Innate recognition of intracellular bacteria

Modulation and Determination of the Status of Inflammasomes in Leishmania-Infected Macrophages

Leishmania, an intra-macrophage kinetoplastid parasite, modulates a vast array of defensive mechanisms of the host macrophages to create a comfortable environment for their survival. When the host encounters intracellular pathogens, a multimeric protein complex called NLRP3 inflammasome gets turned on, leading to caspase-1 activation-mediated maturation of IL-1β from its pro-form. However, Leishmania often manages to neutralize inflammasome activation by manipulating negative regulatory molecules of the host itself. Exhaustion of NLRP3 and pro-IL-1β result from decreased NF-κB activity in infection, which was attributed to increased expression of A20, a negative regulator of NF-κB signalling. Moreover, reactive oxygen species, another key requirement for inflammasome activation, are inhibited by mitochondrial uncoupling protein 2 (UCP2) which is upregulated by Leishmania. Inflammasome activation is a complex event and procedures involved in monitoring inflammasome activation need to be accurate and error-free. In this chapter, we summarize the protocol that includes various experimental procedures required for the determination of the status of inflammasomes in Leishmania-infected macrophages.

Tuning Bacterial Morphology to Enhance Anticancer Vaccination

Morphology tuning is a potent strategy to modulate physiological effects of synthetic biomaterials, but it is rarely explored in microbe-based biochemicals due to the lack of artificial adjustability. Inspired by the interesting phenomenon of microbial transformation, Escherichia coli is rationally adjusted into filamentous morphology-adjusted bacteria (MABac) via chemical stimulation to prepare a bacteria-based vaccine adjuvant/carrier. Inactivated MABac display stronger immunogenicity and special delivery patterns (phagosome escape and cytoplasmic retention) that are sharply distinct from the short rod-shaped bacteria parent (Bac). Transcriptomic study further offers solid evidence for deeply understanding the in vivo activity of MABac-based vaccine, which more effectively motivates multiple cytosolic immune pathways (such as NOD-like receptors and STING) and induces pleiotropic immune responses in comparison with Bac. Harnessing the special functions caused by morphology tuning, the MABac-based adjuvant/carrier significantly improves the immunogenicity and delivery profile of cancer antigens in vivo, thus boosting cancer-specific immunity against the melanoma challenge. This study validates the feasibility of tuning bacterial morphology to improve their biological effects, establishing a facile engineering strategy that upgrades bacterial properties and functions without complex procedures like gene editing.

Play the plug: How bacteria modify recognition by host receptors?

The diverse microbial community that colonizes the gastrointestinal tract has remarkable effects on the host immune system and physiology resulting in homeostasis or disease. In both scenarios, the gut microbiota interacts with their host through ligand-receptor binding whereby the downstream signaling processes determine the outcome of the interaction as disease or the counteractive immune responses of the host. Despite several studies on microbe-host interactions and the mechanisms by which this intricate process happens, a comprehensive and updated inventory of known ligand-receptor interactions and their roles in disease is paramount. The ligands which originate as a result of microbial responses to the host environment contribute to either symbiotic or parasitic relationships. On the other hand, the host receptors counteract the ligand actions by mounting a neutral or an innate response. The varying degrees of polymorphic changes in the host receptors contribute to specificity of interaction with the microbial ligands. Additionally, pathogenic microbes manipulate host receptors with endogenous enzymes belonging to the effector protein family. This review focuses on the diversity and similarity in the gut microbiome-host interactions both in health and disease conditions. It thus establishes an overview that can help identify potential therapeutic targets in response to critically soaring antimicrobial resistance as juxtaposed to tardy antibiotic development research.

Analysis of mRNA and circRNA Expression Profiles of Bovine Monocyte-Derived Macrophages Infected With Mycobacterium avium subsp. paratuberculosis

Mycobacterium avium subsp. paratuberculosis (MAP) is the pathogen of Johne’s disease (paratuberculosis), which mainly causes chronic infectious granulomatous enteritis in ruminants and has brought huge economic losses to animal husbandry. As a specific intracellular pathogen, when MAP invades the body, it is internalized by macrophages where it is able to replicate by inhibition of the phagosome maturation, escaping the host immune system and surviving, which leads to the spread of the disease. More recent studies have shown that circRNA is involved in many pathological and physiological processes of the body as the molecular sponge of miRNA, the scaffold of RNA binding protein and having the characteristic of being able to translate into protein. In this study, the mRNA and circRNA expression profiles of MAP-infected bovine monocyte-macrophages and uninfected bovine cells were analyzed by high-throughput sequencing. A total of 618 differentially expressed mRNA were screened out, including 322 upregulated mRNA and 296 downregulated mRNA. In addition, the analysis of circRNA differential expression profile showed 39 differentially expressed genes including 12 upregulated and 27 downregulated genes. Moreover, differential genes belonging to cytokine activity, chemokine activity, inflammatory reaction, apoptosis, and other functional groups related to macrophage immune response were significantly enriched in Gene Ontology (GO). Multiple signal pathways including NF-κB, MAPK, Toll-like receptor, IL-17, JAK-STAT, and other signaling pathways related to activating macrophage immune response were significantly enriched in Kyoto Encyclopedia of Genes and Genomes (KEGG). In addition, RT-qPCR technology verified the accuracy of the mRNA sequencing results. In this study, we have obtained the transcriptome information of mRNA and circRNA of bovine monocyte-macrophage infected with MAP. These results will provide data support for the further study of mRNA–miRNA–circRNA network and immune escape mechanism of MAP and will enrich the knowledge of the molecular immune mechanisms of Johne’s disease as well.

Integrated Full-Length Transcriptome and RNA-Seq to Identify Immune System Genes from the Skin of Sperm Whale (Physeter macrocephalus)

Cetaceans are a group of secondary aquatic mammals whose ancestors returned to the ocean from land, and during evolution, their immune systems adapted to the aquatic environment. Their skin, as the primary barrier to environmental pathogens, supposedly evolved to adapt to a new living environment. However, the immune system in the skin of cetaceans and the associated molecular mechanisms are still largely unknown. To better understand the immune system, we extracted RNA from the sperm whale's (Physeter macrocephalus) skin and performed PacBio full-length sequencing and RNA-seq sequencing. We obtained a total of 96,350 full-length transcripts with an average length of 1705 bp and detected 5150 genes that were associated with 21 immune-related pathways by gene annotation enrichment analysis. Moreover, we found 89 encoding genes corresponding to 33 proteins were annotated in the NOD-like receptor (NLR)-signaling pathway, including NOD1, NOD2, RIP2, and NF-kB genes, which were discussed in detail and predicted to play essential roles in the immune system of the sperm whale. Furthermore, NOD1 was highly conservative during evolution by the sequence comparison and phylogenetic tree. These results provide new information about the immune system in the skin of cetaceans, as well as the evolution of immune-related genes.

Salmonella infection induced intestinal crypt hyperplasia through Wnt/β-catenin pathway in chicken

S. Pullorum is a causative agent of enteric disease of poultry with serious diarrhea. However, the detailed mechanism behind its injury to intestinal mucosa barrier, especially for intestinal stem cells, is unclear. In this study, S. Pullorum were orally administrated to 3 days old chicken to investigate the pathogenesis of S. Pullorum on intestinal mucosal barrier, especially on the proliferation of epithelial cells. We found that S. Pullorum could colonize in the cecum and invade into the liver through intestinal mucosa damage, which caused obvious pathological changes in liver and intestine and even leaded to death, as well as significant reduction of body weight. We also found that S. Pullorum infection enhanced the mRNA expression of IL-1β and IL-6 through TLR4/MyD88 pathway, which was also further verified by the increased lipopolysaccharide (LPS) levels in serum. Furthermore, S. Pullorum increased the depth of crypt and density of PCNA⁺ cells significantly through the over-activation of Wnt/β-catenin signaling pathway. The expression of intestinal stem cells markers Lgr5 and Bmi1 was also increased after S. Pullorum infection to support the crypt hyperplasia. In addition, we verified that S. Pullorum infection enhanced the mRNA expression of IL-1β, TLR4, Lgr5 and Bmi1. Our study indicated that S. Pullorum infection damaged the intestinal mucosa barrier to induce diarrhea, affected the abnormal proliferation of intestinal stem cells by over-activation of Wnt/β-catenin pathway in chicken.

Microglial NLRP3 inflammasome activation in multiple sclerosis

Multiple sclerosis (MS) is a chronic, autoimmune and neuroinflammatory disease of the central nervous system (CNS) mediated by autoreactive T cells directed against myelin antigens. Although the crucial role of adaptive immunity is well established in MS, the contribution of innate immunity has only recently been appreciated. Microglia are the main innate immune cells of the CNS. Similar to other myeloid cells, microglia recognize both exogenous and host-derived endogenous danger signals through pattern recognition receptors (PRRs) localized on their cell surface such as Toll Like receptor 4, or in the cytosol such as NLRP3. The second one is the sensor protein of the multi-molecular NLRP3 inflammasome complex in activated microglia that promotes the maturation and secretion of proinflammatory cytokines, interleukin-1β and interleukin-18. Overactivation of microglia and aberrant activation of the NLRP3 inflammasome have been implicated in the pathogenesis of MS. Indeed, experimental data, together with post-mortem and clinical studies have revealed an increased expression of NLRP3 inflammasome complex elements in microglia and other immune cells. In this review, we focus on microglial NLRP3 inflammasome activation in MS. First, we overview the basic knowledge about MS, microglia and the NLRP3 inflammasome. Then, we summarize studies about microglial NLRP3 inflammasome activation in MS and its animal models. We also highlight experimental therapeutic approaches that target different steps of NLRP inflammasome activation. Finally, we discuss future research avenues and new methods in this rapidly evolving area.

The GRA15 protein from Toxoplasma gondii enhances host defense responses by activating the interferon stimulator STING

Toxoplasma gondii is an important neurotropic pathogen that establishes latent infections in humans that can cause toxoplasmosis in immunocompromised individuals. It replicates inside host cells and has developed several strategies to manipulate host immune responses. However, the cytoplasmic pathogen-sensing pathway that detects T. gondii is not well-characterized. Here, we found that cyclic GMP-AMP synthase (cGAS), a sensor of foreign dsDNA, is required for activation of anti-T. gondii immune signaling in a mouse model. We also found that mice deficient in STING (Sting ^gt/gt mice) are much more susceptible to T. gondii infection than WT mice. Of note, the induction of inflammatory cytokines, type I IFNs, and interferon-stimulated genes in the spleen from Sting ^gt/gt mice was significantly impaired. Sting ^gt/gt mice exhibited more severe symptoms than cGAS-deficient mice after T. gondii infection. Interestingly, we found that the dense granule protein GRA15 from T. gondii is secreted into the host cell cytoplasm and then localizes to the endoplasmic reticulum, mediated by the second transmembrane motif in GRA15, which is essential for activating STING and innate immune responses. Mechanistically, GRA15 promoted STING polyubiquitination at Lys-337 and STING oligomerization in a TRAF protein-dependent manner. Accordingly, GRA15-deficient T. gondii failed to elicit robust innate immune responses compared with WT T. gondii. Consequently, GRA15^-/- T. gondii was more virulent and caused higher mortality of WT mice but not Sting ^gt/gt mice upon infection. Together, T. gondii infection triggers cGAS/STING signaling, which is enhanced by GRA15 in a STING- and TRAF-dependent manner.

Acinetobacter baumannii outer membrane protein 34 elicits NLRP3 inflammasome activation via mitochondria-derived reactive oxygen species in RAW264.7 macrophages

Acinetobacter baumannii (A. baumannii) is a Gram-negative bacterium, which acts as an opportunistic pathogen and causes hospital-acquired pneumonia and bacteremia by infecting the alveoli of epithelial cells and macrophages. Evidence reveals that A. baumannii outer membrane protein 34 (Omp34) elicits cellular immune responses and inflammation. The innate immunity NOD-like receptor 3 (NLRP3) inflammasome exerts critical function against pneumonia caused by A. baumannii infection, however, the role of Omp34 in the activation of the NLRP3 inflammasome and its corresponding regulatory mechanism are not clearly elucidated. The present study aimed to investigate whether Omp34 elicited NLRP3 inflammasome activation through the mitochondria-derived reactive oxygen species (ROS). Our results showed that Omp34 triggered cell pyroptosis by up-regulating the expression of NLRP3 inflammasome-associated proteins and IL-1β release in a time- and dose-dependent manner. Omp34 induced the expression of caspase-1-p10 and IL-1β, which was significantly attenuated by NLRP3 gene silencing in RAW264.7 mouse macrophage cells. Additionally, Omp34 stimulated RAW264.7 mitochondria to generate ROS, while the ROS scavenger Mito-TEMPO inhibited the Omp34-triggered expression of NLRP3 inflammasome-associated proteins and IL-1β synthesis. The above findings indicate that mitochondria-derived ROS play an important role in the process of NLRP3 inflammasome activation. In summary, our study demonstrates that the A. baumannii pathogen pattern recognition receptor Omp34 activates NLRP3 inflammasome via mitochondria-derived ROS in RAW264.7 cells. Accordingly, down-regulating the mitochondria-derived ROS prevents the severe infection consequences caused by A. baumannii-induced NLRP3 inflammasome hyper-activation.

Cigarette smoking is associated with an altered vaginal tract metabolomic profile

Cigarette smoking has been associated with both the diagnosis of bacterial vaginosis (BV) and a vaginal microbiota lacking protective Lactobacillus spp. As the mechanism linking smoking with vaginal microbiota and BV is unclear, we sought to compare the vaginal metabolomes of smokers and non-smokers (17 smokers/19 non-smokers). Metabolomic profiles were determined by gas and liquid chromatography mass spectrometry in a cross-sectional study. Analysis of the 16S rRNA gene populations revealed samples clustered into three community state types (CSTs) ---- CST-I (L. crispatus-dominated), CST-III (L. iners-dominated) or CST-IV (low-Lactobacillus). We identified 607 metabolites, including 12 that differed significantly (q-value < 0.05) between smokers and non-smokers. Nicotine, and the breakdown metabolites cotinine and hydroxycotinine were substantially higher in smokers, as expected. Among women categorized to CST-IV, biogenic amines, including agmatine, cadaverine, putrescine, tryptamine and tyramine were substantially higher in smokers, while dipeptides were lower in smokers. These biogenic amines are known to affect the virulence of infective pathogens and contribute to vaginal malodor. Our data suggest that cigarette smoking is associated with differences in important vaginal metabolites, and women who smoke, and particularly women who are also depauperate for Lactobacillus spp., may have increased susceptibilities to urogenital infections and increased malodor.

Leishmania donovani inhibits inflammasome-dependent macrophage activation by exploiting the negative regulatory proteins A20 and UCP2

In visceral leishmaniasis, we found that the antileishmanial drug Amp B produces a higher level of IL-1β over the infected control. Moreover, administering anti-IL-1β antibody to infected Amp B-treated mice showed significantly less parasite clearance. Investigation revealed that Leishmania inhibits stimuli-induced expression of a multiprotein signaling platform, NLRP3 inflammasome, which in turn inhibits caspase-1 activation mediated maturation of IL-1β from its pro form. Attenuation of NLRP3 and pro-IL-1β in infection was found to result from decreased NF-κB activity. Transfecting infected cells with constitutively active NF-κB plasmid increased NLRP3 and pro-IL-1β expression but did not increase mature IL-1β, suggesting that IL-1β maturation requires a second signal, which was found to be reactive oxygen species (ROS). Decreased NF-κB was attributed to increased expression of A20, a negative regulator of NF-κB signaling. Silencing A20 in infected cells restored NLRP3 and pro-IL-1β expression, but also increased matured IL-1β, implying an NF-κB-independent A20-modulated IL-1β maturation. Macrophage ROS is primarily regulated by mitochondrial uncoupling protein 2 (UCP2), and UCP2-silenced infected cells showed an increased IL-1β level. Short hairpin RNA-mediated knockdown of A20 and UCP2 in infected mice independently documented decreased liver and spleen parasite burden and increased IL-1β production. These results suggest that Leishmania exploits A20 and UCP2 to impair inflammasome activation for disease propagation.-Gupta, A. K., Ghosh, K., Palit, S., Barua, J., Das, P. K., Ukil, A. Leishmania donovani inhibits inflammasome-dependent macrophage activation by exploiting the negative regulatory proteins A20 and UCP2.

Francisella noatunensis subsp. noatunensis invades, survives and replicates in Atlantic cod cells

Systemic infection caused by the facultative intracellular bacterium Francisella noatunensis subsp. noatunensis remains a disease threat to Atlantic cod Gadus morhua L. Future prophylactics could benefit from better knowledge on how the bacterium invades, survives and establishes infection in its host cells. Here, facilitated by the use of a gentamicin protection assay, this was studied in primary monocyte/macrophage cultures and an epithelial-like cell line derived from Atlantic cod larvae (ACL cells). The results showed that F. noatunensis subsp. noatunensis is able to invade primary monocyte/macrophages, and that the actin-polymerisation inhibitor cytochalasin D blocked internalisation, demonstrating that the invasion is mediated through phagocytosis. Interferon gamma (IFNγ) treatment of cod macrophages prior to infection enhanced bacterial invasion, potentially by stimulating macrophage activation in an early step in host defence against F. noatunensis subsp. noatunensis infections. We measured a rapid drop of the initial high levels of internalised bacteria in macrophages, indicating the presence and action of a cellular immune defence mechanism before intracellular bacterial replication took place. Low levels of bacterial internalisation and replication were detected in the epithelial-like ACL cells. The capacity of F. noatunensis subsp. noatunensis to enter, survive and even replicate within an epithelial cell line may play an important role in its ability to infect live fish and transverse epithelial barriers to reach the bacterium's main target cells-the macrophage.

Dendritic Cell-Secreted Cytotoxic T-Lymphocyte-Associated Protein-4 Regulates the T-cell Response by Downmodulating Bystander Surface B7

The remarkable functional plasticity of professional antigen-presenting cells (APCs) allows the adaptive immune system to respond specifically to an incredibly diverse array of potential pathogenic insults; nonetheless, the specific molecular effectors and mechanisms that underpin this plasticity remain poorly characterized. Cytotoxic T-lymphocyte-associated protein-4 (CTLA-4), the target of the blockbuster cancer immunotherapeutic ipilimumab, is one of the most well-known and well-studied members of the B7 superfamily and negatively regulates T cell responses by a variety of known mechanisms. Although CTLA-4 is thought to be expressed almost exclusively among lymphoid lineage hematopoietic cells, a few reports have indicated that nonlymphoid APCs can also express the CTLA-4 mRNA transcript and that transcript levels can be regulated by external stimuli. In this study, we substantially build upon these critical observations, definitively demonstrating that mature myeloid lineage dendritic cells (DC) express significant levels of intracellular CTLA-4 that they constitutively secrete in microvesicular structures. CTLA-4(+) microvesicles can competitively bind B7 costimulatory molecules on bystander DC, resulting in downregulation of B7 surface expression with significant functional consequences for downstream CD8(+) T-cell responses. Hence, the data indicate a previously unknown role for DC-derived CTLA-4 in immune cell functional plasticity and have significant implication for the design and implementation of immunomodulatory strategies intended to treat cancer and infectious disease.

Coordinated augmentation of NFAT and NOD signaling mediates proliferative VSMC phenotype switch under hyperinsulinemia

AIM

Although hyperglycemia has been demonstrated to play a significant role in the vascular disease associated with type 2 diabetes, the mechanisms underlying hyperinsulinemia mediated vascular dysfunction are not well understood. We have analyzed whether hyperinsulinemia could activate NFAT (Nuclear factor of activated T cells) signaling and thereby influence vascular smooth muscle cell (VSMC) migration and proliferation, a major event in the progression of atherosclerosis.

METHODS AND RESULTS

Human aortic VSMCs upon chronic insulin treatment exhibited increased expression of NFATc1 both at the mRNA and protein levels. The mechanistic role of NFAT in VSMC migration and proliferation was examined using 11R-VIVIT, a cell permeable NFAT specific inhibitor, where it reduced the insulin effect on VSMC, which was further substantiated by over expression or silencing of NFATc1gene (p < 0.05). This study also report for the first time the role of NFAT in NOD (Nucleotide oligomerization domain) mediated innate immune signaling and its significance in insulin effect on VSMCs. mRNA expression of NOD was up regulated when cells were treated with insulin or ligands whereas pretreatment with 11R-VIVIT reversed this effect (p < 0.05). Our study uphold the clinical significance as we observed an increased mRNA expression of NFATc1 in monocytes isolated from patients with type 2 diabetes which correlated positively with insulin resistance and glycemic load (p < 0.05).

DISCUSSION

This study suggests that targeted NFAT inhibition can be an effective strategy to coordinately quench insulin induced proliferative and inflammatory responses along with innate immunity alterations in vascular smooth muscle cells, which underlie atherosclerosis.

Innate immunity in tuberculosis: how the sensing of mycobacteria and tissue damage modulates macrophage death

The success of Mycobacterium tuberculosis as a human pathogen has been attributed to the ability of the bacillus to proliferate inside macrophages and to induce cell death. This review describes how the sensors of the innate immune system modulate the cell death pathways in infected macrophages and, consequently, the pathogenesis of tuberculosis.

Colon carcinogenesis in wild type and immune compromised mice after treatment with azoxymethane, and azoxymethane with dextran sodium sulfate

The association between inflammation and the risk of colorectal cancer (CRC) is well documented in animal models and in humans, but the mechanistic role of inflammation in CRC is less well understood. To address this question, the induction of colon tumors was evaluated in (i) wild type (WT) and athymic BALB/c mice treated with the colon carcinogen azoxymethane (AOM) as a single agent, and (ii) in an inflammation model of colon cancer employing AOM and dextran sodium sulfate (DSS) in WT, athymic, TCRβ(-/-) , TCRδ(-/-) and TCRβ(-/-) TCRδ(-/-) C57Bl/6 mice. The athymic BALB/c mice treated with only AOM developed 90% fewer tumors than the WT mice. The difference in response was not due to metabolic activation of AOM or repair of DNA adducts. In the inflammation model using a standard sequential exposure to AOM followed by DSS treatment, the tumor incidence in WT mice was 58% with 7 adenomas and 6 adenocarcinomas. In contrast, the TCRβ(-/-) , TCRδ(-/-) and TCRβ(-/-) TCRδ(-/-) C57Bl/6 mice showed adenoma incidences of 10, 33, and 11%, respectively, and none of the immune compromised mice developed adenocarcinomas. When the DSS exposure was increased and the AOM lowered, no difference was observed between WT and TCRβ(-/-) mice due to an increase in the incidence in the TCR null mice without concomitant increase in the WT mice. No tumors were observed in mice treated with AOM or DSS alone. © 2015 Wiley Periodicals, Inc.

Ultrapure LPS induces inflammatory and antibacterial responses attenuated in vitro by exogenous sera in Atlantic cod and Atlantic salmon

Phagocyte recognition of lipopolysaccharide (LPS) is an early key event for triggering the host innate immune response necessary for clearance of invading bacteria. The ability of fishes to recognise LPS has been questioned as contradictory results have been presented. We show here that monocyte/macrophage cultures from Atlantic cod (Gadus morhua) and Atlantic salmon (Salmo salar) respond with an increased expression of inflammatory and antibacterial genes to both crude and ultrapure Escherichia coli LPS. Crude LPS produces higher induction than the ultrapure LPS type in both species in vitro as well as in vivo in cod injected with LPS. Crude LPS gave, in contrast to ultrapure LPS, an additional weak up-regulation of antiviral genes in salmon macrophages, most likely because of contaminants in the LPS preparation. Increased levels of chicken (c)-type lysozyme transcripts and enzyme activity were measured in salmon macrophages following ultrapure LPS stimulation demonstrating not only increased transcription but also translation. Simultaneous use and even pre-treatment with bovine sera suppressed the LPS-induced expression thereby reflecting the presence of transcription inhibitory components in sera. Together, these findings show that both cod and salmon recognise LPS per se and that the observed induction is highly dependent on the absence of sera.

Analysis of the Bovine Monocyte-Derived Macrophage Response to Mycobacterium avium Subspecies Paratuberculosis Infection Using RNA-seq

Johne's disease, caused by infection with Mycobacterium avium subsp. paratuberculosis, (MAP), is a chronic intestinal disease of ruminants with serious economic consequences for cattle production in the United States and elsewhere. During infection, MAP bacilli are phagocytosed and subvert host macrophage processes, resulting in subclinical infections that can lead to immunopathology and dissemination of disease. Analysis of the host macrophage transcriptome during infection can therefore shed light on the molecular mechanisms and host-pathogen interplay associated with Johne's disease. Here, we describe results of an in vitro study of the bovine monocyte-derived macrophage (MDM) transcriptome response during MAP infection using RNA-seq. MDM were obtained from seven age- and sex-matched Holstein-Friesian cattle and were infected with MAP across a 6-h infection time course with non-infected controls. We observed 245 and 574 differentially expressed (DE) genes in MAP-infected versus non-infected control samples (adjusted P value ≤0.05) at 2 and 6 h post-infection, respectively. Functional analyses of these DE genes, including biological pathway enrichment, highlighted potential functional roles for genes that have not been previously described in the host response to infection with MAP bacilli. In addition, differential expression of pro- and anti-inflammatory cytokine genes, such as those associated with the IL-10 signaling pathway, and other immune-related genes that encode proteins involved in the bovine macrophage response to MAP infection emphasize the balance between protective host immunity and bacilli survival and proliferation. Systematic comparisons of RNA-seq gene expression results with Affymetrix(®) microarray data generated from the same experimental samples also demonstrated that RNA-seq represents a superior technology for studying host transcriptional responses to intracellular infection.

Expression and protective role of two novel NACHT-containing proteins in pathogen infection

Lower vertebrates have been found to possess over 200 NACHT-domain encoding genes; but, to date, very little is known about their functional activity. This article describes the sequences and expression analysis of two zebrafish NACHT-containing proteins, namely NALPL1 and NALPL2. In addition, the functions of zebrafish NALPL1 and NALPL2, which are absent for both amino-terminal effector-binding domain (EBD) and carboxy-terminal ligand-recognition domain (LRD), were investigated for the first time in fish species. The predicted NALPL1 and NALPL2 proteins consist of 651 and 847 amino acids (aa), respectively, with both molecules only containing NACHT domain, which were different from other NACHT-family members. Phylogenetic analysis showed that zebrafish NALPL1 and NALPL2 have a closer relationship with mammalian NALP subfamily than NOD subfamily. The differential expression patterns of NALPL1 and NALPL2 in development stages and organs were observed, suggesting the difference of action phase and effector organ of NALPL1 and NALPL2. When the modulation of NALPL1 and NALPL2 in pathogen infection was analyzed, it was found that the two molecules were upregulated by both bacterial and viral infection. Overexpression of NALPL1 and NALPL2 resulted in significant inhibition for intracellular Edwardsiella tarda growth. Further studies demonstrated that NALPL1 and NALPL2 also contributed to protection against viral infection. These results demonstrate that both NALPL1 and NALPL2 are important intracellular proteins in host surveillance against both bacterial and viral infection. Interestingly, the expression of downstream signaling genes was not affected by the overexpression of NALPL1 or NALPL2, but NOD1 and MDA5 were upregulated by NALPL1 or NALPL2 overexpression, suggesting that they likely act in pathogen infection through the interaction with other PRRs.

Role of vascular smooth muscle cell in the inflammation of atherosclerosis

Atherosclerosis is a pathologic process occurring within the artery, in which many cell types, including T cell, macrophages, endothelial cells, and smooth muscle cells, interact, and cause chronic inflammation, in response to various inner- or outer-cellular stimuli. Atherosclerosis is characterized by a complex interaction of inflammation, lipid deposition, vascular smooth muscle cell proliferation, endothelial dysfunction, and extracellular matrix remodeling, which will result in the formation of an intimal plaque. Although the regulation and function of vascular smooth muscle cells are important in the progression of atherosclerosis, the roles of smooth muscle cells in regulating vascular inflammation are rarely focused upon, compared to those of endothelial cells or inflammatory cells. Therefore, in this review, we will discuss here how smooth muscle cells contribute or regulate the inflammatory reaction in the progression of atherosclerosis, especially in the context of the activation of various membrane receptors, and how they may regulate vascular inflammation.

TB or not TB: that is no longer the question

Tuberculosis (TB) remains a devastating infectious disease and, with the emergence of multidrug-resistant forms, represents a major global threat. Much of our understanding of pathogenic and immunologic mechanisms in TB has derived from studies in experimental animals. However, it is becoming increasingly clear in TB as well as in other inflammatory diseases that there are substantial differences in immunological responses of humans not found or predicted by animal studies. Thus, it is critically important to understand mechanisms of pathogenesis and immunological protection in humans. In this review, we will address the key immunological question: What are the necessary and sufficient immune responses required for protection against TB infection and disease in people-specifically protection against infection, protection against the establishment of latency or persistence, and protection against transitioning from latent infection to active disease.

Differential macrophage response to slow- and fast-growing pathogenic mycobacteria

Nontuberculous mycobacteria (NTM) have recently been recognized as important species that cause disease even in immunocompetent individuals. The mechanisms that these species use to infect and persist inside macrophages are not well characterised. To gain insight concerning this process we used THP-1 macrophages infected with M. abscessus, M. fortuitum, M. celatum, and M. tuberculosis. Our results showed that slow-growing mycobacteria gained entrance into these cells with more efficiency than fast-growing mycobacteria. We have also demonstrated that viable slow-growing M. celatum persisted inside macrophages without causing cell damage and without inducing reactive oxygen species (ROS), as M. tuberculosis caused. In contrast, fast-growing mycobacteria destroyed the cells and induced high levels of ROS. Additionally, the macrophage cytokine pattern induced by M. celatum was different from the one induced by either M. tuberculosis or fast-growing mycobacteria. Our results also suggest that, in some cases, the intracellular survival of mycobacteria and the immune response that they induce in macrophages could be related to their growth rate. In addition, the modulation of macrophage cytokine production, caused by M. celatum, might be a novel immune-evasion strategy used to survive inside macrophages that is different from the one reported for M. tuberculosis.

Preferential silent survival of intracellular bacteria in hemoglobin-primed macrophages

Hemolysis releases hemoglobin (Hb), a prooxidant, into circulation. While the heme iron is a nutrient for the invading pathogens, it releases ROS, which is both microbicidal and cytotoxic, making it a double-edged sword. Previously, we found a two-pass detoxification mechanism involving the endocytosis of Hb into monocytes in collaboration with vascular endothelial cells to overcome oxidative damage. This prompted us to examine the effect of Hb priming on host cell viability and intracellular bacterial clearance during a hemolytic infection. Here, we demonstrate that Hb-primed macrophages harbor a higher intracellular bacterial load but with suppressed apoptosis. p-ERK and p-p38 MAPK were significantly downregulated, with concomitant impairment of Bax and downstream caspases. The Hb-primed cells harboring intracellular bacteria upregulated anti-inflammatory IL-10 and downregulated proinflammatory TNF-α, which further enhanced the infectivity of the neighboring cells. Our findings suggest that opportunistic intracellular pathogens exploit the Hb-scavenging machinery of the host to silently persist within the circulating phagocytes by suppressing apoptosis while escaping immune surveillance.

SQSTM1/p62/A170 regulates the severity of Legionella pneumophila pneumonia by modulating inflammasome activity

Sequestosome1/A170/p62 (SQSTM1) is a scaffold multifunctional protein involved in several cellular events, such as signal transduction, cell survival, cell death, and inflammation. SQSTM1 expression by macrophages is induced in response to environmental stresses; however, its role in macrophage-mediated host responses to environmental stimuli, such as infectious pathogens, remains unclear. In this study, we investigated the role of SQSTM1 in host responses to Legionella pneumophila, an intra-cellular pathogen that infects macrophages, in both an SQSTM1-deficient (SQSTM1(-/-) ) mouse model and macrophages from these mice. Compared with wild-type (WT) macrophages, the production and secretion of the proinflammatory cytokine IL-1β was significantly enhanced in SQSTM1(-/-) macrophages after infection with L. pneumophila. Inflammasome activity, indicated by the level of IL-18 and caspase-1 activity, was also elevated in SQSTM1(-/-) macrophages after infection with L. pneumophila. SQSTM1 may interact with nucleotide-binding oligomerization domain-like receptor family, caspase recruitment domain-containing 4 and nucleotide-binding oligomerization domain like receptor family, pyrin domain containing 3 proteins to inhibit their self-dimerization. Acute pulmonary inflammation induced by L. pneumophila and silica was enhanced in SQSTM1(-/-) mice with an increase in IL-1β levels in the bronchoalveolar lavage fluids. These findings suggest that SQSTM1 is a negative regulator of acute pulmonary inflammation, possibly by regulating inflammasome activity and subsequent proinflammatory cytokine production.

Improving vaccines by incorporating immunological coadjuvants

While vaccination continues to be the most successful interventionist health policy to date, infectious disease remains a significant cause of death worldwide. A primary reason that vaccination is not able to generate effective immunity is a lack of appropriate adjuvants capable of initiating the desired immune response. Adjuvant combinations can potentially overcome this problem; however, the possible permutations to consider, which include the route and kinetics of vaccination, as well as combinations of adjuvants, are practically limitless. This review aims to summarize the current understanding of adjuvants and related immunological processes and how this knowledge can and has been applied to the strategic selection of adjuvant combinations as components of vaccines against human infectious disease.

Reciprocal effects of Guizhi decoction to the Guizhi decoction syndrome by toll-like receptor mRNA expression and cytokines secretion

OBJECTIVE

To explore the pathological mechanisms of Guizhi Decoction () syndrome and the therapeutic molecular mechanisms of the Guizhi Decoction, Mahuang Decoction (), Sangju Decoction ( ) and Yinqiao Powder (), as well as the potentially biological basis that Guizhi Decoction is most effective only for the patients with Guizhi Decoction syndrome in clinical practice.

METHODS

We first got serum samples from the patients suffering from both upper respiratory tract infection and Guizhi Decoction syndrome identified by the doctors of Chinese medicine (CM) in the clinic. Four formulas with therapeutic actions of pungent warmth or pungent coolness for superficial syndromes were chosen and four kinds of rat serum samples each containing one of the above-mentioned herbal formulas were collected, then the effects of Guizhi Decoction syndromes' patient serum as well as the effects of sera containing the formulas after being stimulated by the patient serum samples on both the mRNA expression of certain toll-like receptor (TLR) subtypes and the release of some inflammatory cytokines in RAW264.7 cells were tested and analyzed in vitro.

RESULTS

The expression of TLR-3, TLR-4 and TLR-9 mRNA among the 9 tested TLR subforms were up-regulated in the macrophages stimulated by the sera from untreated upper respiratory infection patients with the Guizhi Decoction syndrome (symptomcomplex). The products such as interleukin (IL)-1β, IL-6, tumor necrosis factor (TNF)-α and interferon (IFN)-β from stimulated macrophages through TLR signaling pathways were also increased correspondingly. Interestingly, the changes induced by the Guizhi Decoction syndrome patients' sera were masked significantly after the macrophages were incubated with the sera from donors treated with Guizhi Decoction. Similarly, the three other exterior-releasing formulas were all effective in reversing the up-regulated changes of certain TLR subforms to different degrees, but both the number of targeted TLRs and efficacy of them seemed to be inferior to that of Guizhi Decoction.

CONCLUSION

Evidence from these experiments might contribute to the scientific explanation of both the pharmacological mechanisms of Guizhi Decoction and also the CM theory that Guizhi Decoction is specifically prescribed for the treatment of Guizhi Decoction syndrome (The gearing formula to the symptom-complex).

TLR2 and Nod2 mediate resistance or susceptibility to fatal intracellular Ehrlichia infection in murine models of ehrlichiosis

Our murine models of human monocytic ehrlichiosis (HME) have shown that severe and fatal ehrlichiosis is due to generation of pathogenic T cell responses causing immunopathology and multi-organ failure. However, the early events in the liver, the main site of infection, are not well understood. In this study, we examined the liver transcriptome during the course of lethal and nonlethal infections caused by Ixodes ovatus Ehrlichia and Ehrlichia muris, respectively. On day 3 post-infection (p.i.), although most host genes were down regulated in the two groups of infected mice compared to naïve counterparts, lethal infection induced significantly higher expression of caspase 1, caspase 4, nucleotide binding oligomerization domain-containing proteins (Nod1), tumor necrosis factor-alpha, interleukin 10, and CCL7 compared to nonlethal infection. On day 7 p.i., lethal infection induced highly significant upregulation of type-1 interferon, several inflammatory cytokines and chemokines, which was associated with increased expression levels of Toll-like receptor-2 (TLR2), Nod2, MyD88, nuclear factor-kappa B (NF-kB), Caspase 4, NLRP1, NLRP12, Pycard, and IL-1β, suggesting enhanced TLR signals and inflammasomes activation. We next evaluated the participation of TLR2 and Nod2 in the host response during lethal Ehrlichia infection. Although lack of TLR2 impaired bacterial elimination and increased tissue necrosis, Nod2 deficiency attenuated pathology and enhanced bacterial clearance, which correlated with increased interferon-γ and interleukin-10 levels and a decreased frequency of pathogenic CD8(+) T cells in response to lethal infection. Thus, these data indicate that Nod2, but not TLR2, contributes to susceptibility to severe Ehrlichia-induced shock. Together, our studies provide, for the first time, insight into the diversity of host factors and novel molecular pathogenic mechanisms that may contribute to severe HME.

Exploring the immune response of porcine mesenteric lymph nodes to Salmonella enterica serovar Typhimurium: an analysis of transcriptional changes, morphological alterations and pathogen burden

Infections caused by Salmonella enterica serovar Typhimurium (S. typhimurium) cause important economic problems in the swine industry and threaten the integrity of a safe and healthy food supply. Controlling the prevalence of Salmonella in pig production requires a thorough knowledge of the response processes that occurs in the gut associated immune tissues. To explore the in vivo porcine response to S. typhimurium, MLN samples from four control pigs and twelve infected animals at 1, 2 and 6 days post infection (dpi) were collected to quantify the mRNA expression of gene coding for 42 innate immune-related molecules. In addition, the presence of S. typhimurium in MLN was examined and its effect on tissue micro-anatomy. Higher S. typhimurium loads were observed at 2dpi, triggering an innate immune response, marked by a substantial infiltration of phagocytes and up-regulation of pro-inflammatory genes. Such response resulted in a significant decrease in pathogen burden in MLN at 6dpi, although Salmonella could not be completely eliminated from tissue. Furthermore, our results suggest that in porcine infections, S. typhimurium might interferes with dendritic cell-T cell interactions and this strategy could be involved in the conversion of Salmonella infected pigs to a carrier state.

A therapeutic vaccine using Salmonella-modified tumor cells combined with interleukin-2 induces enhanced antitumor immunity in B-cell lymphoma

Therapeutic vaccination holds potential as complementary treatment for non-Hodgkin's lymphoma (NHL). B-NHL cells are antigen-presenting cells, but they cannot elicit proper antitumor responses because they lack expression of co-stimulatory molecules. Here, we report a novel approach to design improved whole tumor cell vaccines for B-NHL. We demonstrated that Salmonella infection significantly up-regulates CD80, CD86, CD40 and MHC II expression in lymphoma cells, and that therapeutic vaccination with infected and then irradiated lymphoma cells combined with IL-2 elicits strong anti-tumor specific immunity and extended survival in lymphoma-bearing mice. This may represent the basis of an effective immunotherapy against B-NHL that could be easily translated into the clinics.

Bacterial peptidoglycan-derived molecules activate Candida albicans hyphal growth

Serum strongly induces the yeast-to-hypha growth transition in the human fungal pathogen Candida albicans, playing an important role in infection. However, identity of the serum inducer(s) and its sensor remain poorly defined. We used NMR to analyze the chromatographic serum fractionations enriched for the hypha-inducing activity and found structures resembling subunits of bacterial peptidoglycan (PGN). We then confirmed that several purified and synthetic muramyl dipeptides (MDPs), subunits of PGN, can indeed strongly promote C. albicans hyphal growth. Taking cue from the recognition of MDPs by the mammalian bacterial sensor Nod2 using its leucine-rich-repeat (LRR) domain, we discovered that MDPs activate the adenylyl cyclase Cyr1 by binding to its LRR domain. The cAMP/PKA signaling pathway is well known to control hyphal morphogenesis and other infection-related traits. Given the abundance of PGN at the large intestinal epithelial surface, a natural habitat and invasion site for C. albcians, our findings have important implications in the mechanisms of infection by this pathogen.

Activation of an NLRP3 inflammasome restricts Mycobacterium kansasii infection

Mycobacterium kansasii has emerged as an important nontuberculous mycobacterium pathogen, whose incidence and prevalence have been increasing in the last decade. M. kansasii can cause pulmonary tuberculosis clinically and radiographically indistinguishable from that caused by Mycobacterium tuberculosis infection. Unlike the widely-studied M. tuberculosis, little is known about the innate immune response against M. kansasii infection. Although inflammasome activation plays an important role in host defense against bacterial infection, its role against atypical mycobacteria remains poorly understood. In this report, the role of inflammasome activity in THP-1 macrophages against M. kansasii infection was studied. Results indicated that viable, but not heat-killed, M. kansasii induced caspase-1-dependent IL-1β secretion in macrophages. The underlying mechanism was found to be through activation of an inflammasome containing the NLR (Nod-like receptor) family member NLRP3 and the adaptor protein ASC (apoptosis-associated speck-like protein containing a CARD). Further, potassium efflux, lysosomal acidification, ROS production and cathepsin B release played a role in M. kansasii-induced inflammasome activation. Finally, the secreted IL-1β derived from caspase-1 activation was shown to restrict intracellular M. kansasii. These findings demonstrate a biological role for the NLRP3 inflammasome in host defense against M. kansasii.

The amphioxus genome provides unique insight into the evolution of immunity

Immune systems evolve as essential strategies to maintain homeostasis with the environment, prevent microbial assault and recycle damaged host tissues. The immune system is composed of two components, innate and adaptive immunity. The former is common to all animals while the latter consists of a vertebrate-specific system that relies on somatically derived lymphocytes and is associated with near limitless genetic diversity as well as long-term memory. Deuterostome invertebrates provide a view of immune repertoires in phyla that immediately predate the origins of vertebrates. Genomic studies in amphioxus, a cephalochordate, have revealed homologs of genes encoding most innate immune receptors found in vertebrates; however, many of the gene families have undergone dramatic expansions, greatly increasing the innate immune repertoire. In addition, domain-swapping accounts for the innovation of new predicted pathways of receptor function. In both amphioxus and Ciona, a urochordate, the VCBPs (variable region containing chitin-binding proteins), which consist of immunoglobulin V (variable) and chitin binding domains, mediate recognition through the V domains. The V domains of VCBPs in amphioxus exhibit high levels of allelic complexity that presumably relate to functional specificity. Various features of the amphioxus immune repertoire reflect novel selective pressures, which likely have resulted in innovative strategies. Functional genomic studies underscore the value of amphioxus as a model for studying innate immunity and may help reveal how unique relationships between innate immune receptors and both pathogens and symbionts factored in the evolution of adaptive immune systems.

Sub-lethal levels of carvacrol reduce Salmonella Typhimurium motility and invasion of porcine epithelial cells

The European ban on the use of antibiotic growth promotors has increased the search for new alternatives to prevent pig intestinal microbial diseases and to stimulate growth. The addition of essential oils or components thereof, such as carvacrol, to pig feed is a promising alternative. In this report we determined the effect of sub-lethal concentrations of carvacrol on Salmonella Typhimurium. At concentrations where growth of Salmonella was not inhibited, carvacrol completely inhibited motility of the bacterium. This loss of motility was not due to the loss of the flagellum or to ATP shortage upon carvacrol treatment. Adhesion of Salmonella to IPEC-J2, porcine intestinal epithelial cells, was not affected by carvacrol but invasion was significantly reduced. In addition, the epithelial gene expression of porcine β-defensin 2, an innate immune response to Salmonella infection, was reduced when Salmonella was exposed to carvacrol. This indicates that invasion but not adhesion of Salmonella triggers the porcine β-defensin 2 expression of porcine epithelial cells.

Intracellular localisation and innate immune responses following Francisella noatunensis infection of Atlantic cod (Gadus morhua) macrophages

The facultative intracellular bacterium Francisella noatunensis causes francisellosis in Atlantic cod (Gadus morhua), but little is known about its survival strategies or how these bacteria evade the host immune response. In this study we show intracellular localisation of F. noatunensis in cod macrophages using indirect immunofluorescence techniques and green fluorescent labelled bacteria. Transmission electron microscopy revealed that F. noatunensis was enclosed by a phagosomal membrane during the initial phase of infection. Bacteria were at a later stage of the infection found in large electron-lucent zones, apparently surrounded by a partially intact or disintegrated membrane. Immune electron microscopy demonstrated the release of bacterial derived vesicles from intracellular F. noatunensis, an event suspected of promoting phagosomal membrane degradation and allowing escape of the bacteria to cytoplasm. Studies of macrophages infected with F. noatunensis demonstrated a weak activation of the inflammatory response genes as measured by increased expression of the Interleukin (IL)-1β and IL-8. In comparison, a stronger induction of gene expression was found for the anti-inflammatory IL-10 indicating that the bacterium exhibits a role in down-regulating the inflammatory response. Expression of the p40 subunit of IL-12/IL-17 genes was highly induced during infection suggesting that F. noatunensis promotes T cell polarisation. The host macrophage responses studied here showed low ability to distinguish between live and inactivated bacteria, although other types of responses could be of importance for such discriminations. The immunoreactivity of F. noatunensis lipopolysaccharide (LPS) was very modest, in contrast to the strong capacity of Escherichia coli LPS to induce inflammatory responsive genes. These results suggest that F. noatunensis virulence mechanisms cover many strategies for intracellular survival in cod macrophages.

Development of recombinant vaccines in lactobacilli for elimination of salmonella

Many Lactobacillus and Lactococcus strains are generally regarded as safe for consumption because they are utilized for food fermentation or inhabit the intestinal mucosa as commensals. Recently, vaccine delivery systems using lactic acid bacteria (LAB) have been under development. Our research group has been investigating the development of oral mucosal vaccines against Salmonella enterica serovar Enteritidis (SE) using Lactobacillus casei IGM393 as an antigen delivery vehicle. Recombinant lactobacilli expressing SE antigens, FliC, SipC, and OmpC, have been constructed and orally administered to mice. Antigen specific immune responses and protective immunity were elicited after the immunization. For adjuvant-delivery, IL-1β-secreting L. casei was also engineered and its effects evaluated in vitro and in vivo. This article reviews a novel approach to the elimination of Salmonella via the development of a vaccine in lactobacilli.

Role of SPI-1 secreted effectors in acute bovine response to Salmonella enterica Serovar Typhimurium: a systems biology analysis approach

Salmonella enterica Serovar Typhimurium (S. Typhimurium) causes enterocolitis with diarrhea and polymorphonuclear cell (PMN) influx into the intestinal mucosa in humans and calves. The Salmonella Type III Secretion System (T3SS) encoded at Pathogenicity Island I translocates Salmonella effector proteins SipA, SopA, SopB, SopD, and SopE2 into epithelial cells and is required for induction of diarrhea. These effector proteins act together to induce intestinal fluid secretion and transcription of C-X-C chemokines, recruiting PMNs to the infection site. While individual molecular interactions of the effectors with cultured host cells have been characterized, their combined role in intestinal fluid secretion and inflammation is less understood. We hypothesized that comparison of the bovine intestinal mucosal response to wild type Salmonella and a SipA, SopABDE2 effector mutant relative to uninfected bovine ileum would reveal heretofore unidentified diarrhea-associated host cellular pathways. To determine the coordinated effects of these virulence factors, a bovine ligated ileal loop model was used to measure responses to wild type S. Typhimurium (WT) and a ΔsipA, sopABDE2 mutant (MUT) across 12 hours of infection using a bovine microarray. Data were analyzed using standard microarray analysis and a dynamic bayesian network modeling approach (DBN). Both analytical methods confirmed increased expression of immune response genes to Salmonella infection and novel gene expression. Gene expression changes mapped to 219 molecular interaction pathways and 1620 gene ontology groups. Bayesian network modeling identified effects of infection on several interrelated signaling pathways including MAPK, Phosphatidylinositol, mTOR, Calcium, Toll-like Receptor, CCR3, Wnt, TGF-β, and Regulation of Actin Cytoskeleton and Apoptosis that were used to model of host-pathogen interactions. Comparison of WT and MUT demonstrated significantly different patterns of host response at early time points of infection (15 minutes, 30 minutes and one hour) within phosphatidylinositol, CCR3, Wnt, and TGF-β signaling pathways and the regulation of actin cytoskeleton pathway.

Immune functions of the skin

The skin, the body's largest organ, helps to secure the integrity of the host and, at the same time, allows the individual to communicate with the outside world. This finely tuned balance between protection from harmful pathogens (mostly microorganisms) and bidirectional signal exchange is provided by a network of structural, cellular, and molecular elements that are collectively referred to as the skin barrier. This "gateway" has a physical, chemical, and immunologic component. The role of the latter is to elicit a powerful defense reaction in the case of danger and, at the same time, to prevent such a reaction against innocuous substances. Immune responses originating in the skin are mounted and executed by cells and molecules of the innate or the adaptive immune system. Innate reactions are typically rapid, poorly discriminating, and do not exhibit memory. Adaptive responses, in contrast, show a high degree of specificity as well as memory but need a protracted time for their development. As a consequence, innate and adaptive responses are consecutive events influencing each other. In fact, we now know that the type and magnitude of the innate reactions govern and often determine the quality and quantity of adaptive responses.

Mycobacterium abscessus activates the NLRP3 inflammasome via Dectin-1-Syk and p62/SQSTM1

Numerous atypical mycobacteria, including Mycobacterium abscessus (Mabc), cause nontuberculous mycobacterial infections, which present a serious public health threat. Inflammasome activation is involved in host defense and the pathogenesis of autoimmune diseases. However, inflammasome activation has not been widely characterized in human macrophages infected with atypical mycobacteria. Here, we demonstrate that Mabc robustly activates the nucleotide binding and oligomerization domain-like receptor family pyrin domain containing 3 (NLRP3) inflammasome via dectin-1/Syk-dependent signaling and the cytoplasmic scaffold protein p62/SQSTM1 (p62) in human macrophages. Both dectin-1 and Toll-like receptor 2 (TLR2) were required for Mabc-induced mRNA expression of pro-interleukin (IL)-1β, cathelicidin human cationic antimicrobial protein-18/LL-37 and β-defensin 4 (DEFB4). Dectin-1-dependent Syk signaling, but not that of MyD88, led to the activation of caspase-1 and secretion of IL-1β through the activation of an NLRP3/apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) inflammasome. Additionally, potassium efflux was required for Mabc-induced NLRP3/ASC inflammasome activation. Furthermore, Mabc-induced p62 expression was critically involved in NLRP3 inflammasome activation in human macrophages. Finally, NLRP3/ASC was critical for the inflammasome in antimicrobial responses to Mabc infection. Taken together, these data demonstrate the induction mechanism of the NLRP3/ASC inflammasome and its role in innate immunity to Mabc infection.

Chemokine response induced by Chlamydia trachomatis in prostate derived CD45+ and CD45- cells

The role of innate cells and their receptors within the male genital tract remains poorly understood. Much less is known about the relative contribution of different genital tract cells such as epithelial/stromal cells and resident leucocytes. In this study, we examined innate immune responses to Chlamydia trachomatis by prostate epithelial/stromal cells and prostate resident leucocytes. Murine prostate primary cultures were performed and leucocyte and epithelial/stromal cells were sorted based on surface protein expression of CD45 by magnetism-activated cell sorting or fluorescence-activated cell sorting. Prostate derived CD45- and CD45+ cells were infected with C. trachomatis and chemokine secretion assayed by ELISA. Similar experiments were performed using prostate CD45+ and CD45- cells from myeloid differentiation factor 88 (Myd88(-/-)) mice or toll-like receptor (Tlr2(-/-)) and Tlr4(mutant) double-deficient mice. Moreover, a TLR-signalling pathway array was used to screen changes in different genes involved in TLR-signalling pathways by real-time PCR. Prostate derived CD45- and CD45+ cells responded to chlamydial infection with the production of different chemokines. Both populations expressed genes involved in TLR signalling and required to respond to pathogen-associated molecular patterns and to C. trachomatis infection. Both populations required the adaptor molecule MYD88 to elicit chemokine response against C. trachomatis. TLR2-TLR4 was essential for chemokine production by CD45+ prostate derived cells, but in their absence, CD45- cells still produced significant levels of chemokines. We demonstrate that C. trachomatis is differentially recognised by prostate derived CD45+ and CD45- cells and suggest that diverse strategies are taking place in the local microenvironment of the host in response to the infection.

Autophagy signaling through reactive oxygen species

Autophagy is a degradative pathway that involves delivery of cytoplasmic components, including proteins, organelles, and invaded microbes to the lysosome for digestion. Autophagy is implicated in the pathology of various human diseases. The association of autophagy to inflammatory bowel diseases is consistent with recent discoveries of its role in immunity. A complex of signaling pathways control the induction of autophagy in different cellular contexts. Reactive oxygen species (ROS) are highly reactive oxygen free radicals or non-radical molecules that are generated by multiple mechanisms in cells, with the nicotinamide adenine dinucleotide phosphate (NADPH) oxidases and mitochondria as major cellular sources. These ROS are important signaling molecules that regulate many signal-transduction pathways and play critical roles in cell survival, death, and immune defenses. ROS were recently shown to activate starvation-induced autophagy, antibacterial autophagy, and autophagic cell death. Current findings implicate ROS in the regulation of autophagy through distinct mechanisms, depending on cell types and stimulation conditions. Conversely, autophagy can also suppress ROS production. Understanding the mechanisms behind ROS-induced autophagy will provide significant therapeutic implications for related diseases.

The anti-inflammatory and antibacterial basis of human omental defense: selective expression of cytokines and antimicrobial peptides

BACKGROUND

The wound healing properties of the human omentum are well known and have extensively been exploited clinically. However, the underlying mechanisms of these effects are not well understood. We hypothesize that the omentum tissue promotes wound healing via modulation of anti-inflammatory pathways, and because the omentum is rich in adipocytes, the adipocytes may modulate the anti-inflammatory response. Factors released by human omentum may affect healing, inflammation and immune defense.

METHODOLOGY

Six human omentum tissues (non obese, free from malignancy, and any other systemic disorder) were obtained during diagnostic laparoscopies having a negative outcome. Healthy oral mucosa (obtained from routine oral biopsies) was used as control. Cultured adipocytes derived from human omentum were exposed to lipopolysaccharide (LPS) (1-50 ng/mL) for 12-72 hours to identify the non-cytotoxic doses. Levels of expression (mRNA and protein) were carried out for genes associated with pro- and anti-inflammatory cytokine responses and antibacterial/antimicrobial activity using qRT-PCR, western blotting, and cell-based ELISA assays.

RESULTS

The study shows significant higher levels of expression (mRNA and protein) of several specific cytokines, and antibacterial peptides in the omentum tissues when compared to oral sub-mucosal tissues. In the validation studies, primary cultures of adipocytes, derived from human omentum were exposed to LPS (5 and 10 ng/mL) for 24 and 48 h. The altered expressions were more pronounced in cultured adipocytes cells when exposed to LPS as compared to the omentum tissue.

CONCLUSIONS/SIGNIFICANCE

Perhaps, this is the first report that provides evidence of expressional changes in pro- and anti-inflammatory cytokines and antibacterial peptides in the normal human omentum tissue as well as adipocytes cultured from this tissue. The study provides new insights on the molecular and cellular mechanisms of healing and defense by the omentum, and suggests the potential applicability of cultured adipocytes derived from the omentum for future therapeutic applications.

Candidate gene and genome-wide association studies of Mycobacterium avium subsp. paratuberculosis infection in cattle and sheep: a review

Paratuberculosis (Johne's disease), caused by Mycobacterium avium subspecies paratuberculosis, is responsible for significant economic losses in livestock industries worldwide. This organism is also of public health concern due to an unconfirmed link to Crohn's disease. Susceptibility to paratuberculosis has been suggested to have a genetic component. In livestock, a number of candidate genes have been studied, selected on their association to susceptibility in other mycobacterial diseases, their known role in disease pathogenesis or links to susceptibility of humans to Crohn's disease. These genes include solute carrier family 11 member 1 (SLC11A1, formerly NRAMP1), toll-like receptors, caspase associated recruitment domain 15 (CARD15, formerly NOD2), major histocompatibility complex (MHC) and cytokines (interleukin-10 and interferon-gamma) and their receptors. Genome wide association studies have attempted to confirm associations found and identify new genes involved in pathogenesis and susceptibility. There are a number of limitations and difficulties in these approaches, some peculiar to paratuberculosis but others generally applicable to identification of genetic associations for complex traits. The technical approaches and available information for paratuberculosis have expanded rapidly, particularly relating to sheep and cattle. Here we review the current published evidence for a genetic association with paratuberculosis susceptibility, technological advances that have progressed the field and potential avenues for future research.

Intestinal dendritic cells: their role in bacterial recognition, lymphocyte homing, and intestinal inflammation

Dendritic cells (DCs) play a key role in discriminating between commensal microorganisms and potentially harmful pathogens and in maintaining the balance between tolerance and active immunity. The regulatory role of DC is of particular importance in the gut where the immune system lies in intimate contact with the highly antigenic external environment. Intestinal DC constantly survey the luminal microenvironment. They act as sentinels, acquiring antigens in peripheral tissues before migrating to secondary lymphoid organs to activate naive T cells. They are also sensors, responding to a spectrum of environmental cues by extensive differentiation or maturation. Recent studies have begun to elucidate mechanisms for functional specializations of DC in the intestine that may include the involvement of retinoic acid and transforming growth factor-β. Specialized CD103(+) intestinal DC can promote the differentiation of Foxp3(+) regulatory T cells via a retinoic acid-dependent process. Different DC outcomes are, in part, influenced by their exposure to microbial stimuli. Evidence is also emerging of the close interaction between bacteria, epithelial cells, and DC in the maintenance of intestinal immune homeostasis. Here we review recent advances of functionally specialized intestinal DC and their mechanisms of antigen uptake and recognition. We also discuss the interaction of DC with intestinal microbiota and their ability to orchestrate protective immunity and immune tolerance in the host. Lastly, we describe how DC functions are altered in intestinal inflammation and their emerging potential as a therapeutic target in inflammatory bowel disease.

The Opportunistic Pathogen Listeria monocytogenes: Pathogenicity and Interaction with the Mucosal Immune System

Listeria monocytogenes is an opportunistic foodborne pathogen causing listeriosis, an often fatal infection leading to meningitis, sepsis, or infection of the fetus and abortion in susceptible individuals. It was recently found that the bacterium can also cause acute, self-limiting febrile gastroenteritis in healthy individuals. In the intestinal tract, L. monocytogenes penetrates the mucosa directly via enterocytes, or indirectly via invasion of Peyer's patches. Animal models for L. monocytogenes infection have provided many insights into the mechanisms of pathogenesis, and the development of new model systems has allowed the investigation of factors that influence adaptation to the gastrointestinal environment as well as adhesion to and invasion of the intestinal mucosa. The mucosal surfaces of the gastrointestinal tract are permanently exposed to an enormous antigenic load derived from the gastrointestinal microbiota present in the human bowel. The integrity of the important epithelial barrier is maintained by the mucosal immune system and its interaction with the commensal flora via pattern recognition receptors (PRRs). Here, we discuss recent advances in our understanding of the interaction of L. monocytogenes with the host immune system that triggers the antibacterial immune responses on the mucosal surfaces of the human gastrointestinal tract.

The innate immune response in leprosy

Investigation into the innate immune response in leprosy has provided insight into immunoregulation in human infectious disease. Key advances include the role of pattern recognition receptors in recognizing pathogen-associated molecular patterns of Mycobacterium leprae, cytokine release by innate immune cells, macrophage and dendritic cell differentiation, as well as antimicrobial effector pathways. These insights provide targets for therapeutic intervention in modulating the course of leprosy and other chronic infectious diseases.

Mouse macrophages are permissive to motile Legionella species that fail to trigger pyroptosis

Legionella pneumophila, a motile opportunistic pathogen of humans, is restricted from replicating in the lungs of C57BL/6 mice. Resistance of mouse macrophages to L. pneumophila depends on recognition of cytosolic flagellin. Once detected by the NOD-like receptors Naip5 and Ipaf (Nlrc4), flagellin triggers pyroptosis, a proinflammatory cell death. In contrast, motile strains of L. parisiensis and L. tucsonensis replicate profusely within C57BL/6 macrophages, similar to flagellin-deficient L. pneumophila. To gain insight into how motile species escape innate defense mechanisms of mice, we compared their impacts on macrophages. L. parisiensis and L. tucsonensis do not induce proinflammatory cell death, as measured by lactate dehydrogenase (LDH) release and interleukin-1beta (IL-1beta) secretion. However, flagellin isolated from L. parisiensis and L. tucsonensis triggers cell death and IL-1beta secretion when transfected into the cytosol of macrophages. Neither strain displays three characteristics of the canonical L. pneumophila Dot/Icm type IV secretion system: sodium sensitivity, LAMP-1 evasion, and pore formation. Therefore, we postulate that when L. parisiensis and L. tucsonensis invade a mouse macrophage, flagellin is confined to the phagosome, protecting the bacteria from recognition by the cytosolic surveillance system and allowing Legionella to replicate. Despite their superior capacity to multiply in mouse macrophages, L. parisiensis and L. tucsonensis have been associated with only two cases of disease, both in renal transplant patients. These results point to the complexity of disease, a product of the pathogenic potential of the microbe, as defined in the laboratory, and the capacity of the host to mount a measured defense.