M. tuberculosis-Initiated Human Mannose Receptor Signaling Regulates Macrophage Recognition and Vesicle Trafficking by FcRγ-Chain, Grb2, and SHP-1

Macrophages exploit the mannose receptor and JAK-STAT1-MHC-II pathway to drive antigen presentation and the antimycobacterial immune response after BCG vaccination

Tuberculosis (TB), caused by Mycobacterium tuberculosis ( M. tb), remains one of the leading causes of fatal infectious diseases worldwide. The only licensed vaccine, Mycobacterium bovis Bacillus Calmette-Guérin (BCG), has variable efficacy against TB in adults. Insufficiency of immune cell function diminishes the protective effects of the BCG vaccine. It is critical to clarify the mechanism underlying the antimycobacterial immune response during BCG vaccination. Macrophage mannose receptor (MR) is important for enhancing the uptake and processing of glycoconjugated antigens from pathogens for presentation to T cells, but the roles of macrophage MR in the BCG-induced immune response against M. tb are not yet clear. Here, we discover that macrophage MR deficiency impairs the antimycobacterial immune response in BCG-vaccinated mice. Mechanistically, macrophage MR triggers JAK-STAT1 signaling, which promotes antigen presentation via upregulated MHC-II and induces IL-12 production by macrophages, contributing to CD4 + T cell activation and IFN-γ production. MR deficiency in macrophages reduces the vaccine efficacy of BCG and increases susceptibility to M. tb H37Ra challenge in mice. Our results suggest that MR is critical for macrophage antigen presentation and the antimycobacterial immune response to BCG vaccination and offer valuable guidance for the preventive strategy of BCG immunization.

Cutting Edge: Cytosolic Receptor AIM2 Is Induced by Peroxisome Proliferator-activated Receptor γ following Mycobacterium tuberculosis Infection of Human Macrophages but Does Not Contribute to IL-1β Release

AIM2 (absent in melanoma 2), an inflammasome component, mediates IL-1β release in murine macrophages and cell lines. AIM2 and IL-1β contribute to murine control of Mycobacterium tuberculosis (M.tb) infection, but AIM2's impact in human macrophages, the primary niche for M.tb, remains unclear. We show that M.tb, Mycobacterium bovis bacillus Calmette-Guérin (BCG), and M. smegmatis induce AIM2 expression in primary human macrophages. M.tb-induced AIM2 expression is peroxisome proliferator-activated receptor γ (PPARγ)-dependent and M.tb ESX-1-independent, whereas BCG- and M. smegmatis-induced AIM2 expression is PPARγ-independent. PPARγ and NLRP3, but not AIM2, are important for IL-1β release in response to M.tb, and NLRP3 colocalizes with M.tb. This is in contrast to the role for AIM2 in inflammasome activation in mice and peritoneal macrophages. Altogether, we show that mycobacteria induce AIM2 expression in primary human macrophages, but AIM2 does not contribute to IL-1β release during M.tb infection, providing further evidence that AIM2 expression and function are regulated in a cell- and/or species-specific manner.

Pathogenicity and virulence of Mycobacterium tuberculosis

Mycobacterium tuberculosis (Mtb) is the causative agent of tuberculosis, an infectious disease with one of the highest morbidity and mortality rates worldwide. Leveraging its highly evolved repertoire of non-protein and protein virulence factors, Mtb invades through the airway, subverts host immunity, establishes its survival niche, and ultimately escapes in the setting of active disease to initiate another round of infection in a naive host. In this review, we will provide a concise synopsis of the infectious life cycle of Mtb and its clinical and epidemiologic significance. We will also take stock of its virulence factors and pathogenic mechanisms that modulate host immunity and facilitate its spread. Developing a greater understanding of the interface between Mtb virulence factors and host defences will enable progress toward improved vaccines and therapeutics to prevent and treat tuberculosis.

Detoxified pneumolysin derivative ΔA146Ply inhibits triple- negative breast cancer metastasis mainly via mannose receptor-mediated autophagy inhibition

The detoxified pneumolysin derivative ΔA146Ply has been proven to have a direct anti-triple negative breast cancer effect by our group, but its work model remains unclear. In this study, we focused on its ability to inhibit triple-negative breast cancer metastasis. We found that ΔA146Ply suppressed the migration and invasion of triple-negative breast cancer cells by activating mannose receptor and toll-like receptor 4. Their activation triggers the activation of the mammalian target of rapamycin signaling, sequentially leading to autophagy, transforming growth factor-β1, and epithelial-mesenchymal transition inhibition. Furthermore, the combination of doxorubicin and ΔA146Ply significantly inhibited triple-negative breast cancer progression and prolonged survival in tumor-bearing mice. Taken together, our study provides an alternative microbiome-based mannose receptor-targeted therapy for triple-negative breast cancer and a novel theoretical and experimental basis for the downstream signaling pathway of the mannose receptor.

Dermatophyte infection: from fungal pathogenicity to host immune responses

Dermatophytosis is a common superficial infection caused by dermatophytes, a group of pathogenic keratinophilic fungi. Apart from invasion against skin barrier, host immune responses to dermatophytes could also lead to pathologic inflammation and tissue damage to some extent. Therefore, it is of great help to understand the pathogenesis of dermatophytes, including fungal virulence factors and anti-pathogen immune responses. This review aims to summarize the recent advances in host-fungal interactions, focusing on the mechanisms of anti-fungal immunity and the relationship between immune deficiency and chronic dermatophytosis, in order to facilitate novel diagnostic and therapeutic approaches to improve the outcomes of these patients.

Role of pattern recognition receptors in sensing Mycobacterium tuberculosis

Mycobacterium tuberculosis is one of the major invasive intracellular pathogens causing most deaths by a single infectious agent. The interaction between host immune cells and this pathogen is the focal point of the disease, Tuberculosis. Host immune cells not only mount the protective action against this pathogen but also serve as the primary niche for growth. Thus, recognition of this pathogen by host immune cells and following signaling cascades are key dictators of the disease state. Immune cells, mainly belonging to myeloid cell lineage, recognize a wide variety of Mycobacterium tuberculosis ligands ranging from carbohydrate and lipids to proteins to nucleic acids by different membrane-bound and soluble pattern recognition receptors. Simultaneous interaction between different host receptors and pathogen ligands leads to immune-inflammatory response as well as contributes to virulence. This review summarizes the contribution of pattern recognition receptors of host immune cells in recognizing Mycobacterium tuberculosis and subsequent initiation of signaling pathways to provide the molecular insight of the specific Mtb ligands interacting with specific PRR, key adaptor molecules of the downstream signaling pathways and the resultant effector functions which will aid in identifying novel drug targets, and developing novel drugs and adjuvants.

Mycobacterium tuberculosis and its clever approaches to escape the deadly macrophage

Mycobacterium tuberculosis (Mt.b), a deadly disease causer, is a facultative parasite. This microorganism has developed several methods to defend itself, once internalized within specialised vacuoles in the macrophages. A wide array of receptors like the complement receptor mannose receptors, scavenger receptor assists the entry of the microbe within the phagocytic macrophages. However, Mt.b is clever enough to protect itself from the hostile environment of the macrophage thereby prevailing within it. The microbe can efficiently inhibit processes like phagosome-lysosome fusion, acidification of phagosomes, release of proinflammatory cytokines and stop crucial events like apoptosis. Additionally, it also adopts resistance to killing by reactive oxygen intermediates and reactive nitrogen intermediates. There are multiple genes both in host and the pathogen which are involved in this successful survival of Mt.b. The regulation of phagolysosome fusion is mediated by proteins such as Coronin, TlyA, SapM, PnkG, EsxH. The microbe has certain mechanisms to even acquire iron from the host cell, to withstand iron deprivation as a mode of host's defence mechanism. This review focuses on the various defensive adaptations acquired by Mt.b for fighting against the deprived conditions existing within the macrophages and their capability of proliferating successfully within it, thereby resulting in a diseased condition.

Identification of a novel amphioxus leucine-rich repeat receptor involved in phagocytosis reveals a role for Slit2-N-type LRR in bacterial elimination

The basal chordate amphioxus is a model for tracing the origin and evolution of vertebrate immunity. To explore the evolution of immunoreceptor signaling pathways, we searched the associated receptors of the amphioxus B. belcheri (Bb) homolog of immunoreceptor signaling adaptor protein Grb2. Mass-spectrum analysis of BbGrb2 immunoprecipitates from B. belcheri intestine lysates revealed a folate receptor (FR) domain- and leucine-rich repeat (LRR)-containing protein (FrLRR). Sequence and structural analysis showed that FrLRR is a membrane protein with a predicted curved solenoid structure. The N-terminal Fr domain contains very few folate-binding sites; the following LRR region is a Slit2-type LRR, and a GPI-anchored site was predicted at the C-terminus. RT-PCR analysis showed FrLRR is a transcription-mediated fusion gene of BbFR-like and BbSlit2-N-like genes. Genomic DNA structure analysis implied the B. belcheri FrLRR gene locus and the corresponding locus in B. floridae might be generated by exon shuffling of a Slit2-N-like gene into an FR gene. RT-qPCR, immunostaining and immunoblot results showed that FrLRR was primarily distributed in B. belcheri intestinal tissue. We further demonstrated that FrLRR localized to the cell membrane and lysosomes. Functionally, FrLRR mediated and promoted bacteria-binding and phagocytosis, and FrLRR antibody blocking or Grb2 knockdown inhibited FrLRR-mediated phagocytosis. Interestingly, we found that human Slit2-N (hSlit2-N) also mediated direct bacteria-binding and phagocytosis which was inhibited by Slit2-N antibody blocking or Grb2 knockdown. Together, these results indicate FrLRR and hSlit2-N may function as phagocytotic-receptors to promote phagocytosis through Grb2, implying the Slit2-N-type-LRR-containing proteins play a role in bacterial binding and elimination.

Activation of transcription factor CREB in human macrophages by Mycobacterium tuberculosis promotes bacterial survival, reduces NF-kB nuclear transit and limits phagolysosome fusion by reduced necroptotic signaling

Macrophages are a first line of defense against pathogens. However, certain invading microbes modify macrophage responses to promote their own survival and growth. Mycobacterium tuberculosis (M.tb) is a human-adapted intracellular pathogen that exploits macrophages as an intracellular niche. It was previously reported that M.tb rapidly activates cAMP Response Element Binding Protein (CREB), a transcription factor that regulates diverse cellular responses in macrophages. However, the mechanism(s) underlying CREB activation and its downstream roles in human macrophage responses to M.tb are largely unknown. Herein we determined that M.tb-induced CREB activation is dependent on signaling through MAPK p38 in human monocyte-derived macrophages (MDMs). Using a CREB-specific inhibitor, we determined that M.tb-induced CREB activation leads to expression of immediate early genes including COX2, MCL-1, CCL8 and c-FOS, as well as inhibition of NF-kB p65 nuclear localization. These early CREB-mediated signaling events predicted that CREB inhibition would lead to enhanced macrophage control of M.tb growth, which we observed over days in culture. CREB inhibition also led to phosphorylation of RIPK3 and MLKL, hallmarks of necroptosis. However, this was unaccompanied by cell death at the time points tested. Instead, bacterial control corresponded with increased colocalization of M.tb with the late endosome/lysosome marker LAMP-1. Increased phagolysosomal fusion detected during CREB inhibition was dependent on RIPK3-induced pMLKL, indicating that M.tb-induced CREB signaling limits phagolysosomal fusion through inhibition of the necroptotic signaling pathway. Altogether, our data show that M.tb induces CREB activation in human macrophages early post-infection to create an environment conducive to bacterial growth. Targeting certain aspects of the CREB-induced signaling pathway may represent an innovative approach for development of host-directed therapeutics to combat TB.

The diverse roles of C-type lectin-like receptors in immunity

Our understanding of the C-type lectin-like receptors (CTLRs) and their functions in immunity have continued to expand from their initial roles in pathogen recognition. There are now clear examples of CTLRs acting as scavenger receptors, sensors of cell death and cell transformation, and regulators of immune responses and homeostasis. This range of function reflects an extensive diversity in the expression and signaling activity between individual CTLR members of otherwise highly conserved families. Adding to this diversity is the constant discovery of new receptor binding capabilities and receptor-ligand interactions, distinct cellular expression profiles, and receptor structures and signaling mechanisms which have expanded the defining roles of CTLRs in immunity. The natural killer cell receptors exemplify this functional diversity with growing evidence of their activity in other immune populations and tissues. Here, we broadly review select families of CTLRs encoded in the natural killer cell gene complex (NKC) highlighting key receptors that demonstrate the complex multifunctional capabilities of these proteins. We focus on recent evidence from research on the NKRP1 family of CTLRs and their interaction with the related C-type lectin (CLEC) ligands which together exhibit essential immune functions beyond their defined activity in natural killer (NK) cells. The ever-expanding evidence for the requirement of CTLR in numerous biological processes emphasizes the need to better understand the functional potential of these receptor families in immune defense and pathological conditions.

IL-4 and helminth infection downregulate MINCLE-dependent macrophage response to mycobacteria and Th17 adjuvanticity

The myeloid C-type lectin receptor (CLR) MINCLE senses the mycobacterial cell wall component trehalose-6,6'-dimycolate (TDM). Recently, we found that IL-4 downregulates MINCLE expression in macrophages. IL-4 is a hallmark cytokine in helminth infections, which appear to increase the risk for mycobacterial infection and active tuberculosis. Here, we investigated functional consequences of IL-4 and helminth infection on MINCLE-driven macrophage activation and Th1/Th17 adjuvanticity. IL-4 inhibited MINCLE and cytokine induction after macrophage infection with Mycobacterium bovis bacille Calmette-Guerin (BCG). Infection of mice with BCG upregulated MINCLE on myeloid cells, which was inhibited by IL-4 plasmid injection and by infection with the nematode Nippostrongylus brasiliensis in monocytes. To determine the impact of helminth infection on MINCLE-dependent immune responses, we vaccinated mice with a recombinant protein together with the MINCLE ligand trehalose-6,6-dibehenate (TDB) as adjuvant. Concurrent infection with N. brasiliensis or with Schistosoma mansoni promoted T cell-derived IL-4 production and suppressed Th1/Th17 differentiation in the spleen. In contrast, helminth infection did not reduce Th1/Th17 induction by TDB in draining peripheral lymph nodes, where IL-4 levels were unaltered. Upon use of the TLR4-dependent adjuvant G3D6A, N. brasiliensis infection impaired selectively the induction of splenic antigen-specific Th1 but not of Th17 cells. Inhibition of MINCLE-dependent Th1/Th17 responses in mice infected with N. brasiliensis was dependent on IL-4/IL-13. Thus, helminth infection attenuated the Th17 response to MINCLE-dependent immunization in an organ- and adjuvant-specific manner via the Th2 cytokines IL-4/IL-13. Taken together, our results demonstrate downregulation of MINCLE expression on monocytes and macrophages by IL-4 as a possible mechanism of thwarted Th17 vaccination responses by underlying helminth infection.

Influenza A virus modulates ACE2 expression and SARS-CoV-2 infectivity in human cardiomyocytes

Influenza A virus (IAV) and SARS-CoV-2 virus are both acute respiratory viruses currently circulating in the human population. This study aims to determine the impact of IAV infection on SARS-CoV-2 pathogenesis and cardiomyocyte function. Infection of human bronchial epithelial cells (HBEC), A549 cells, lung fibroblasts (HLF), monocyte derived macrophages (MDMs), cardiac fibroblasts (HCF) and hiPSC-derived cardiomyocytes with IAV enhanced the expression of ACE2, the SARS-CoV-2 receptor. Similarly, IAV infection increased levels of ACE2 in the lungs of mice and humans. Of interest, we detected heavily glycosylated form of ACE2 in hiPSC-CMs and poorly glycosylated ACE2 in other cell types. Also, prior IAV infection enhances SARS-CoV-2 spike protein binding and viral entry in all cell types. However, efficient SARS-CoV-2 replication was uniquely inhibited in cardiomyocytes. Glycosylation of ACE2 correlated with enzymatic conversion of its substrate Ang II, induction of eNOS and nitric oxide production, may provide a potential mechanism for the restricted SARS-CoV-2 replication in cardiomyocytes.

Immune evasion and provocation by Mycobacterium tuberculosis

Mycobacterium tuberculosis, the causative agent of tuberculosis, has infected humans for millennia. M. tuberculosis is well adapted to establish infection, persist in the face of the host immune response and be transmitted to uninfected individuals. Its ability to complete this infection cycle depends on it both evading and taking advantage of host immune responses. The outcome of M. tuberculosis infection is often a state of equilibrium characterized by immunological control and bacterial persistence. Recent data have highlighted the diverse cell populations that respond to M. tuberculosis infection and the dynamic changes in the cellular and intracellular niches of M. tuberculosis during the course of infection. M. tuberculosis possesses an arsenal of protein and lipid effectors that influence macrophage functions and inflammatory responses; however, our understanding of the role that specific bacterial virulence factors play in the context of diverse cellular reservoirs and distinct infection stages is limited. In this Review, we discuss immune evasion and provocation by M. tuberculosis during its infection cycle and describe how a more detailed molecular understanding is crucial to enable the development of novel host-directed therapies, disease biomarkers and effective vaccines.

Revisiting Leishmania GP63 host cell targets reveals a limited spectrum of substrates

Colonization of host phagocytic cells by Leishmania metacyclic promastigotes involves several parasite effectors, including the zinc-dependent metalloprotease GP63. The major mode of action of this virulence factor entails the cleavage/degradation of host cell proteins. Given the potent proteolytic activity of GP63, identification of its substrates requires the adequate preparation of cell lysates to prevent artefactual degradation during cell processing. In the present study, we re-examined the cleavage/degradation of reported GP63 substrates when GP63 activity was efficiently neutralized during the preparation of cell lysates. To this end, we infected bone marrow-derived macrophages with either wild type, Δgp63, and Δgp63+GP63 L. major metacyclic promastigotes for various time points. We prepared cell lysates in the absence or presence of the zinc-metalloprotease inhibitor 1,10-phenanthroline and examined the levels and integrity of ten previously reported host cell GP63 substrates. Inhibition of GP63 activity with 1,10-phenanthroline during the processing of macrophages prevented the cleavage/degradation of several previously described GP63 targets, including PTP-PEST, mTOR, p65RelA, c-Jun, VAMP3, and NLRP3. Conversely, we confirmed that SHP-1, Synaptotagmin XI, VAMP8, and Syntaxin-5 are bona fide GP63 substrates. These results point to the importance of efficiently inhibiting GP63 activity during the preparation of Leishmania-infected host cell lysates. In addition, our results indicate that the role of GP63 in Leishmania pathogenesis must be re-evaluated.

Receptor-kinase EGFR-MAPK adaptor proteins mediate the epithelial response to Candida albicans via the cytolytic peptide toxin, candidalysin

Candida albicans (C. albicans) is a dimorphic commensal human fungal pathogen that can cause severe oropharyngeal candidiasis (oral thrush) in susceptible hosts. During invasive infection, C. albicans hyphae invade oral epithelial cells (OECs) and secrete candidalysin, a pore-forming cytolytic peptide that is required for C. albicans pathogenesis at mucosal surfaces. Candidalysin is produced in the hyphal invasion pocket and triggers cell damage responses in OECs. Candidalysin also activates multiple MAPK-based signaling events that collectively drive the production of downstream inflammatory mediators that coordinate downstream innate and adaptive immune responses. The activities of candidalysin are dependent on signaling through the epidermal growth factor receptor (EGFR). Here, we interrogated known EGFR-MAPK signaling intermediates for their roles mediating the OEC response to C. albicans infection. Using RNA silencing and pharmacological inhibition, we identified five key adaptors, including growth factor receptor-bound protein 2 (Grb2), Grb2-associated binding protein 1 (Gab1), Src homology and collagen (Shc), SH2-containing protein tyrosine phosphatase-2 (Shp2), and casitas B-lineage lymphoma (c-Cbl). We determined that all of these signaling effectors were inducibly phosphorylated in response to C. albicans. These phosphorylation events occurred in a candidalysin-dependent manner and additionally required EGFR phosphorylation, matrix metalloproteinases (MMPs), and cellular calcium flux to activate a complete OEC response to fungal infection. Of these, Gab1, Grb2, and Shp2 were the dominant drivers of ERK1/2 activation and the subsequent production of downstream innate-acting cytokines. Together, these results identify the key adaptor proteins that drive the EGFR signaling mechanisms that underlie oral epithelial responses to C. albicans.

Antifungal immunity mediated by C-type lectin receptors may be a novel target in immunotherapy for urothelial bladder cancer

Immunotherapies, such as immune-checkpoint blockade and adoptive T-cell therapy, offer novel treatment options with good efficacy for patients with urothelial bladder cancer. However, heterogeneity and therapeutic resistance have limited the use of immunotherapy. Further research into immune-regulatory mechanisms in bladder cancer is urgently required. Emerging evidence demonstrates that the commensal microbiota and its interactions with host immunity play pivotal roles in a variety of physiological and pathological processes, including in cancer. The gut microbiota has been identified as a potentially effective target of treatment that can be synergized with immunotherapy. The urothelial tract is also a key site for multiple microbes, although the immune-regulatory role of the urinary microbiome in the process of carcinogenesis of bladder cancer remains to be elucidated. We performed a comprehensive analysis of the expression and biological functions of C-type lectin receptors (CLRs), which have been recognized as innate pathogen-associated receptors for fungal microbiota, in bladder cancer. In line with previous research on fungal colonization of the urothelial tract, we found that CLRs, including Dectin-1, Dectin-2, Dectin-3, and macrophage-inducible Ca²⁺-dependent lectin receptor (Mincle), had a significant association with immune infiltration in bladder cancer. Multiple innate and adaptive pathways are positively correlated with the upregulation of CLRs. In addition, we found a significant correlation between the expression of CLRs and a range of immune-checkpoint proteins in bladder cancer. Based on previous studies and our findings, we hypothesize that the urinary mycobiome plays a key role in the pathogenesis of bladder cancer and call for more research on CLR-mediated anti-fungal immunity against bladder cancer as a novel target for immunotherapy in urothelial bladder cancer.

Affinity-Driven Site-Specific High Mannose Modification Determines the Structural Polymerization and Function of Tetrameric IgM in a Primitive Vertebrate

Teleost tetramer IgM is the predominant Ig in the immune system and plays essential roles in host defense against microbial infection. Due to variable disulfide polymerization of the monomeric subunits, tetrameric IgM possesses considerable structural diversity. Previous work indicated that the teleost IgM H chain was fully occupied with complex-type N-glycans. However, after challenge with trinitrophenyl (TNP) Ag, the complex N-glycans in the Asn-509 site of Oreochromis niloticus IgM H chain transformed into high mannose. This study, therefore, was conducted to examine the functional roles of the affinity-related high-mannose modification in tilapia IgM. The TNP-specific IgM Ab affinity maturation was revealed in tilapia over the response. A positive correlation between TNP-specific IgM affinity and its disulfide polymerization level of isomeric structure was demonstrated. Mass spectrometric analysis indicated that the relationship between IgM affinity and disulfide polymerization was associated with the Asn-509 site-specific high-mannose modification. Furthermore, the increase of high mannose content promoted the combination of IgM and mannose receptor (MR) on the surface of phagocytes. Moreover, the increased interaction of IgM and MR amplified the phagocytic ability of phagocytes to Streptococcus agalactiae. To our knowledge, this study demonstrates that site-specific high-mannose modification associates with IgM Ab affinity and its structural disulfide polymerization and amplifies the phagocytosis of phagocytes by the combination of IgM and MR. The present study provides evidence for understanding the association of IgM structure and function during the evolution of the immune system.

A Fun-Guide to Innate Immune Responses to Fungal Infections

Immunocompromised individuals are at high risk of developing severe fungal infections with high mortality rates, while fungal pathogens pose little risk to most healthy people. Poor therapeutic outcomes and growing antifungal resistance pose further challenges for treatments. Identifying specific immunomodulatory mechanisms exploited by fungal pathogens is critical for our understanding of fungal diseases and development of new therapies. A gap currently exists between the large body of literature concerning the innate immune response to fungal infections and the potential manipulation of host immune responses to aid clearance of infection. This review considers the innate immune mechanisms the host deploys to prevent fungal infection and how these mechanisms fail in immunocompromised hosts. Three clinically relevant fungal pathogens (Candida albicans, Cryptococcus spp. and Aspergillus spp.) will be explored. This review will also examine potential mechanisms of targeting the host therapeutically to improve outcomes of fungal infection.

Talaromyces marneffei Influences Macrophage Polarization and Sterilization Ability via the Arginine Metabolism Pathway in Vitro

The opportunistic fungal pathogen Talaromyces marneffei, which is endemic across a narrow band of tropical Southeast Asia and southern China, is an intracellular pathogen that causes systemic and lethal infection through the mononuclear phagocyte system. The mechanisms by which T. marneffei successfully replicates and escapes the immune system remain unclear. To investigate the role of arginine metabolism in the escape of T. marneffei from killer macrophages, we assessed inducible nitric oxide synthase (iNOS) and arginase expression, nitric oxide (NO) production, arginase and phagocytic activity, and the killing of T. marneffei in a coculture system. Our results indicate that T. marneffei induced macrophage polarization toward the M2 phenotype and regulated the arginine metabolism pathway by prolonging infection, thereby reducing antimicrobial activity and promoting fungal survival. Moreover, inhibiting T. marneffei-induced macrophage arginase activity with Nω-hydroxy-nor-arginine restored NO synthesis and strengthened fungal killing. These findings indicate that T. marneffei affects macrophage polarization and inhibits macrophage antimicrobial function via the arginine metabolism pathway.

Pathogenesis of SARS-CoV-2 and Mycobacterium tuberculosis Coinfection

Coronavirus disease-2019 (COVID-19), caused by SARS-CoV-2, is an infectious disease that poses severe threats to global public health and significant economic losses. The COVID-19 global burden is rapidly increasing, with over 246.53 million COVID-19 cases and 49.97 million deaths reported in the WHO 2021 report. People with compromised immunity, such as tuberculosis (TB) patients, are highly exposed to severe COVID-19. Both COVID-19 and TB diseases spread primarily through respiratory droplets from an infected person to a healthy person, which may cause pneumonia and cytokine storms, leading to severe respiratory disorders. The COVID-19-TB coinfection could be fatal, exacerbating the current COVID-19 pandemic apart from cellular immune deficiency, coagulation activation, myocardial infarction, and other organ dysfunction. This study aimed to assess the pathogenesis of SARS-CoV-2-Mycobacterium tuberculosis coinfections. We provide a brief overview of COVID19-TB coinfection and discuss SARS-CoV-2 host cellular receptors and pathogenesis. In addition, we discuss M. tuberculosis host cellular receptors and pathogenesis. Moreover, we highlight the impact of SARS-CoV-2 on TB patients and the pathological pathways that connect SARS-CoV-2 and M. tuberculosis infection. Further, we discuss the impact of BCG vaccination on SARS-CoV-2 cases coinfected with M. tuberculosis, as well as the diagnostic challenges associated with the coinfection.

Tuberculosis and Autoimmunity

Tuberculosis remains a common and dangerous chronic bacterial infection worldwide. It is long-established that pathogenesis of many autoimmune diseases is mainly promoted by inadequate immune responses to bacterial agents, among them Mycobacterium tuberculosis. Tuberculosis is a multifaceted process having many different outcomes and complications. Autoimmunity is one of the processes characteristic of tuberculosis; the presence of autoantibodies was documented by a large amount of evidence. The role of autoantibodies in pathogenesis of tuberculosis is not quite clear and widely disputed. They are regarded as: (1) a result of imbalanced immune response being reactive in nature, (2) a critical part of TB pathogenicity, (3) a beginning of autoimmune disease, (4) a protective mechanism helping to eliminate microbes and infected cells, and (5) playing dual role, pathogenic and protective. There is no single autoimmunity-mechanism development in tuberculosis; different pathways may be suggested. It may be excessive cell death and insufficient clearance of dead cells, impaired autophagy, enhanced activation of macrophages and dendritic cells, environmental influences such as vitamin D insufficiency, and genetic polymorphism, both of Mycobacterium tuberculosis and host.

Tuberculosis pathophysiology and anti-VEGF intervention

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A review of tuberculosis pathophysiology reveals only a few pharmaceutical targets.

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Current drugs focus on targeting the bacteria and its replication.

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One target revealed by analyzing tuberculosis pathophysiology is VEGF released by macrophages.

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One Anti-VEGF-A drug has shown promise in treating disseminated tuberculosis.

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We should clinically evaluate all Anti-VEGF and Anti-VEGFR drugs with current FDA approval for treating cancer for tuberculosis intervention.

The pathophysiological understanding of tuberculosis is growing, and with this growth comes the possibility of applying established pharmaceuticals in new ways. These new ways interlude with the many mechanisms by which the intracellular pathogen, Mycobacterium tuberculosis, thrives in its human host. This article will discuss those mechanisms in the context of the pathophysiological processes associated with tuberculosis. Tuberculosis is a disease that results in systemic lesions arising from bacterial-immune interactions. The pathophysiology of this disease proceeds as aerosolization, phagocytosis, phagolysosome blockage and replication, T- helper response, granuloma formation, clinical manifestations, and concluding with active disease and transmission. Herein are the brief details of each of these processes. The conclusion of this article will be current tuberculosis treatments and future promising pharmacological directions. Particularly using the anti-vascular endothelial growth factor treatments currently used in cancer therapy, which are rationally presented with support from case studies. The purpose of this article is thus to present the pathophysiology of tuberculosis to convince the reader of the logical theory behind why anti-VEGF intervention should be used in tuberculosis treatment.

Soluble C-Type Lectin-Receptor Ligands Stimulate ROS Production in Dendritic Cells and Potentiate Killing of MRSA as Well as the MRSA Induced IL-12 Production

Methicillin resistant Staphylococcus aureus (MRSA) has developed resistance to most β-lactam antibiotics leaving few treatment options against infections with MRSA. Through mannose receptors, mannan potentiates IL-12 production induced by Gram-positive bacteria, a cytokine crucial in the clearance of S. aureus infection. We investigated the IL-12 potentiating effect of mannan pre-treatment of bone marrow-derived dendritic cells prior to stimulation with clinical MRSA strains. Mannan almost doubled IL-12 as well as IFN-β production in response to USA300, also when USA300 was treated with the β-lactam cefoxitin. The MRSA-induced IL-12 production was dependent on bacterial uptake and reactive oxygen species (ROS). Mannan alone induced ROS production, and in combination with USA300, the ROS produced corresponded to the sum induced by mannan and USA300. Addition of a monoclonal antibody against the mannose receptor likewise enhanced USA300-induced IL-12 and induced ROS production. Mannan addition further increased the endocytosis as well as the rate of endosomal killing of bacteria. Pre-treatment with soluble β-glucans also induced ROS and potentiated the USA300-induced IL-12 indicating that other C-type receptors may play a similar role. In the presence of the pro-inflammatory mediators, GM-CSF or IFN-γ, the mannan-enhanced IL-12 production increased further. The USA300-induced and the mannan-facilitated enhanced IFN-β and IL-12 showed same dependency on MAPK c-Jun N-terminal kinase signaling, suggesting that mannan enhances the signals already induced by the bacteria, rather than changing them. We suggest that the C-type lectin-induced ROS production is a key factor in the IFN-β and IL-12 potentiation.

Vector and Host C-Type Lectin Receptor (CLR)-Fc Fusion Proteins as a Cross-Species Comparative Approach to Screen for CLR-Rift Valley Fever Virus Interactions

Rift Valley fever virus (RVFV) is a mosquito-borne bunyavirus endemic to Africa and the Arabian Peninsula, which causes diseases in humans and livestock. C-type lectin receptors (CLRs) represent a superfamily of pattern recognition receptors that were reported to interact with diverse viruses and contribute to antiviral immune responses but may also act as attachment factors or entry receptors in diverse species. Human DC-SIGN and L-SIGN are known to interact with RVFV and to facilitate viral host cell entry, but the roles of further host and vector CLRs are still unknown. In this study, we present a CLR–Fc fusion protein library to screen RVFV–CLR interaction in a cross-species approach and identified novel murine, ovine, and Aedes aegypti RVFV candidate receptors. Furthermore, cross-species CLR binding studies enabled observations of the differences and similarities in binding preferences of RVFV between mammalian CLR homologues, as well as more distant vector/host CLRs.

AutoCellANLS: An Automated Analysis System for Mycobacteria-Infected Cells Based on Unstained Micrograph

The detection of Mycobacterium tuberculosis (Mtb) infection plays an important role in the control of tuberculosis (TB), one of the leading infectious diseases in the world. Recent advances in artificial intelligence-aided cellular image processing and analytical techniques have shown great promises in automated Mtb detection. However, current cell imaging protocols often involve costly and time-consuming fluorescence staining, which has become a major bottleneck for procedural automation. To solve this problem, we have developed a novel automated system (AutoCellANLS) for cell detection and the recognition of morphological features in the phase-contrast micrographs by using unsupervised machine learning (UML) approaches and deep convolutional neural networks (CNNs). The detection algorithm can adaptively and automatically detect single cells in the cell population by the improved level set segmentation model with the circular Hough transform (CHT). Besides, we have designed a Cell-net by using the transfer learning strategies (TLS) to classify the virulence-specific cellular morphological changes that would otherwise be indistinguishable to the naked eye. The novel system can simultaneously classify and segment microscopic images of the cell populations and achieve an average accuracy of 95.13% for cell detection, 95.94% for morphological classification, 94.87% for sensitivity, and 96.61% for specificity. AutoCellANLS is able to detect significant morphological differences between the infected and uninfected mammalian cells throughout the infection period (2 hpi/12 hpi/24 hpi). Besides, it has overcome the drawback of manual intervention and increased the accuracy by more than 11% compared to our previous work, which used AI-aided imaging analysis to detect mycobacterial infection in macrophages. AutoCellANLS is also efficient and versatile when tailored to different cell lines datasets (RAW264.7 and THP-1 cell). This proof-of concept study provides a novel venue to investigate bacterial pathogenesis at a macroscopic level and offers great promise in the diagnosis of bacterial infections.

Immunobiology of Carbohydrates: Implications for Novel Vaccine and Adjuvant Design Against Infectious Diseases

Carbohydrates are ubiquitous molecules expressed on the surface of nearly all living cells, and their interaction with carbohydrate-binding proteins is critical to many immunobiological processes. Carbohydrates are utilized as antigens in many licensed vaccines against bacterial pathogens. More recently, they have also been considered as adjuvants. Interestingly, unlike other types of vaccines, adjuvants have improved immune response to carbohydrate-based vaccine in humans only in a few cases. Furthermore, despite the discovery of many new adjuvants in the last years, aluminum salts, when needed, remain the only authorized adjuvant for carbohydrate-based vaccines. In this review, we highlight historical and recent advances on the use of glycans either as vaccine antigens or adjuvants, and we review the use of currently available adjuvants to improve the efficacy of carbohydrate-based vaccines. A better understanding of the mechanism of carbohydrate interaction with innate and adaptive immune cells will benefit the design of a new generation of glycan-based vaccines and of immunomodulators to fight both longstanding and emerging diseases.

An all-in-one nanomaterial derived from rGO-MoS2 for photo/chemotherapy of tuberculosis

A combination of therapeutic modalities has recently emerged as an alternative technique for combating Mycobacterium tuberculosis.

Expression and functional characterization of the mannose receptor (MR) from Nile tilapia (Oreochromis niloticus) in response to bacterial infection

Mannose receptor (MR) as a member of the pattern recognition receptors (PRRs) plays an important role in the immune response. In mammals, the role of MR in the regulation of phagocytosis is clarified; however, its contribution to opsonize phagocytosis remains unclear in bony fish. In this study, the expression pattern of Nile tilapia mannose receptor gene (OnMR) was investigated and its regulation of the phagocytosis of monocytes/macrophages to pathogenic bacteria was identified. The full-length of OnMR open reading frame is 4314 bp, encoding a peptide containing 1437 amino acid residues. The deduced amino acid sequence revealed that OnMR contained a cysteine-rich domain, a fibronectin type II domain, multiple C-type lectin-like domains, a transmembrane domain and a short cytoplasmic domain. Tissue distribution analysis showed the OnMR transcripts was widely distribute in the ten detected tissues, and highly expressed in head kidney, hind kidney, intestine and spleen. After S. agalactiae and A. hydrophila infection, the expression of OnMR in head kidney and spleen increased significantly. Moreover, the expression of OnMR in MO/Mø were also upregulated post the infection of bacteria and mannose solutions in vitro. This suggested that MR, as a mannose receptor on macrophage surface, could respond strongly to the stimulation of pathogenic bacteria. In addition, the (r)OnMR protein could effectively bind and agglutinate S. agalactiae and A. hydrophila, and regulate the phagocytic ability of monocytes/macrophages to pathogenic bacteria. These results suggest that OnMR is involved in response against bacterial infection in Nile tilapia, and this study will help us better understand the function of MR in teleost fish.

Carbohydrates from Pseudomonas aeruginosa biofilms interact with immune C-type lectins and interfere with their receptor function

Bacterial biofilms represent a challenge to the healthcare system because of their resilience against antimicrobials and immune attack. Biofilms consist of bacterial aggregates embedded in an extracellular polymeric substance (EPS) composed of polysaccharides, nucleic acids and proteins. We hypothesised that carbohydrates could contribute to immune recognition of Pseudomonas aeruginosa biofilms by engaging C-type lectins. Here we show binding of Dendritic Cell-Specific Intercellular adhesion molecule-3-Grabbing Non-integrin (DC-SIGN, CD209), mannose receptor (MR, CD206) and Dectin-2 to P. aeruginosa biofilms. We also demonstrate that DC-SIGN, unlike MR and Dectin-2, recognises planktonic P. aeruginosa cultures and this interaction depends on the presence of the common polysaccharide antigen. Within biofilms DC-SIGN, Dectin-2 and MR ligands appear as discrete clusters with dispersed DC-SIGN ligands also found among bacterial aggregates. DC-SIGN, MR and Dectin-2 bind to carbohydrates purified from P. aeruginosa biofilms, particularly the high molecular weight fraction (HMW; >132,000 Da), with K_Ds in the nM range. These HMW carbohydrates contain 74.9–80.9% mannose, display α-mannan segments, interfere with the endocytic activity of cell-associated DC-SIGN and MR and inhibit Dectin-2-mediated cellular activation. In addition, biofilm carbohydrates reduce the association of the DC-SIGN ligand Lewis^x, but not fucose, to human monocyte-derived dendritic cells (moDCs), and alter moDC morphology without affecting early cytokine production in response to lipopolysaccharide or P. aeruginosa cultures. This work identifies the presence of ligands for three important C-type lectins within P. aeruginosa biofilm structures and purified biofilm carbohydrates and highlights the potential for these receptors to impact immunity to P. aeruginosa infection.

Targeting M2 Macrophages Alleviates Airway Inflammation and Remodeling in Asthmatic Mice via miR-378a-3p/GRB2 Pathway

Background: Asthma is a complex respiratory disease characterized by airway inflammation and remodeling. MicroRNAs (miRNAs) mediate various cellular processes including macrophage polarization and play an important role in the pathogenesis of asthma. In present study, we aimed to screen miRNA profiling involved in macrophage polarization and investigate its possible functions and mechanisms.

Methods: An OVA-sensitized mouse model was established and 2-chloroadenosine (2-CA) was used to interfere with macrophages. The airway inflammation and remodeling were assessed. The identification and function of M2 alveolar macrophages were assessed by flow cytometry, RT-qPCR, arginase activity and co-culture experiment. Microarray screening was used to select miRNAs which were related to macrophage polarization and RNA interference (RNAi) technique was performed to confirm the function of the selected miRNA and its target gene.

Results: Alveolar macrophages of asthmatic mice showed significant M2 polarization. 2-CA alleviated airway inflammation and remodeling as well as M2 polarization. In vitro, IL-4-induced M2 macrophages promoted the proliferation of α-SMA-positive cells. And miRNA profiling showed a remarkable increased expression of miR-378a-3p in IL-4 induced M2 macrophages. Dual luciferase reporter assay confirmed growth factor receptor binding protein 2 (GRB2) was a target gene of miR-378a-3p. A miR-378a-3p inhibitor and knockdown of GRB2 repolarized alveolar macrophages from M1 to M2 phenotype.

Conclusion: Our findings suggest that miR-378a-3p/GRB2 pathway regulates the polarization of alveolar macrophages which acts as a potential therapeutic target for airway inflammation and remodeling in asthma.

Exploring the Use of Medicinal Plants and Their Bioactive Derivatives as Alveolar NLRP3 Inflammasome Regulators during Mycobacterium tuberculosis Infection

Mycobacterium tuberculosis, the causative agent of tuberculosis (TB), is a successful intracellular pathogen that is responsible for the highest mortality rate among diseases caused by bacterial infections. During early interaction with the host innate cells, M. tuberculosis cell surface antigens interact with Toll like receptor 4 (TLR4) to activate the nucleotide-binding domain, leucine-rich-repeat containing family, pyrin domain-containing 3 (NLRP3) canonical, and non-canonical inflammasome pathways. NLRP3 inflammasome activation in the alveoli has been reported to contribute to the early inflammatory response that is needed for an effective anti-TB response through production of pro-inflammatory cytokines, including those of the Interleukin 1 (IL1) family. However, overstimulation of the alveolar NLRP3 inflammasomes can induce excessive inflammation that is pathological to the host. Several studies have explored the use of medicinal plants and/or their active derivatives to inhibit excessive stimulation of the inflammasomes and its associated factors, thus reducing immunopathological response in the host. This review describes the molecular mechanism of the NLRP3 inflammasome activation in the alveoli during M. tuberculosis infection. Furthermore, the mechanisms of inflammasome inhibition using medicinal plant and their derivatives will also be explored, thus offering a novel perspective on the alternative control strategies of M. tuberculosis-induced immunopathology.

Novel Role for Macrophage Galactose-Type Lectin-1 to Regulate Innate Immunity against Mycobacterium tuberculosis

Tuberculosis (TB) caused by infection with Mycobacterium tuberculosis is characterized by inflammatory pathology and poorly understood mechanisms of innate immunity. Pattern recognition receptors, expressed on the surface of macrophages, determine the balance of inflammatory and antimicrobial functions that influence disease outcome. Carbohydrate moieties displayed by mycobacteria can serve as pattern recognition receptor ligands for some members of the C-type lectin receptor (CLR) family, interactions that mediate a variety of incompletely understood immune outcomes. This work identifies a novel role for the CLR macrophage galactose-type lectin (MGL)-1 in a mouse model (C57BL/6 and MGL-1^-/-) of experimental TB. Murine macrophages upregulated MGL-1 following in vitro exposure to M. tuberculosis, whereas MGL⁺ cells accumulated at sites of mycobacteria-driven inflammation in the lung. Pulmonary macrophages from MGL-1-deficient mice displayed increased production of proinflammatory cytokines (IL-1β, IL-6, and IFN-γ) that were associated with greater lipid accumulation, following M. tuberculosis infection. Surprisingly, for a CLR, we also observed MGL-1-dependent antimycobacterial activity as evidenced by greater M. tuberculosis proliferation in bone marrow-derived macrophages, and the lung, of MGL-1-deficient mice. Differential transcriptome analysis further revealed that loss of MGL-1 perturbs the activation of various genes involved in the regulation of inflammation and lipid metabolism in the setting of M. tuberculosis infection. These results identify MGL-1 signaling as an important mechanism that regulates innate immunity against M. tuberculosis and indicates the potential for the MGL pathway as a novel therapeutic target for anti-TB immunity.

Mannose receptor (CD206) activation in tumor-associated macrophages enhances adaptive and innate antitumor immune responses

Solid tumors elicit a detectable immune response including the infiltration of tumor-associated macrophages (TAMs). Unfortunately, this immune response is co-opted into contributing toward tumor growth instead of preventing its progression. We seek to reestablish an antitumor immune response by selectively targeting surface receptors and endogenous signaling processes of the macrophage subtypes driving cancer progression. RP-182 is a synthetic 10-mer amphipathic analog of host defense peptides that selectively induces a conformational switch of the mannose receptor CD206 expressed on TAMs displaying an M2-like phenotype. RP-182-mediated activation of this receptor in human and murine M2-like macrophages elicits a program of endocytosis, phagosome-lysosome formation, and autophagy and reprograms M2-like TAMs to an antitumor M1-like phenotype. In syngeneic and autochthonous murine cancer models, RP-182 suppressed tumor growth, extended survival, and was an effective combination partner with chemo- or immune checkpoint therapy. Antitumor activity of RP-182 was also observed in CD206^high patient-derived xenotransplantation models. Mechanistically, via selective reduction of immunosuppressive M2-like TAMs, RP-182 improved adaptive and innate antitumor immune responses, including increased cancer cell phagocytosis by reprogrammed TAMs.

Mannose-conjugated chitosan nanoparticles for delivery of Rifampicin to Osteoarticular tuberculosis

Tuberculosis (TB) is a potentially fatal contagious disease and is a second leading infectious cause of death in the world. Osteoarticular TB is treated using standard regimen of 1st and 2nd line anti-tubercular drugs (ATDs) for extensive period of 8-20 months. These drugs are commonly administered in high doses by oral route or by intravenous route, because of their compromised bioavailability. The common drawbacks associated with conventional therapy are poor patient compliance due to long treatment period, frequent and high dosing, and toxicity. This aspect marks for the need of formulations to eliminate these drawbacks. MTB is an intracellular pathogen of mononuclear phagocyte. This attribute makes nanotherapeutics an ideal approach for MTB treatment as macrophages capture nano forms. Polymeric nanoparticles are removed from the body by opsonization and phagocytosis, which forms an ideal strategy to target macrophage containing mycobacteria. To further improve targetability, the nanoparticles are conjugated with ligand, which serves as an easy substrate for the receptors present on the macrophage surface. The purpose of present work was to develop intra-articular injectable in situ gelling system containing polymeric nanoparticles, which would have promising advantages over conventional method of treatment. The rationale behind formulating nanoparticle incorporated in situ gel-based system was to ensure localization of the formulation in intra-articular cavity along with sustained release and conjugation of nanoparticles with mannose as ligand to improve uptake by macrophages. Rifampicin standard ATD was formulated into chitosan nanoparticles. Chitosan with 85% degree of deacetylation (DDA) and sodium tripolyphosphate (TPP) as the crosslinking agent was used for preparing nanoparticles. The percent entrapment was found to be about 71%. The prepared nanoparticles were conjugated with mannose. Conjugation of ligand was ascertained by performing Fourier transformed infrared spectroscopy. The particle size was found to be in the range of 130-140 nm and zeta potential of 38.5 mV. Additionally, we performed scanning electron microscopy to characterize the surface morphology of ligand-conjugated nanoparticles. The conjugated chitosan nanoparticles were incorporated into in situ gelling system comprising Poloxamer 407 and HPMC K4M. The gelling system was evaluated for viscosity, gelling characteristics, and syringeability. The drug release from conjugated nanoparticles incorporated in in situ gel was found to be about 70.3% at the end of 40 h in simulated synovial fluid following zero-order release kinetics. Based on the initial encouraging results obtained, the nanoparticles are being envisaged for ex vivo cellular uptake study using TB-infected macrophages.

The Influence of Polysaccharides-Based Material on Macrophage Phenotypes

Macrophage polarization is a key factor in determining the success of implanted tissue engineering scaffolds. Polysaccharides (derived from plants, animals, and microorganisms) are known to modulate macrophage phenotypes by recognizing cell membrane receptors. Numerous studies have developed polysaccharide-based materials into functional biomaterial substrates for tissue regeneration and pharmaceutical application due to their immunostimulatory activities and anti-inflammatory response. They are used as hydrogel substrates, surface coatings, and drug delivery carriers. In addition to their innate immunological functions, the newly endowed physical and chemical properties, including substrate modulus, pore size/porosity, surface binding chemistry, and the mole ratio of polysaccharides in hybrid materials may regulate macrophage phenotypes more precisely. Growing evidence indicates that the sulfation pattern of glycosaminoglycans and proteoglycans expressed on polarized macrophages leads to the changes in protein binding, which may alter macrophage phenotype and influence the immune response. A comprehensive understanding of how different types of polysaccharide-based materials alter macrophage phenotypic changes can be beneficial to predict transplantation/implantation outcomes. This review focuses on recent advances in promoting wound healing and balancing macrophage phenotypes using polysaccharide-based substrates/coatings and new directions to address the limitations in the current understanding of macrophage responses to polysaccharides.

C-type lectin receptors MR and DC-SIGN are involved in recognition of hemocyanins, shaping their immunostimulatory effects on human dendritic cells

Hemocyanins are used as immunomodulators in clinical applications because they induce a strong Th1-biased cell-mediated immunity, which has beneficial effects. They are multiligand glycosylated molecules with abundant and complex mannose-rich structures. It remains unclear whether these structures influence hemocyanin-induced immunostimulatory processes in human APCs. We have previously shown that hemocyanin glycans from Concholepas concholepas (CCH), Fissurella latimarginata (FLH), and Megathura crenulata (KLH), participate in their immune recognition and immunogenicity in mice, interacting with murine C-type lectin receptors (CLRs). Here, we studied the interactions of these hemocyanins with two major mannose-binding CLRs on monocyte-derived human DCs: MR (mannose receptor) and DC-SIGN (DC-specific ICAM-3-grabbing nonintegrin). Diverse analyses showed that hemocyanins are internalized by a mannose-sensitive mechanism. This process was calcium dependent. Moreover, hemocyanins colocalized with MR and DC-SIGN, and were partly internalized through clathrin-mediated endocytosis. The hemocyanin-mediated proinflammatory cytokine response was impaired when using deglycosylated FLH and KLH compared to CCH. We further showed that hemocyanins bind to human MR and DC-SIGN in a carbohydrate-dependent manner with affinity constants in the physiological concentration range. Overall, we showed that these three clinically valuable hemocyanins interact with human mannose-sensitive CLRs, initiating an immune response and promoting a Th1 cell-driving potential.

Computational discovery and ex-vivo validation study of novel antigenic vaccine candidates against tuberculosis

Tuberculosis (TB) is a complex infectious bacterial disease, which has evolved with highly successful mechanisms to interfere with host defenses and existing classes of antibiotics to resist eradication. The single obtainable TB vaccine, Bacille Calmette-Guerin (BCG) has failed to provide regular defense for respiratory TB in adults. In this study, a bioinformatics and immunoinformatics approach was applied on Mycobacterium tuberculosis (Mtb) H37Rv proteomes to discover the potential subunit vaccine candidates that elicit both tuberculosis-specific T-cells and B-cell immune response. A total of 4049 proteins of MtbH37RvMtbH37Rv were retrieved and subjected to in silico sequence-based analysis. Finally, five (P9WL69 (Rv2599), P9WIG1 (Rv0747), P9WLQ1 (Rv1987), O53608 (Rv0063), O06624 (Rv1566c)) novel putative proteins were selected. Among the five putative antigenic vaccine candidates, P9WL69 protein was selected for the ex-vivo validation study. The P9WL69 protein encoding gene was amplified and cloned on pET21b vector. The success of the recombinant clone (pET21b-RV2599) was confirmed by colony PCR, insert release test and sequencing. Furthermore, the identified epitopes of the P9WL69 protein were considered for in silico docking and molecular dynamics simulation study using Toll-like Receptors (TLRs) (TLR-2, TLR-4, TLR-9), Mannose receptor, and Myeloid differentiation 88 (MYD88) to understand their binding affinity towards the development of immunogenic vaccines against tuberculosis.

From infection niche to therapeutic target: the intracellular lifestyle of Mycobacterium tuberculosis

Mycobacterium tuberculosis (Mtb) is an obligate human pathogen killing millions of people annually. Treatment for tuberculosis is lengthy and complicated, involving multiple drugs and often resulting in serious side effects and non-compliance. Mtb has developed numerous complex mechanisms enabling it to not only survive but replicate inside professional phagocytes. These mechanisms include, among others, overcoming the phagosome maturation process, inhibiting the acidification of the phagosome and inhibiting apoptosis. Within the past decade, technologies have been developed that enable a more accurate understanding of Mtb physiology within its intracellular niche, paving the way for more clinically relevant drug-development programmes. Here we review the molecular biology of Mtb pathogenesis offering a unique perspective on the use and development of therapies that target Mtb during its intracellular life stage.

Cy3-tilmanocept labeling of macrophages in joints of mice with antibody-induced arthritis and synovium of human patients with rheumatoid arthritis

γ-Tilmanocept (^99m Tc-tilmanocept) is a receptor-directed, radiolabeled tracer that is FDA-approved for guiding sentinel lymph node biopsy. Tilmanocept binds the C-type lectin mannose receptor (MR, CD206) on macrophages. In this study, nonradioactive, fluorescently-labeled Cy3-tilmanocept was used to detect CD206⁺ mononuclear cells in the cartilage of mice with antibody-induced arthritis and in the synovial fluid and tissue of human subjects with rheumatoid arthritis (RA) for comparison with osteoarthritis (OA), and healthy volunteer (HV) controls. Murine arthritis was induced by injection of monoclonal anti-cartilage antibody followed by injection of Escherichia coli lipopolysaccharide. Post-arthritis development (7-11 days), the mice were injected intravenously with Cy3-tilmanocept followed by in vivo and ex vivo epifluorescence imaging. Two-photon imaging, immunofluorescence, and immunohistochemistry were used to identify articular and synovial macrophages (CD206, F4/80, and Cy3-tilmanocept binding) in murine tissues. Cy3-tilmanocept epifluorescence was present in arthritic knees and elbows of murine tissues; no radiographic changes were noted in the skeletons. However, inflammatory arthritic changes were apparent by histopathology and immunohistochemistry (F4/80), immunofluorescence (CD206) and Cy3-tilmanocept binding. In human RA synovial fluid, Cy3-tilmanocept staining correlated with CD206⁺ /CD16⁺ cells; negligible labeling was observed in OA samples. Cy3-tilmanocept colocalized with CD206 and staining was significantly higher in RA synovial tissue compared to OA or HV. Our results demonstrate that imaging with Cy3-tilmanocept can detect in vivo inflammatory, CD206⁺ macrophages in an early arthritis animal model and in human RA patients. These data establish a novel tool for preclinical research of early arthritis and have implications for early RA detection and monitoring of therapeutic efficacy in humans.

Dual antitubercular drug loaded liposomes for macrophage targeting: development, characterisation, ex vivo and in vivo assessment

AIM

The present study was conducted to formulate and investigate liposomes for the dual drug delivery based on anti-tubercular drug(s) combination i.e. Isoniazid (INH) and Rifampicin (RIF).

MATERIALS AND METHODS

Mannosylated and non mannosylated liposomes were prepared by lipid thin film hydration method, using DSPC: Chol at a molar ratio 6:4 while in case of mannosylated liposomes DSPC: Chol: Man-C4-Chol at a molar ratio 6.0:3.5:0.5 were used and extensively characterised. The particle size and zeta potential were recorded to be 1.29 ± 0.24 µm and -9.1 ± 0.11 mV. The drug entrapment (%) was recorded to be 84.7 ± 1.25% for Rifampicin and 31.8 ± 0.12% for Isoniazid.

RESULTS

The antitubercular activity studied in Balb/C mice was maximum in the case of mannosylated liposomes. The biodistribution studies also revealed higher drug(s) concentration (accumulation) maintained over a protracted period.

CONCLUSIONS

The liposomal preparations are passively as well as actively uptaken by the alveolar macrophages which are the cellular tropics of infection. The mannosylated liposomes appear to be a potential carrier for dual drug delivery and targeted antitubercular therapy.

Review on Auricularia auricula-judae as a Functional Food: Growth, Chemical Composition, and Biological Activities

Although the application of Auricularia auricula-judae (AAJ) for health purposes has a long tradition in Asia, there is a lack of research on the functional nutrition of AAJ; the current research focused on polysaccharides has been too unitary compared to other mushrooms in recent years. Identification, extraction, and large-scale production of biologically active substances have emerged as critical determinants that determine AAJ becoming a functional food. AAJ is being treated in a restrained manner, despite having significant potential as a drug or a source of pure bioactive substances. Functional ingredients of mushrooms and AAJ have emerged as a new impetus for researchers interested in developing functional foods. This review presents an overview of current studies relevant to nutrition and the application of AAJ. The physiological conditions of AAJ and the corresponding functional ingredients beneficial to human health are reviewed to better understand the function and mechanisms of different nutrient contents. Relevant methods for evaluating the efficiency of extraction are also summarized. Finally, current limitations and the future scope for functional ingredients of AAJ are identified and discussed.

Evolution of Drug-Resistant Mycobacterium tuberculosis Strains and Their Adaptation to the Human Lung Environment

In the last two decades, multi (MDR), extensively (XDR), extremely (XXDR) and total (TDR) drug-resistant Mycobacterium tuberculosis (M.tb) strains have emerged as a threat to public health worldwide, stressing the need to develop new tuberculosis (TB) prevention and treatment strategies. It is estimated that in the next 35 years, drug-resistant TB will kill around 75 million people and cost the global economy $16.7 trillion. Indeed, the COVID-19 pandemic alone may contribute with the development of 6.3 million new TB cases due to lack of resources and enforced confinement in TB endemic areas. Evolution of drug-resistant M.tb depends on numerous factors, such as bacterial fitness, strain's genetic background and its capacity to adapt to the surrounding environment, as well as host-specific and environmental factors. Whole-genome transcriptomics and genome-wide association studies in recent years have shed some insights into the complexity of M.tb drug resistance and have provided a better understanding of its underlying molecular mechanisms. In this review, we will discuss M.tb phenotypic and genotypic changes driving resistance, including changes in cell envelope components, as well as recently described intrinsic and extrinsic factors promoting resistance emergence and transmission. We will further explore how drug-resistant M.tb adapts differently than drug-susceptible strains to the lung environment at the cellular level, modulating M.tb-host interactions and disease outcome, and novel next generation sequencing (NGS) strategies to study drug-resistant TB.

Perspectives and Advances in the Understanding of Tuberculosis

Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis (TB), remains a leading cause of death due to infection in humans. To more effectively combat this pandemic, many aspects of TB control must be developed, including better point of care diagnostics, shorter and safer drug regimens, and a protective vaccine. To address all these areas of need, better understanding of the pathogen, host responses, and clinical manifestations of the disease is required. Recently, the application of cutting-edge technologies to the study of Mtb pathogenesis has resulted in significant advances in basic biology, vaccine development, and antibiotic discovery. This leaves us in an exciting era of Mtb research in which our understanding of this deadly infection is improving at a faster rate than ever, and renews hope in our fight to end TB. In this review, we reflect on what is known regarding Mtb pathogenesis, highlighting recent breakthroughs that will provide leverage for the next leaps forward in the field.

Caspofungin suppresses zymosan-induced cytokine and chemokine release in THP-1 cells: possible involvement of the spleen tyrosine kinase pathway

Systemic inflammatory response syndrome and sepsis are considered to contribute to hypercytokinemia in both patients with severe infection and immunocompromised condition. Past research has demonstrated that antibiotics and antifungals not only have antimicrobial efficacy but also affect the immune system. We previously examined whether immune cells were modulated by antibiotics such as tetracyclines or macrolides. The modulation of lipopolysaccharide-stimulated cells by those agents was elucidated. However, few reports about the modulation of the immune system by antifungal agents were found. In this study, the production of pro-inflammatory cytokines and chemokines and signaling pathways involved were investigated in zymosan-activated THP-1 cells. The effects were examined using antifungal agents such as echinocandin including caspofungin (CAS) and micafungin. Pro-inflammatory cytokine and chemokine levels were determined using enzyme-linked immunosorbent assay. Protein phosphorylation was evaluated by western blot analysis. CAS significantly decreased zymosan-induced pro-inflammatory cytokine and chemokine release in THP-1 cells. CAS (30 µg/mL) also downregulated tumor necrosis factor alpha levels, as shown by enzyme-linked immunosorbent assay. In western blot analysis, inhibitor of nuclear factor-kappa-B alpha, p38, c-Jun N-terminal kinase, extracellular signal-regulated kinase, and nuclear factor of activated T-cells phosphorylation and activation of caspase-1 and spleen tyrosine kinase (Syk) were downregulated. The major underlying mechanism of pro-inflammatory cytokine and chemokine suppression by CAS is to inhibit activation of Syk and its downstream signaling molecules. Based on the results, it can be concluded that CAS activity possibly involves Syk signaling pathways and has potential to prevent hypercytokinemia in fungal sepsis.

Runx proteins mediate protective immunity against Leishmania donovani infection by promoting CD40 expression on dendritic cells

The level of CD40 expression on dendritic cells (DCs) plays a decisive role in disease protection during Leishmania donovani (LD) infection. However, current understanding of the molecular regulation of CD40 expression remains elusive. Using molecular, cellular and functional approaches, we identified a role for Runx1 and Runx3 transcription factors in the regulation of CD40 expression in DCs. In response to lipopolysaccharide (LPS), tumor necrosis factor alpha (TNFα) or antileishmanial drug sodium antimony gluconate (SAG), both Runx1 and Runx3 translocated to the nucleus, bound to the CD40 promoter and upregulated CD40 expression on DCs. These activities of Runx proteins were mediated by the upstream phosphatidylinositol 3-kinase (PI3K)-Akt pathway. Notably, LD infection attenuated LPS- or TNFα-induced CD40 expression in DCs by inhibiting PI3K-Akt-Runx axis via protein tyrosine phosphatase SHP-1. In contrast, CD40 expression induced by SAG was unaffected by LD infection, as SAG by blocking LD-induced SHP-1 activation potentiated PI3K-Akt signaling to drive Runx-mediated CD40 upregulation. Adoptive transfer experiments further showed that Runx1 and Runx3 play a pivotal role in eliciting antileishmanial immune response of SAG-treated DCs in vivo by promoting CD40-mediated type-1 T cell responses. Importantly, antimony-resistant LD suppressed SAG-induced CD40 upregulation on DCs by blocking the PI3K-Akt-Runx pathway through sustained SHP-1 activation. These findings unveil an immunoregulatory role for Runx proteins during LD infection.

Interplay between C-type lectin receptors and microRNAs in cellular homeostasis and immune response

C-type lectin receptors (CLRs) belong to the family of pattern recognition receptors (PRRs). They have a critical role to play in the regulation of a range of physiological functions including development, respiration, angiogenesis, inflammation, and immunity. CLRs can recognize distinct and conserved exogenous pathogen-associated as well as endogenous damage-associated molecular patterns. These interactions set off downstream signaling cascades, leading to the production of inflammatory mediators, activation of effector immune cells as well as regulation of the developmental and physiological homeostasis. CLR signaling must be tightly controlled to circumvent the excessive inflammatory burden and to maintain the cellular homeostasis. Recently, MicroRNAs (miRNAs) have been shown to be important regulators of expression of CLRs and their downstream signaling. The delicate balance between miRNAs and CLRs seems crucial in almost all aspects of multicellular life. Any dysregulations in the miRNA-CLR axes may lead to tumorigenesis or inflammatory diseases. Here, we present an overview of the current understanding of the central role of miRNAs in the regulation of CLR expression, profoundly impacting upon homeostasis and immunity, and thus, development of therapeutics against immune disorders.