critically to health via its role as a barrier tissue, carefully regulating passage of key substrates while also providing defense against exogenous threats. Immunological processes are integral to almost every skin function and paramount to our ability to live symbiotically with skin commensal microbes and other environmental stimuli. While many parallels can be drawn to immunobiology at other mucosal sites, skin immunity demonstrates unique features that relate to its distinct topography, chemical composition and microbial ecology. Here we provide an overview of skin as an immune organ, with reference to the broader context of mucosal immunology. We review paradigms of innate as well as adaptive immune function and highlight how skin-specific structures such as hair follicles and sebaceous glands interact and contribute to these processes. Finally, we highlight for the mucosal immunology community a few emerging areas of interest for the skin immunity field moving forward.

Spliced or Unspliced, That Is the Question: The Biological Roles of XBP1 Isoforms in Pathophysiology

X-box binding protein 1 (XBP1) is a member of the CREB/ATF basic region leucine zipper family transcribed as the unspliced isoform (XBP1-u), which, upon exposure to endoplasmic reticulum stress, is spliced into its spliced isoform (XBP1-s). XBP1-s interacts with the cAMP response element of major histocompatibility complex class II gene and plays critical role in unfolded protein response (UPR) by regulating the transcriptional activity of genes involved in UPR. XBP1-s is also involved in other physiological pathways, including lipid metabolism, insulin metabolism, and differentiation of immune cells. Its aberrant expression is closely related to inflammation, neurodegenerative disease, viral infection, and is crucial for promoting tumor progression and drug resistance. Meanwhile, recent studies reported that the function of XBP1-u has been underestimated, as it is not merely a precursor of XBP1-s. Instead, XBP-1u is a critical factor involved in various biological pathways including autophagy and tumorigenesis through post-translational regulation. Herein, we summarize recent research on the biological functions of both XBP1-u and XBP1-s, as well as their relation to diseases.

Pathogen Receptor Membrane-Coating Facet Structures Boost Nanomaterial Immune Escape and Antibacterial Performance

Nanomaterials show great potential for the treatment of bacterial infections, but their effects remain limited by low antibacterial efficiency and immune clearance. Facet-dependent nanozymes coated with pathogen receptor membranes were fabricated, providing an approach for producing superphotothermal antibacterial nanomaterials with high biocompatibility and low immune clearance. (100)- and (112)-Faceted CuFeSe₂ presented excellent photothermal conversion efficiency (46%). However, the peroxidase-like activity of (100)-faceted CuFeSe₂ enhanced the decomposition of H₂O₂ to hydroxyl radicals (^•OH) and was markedly greater than that of (112)-faceted CuFeSe₂, with nearly 100% of Staphylococcus aureus being killed under near-infrared (NIR) irradiation. Importantly, bacteria-pretreated immune membranes (i.e., pathogen receptor membranes) coated with CuFeSe₂ exhibited superior S. aureus-binding ability, presented obvious immune-evading capability, and resulted in targeted delivery to infected sites. As a proof-of-principle demonstration, these findings hold promise for the use of pathogen receptor membrane-coated facet-dependent nanomaterials in clinical applications and the treatment of bacterial infections.

Protection against neonatal respiratory viral infection via maternal treatment during pregnancy with the benign immune training agent OM-85

Objectives

Incomplete maturation of immune regulatory functions at birth is antecedent to the heightened risk for severe respiratory infections during infancy. Our forerunner animal model studies demonstrated that maternal treatment with the microbial‐derived immune training agent OM‐85 during pregnancy promotes accelerated postnatal maturation of mechanisms that regulate inflammatory processes in the offspring airways. Here, we aimed to provide proof of concept for a novel solution to reduce the burden and potential long‐term sequelae of severe early‐life respiratory viral infection through maternal oral treatment during pregnancy with OM‐85, already in widespread human clinical use.

Methods

In this study, we performed flow cytometry and targeted gene expression (RT‐qPCR) analysis on lungs from neonatal offspring whose mothers received oral OM‐85 treatment during pregnancy. We next determined whether neonatal offspring from OM‐85 treated mothers demonstrate enhanced protection against lethal lower respiratory infection with mouse‐adapted rhinovirus (vMC₀), and associated lung immune changes.

Results

Offspring from mothers treated with OM‐85 during pregnancy display accelerated postnatal seeding of lung myeloid populations demonstrating upregulation of function‐associated markers. Offspring from OM‐85 mothers additionally exhibit enhanced expression of TLR4/7 and the IL‐1β/NLRP3 inflammasome complex within the lung. These treatment effects were associated with enhanced capacity to clear an otherwise lethal respiratory viral infection during the neonatal period, with concomitant regulation of viral‐induced IFN response intensity.

Conclusion

These results demonstrate that maternal OM‐85 treatment protects offspring against lethal neonatal respiratory viral infection by accelerating development of innate immune mechanisms crucial for maintenance of local immune homeostasis in the face of pathogen challenge.

Counter Regulation of Spic by NF-κB and STAT Signaling Controls Inflammation and Iron Metabolism in Macrophages

Activated macrophages must carefully calibrate their inflammatory responses to balance efficient pathogen control with inflammation-mediated tissue damage, but the molecular underpinnings of this "balancing act" remain unclear. Using genetically engineered mouse models and primary macrophage cultures, we show that Toll-like receptor (TLR) signaling induces the expression of the transcription factor Spic selectively in patrolling monocytes and tissue macrophages by a nuclear factor κB (NF-κB)-dependent mechanism. Functionally, Spic downregulates pro-inflammatory cytokines and promotes iron efflux by regulating ferroportin expression in activated macrophages. Notably, interferon-gamma blocks Spic expression in a STAT1-dependent manner. High levels of interferon-gamma are indicative of ongoing infection, and in its absence, activated macrophages appear to engage a "default" Spic-dependent anti-inflammatory pathway. We also provide evidence for the engagement of this pathway in sterile inflammation. Taken together, our findings uncover a pathway wherein counter-regulation of Spic by NF-κB and STATs attune inflammatory responses and iron metabolism in macrophages.

Dendritic Cell Tumor Vaccination via Fc Gamma Receptor Targeting: Lessons Learned from Pre-Clinical and Translational Studies

Despite significant recent improvements in the field of immunotherapy, cancer remains a heavy burden on patients and healthcare systems. In recent years, immunotherapies have led to remarkable strides in treating certain cancers. However, despite the success of checkpoint inhibitors and the advent of cellular therapies, novel strategies need to be explored to (1) improve treatment in patients where these approaches fail and (2) make such treatments widely and financially accessible. Vaccines based on tumor antigens (Ag) have emerged as an innovative strategy with the potential to address these areas. Here, we review the fundamental aspects relevant for the development of cancer vaccines and the critical role of dendritic cells (DCs) in this process. We first offer a general overview of DC biology and routes of Ag presentation eliciting effective T cell-mediated immune responses. We then present new therapeutic avenues specifically targeting Fc gamma receptors (FcγR) as a means to deliver antigen selectively to DCs and its effects on T-cell activation. We present an overview of the mechanistic aspects of FcγR-mediated DC targeting, as well as potential tumor vaccination strategies based on preclinical and translational studies. In particular, we highlight recent developments in the field of recombinant immune complex-like large molecules and their potential for DC-mediated tumor vaccination in the clinic. These findings go beyond cancer research and may be of relevance for other disease areas that could benefit from FcγR-targeted antigen delivery, such as autoimmunity and infectious diseases.

A multi-herb-combined remedy to overcome hyper-inflammatory response by reprogramming transcription factor profile and shaping monocyte subsets

Traditional Chinese multi-herb-combined prescriptions usually show better performance than a single agent since a group of effective compounds interfere multiple disease-relevant targets simultaneously. Huang-Lian-Jie-Du decoction is a remedy made of four herbs that are widely used to treat oral ulcers, gingivitis, and periodontitis. However, the active ingredients and underlying mechanisms are not clear. To address these questions, we prepared a water extract solution of Huang-Lian-Jie-Du decoction (HLJDD), called it as WEH (Water Extract Solution of HLJDD), and used it to treat LPS-induced systemic inflammation in mice. We observed that WEH attenuated inflammatory responses including reducing production of cytokines, chemokines and interferons (IFNs), further attenuating emergency myelopoiesis, and preventing mice septic lethality. Upon LPS stimulation, mice pretreated with WEH increased circulating Ly6C^- patrolling and splenic Ly6C⁺ inflammatory monocytes. The acute myelopoiesis related transcriptional factor profile was rearranged by WEH. Mechanistically we confirmed that WEH interrupted LPS/TLR4/CD14 signaling-mediated downstream signaling pathways through its nine principal ingredients, which blocked LPS stimulated divergent signaling cascades, such as activation of NF-κB, p38 MAPK, and ERK1/2. We conclude that the old remedy blunts LPS-induced "danger" signal recognition and transduction process at multiple sites. To translate our findings into clinical applications, we refined the crude extract into a pure multicomponent drug by directly mixing these nine chemical entities, which completely reproduced the effect of protecting mice from lethal septic shock. Finally, we reduced a large number of compounds within a multi-herb water extract to seven-chemical combination that exhibited superior therapeutic efficacy compared with WEH.

miR-181a Modulation of ERK-MAPK Signaling Sustains DC-SIGN Expression and Limits Activation of Monocyte-Derived Dendritic Cells

DC-SIGN⁺ monocyte-derived dendritic cells (mo-DCs) play important roles in bacterial infections and inflammatory diseases, but the factors regulating their differentiation and proinflammatory status remain poorly defined. Here, we identify a microRNA, miR-181a, and a molecular mechanism that simultaneously regulate the acquisition of DC-SIGN expression and the activation state of DC-SIGN⁺ mo-DCs. Specifically, we show that miR-181a promotes DC-SIGN expression during terminal mo-DC differentiation and limits its sensitivity and responsiveness to TLR triggering and CD40 ligation. Mechanistically, miR-181a sustains ERK-MAPK signaling in mo-DCs, thereby enabling the maintenance of high levels of DC-SIGN and a high activation threshold. Low miR-181a levels during mo-DC differentiation, induced by inflammatory signals, do not support the high phospho-ERK signal transduction required for DC-SIGN^hi mo-DCs and lead to development of proinflammatory DC-SIGN^lo/- mo-DCs. Collectively, our study demonstrates that high DC-SIGN expression levels and a high activation threshold in mo-DCs are linked and simultaneously maintained by miR-181a.

The Peptide Vaccine of the Future

The approach of peptide-based anticancer vaccination has proven the ability to induce cancer-specific immune responses in multiple studies for various cancer entities. However, clinical responses remain so far limited to single patients and broad clinical applicability was not achieved. Therefore, further efforts are required to improve peptide vaccination in order to integrate this low-side-effect therapy into the clinical routine of cancer therapy. To design clinically effective peptide vaccines in the future, different issues have to be addressed and optimized comprising antigen target selection as well as choice of optimal adjuvants and vaccination schedules. Furthermore, the combination of peptide-based vaccines with other immuno- and molecular targeted therapies as well as the development of predictive biomarkers could further improve efficacy. In this review, current approaches in the development of peptide-based vaccines and critical implications for optimal vaccine design are discussed.

Illuminating the Role of Vitamin A in Skin Innate Immunity and the Skin Microbiome: A Narrative Review

Vitamin A is a fat-soluble vitamin that plays an important role in skin immunity. Deficiencies in Vitamin A have been linked to impaired immune response and increased susceptibility to skin infections and inflammatory skin disease. This narrative review summarizes recent primary evidence that elucidates the role of vitamin A and its derivatives on innate immune regulators through mechanisms that promote skin immunity and sustain the skin microbiome.

Bacterial products in donor airways prevent the induction of lung transplant tolerance

Although postoperative bacterial infections can trigger rejection of pulmonary allografts, the impact of bacterial colonization of donor grafts on alloimmune responses to transplanted lungs remains unknown. Here, we tested the hypothesis that bacterial products present within donor grafts at the time of implantation promote lung allograft rejection. Administration of the toll-like receptor 2 (TLR2) agonist Pam₃ Cys₄ to Balb/c wild-type grafts triggered acute cellular rejection after transplantation into B6 wild-type recipients that received perioperative costimulatory blockade. Pam₃ Cys₄ -triggered rejection was associated with an expansion of CD8⁺ T lymphocytes and CD11c⁺ CD11b^hi MHC (major histocompatibility complex) class II⁺ antigen-presenting cells within the transplanted lungs. Rejection was prevented when lungs were transplanted into TLR2-deficient recipients but not when MyD88-deficient donors were used. Adoptive transfer of B6 wild-type monocytes, but not T cells, following transplantation into B6 TLR2-deficient recipients restored the ability of Pam₃ Cys₄ to trigger acute cellular rejection. Thus, we have demonstrated that activation of TLR2 by a bacterial lipopeptide within the donor airways prevents the induction of lung allograft tolerance through a process mediated by recipient-derived monocytes. Our work suggests that donor lungs harboring bacteria may precipitate an inflammatory response that can facilitate allograft rejection.

Pathogenesis and Host Immune Response in Leprosy

Leprosy is an ancient insidious disease caused by Mycobacterium leprae, where the skin and peripheral nerves undergo chronic granulomatous infections, leading to sensory and motor impairment with characteristic deformities. Susceptibility to leprosy and its disease state are determined by the manifestation of innate immune resistance mediated by cells of monocyte lineage. Due to insufficient innate resistance, granulomatous infection is established, influencing the specific cellular immunity. The clinical presentation of leprosy ranges between two stable polar forms (tuberculoid to lepromatous) and three unstable borderline forms. The tuberculoid form involves Th1 response, characterized by a well demarcated granuloma, infiltrated by CD4⁺ T lymphocytes, containing epitheloid and multinucleated giant cells. In the lepromatous leprosy, there is no characteristic granuloma but only unstructured accumulation of ineffective macrophages containing engulfed pathogens. Th1 response, characterised by IFN-γ and IL-2 production, activates macrophages in order to kill intracellular pathogens. Conversely, a Th2 response, characterized by the production of IL-4, IL-5 and IL-10, helps in antibody production and consequently downregulates the cell-mediated immunity induced by the Th1 response. M. lepare has a long generation time and its inability to grow in culture under laboratory conditions makes its study challenging. The nine-banded armadillo still remains the best clinical and immunological model to study host-pathogen interaction in leprosy. In this chapter, we present cellular morphology and the genomic uniqueness of M. leprae, and how the pathogen shows tropism for Schwann cells, macrophages and dendritic cells.

Immunology of leprosy

Leprosy is a disease caused by Mycobacterium leprae (ML) with diverse clinical manifestations, which are strongly correlated with the host's immune response. Skin lesions may be accompanied by peripheral neural damage, leading to sensory and motor losses, as well as deformities of the hands and feet. Both innate and acquired immune responses are involved, but the disease has been classically described along a Th1/Th2 spectrum, where the Th1 pole corresponds to the most limited presentations and the Th2 to the most disseminated ones. We discuss this dichotomy in the light of current knowledge of cytokines, Th subpopulations and regulatory T cells taking part in each leprosy presentation. Leprosy reactions are associated with an increase in inflammatory activity both in limited and disseminated presentations, leading to a worsening of previous symptoms or the development of new symptoms. Despite the efforts of many research groups around the world, there is still no adequate serological test for diagnosis in endemic areas, hindering the eradication of leprosy in these regions.

An Overview of Astrocyte Responses in Genetically Induced Alzheimer's Disease Mouse Models

Alzheimer's disease (AD) is the most common form of dementia. Despite many years of intense research, there is currently still no effective treatment. Multiple cell types contribute to disease pathogenesis, with an increasing body of data pointing to the active participation of astrocytes. Astrocytes play a pivotal role in the physiology and metabolic functions of neurons and other cells in the central nervous system. Because of their interactions with other cell types, astrocyte functions must be understood in their biologic context, thus many studies have used mouse models, of which there are over 190 available for AD research. However, none appear able to fully recapitulate the many functional changes in astrocytes reported in human AD brains. Our review summarizes the observations of astrocyte biology noted in mouse models of familial and sporadic AD. The limitations of AD mouse models will be discussed and current attempts to overcome these disadvantages will be described. With increasing understanding of the non-neuronal contributions to disease, the development of new methods and models will provide further insights and address important questions regarding the roles of astrocytes and other non-neuronal cells in AD pathophysiology. The next decade will prove to be full of exciting opportunities to address this devastating disease.

Mycobacterium leprae induces a tolerogenic profile in monocyte-derived dendritic cells via TLR2 induction of IDO

The enzyme IDO‐1 is involved in the first stage of tryptophan catabolism and has been described in both microbicidal and tolerogenic microenvironments. Previous data from our group have shown that IDO‐1 is differentially regulated in the distinctive clinical forms of leprosy. The present study aims to investigate the mechanisms associated with IDO‐1 expression and activity in human monocyte‐derived dendritic cells (mDCs) after stimulation with irradiated Mycobacterium leprae and its fractions. M. leprae and its fractions induced the expression and activity of IDO‐1 in human mDCs. Among the stimuli studied, irradiated M. leprae and its membrane fraction (MLMA) induced the production of proinflammatory cytokines TNF and IL‐6 whereas irradiated M. leprae and its cytosol fraction (MLSA) induced an increase in IL‐10. We investigated if TLR2 activation was necessary for IDO‐1 induction in mDCs. We observed that in cultures treated with a neutralizing anti‐TLR2 antibody, there was a decrease in IDO‐1 activity and expression induced by M. leprae and MLMA. The same effect was observed when we used a MyD88 inhibitor. Our data demonstrate that coculture of mDCs with autologous lymphocytes induced an increase in regulatory T (Treg) cell frequency in MLSA‐stimulated cultures, showing that M. leprae constituents may play opposite roles that may possibly be related to the dubious effect of IDO‐1 in the different clinical forms of disease. Our data show that M. leprae and its fractions are able to differentially modulate the activity and functionality of IDO‐1 in mDCs by a pathway that involves TLR2, suggesting that this enzyme may play an important role in leprosy immunopathogenesis.

Inhibition of TLR2/TLR4 alleviates the Neisseria gonorrhoeae infection damage in human endometrial epithelial cells via Nrf2 and NF-Kβsignaling

BACKGROUND

Neisseria gonorrhoeae (N.g) is Gram-negative bacteria and can lead to endometritis in female. Toll-like receptors regulate immune response in various diseases. However, the roles of TLR2 and TLR4 in. Neisseria gonorrhoeae-induced infection damage in human endometrial epithelia were investigated.

METHODS

hEECs were infected with N.g (MOI 10 and 100) and cell viability and apoptosis were measured by CCK8 and flow cytometry assays in both infected groups with the uninfected normal hEECs as negative control. TLR2/TLR4 proteins were measured by ELISA method. Pro-inflammatory markers NLRP3, PGES (PGE2) and TNF-α were assessed by RT-qPCR (mRNA expression) and Elisa (protein concentrations). Transfection assays were performed to up- or down- regulate expression of TLR2 and TLR4 so as to study the functions of TLR2/TLR4 in. N.g-infected hEECs, followed by apoptosis and inflammation assessment. Similarly, we explored the interactions between TLR2/TLR4 and Nrf2/NF-κB/p65 by knocking down TLR2/TLR4 to detect the signaling and further regulating the signaling to evaluate TLR2/ TLR4, apoptosis and inflammation in cells.

RESULTS

N.g suppressed cell viabilities and induced cell apoptosis and inflammation. TLR2/TLR4 downregulation inhibited the infection damage. Nrf2 was activated while NF-κB/p65 was depleted as TLR2/ TLR4 was knocked down. Activation of Nrf2 and inhibition of NF-κB resulted in decrease of TLR2/TLR4, which could retard apoptosis and inflammation induced by N.g infection.

CONCLUSION

TLR2/TLR4 depletion could alleviate the N.g-infected hEECs via Nrf2/NF-kB signaling, suggesting that TLR2/TLR4 inhibitors might serve as a treatment to reduce N.g infection in human endometrial epithelia.

Novel Sca-1+ macrophages modulate the pathogenic progress of endotoxemia

Macrophages are important innate immune cells that play crucial roles in inflammatory responses. Accumulating evidence has demonstrated macrophage heterogeneity based on biomarkers, functions, and localization. Here, we report a novel stem cell antigen-1 (Sca-1)-positive macrophage population induced in the pathological conditions caused by lipopolysaccharide (LPS). Sca-1 is only upregulated in macrophages but not in monocytes and neutrophils upon LPS injection. Sca-1⁺ macrophages develop from resident peritoneal macrophages. LPS-induced Sca-1⁺ macrophage generation was partly blocked by anti-IFN-γ antibody, suggesting a role of IFN-γ in the process. LPS-stimulated production of IL-6, TNF-α, and CCL2 is significantly lower in Sca-1⁺ macrophages compared to their counterpart Sca-1^- macrophages. Depletion of Sca-1⁺ macrophages using anti-Sca-1 antibody significantly increased survival rate and reduced lung and kidney damage in an LPS-induced sepsis model. Taken together, we discovered a novel population of Sca-1⁺ macrophages in LPS-induced septic conditions.

Schistosome and intestinal helminth modulation of macrophage immunometabolism

Macrophages are fundamental to sustain physiological equilibrium and to regulate the pathogenesis of parasitic and metabolic processes. The functional heterogeneity and immune responses of macrophages are shaped by cellular metabolism in response to the host's intrinsic factors, environmental cues and other stimuli during disease. Parasite infections induce a complex cascade of cytokines and metabolites that profoundly remodel the metabolic status of macrophages. In particular, helminths polarize macrophages to an M2 state and induce a metabolic shift towards reliance on oxidative phosphorylation, lipid oxidation and amino acid metabolism. Accumulating data indicate that helminth-induced activation and metabolic reprogramming of macrophages underlie improvement in overall whole-body metabolism, denoted by improved insulin sensitivity, body mass in response to high-fat diet and atherogenic index in mammals. This review aims to highlight the metabolic changes that occur in human and murine-derived macrophages in response to helminth infections and helminth products, with particular interest in schistosomiasis and soil-transmitted helminths.

Advances in the Immunology and Genetics of Leprosy

Leprosy, a disease caused by the intracellular parasite Mycobacterium leprae or Mycobacterium lepromatosis, has affected humans for more than 4,000 years and is a stigmatized disease even now. Since clinical manifestations of leprosy patients present as an immune-related spectrum, leprosy is regarded as an ideal model for studying the interaction between host immune response and infection; in fact, the landscape of leprosy immune responses has been extensively investigated. Meanwhile, leprosy is to some extent a genetic disease because the genetic factors of hosts have long been considered major contributors to this disease. Many immune-related genes have been discovered to be associated with leprosy. However, immunological and genetic findings have rarely been studied and discussed together, and as a result, the effects of gene variants on leprosy immune responses and the molecular mechanisms of leprosy pathogenesis are largely unknown. In this context, we summarized advances in both the immunology and genetics of leprosy and discussed the perspective of the combination of immunological and genetic approaches in studying the molecular mechanism of leprosy pathogenesis. In our opinion, the integrating of immunological and genetic approaches in the future may be promising to elucidate the molecular mechanism of leprosy onset and how leprosy develops into different types of leprosy.

Extracellular Vesicles Derived Human-miRNAs Modulate the Immune System in Type 1 Diabetes

Extracellular vesicles with their molecular cargo can modulate target cell response and may affect the pathogenesis of diseases. The extracellular vesicles containing micro-RNAs (miRNAs), which are often studied as disease biomarkers, but rarely as mediators of the disease development. The role of extracellular vesicles derived miRNAs in type 1 diabetes is currently not well established. We observed a fraction of blood plasma extracellular vesicles positive for membrane proteins potentially associated with insulin-producing beta-cells and identified differentially expressed extracellular vesicles derived miRNAs in individuals with type 1 diabetes. These differentially expressed extracellular vesicles derived human miRNAs in participants with type 1 diabetes and participants with Langerhans islets beta-cells destruction showed the ability to activate TLR7/8 signaling cascade and increase activation as well as cytotoxicity of the effector blood immune cells with cytokine and chemokine release. Our results illustrate extracellular vesicles derived human miRNAs as modulators of the immune system in type 1 diabetes autoimmunity, providing potentially new insight into the pathogenesis of the disease, and novel molecular targets for intervention and type 1 diabetes prevention.

Glucolipotoxicity: A Proposed Etiology for Wooden Breast and Related Myopathies in Commercial Broiler Chickens

Wooden breast is one of several myopathies of fast-growing commercial broilers that has emerged as a consequence of intensive selection practices in the poultry breeding industry. Despite the substantial economic burden presented to broiler producers worldwide by wooden breast and related muscle disorders such as white striping, the genetic and etiological underpinnings of these diseases are still poorly understood. Here we propose a new hypothesis on the primary causes of wooden breast that implicates dysregulation of lipid and glucose metabolism. Our hypothesis addresses recent findings that have suggested etiologic similarities between wooden breast and type 2 diabetes despite their phenotypic disparities. Unlike in mammals, dysregulation of lipid and glucose metabolism is not accompanied by an increase in plasma glucose levels but generates a unique skeletal muscle phenotype, i.e., wooden breast, in chickens. We hypothesize that these phenotypic disparities result from a major difference in skeletal muscle glucose transport between birds and mammals, and that the wooden breast phenotype most closely resembles complications of diabetes in smooth and cardiac muscle of mammals. Additional basic research on wooden breast and related muscle disorders in commercial broiler chickens is necessary and can be informative for poultry breeding and production as well as for human health and disease. To inform future studies, this paper reviews the current biological knowledge of wooden breast, outlines the major steps in its proposed pathogenesis, and examines how selection for production traits may have contributed to its prevalence.

Cellular, Molecular, and Immunological Characteristics of Langhans Multinucleated Giant Cells Programmed by IL-15

Langhans multinucleated giant cells (LGCs) are a specific type of multinucleated giant cell containing a characteristic horseshoe-shaped ring of nuclei that are present within granulomas of infectious etiology. Although cytokines that trigger macrophage activation (such as IFN-γ) induce LGC formation, it is not clear whether cytokines that trigger macrophage differentiation contribute to LGC formation. Here, we found that IL-15, a cytokine that induces M1 macrophage differentiation, programs human peripheral blood adherent cells to form LGCs. Analysis of the IL-15‒treated adherent cell transcriptome identified gene networks for T cells, DNA damage and replication, and IFN-inducible genes that correlated with IL-15 treatment and LGC-type multinucleated giant cell formation. Gene networks enriched for myeloid cells were anticorrelated with IL-15 treatment and LGC formation. Functional studies revealed that T cells were required for IL-15‒induced LGC formation, involving a direct contact with myeloid cells through CD40L-CD40 interaction and IFN-γ release. These data indicate that IL-15 induces LGC formation through the direct interaction of activated T cells and myeloid cells.

C-Type Lectin Receptors in Antifungal Immunity

Most fungal species are harmless to humans and some exist as commensals on mucocutaneous surfaces. Yet many fungi are opportunistic pathogens, causing life-threatening invasive infections when the immune system becomes compromised. The fungal cell wall contains conserved pathogen-associated molecular patterns (PAMPs), which allow the immune system to distinguish between self (endogenous molecular patterns) and foreign material. Sensing of invasive microbial pathogens is achieved through recognition of PAMPs by pattern recognition receptors (PRRs). One of the predominant fungal-sensing PRRs is the C-type lectin receptor (CLR) family. These receptors bind to structures present on the fungal cell wall, eliciting various innate immune responses as well as shaping adaptive immunity. In this chapter, we specifically focus on the four major human fungal pathogens, Candida albicans, Aspergillus fumigatus, Cryptococcus neoformans and Pneumocystis jirovecii, reviewing our current understanding of the CLRs that are involved in their recognition and protection of the host.

Signaling C-Type Lectin Receptors in Antifungal Immunity

We are all exposed to fungal organisms daily, and although many of these organisms are not harmful, billions of people a year contract a fungal infection. Most of these infections are not fatal and can be cleared by the host immune response. However, due to an increase in high-risk populations, the global fungal burden has increased, with more than 1.5 million deaths per year caused by invasive fungal infections. The fungal cell wall is an important surface for interacting with the host immune system as it contains pathogen-associated molecular patterns (PAMPs) which are detected as being foreign by the host pattern recognition receptors (PRRs). C-type lectin receptors are a group of PRRs that play a central role in the protection against invasive fungal infections. Following the recognition of fungal PAMPs, CLRs trigger various innate and adaptive immune responses. In this chapter, we specifically focus on C-type lectin receptors capable of activating downstream signaling pathways, resulting in protective antifungal immune responses. The current roles that these signaling CLRs play in protection against four of the most prevalent fungal infections affecting humans are reviewed. These include Candida albicans, Aspergillus fumigatus, Cryptococcus neoformans and Pneumocystis jirovecii.

The Differentiation of Human Cytomegalovirus Infected-Monocytes Is Required for Viral Replication

Viral dissemination is a key mechanism responsible for persistence and disease following human cytomegalovirus (HCMV) infection. Monocytes play a pivotal role in viral dissemination to organ tissue during primary infection and following reactivation from latency. For example, during primary infection, infected monocytes migrate into tissues and differentiate into macrophages, which then become a source of viral replication. In addition, because differentiated macrophages can survive for months to years, they provide a potential persistent infection source in various organ systems. We broadly note that there are three phases to infection and differentiation of HCMV-infected monocytes: (1) Virus enters and traffics to the nucleus through a virus receptor ligand engagement event that activates a unique signalsome that initiates the monocyte-to-macrophage differentiation process. (2) Following initial infection, HCMV undergoes a "quiescence-like state" in monocytes lasting for several weeks and promotes monocyte differentiation into macrophages. While, the initial event is triggered by the receptor-ligand engagement, the long-term cellular activation is maintained by chronic viral-mediated signaling events. (3) Once HCMV infected monocytes differentiate into macrophages, the expression of immediate early viral (IE) genes is detectable, followed by viral replication and long term infectious viral particles release. Herein, we review the detailed mechanisms of each phase during infection and differentiation into macrophages and discuss the biological significance of the differentiation of monocytes in the pathogenesis of HCMV.

A comprehensive mechanistic review insight into the effects of micronutrients on toll-like receptors functions

Toll-like receptors (TLRs) are the special proteins receptors for recognition of molecules related to the pathogens. In this way, TLRs and secreted cytokines as a result of TLRs activation are involved in the inflammation pathways. So far, in vivo and in vitro studies have demonstrated that micronutrients (vitamins & minerals) with a broad range of effects on body health, can regulate TLRs signaling pathways. Current review aimed at determining the possible mechanisms of micronutrient effects on TLRs functions. In the aspect of gene expression, micronutrients have inconsistent effects on mRNA level of TLRs which are dependent on time, dose and type of studied TLR. Also, some micronutrients affect gene expression of TLRs signaling mediators namely TLRs adaptors like Myeloid differentiation primary response 88 (MyD88). In the aspect of TLRs signaling pathways, nuclear factor-κB (NF-κB) is an important mediator which is regulated by micronutrients. Also, the regulatory effects of micronutrients on phosphorylation reactions may be effective in the activation/inactivation of TLRs signaling mediators. In addition, zinc can regulate TLRs signaling indirectly via the zinc finger proteins which have contradictory effects on TLRs cascade. In conclusion, the relationship between micronutrients and TLRs signaling is complicated and depends on some known internal, external and genetic factors like form of studied micronutrient, cell type, TLR agonist, dose and time of exposure, inflammation, apoptosis, cell cycle, and environmental factors. Some unknown factors may be effective in TLRs response and as a result additional mechanistic studies are needed to elucidate exact effect of micronutrients on TLRs signaling.

The Skin and Intestinal Microbiota and Their Specific Innate Immune Systems

The skin and intestine are active organs of the immune system that are constantly exposed to the outside environment. They support diverse microbiota, both commensal and pathogenic, which encompass bacteria, viruses, fungi, and parasites. The skin and intestine must maintain homeostasis with the diversity of commensal organisms present on epithelial surfaces. Here we review the current literature pertaining to epithelial barrier formation, microbial composition, and the complex regulatory mechanisms governing the interaction between the innate immune system and microbiota in the skin and intestine. We also compare and contrast the skin and intestine—two different organ systems responsible creating a protective barrier against the external environment, each of which has unique mechanisms for interaction with commensal populations and host repair.

Cell Type Specific Expression of Toll-Like Receptors in Human Brains and Implications in Alzheimer's Disease

Toll-like receptors mediate important cellular immune responses upon activation via various pathogenic stimuli such as bacterial or viral components. The activation and subsequent secretion of cytokines and proinflammatory factors occurs in the whole body including the brain. The subsequent inflammatory response is crucial for the immune system to clear the pathogen(s) from the body via the innate and adaptive immune response. Within the brain, astrocytes, neurons, microglia, and oligodendrocytes all bear unique compositions of Toll-like receptors. Besides pathogens, cellular damage and abnormally folded protein aggregates, such as tau and Amyloid beta peptides, have been shown to activate Toll-like receptors in neurodegenerative diseases such as Alzheimer's disease. This review provides an overview of the different cell type-specific Toll-like receptors of the human brain, their activation mode, and subsequent cellular response, as well as their activation in Alzheimer's disease. Finally, we critically evaluate the therapeutic potential of targeting Toll-like receptors for treatment of Alzheimer's disease as well as discussing the limitation of mouse models in understanding Toll-like receptor function in general and in Alzheimer's disease.

Vitamin A Metabolism by Dendritic Cells Triggers an Antimicrobial Response against Mycobacterium tuberculosis

Epidemiological evidence correlates low serum vitamin A (retinol) levels with increased susceptibility to active tuberculosis (TB); however, retinol is biologically inactive and must be converted into its bioactive form, all-trans retinoic acid (ATRA). Given that ATRA triggers a Niemann-Pick type C2 (NPC2)-dependent antimicrobial response against Mycobacterium tuberculosis, we investigated the mechanism by which the immune system converts retinol into ATRA at the site of infection. We demonstrate that granulocyte-macrophage colony-stimulating factor (GM-CSF)-derived dendritic cells (DCs), but not macrophages, express enzymes in the vitamin A metabolic pathway, including aldehyde dehydrogenase 1 family, member a2 (ALDH1A2) and short-chain dehydrogenase/reductase family, member 9 (DHRS9), enzymes capable of the two-step conversion of retinol into ATRA, which is subsequently released from the cell. Additionally, mRNA and protein expression levels of ALDH1A2 and DC marker CD1B were lower in tuberculosis lung tissues than in normal lung. The conditioned medium from DCs cultured with retinol stimulated antimicrobial activity from M. tuberculosis-infected macrophages, as well as the expression of NPC2 in monocytes, which was blocked by specific inhibitors, including retinoic acid receptor inhibitor (RARi) or N,N-diethylaminobenzaldehyde (DEAB), an ALDH1A2 inhibitor. These results indicate that metabolism of vitamin A by DCs transactivates macrophage antimicrobial responses.IMPORTANCE Tuberculosis (TB) is the leading cause of death by a single infectious agent worldwide. One factor that contributes to the success of the microbe is the deficiency in immunomodulatory nutrients, such as vitamin A (retinol), which are prevalent in areas where TB is endemic. Clinical trials show that restoration of systemic retinol levels in active TB patients is ineffective in mitigating the disease; however, laboratory studies demonstrate that activation of the vitamin A pathway in Mycobacterium tuberculosis-infected macrophages triggers an antimicrobial response. Therefore, the goal of this study was to determine the link between host retinol levels and retinoic acid-mediated antimicrobial responses against M. tuberculosis By combining established in vitro models with in situ studies of lung tissue from TB patients, this study demonstrates that the innate immune system utilizes transcellular metabolism leading to activation between dendritic cells and macrophages as a means to combat the pathogen.

A toll-like receptor agonist mimicking microbial signal to generate tumor-suppressive macrophages

Switching macrophages from a pro-tumor type to an anti-tumor state is a promising strategy for cancer immunotherapy. Existing agents, many derived from bacterial components, have safety or specificity concerns. Here, we postulate that the structures of the bacterial signals can be mimicked by using non-toxic biomolecules of simple design. Based on bioactivity screening, we devise a glucomannan polysaccharide with acetyl modification at a degree of 1.8 (acGM-1.8), which specifically activates toll-like receptor 2 (TLR2) signaling and consequently induces macrophages into an anti-tumor phenotype. For acGM-1.8, the degree of acetyl modification, glucomannan pattern, and acetylation-induced assembly are three crucial factors for its bioactivity. In mice, intratumoral injection of acGM-1.8 suppresses the growth of two tumor models, and this polysaccharide demonstrates higher safety than four classical TLR agonists. In summary, we report the design of a new, safe, and specific TLR2 agonist that can generate macrophages with strong anti-tumor potential in mice.

Turning tumour promoting macrophages into an anti-tumour phenotype is an attractive therapeutic strategy. Here, the authors develop a polysaccharide-based structure that mimicks pathogen-associated molecular patterns and, by activating the toll-like receptors on macrophage surface, promotes a safe anti-tumour immune response in mouse models.

Microglial proliferation and monocyte infiltration contribute to microgliosis following status epilepticus

Microglial activation has been recognized as a major contributor to inflammation of the epileptic brain. Seizures are commonly accompanied by remarkable microgliosis and loss of neurons. In this study, we utilize the CX3CR1^GFP/+ CCR2^RFP/+ genetic mouse model, in which CX3CR1⁺ resident microglia and CCR2⁺ monocytes are labeled with GFP and RFP, respectively. Using a combination of time-lapse two-photon imaging and whole-cell patch clamp recording, we determined the distinct morphological, dynamic, and electrophysiological characteristics of infiltrated monocytes and resident microglia, and the evolution of their behavior at different time points following kainic acid-induced seizures. Seizure activated microglia presented enlarged somas with less ramified processes, whereas, infiltrated monocytes were smaller, highly motile cells that lacked processes. Moreover, resident microglia, but not infiltrated monocytes, proliferate locally in the hippocampus after seizure. Microglial proliferation was dependent on the colony-stimulating factor 1 receptor (CSF-1R) pathway. Pharmacological inhibition of CSF-1R reduced seizure-induced microglial proliferation, which correlated with attenuation of neuronal death without altering acute seizure behaviors. Taken together, we demonstrated that proliferation of activated resident microglia contributes to neuronal death in the hippocampus via CSF-1R after status epilepticus, providing potential therapeutic targets for neuroprotection in epilepsy.

Harnessing Dendritic Cells for Poly (D,L-lactide-co-glycolide) Microspheres (PLGA MS)-Mediated Anti-tumor Therapy

With emerging success in fighting off cancer, chronic infections, and autoimmune diseases, immunotherapy has become a promising therapeutic approach compared to conventional therapies such as surgery, chemotherapy, radiation therapy, or immunosuppressive medication. Despite the advancement of monoclonal antibody therapy against immune checkpoints, the development of safe and efficient cancer vaccine formulations still remains a pressing medical need. Anti-tumor immunotherapy requires the induction of antigen-specific CD8+ cytotoxic T lymphocyte (CTL) responses which recognize and specifically destroy tumor cells. Due to the crucial role of dendritic cells (DCs) in initiating anti-tumor immunity, targeting tumor antigens to DCs has become auspicious in modern vaccine research. Over the last two decades, micron- or nanometer-sized particulate delivery systems encapsulating tumor antigens and immunostimulatory molecules into biodegradable polymers have shown great promise for the induction of potent, specific and long-lasting anti-tumor responses in vivo. Enhanced vaccine efficiency of the polymeric micro/nanoparticles has been attributed to controlled and continuous release of encapsulated antigens, efficient targeting of antigen presenting cells (APCs) such as DCs and subsequent induction of CTL immunity. Poly (D, L-lactide-co-glycolide) (PLGA), as one of these polymers, has been extensively studied for the design and development of particulate antigen delivery systems in cancer therapy. This review provides an overview of the current state of research on the application of PLGA microspheres (PLGA MS) as anti-tumor cancer vaccines in activating and potentiating immune responses attempting to highlight their potential in the development of cancer therapeutics.

CD1b presents self and Borrelia burgdorferi diacylglycerols to human T cells

Lyme disease is a common multisystem disease caused by infection with a tick‐transmitted spirochete, Borrelia burgdorferi and related Borrelia species. The monoglycosylated diacylglycerol known as B. burgdorferi glycolipid II (BbGL‐II) is a major target of antibodies in sera from infected individuals. Here, we show that CD1b presents BbGL‐II to human T cells and that the TCR mediates the recognition. However, we did not detect increased frequency of CD1b‐BbGL‐II binding T cells in the peripheral blood of Lyme disease patients compared to controls. Unexpectedly, mapping the T cell specificity for BbGL‐II‐like molecules using tetramers and activation assays revealed a concomitant response to CD1b‐expressing APCs in absence of BbGL‐II. Further, among all major classes of self‐lipid tested, BbGL‐II responsive TCRs show strong cross‐reactivity to diacylglycerol, a self‐lipid antigen with structural similarities to BbGL‐II. Extending prior work on MHC and CD1b, CD1c, and CD1d proteins, this study provides evidence for cross‐reactive CD1b‐restricted T cell responses to bacterial and self‐antigens, and identifies chemically defined targets for future discovery of self and foreign antigen cross‐reactive T cells.