Expression Of Pattern Recognition Receptors Research Articles

Advances in Targeting the Innate and Adaptive Immune Systems to Cure Chronic Hepatitis B Virus Infection.

“Functional cure” is being pursued as the ultimate endpoint of antiviral treatment in chronic hepatitis B (CHB), which is characterized by loss of HBsAg whether or not anti-HBs antibodies are present. “Functional cure” can be achieved in <10% of CHB patients with currently available therapeutic agents. The dysfunction of specific immune responses to hepatitis B virus (HBV) is considered the major cause of persistent HBV infection. Thus, modulating the host immune system to strengthen specific cellular immune reactions might help eliminate HBV. Strategies are needed to restore/enhance innate immunity and induce HBV-specific adaptive immune responses in a coordinated way. Immune and resident cells express pattern recognition receptors like TLRs and RIG I/MDA5, which play important roles in the induction of innate immunity through sensing of pathogen-associated molecular patterns (PAMPs) and bridging to adaptive immunity for pathogen-specific immune control. TLR/RIG I agonists activate innate immune responses and suppress HBV replication in vitro and in vivo, and are being investigated in clinical trials. On the other hand, HBV-specific immune responses could be induced by therapeutic vaccines, including protein (HBsAg/preS and HBcAg), DNA, and viral vector-based vaccines. More than 50 clinical trials have been performed to assess therapeutic vaccines in CHB treatment, some of which display potential effects. Most recently, using genetic editing technology to generate CAR-T or TCR-T, HBV-specific T cells have been produced to efficiently clear HBV. This review summarizes the progress in basic and clinical research investigating immunomodulatory strategies for curing chronic HBV infection, and critically discusses the rather disappointing results of current clinical trials and future strategies.

Cellular and molecular mechanisms of antifungal innate immunity at epithelial barriers: The role of C-type lectin receptors.

Humans are constantly exposed to fungi, either in the form of commensals at epithelial barriers or as inhaled spores. Innate immune cells play a pivotal role in maintaining commensal relationships and preventing skin, mucosal, or systemic fungal infections due to the expression of pattern recognition receptors that recognize fungal cell wall components and modulate both their activation status and the ensuing adaptive immune response. Commensal fungi also play a critical role in the modulation of homeostasis and disease susceptibility at epithelial barriers. This review will outline cellular and molecular mechanisms of anti-fungal innate immunity focusing on C-type lectin receptors and their relevance in the context of host-fungi interactions at skin and mucosal surfaces in murine experimental models as well as patients susceptible to fungal infections.

Co-incidence of Damage and Microbial Patterns Controls Localized Immune Responses in Roots

SummaryRecognition of microbe-associated molecular patterns (MAMPs) is crucial for the plant’s immune response. How this sophisticated perception system can be usefully deployed in roots, continuously exposed to microbes, remains a mystery. By analyzing MAMP receptor expression and response at cellular resolution in Arabidopsis, we observed that differentiated outer cell layers show low expression of pattern-recognition receptors (PRRs) and lack MAMP responsiveness. Yet, these cells can be gated to become responsive by neighbor cell damage. Laser ablation of small cell clusters strongly upregulates PRR expression in their vicinity, and elevated receptor expression is sufficient to induce responsiveness in non-responsive cells. Finally, localized damage also leads to immune responses to otherwise non-immunogenic, beneficial bacteria. Damage-gating is overridden by receptor overexpression, which antagonizes colonization. Our findings that cellular damage can “switch on” local immune responses helps to conceptualize how MAMP perception can be used despite the presence of microbial patterns in the soil.

Inflammatory Dendritic Cells, Regulated by IL-4 Receptor Alpha Signaling, Control Replication, and Dissemination of Leishmania major in Mice.

Leishmaniasis is a vector-borne disease caused by Leishmania parasites. Macrophages are considered the primary parasite host cell, but dendritic cells (DCs) play a critical role in initiating adaptive immunity and controlling Leishmania infection. Accordingly, our previous study in CD11ccreIL-4Rα−/lox mice, which have impaired IL-4 receptor alpha (IL-4Rα) expression on CD11c+ cells including DCs, confirmed a protective role for IL-4/IL-13-responsive DCs in replication and dissemination of parasites during cutaneous leishmaniasis. However, it was unclear which DC subset/s was executing this function. To investigate this, we infected CD11ccreIL-4Rα−/lox and control mice with L. major GFP+ parasites and identified subsets of infected DCs by flow cytometry. Three days after infection, CD11b+ DCs and CD103+ DCs were the main infected DC subsets in the footpad and draining lymph node, respectively and by 4 weeks post-infection, Ly6C+ and Ly6C− CD11b+ DCs were the main infected DC populations in both the lymph nodes and footpads. Interestingly, Ly6C+CD11b+ inflammatory monocyte-derived DCs but not Ly6C−CD11b+ DCs hosted parasites in the spleen. Importantly, intracellular parasitism was significantly higher in IL-4Rα-deficient DCs. In terms of DC effector function, we found no change in the expression of pattern-recognition receptors (TLR4 and TLR9) nor in expression of the co-stimulatory marker, CD80, but MHCII expression was lower in CD11ccreIL-4Rα−/lox mice at later time-points compared to the controls. Interestingly, in CD11ccreIL-4Rα−/lox mice, which have reduced Th1 responses, CD11b+ DCs had impaired iNOS production, suggesting that DC IL-4Rα expression and NO production is important for controlling parasite numbers and preventing dissemination. Expression of the alternative activation marker arginase was unchanged in CD11b+ DCs in CD11creIL-4Rα−/lox mice compared to littermate controls, but RELM-α was upregulated, suggesting IL-4Rα-independent alternative activation. In summary, L. major parasites may use Ly6C+CD11b+ inflammatory DCs derived from monocytes recruited to infection as “Trojan horses” to migrate to secondary lymphoid organs and peripheral sites, and DC IL-4Rα expression is important for controlling infection.

Dendritic Cells and Microglia Have Non-Redundant Functions in the Inflamed Brain with Protective Effects of Type 1 cDCs

Brain CD11c+ cells share features with microglia and dendritic cells (DCs). Sterile inflammation increases brain CD11c+ cells but their phenotype, origin, and functions remain largely unknown. We report that after cerebral ischemia, microglia attract DCs to the inflamed brain and astroglia produce Flt3 ligand supporting development and expansion of CD11c+ cells. CD11c+ cells in the inflamed brain are a complex population derived from proliferating microglia and infiltrating DCs, including a major subset of OX40L+ conventional cDC2, and also cDC1, plasmacytoid and monocyte-derived DCs. Despite sharing certain morphological features and markers, CD11c+ microglia and DCs display differential expression of pattern recognition receptors and chemokine receptors. DCs excel CD11c- and CD11c+ microglia in the capacity to present antigen through MHC I and MHC II. Of note, cDC1s protect from brain injury after ischemia. We thus reveal novel aspects of the dynamics and functions of brain DCs in regulation of inflammation and immunity.

Toll-Like Receptors Signaling in the Tumor Microenvironment.

The involvement of inflammation in cancer progression is well-established. The immune system can play both tumor-promoting and -suppressive roles, and efforts to harness the immune system to help fight tumor growth are at the forefront of research. Of particular importance is the inflammatory profile at the site of the tumor, with respect to both the leukocyte population numbers, the phenotype of these cells, as well as the contribution of the tumor cells themselves. In this regard, the pro-inflammatory effects of pattern recognition receptor expression and activation in the tumor microenvironment have emerged as a relevant issue both for therapy and to understand tumor development.Pattern recognition receptors (PRRs) were originally recognized as components of immune cells, particularly innate immune cells, as detectors of pathogens. PRR signaling in immune cells activates them, inducing robust antimicrobial responses. In particular, toll-like receptors (TLRs) constitute a family of membrane-bound PRRs which can recognize pathogen-associated molecular patterns (PAMPs) carried by bacteria, virus, and fungi. In addition, PRRs can recognize products generated by stressed cells or damaged tissues, namely damage-associated molecular patterns or DAMPS. Taking into account the role of the immune system in fighting tumors together with the presence of immune cells in the microenvironment of different types of tumors, strategies to activate immune cells via PRR ligands have been envisioned as an anticancer therapeutic approach.In the last decades, it has been determined that PRRs are present and functional on nonimmune cells and that their activation in these cells contributes to the inflammation in the tumor microenvironment. Both tumor-promoting and antitumor effects have been observed when tumor cell PRRs are activated. This argues against nonspecific activation of PRR ligands in the tumor microenvironment as a therapeutic approach. Therefore, the use of PRR ligands for anticancer therapy might benefit from strategies that specifically deliver these ligands to immune cells, thus avoiding tumor cells in some settings. This review focuses on these aspects of TLR signaling in the tumor microenvironment.

Post-natal co-development of the microbiota and gut barrier function follows different paths in the small and large intestine in piglets.

Gut microbiota and intestinal barrier co-develop after birth, establishing a homeostatic state whereby mucosal cells cohabit with commensal bacteria. We hypothesized that this post-natal co-development follows different timings depending on the intestinal site considered. Jejunal, ileal, and colonic luminal contents and mucosa were sampled in suckling piglets at post-natal day (PND) 0, 2, 7, 14, and 28. Jejunal, ileal, and colonic luminal microbiota (evaluated by 16S DNA sequencing followed by beta-diversity analysis) clustered at PND2 but colonic microbiota diverge afterwards (P<.05). Mucosal permeability, evaluated in Ussing chambers, increased with age in the jejunum and ileum (P<.05) but not the colon. Expression of pattern recognition receptor (PRR) exhibited different patterns (gradual or sharp increase, decrease, or no change with age, P<.05) depending on PRR and intestinal site considered. Principal component analysis of mucosa data revealed clear clustering of colonic samples, irrespective of the age and clustering of jejunal and ileal samples, with gradual changes with age. Correlation analysis highlighted three families correlating with mucosal parameters: Enterobacteriaceae in the jejunum, Peptostreptococcaceae in the ileum, and Micrococcaceae in the colon. In conclusion, small and large intestine display close microbiota composition early in life but distinct mucosal phenotype and follow very different post-natal development.

Low expression of RNA sensors impacts Zika virus infection in the lower female reproductive tract

Innate immune responses to Zika virus (ZIKV) are dampened in the lower female reproductive tract (LFRT) compared to other tissues, but the mechanism that underlies this vulnerability is poorly understood. Using tissues from uninfected and vaginally ZIKV-infected macaques and mice, we show that low basal expression of RNA-sensing pattern recognition receptors (PRRs), or their co-receptors, in the LFRT contributes to high viral replication in this tissue. In the LFRT, ZIKV sensing provides limited protection against viral replication, and the sensors are also minimally induced after vaginal infection. While IFNα/β receptor signaling offers minimal protection in the LFRT, it is required to prevent dissemination of ZIKV to other tissues, including the upper FRT. Our findings support a role for RNA-sensing PRRs in the dampened innate immunity against ZIKV in the LFRT compared to other tissues and underlie potential implications for systemic dissemination upon heterosexual transmission of ZIKV in women.

Rhinovirus-induced IFN\u03b2 expression is NF\u03baB-dependent and regulated by the macrophage microenvironment

Macrophages play an important role in asthma pathogenesis both in the inflammatory and resolution phase of the disease. Macrophages can acquire different polarisation states dependent on their microenvironment. It is yet unclear through which mechanism the microenvironment affects the anti-viral response in macrophages. We hypothesized that the macrophage microenvironment regulates rhinovirus-induced IFNβ expression. Murine bone marrow-derived monocytes and human differentiated THP-1 cells were stimulated with M-CSF or GM-CSF and IFNγ or IL-4/IL-13, respectively, to mimic a Th1 or Th2 environment. Macrophages were infected with rhinovirus and gene and protein levels of IFNβ and pattern recognition receptor expression were measured. In subsequent experiments an IκB kinase inhibitor was used to study the involvement of NFκB. Both murine and human M1-like macrophages exhibited higher levels of IFNβ and pattern recognition receptors after rhinovirus infection than M2-like macrophages. Blockage of NFκB resulted in a lower expression of rhinovirus-induced IFNβ in human M1-like macrophages while inducing a higher expression in M2-like macrophages, suggesting that the interferon response towards viral infection was mediated by NFκB. These findings could contribute to a better understanding of mechanisms causing reduced anti-viral responses at viral-induced exacerbations in asthma.

Inhibition of anti-viral responses in intestinal epithelial cells by epigenetic modifying drugs is mediated by a reduction in viral pattern recognition receptor expression and activity

Background: Pattern recognition receptors form an essential part of the host defenses against pathogens, in particular in the intestinal epithelium. However, despite their importance relatively little is understood about the regulation of their expression. Increasing evidence suggesting that epigenetic mechanisms such as DNA methylation and histone acetylation have substantial effects on gene expression and regulation. Epigenetic modifying drugs are now used to treat certain cancers but not a lot is known about their effects on the innate immune system. Thus, we set out to examine the role of such drugs in the expression and function of Toll-like receptors. Methods: Using the HCT116 epithelial cell line, we determined the effects of genetic knockout of the DNA methyltransferases enzymes (DNMTs), as well as pharmacological inhibition of the DNMTs and histone deacetylase complexes (HDACs) on TLR responses to their ligands.Results: Our initial results showed that anti-viral responses were affected by changes in the epigenome, with TLR3 responses showing the most dramatic differences. We determined that inhibition of methylation and acetylation inhibited poly I:C induced increases in signaling protein phosphorylation, as well as increases in cytokine mRNA expression and release. We also observed that treatment with epigenetic modifying drugs were leading to large increases in IRF8 expression, a protein that is a known negative regulator of TLR3. When we overexpressed IRF8 in our WT cells we noticed inhibition of poly I:C responses. Conclusion: This research highlighted the potential immunoregulatory role of epigenetic modifying drugs specifically in response to viral stimulation.

Th1/17-Biased Inflammatory Environment Associated with COPD Alters the Response of Airway Epithelial Cells to Viral and Bacterial Stimuli.

Chronic obstructive pulmonary disease (COPD) is characterized by airway inflammation associated with a Th1/17-biased cytokine environment. Acute exacerbations of COPD (AECOPD) are most often triggered by respiratory infections, which elicit an exaggerated inflammatory response in these patients, via poorly defined mechanisms. We investigated the responses of airway epithelial cells (AECs) to infective stimuli in COPD and the effects of the Th1/17-biased environment on these responses. Cytokine expression was assessed following exposure to virus-like stimuli (poly I:C or imiquimod) or bacterial LPS. The effects of pretreatment with Th1/17 cytokines were evaluated in both primary AECs and the Calu-3 AEC cell line. We found that poly I:C induced increased expression of the proinflammatory cytokines IL1β, IL6, CXCL8, and TNF and IFN-β1 in AECs from both control subjects and COPD patients. Expression of IL1β in response to all 3 stimuli was significantly enhanced in COPD AECs. Primary AECs pretreated with Th1/17 cytokines exhibited enhanced expression of mRNA for proinflammatory cytokines in response to poly I:C. Similarly, Calu-3 cells responded to virus-like/bacterial stimuli with increased expression of proinflammatory cytokines, and a Th1/17 environment significantly enhanced their expression. Furthermore, increased expression of pattern recognition receptors for viruses (TLR3, TLR7, IFIH1, and DDX58) was induced by Th1/17 cytokines, in both primary AECs and Calu-3 cells. These findings suggest that the Th1/17-biased environment associated with COPD may enhance the proinflammatory cytokine response of AECs to viral and bacterial infections and that increased signaling via upregulated receptors may contribute to exaggerated inflammation in virus-induced AECOPD.

Murine astrocytes are responsive to the pro-inflammatory effects of IL-20

Glia are key regulators of inflammatory responses within the central nervous system (CNS) following infection or trauma. We have previously demonstrated the ability of activated astrocytes to rapidly produce pro-inflammatory mediators followed by a transition to an anti-inflammatory cytokine production profile that includes the immunosuppressive cytokine interleukin (IL)-10 and the closely related cytokines IL-19 and IL-24. IL-20, another member of the IL-10 family, is known to modulate immune cell activity in the periphery and we have previously demonstrated that astrocytes constitutively express the cognate receptors for this cytokine. However, the ability of glia to produce IL-20 remains unclear and the effects of this pleiotropic cytokine on glial immune functions have not been investigated. In this study, we report that primary murine and human astrocytes are not an appreciable source of IL-20 following challenge with disparate bacterial species or their components. Importantly, we have determined that astrocyte are responsive to the immunomodulatory actions of this cytokine by showing that recombinant IL-20 administration upregulates microbial pattern recognition receptor expression and induces release of the inflammatory mediator IL-6 by these cells. Taken together, these data suggest that IL-20 acts in a dissimilar manner to other IL-10 family members to augment the inflammatory responses of astrocytes.

Zika Virus Infects Trabecular Meshwork and Causes Trabeculitis and Glaucomatous Pathology in Mouse Eyes.

Zika virus (ZIKV) infection during pregnancy leads to devastating fetal outcomes, including neurological (microcephaly) and ocular pathologies such as retinal lesions, optic nerve abnormalities, chorioretinal atrophy, and congenital glaucoma. Only clinical case reports have linked ZIKV infection to causing glaucoma, a major blinding eye disease. In the present study, we have investigated the role of ZIKV in glaucoma pathophysiology using in vitro and in vivo experimental models. We showed that human primary trabecular meshwork (Pr. TM) cells, as well as a human GTM3 cell line, were permissive to ZIKV infection. ZIKV induced the transcription of various genes expressing pattern recognition receptors (TLR2, TLR3, and RIG-I), cytokines/chemokines (TNF-α, IL-1β, CCL5, and CXCL10), interferons (IFN-α2, IFN-β1, and IFN-γ), and interferon-stimulated genes (ISG15 and OAS2) in Pr. TM cells. ZIKV infection in IFNAR1-/- and wild-type (WT) mouse eyes resulted in increased intraocular pressure (IOP) and the development of chorioretinal atrophy. Anterior chamber (AC) inoculation of ZIKV caused infectivity in iridocorneal angle and TM, leading to the death of TM cells in the mouse eyes. Moreover, anterior segment tissue of infected eyes exhibited increased expression of inflammatory mediators and interferons. Furthermore, ZIKV infection in IFNAR1-/- mice resulted in retinal ganglion cell (RGC) death and loss, coinciding with optic nerve infectivity and disruption of anterograde axonal transport. Because of similarity in glaucomatous pathologies in our study and other experimental glaucoma models, ZIKV infection can be used to study infectious triggers of glaucoma, currently an understudied area of investigation.IMPORTANCE Ocular complications due to ZIKV infection remains a major public health concern because of their ability to cause visual impairment or blindness. Most of the previous studies have shown ZIKV-induced ocular pathology in the posterior segment (i.e., retina) of the eye. However, some recent clinical reports from affected countries highlighted the importance of ZIKV in affecting the anterior segment of the eye and causing congenital glaucoma. Because glaucoma is the second leading cause of blindness worldwide, it is imperative to study ZIKV infection in causing glaucoma to identify potential targets for therapeutic intervention. In this study, we discovered that ZIKV permissively infects human TM cells and evokes inflammatory responses causing trabeculitis. Using a mouse model, we demonstrated that ZIKV infection resulted in higher IOP, increased RGC loss, and optic nerve abnormalities, the classical hallmarks of glaucoma. Collectively, our study provides new insights into ocular ZIKV infection resulting in glaucomatous pathology.

Immunology's Coming of Age.

This treatise describes the development of immunology as a scientific discipline with a focus on its foundation. Toward the end of the nineteenth century, the study of immunology was founded with the discoveries of phagocytosis by Elias Metchnikoff, as well as by Emil Behring's and Paul Ehrlich's discovery of neutralizing antibodies. These seminal studies were followed by the discoveries of bacteriolysis by complement and of opsonization by antibodies, which provided first evidence for cooperation between acquired and innate immunity. In the years that followed, light was shed on the pathogenic corollary of the immune response, describing different types of hypersensitivity. Subsequently, immunochemistry dominated the field, leading to the revelation of the chemical structure of antibodies in the 1960s. Immunobiology was preceded by transplantation biology, which laid the ground for the genetic basis of acquired immunity. With the identification of antibody producers as B lymphocytes and the discovery of T lymphocytes as regulators of acquired immunity, lymphocytes moved into the center of immunologic research. T cells were shown to be genetically restricted and to regulate different leukocyte populations, including B cells and professional phagocytes. The discovery of dendritic cells as major antigen-presenting cells and their surface expression of pattern recognition receptors revealed the mechanisms by which innate immunity instructs acquired immunity. Genetic analysis provided in-depth insights into the generation of antibody diversity by recombination, which in principle was shown to underlie diversity of the T cell receptor, as well. The invention of monoclonal antibodies not only provided ultimate proof for the unique antigen specificity of the antibody-producing plasma cell, it also paved the way for a new era of immunotherapy. Emil Behring demonstrated cure of infectious disease by serum therapy, illustrating how clinical studies can stimulate basic research. The recent discovery of checkpoint control for cancer therapy illustrates how clinical application benefits from insights into basic mechanisms. Last not least, perspectives on immunology progressed from a dichotomy between cellular-unspecific innate immunity and humoral-specific acquired immunity, toward the concept of complementary binarity.

Lung Epithelial Cells Coordinate Innate Lymphocytes and Immunity against Pulmonary Fungal Infection

Lung epithelial cells (LECs) are strategically positioned in the airway mucosa to provide barrier defense. LECs also express pattern recognition receptors and a myriad of immune genes, but their role in immunity is often concealed by the activities of "professional" immune cells, particularly in the context of fungal infection. Here, we demonstrate that NF-κB signaling in LECs is essential for immunity against the pulmonary fungal pathogen Blastomyces dermatitidis. LECs orchestrate innate antifungal immunity by augmenting the numbers of interleukin-17A (IL-17A)- and granulocyte-macrophage colony-stimulating factor (GM-CSF)-producing innate lymphocytes, specifically "natural" Th17 (nTh17) cells. Innate lymphocyte-derived IL-17A and GM-CSF in turn enable phagocyte-driven fungal killing. LECs regulate the numbers of nTh17 cells via the production of chemokines such as CCL20, a process dependent on IL-1α-IL-1 receptor (IL-1R) signaling on LECs. Therefore, LECs orchestrate IL-17A- and GM-CSF-mediated immunity in an IL-1R-dependent manner and represent an essential component of innate immunity to pulmonary fungal pathogens.

Candida albicans at Host Barrier Sites: Pattern Recognition Receptors and Beyond.

Over the last decades, fungal infections have emerged as a growing threat to human health. Although the human body is at potential risk, various body sites host several commensal fungal species, including Candida albicans. In healthy individuals, C. albicans colonizes different mucosal surfaces without causing harm, while under diverse circumstances the fungus can proliferate and cause disease. In this context, the understanding of host–C. albicans interactions in health and during infection may lead to novel therapeutic approaches. Importantly, host cells express pattern recognition receptors (PRRs), which sense conserved fungal structures and orchestrate innate immune responses. Herein, important findings on the topic of the recognition of C. albicans at host barrier sites are discussed. This review briefly summarizes the importance and functions of myeloid PRRs, reviews the fungal recognition and biology of stromal cells, and highlights important C. albicans virulence attributes during site-specific proliferation and invasion.

Macrophage migration inhibitory factor regulates innate γδ T-cell responses via IL-17 expression.

T cells expressing invariant γδ antigen receptors (γδ T cells) bridge innate and adaptive immunity and facilitate barrier responses to pathogens. Macrophage migration inhibitory factor (MIF) is an upstream mediator of host defense that up-regulates the expression of pattern recognition receptors and sustains inflammatory responses by inhibiting activation-induced apoptosis in monocytes and macrophages. Surprisingly, Mif-/- γδ T cells, when compared with wild type, were observed to produce >10-fold higher levels of the proinflammatory cytokine IL-17 after stimulation with gram-positive exotoxins. High-IL-17 expression was associated with the characteristic features of IL-17-producing γδ T (γδ17) cells, including expression of IL-23R, IL-1R1, and the transcription factors RORγt and Sox13. In the gram-positive model of shock mediated by toxic shock syndrome toxin (TSST-1), Mif-/- mice succumbed to death more quickly with increased pulmonary neutrophil accumulation and higher production of cytokines, including IL-1β and IL-23. Mif-/- γδ T cells also produced high levels of IL-17 in response to Mycobacterium lipomannan, and depletion of γδ T cells improved survival from acutely lethal Mycobacterium infection or TSST-1 administration. These data indicate that MIF deficiency is associated with a compensatory amplification of γδ17 cell responses, with implications for innate immunity and IL-17-mediated pathology in situations such as gram-positive toxic shock or Mycobacterium infection.-Kim, H. K., Garcia, A. B., Siu, E., Tilstam, P., Das, R., Roberts, S., Leng, L., Bucala, R. Macrophage migration inhibitory factor regulates innate γδ T-cell responses via IL-17 expression.

Molecular characterization of immune responses of Helicoverpa armigera to infection with the mermithid nematode Ovomermis sinensis

BackgroundMermithid nematodes, such as Ovomermis sinensis, display a broad host range including some lepidopteran pests. Infective juveniles penetrate their host through the cuticle, complete their growth within the hemocoel and eventually kill the host upon their emergence. Hence, mermithid nematodes are considered potential biological control agents of insect pests. Our previous data indicate that the infection rate of O. sinensis on cotton bollworm (Helicoverpa armigera) is low, which may be largely due to the strong immune system of the host. However, current knowledge on the interactions of mermithid nematodes with their hosts and the mechanisms employed by hosts to defend themselves against mermithid nematodes is limited.ResultsHere, we investigated the response of H. armigera to O. sinensis infection. Parasitism by O. sinensis caused a sharp decline in the survival rate of H. armigera. The hemocytic phagocytosis ability, antibacterial activity, and phenoloxidase (PO) activity in plasma of H. armigera increased at 1 d post parasitism (dpp) but decreased at 3 dpp. Further, we investigated gene expression in the fat body of parasitized and non-parasitized H. armigera larvae at 1, 3, and 5 dpp using a digital gene expression system. In total, 41, 60 and 68 immune-related differentially expressed genes were identified at 1, 3, and 5 dpp, respectively. These genes encoded pattern recognition receptors (PRRs), antimicrobial peptides (AMPs), serine proteases (SPs), SP inhibitors, mucins and other immune-related proteins. The expression of most PRRs, AMPs, SPs, and mucins was upregulated in the fat body of larvae at 1 dpp, downregulated at 3 dpp, and then again upregulated at 5 dpp by O. sinensis. The increased expression of SP inhibitors may contribute to the inhibited PO activity at 5 dpp.ConclusionsThis study demonstrates that parasitism by O. sinensis modulates the immune reaction of the host H. armigera by altering the expression of immune-related genes. Our data provide a basis for future investigation of the molecular mechanisms employed by the mermithid nematode O. sinensis to modulate the immunity of the host H. armigera. These data will also likely facilitate the improvement of success in parasitism of H. armigera by O. sinensis.

Evidence of an anti-inflammatory toll-like receptor 9 (TLR 9) pathway in adipocytes.

Adipocytes express various pattern recognition receptors (PRRs) such as Toll-like receptors (TLRs) and actively participate in anti-bacterial and anti-viral host defence. Obesity is associated with adipose tissue PRR expression. The potential role of Toll-like receptor 9 (TLR9) in adipocytes has not yet been investigated. Here, we evaluated TLR9 expression during adipocyte differentiation (AD) of 3T3-L1 adipocytes, in primary murine adipocytes and in different murine and human adipose tissue depots by real-time PCR, immunocytochemistry and immunohistochemistry. TLR9 expression was inhibited using specific siRNA-mediated knockdown, and TLR9 signaling was induced using specific class A, B and C agonistic CpG-oligodeoxynucleotide (ODN) treatment vs ODN controls in 3T3-L1 adipocytes and in primary murine adipocytes from Tlr9wt/wt vs Tlr9-/- mice. We found that TLR9 gene expression is induced during AD and that TLR9 protein is expressed in murine gonadal and human visceral adipocytes. AD depends on intact TLR9 expression. Tlr9-/- mice demonstrate significantly reduced adiponectin serum levels, while siRNA-mediated TLR9 knockdown led to reduced adiponectin mRNA expression in adipocytes. TLR9 ligands (CpG-ODNs) inhibit pro-inflammatory resistin secretion in mature 3T3-L1 adipocytes. Tlr9-/- as compared to Tlr9wt/wt adipocytes exhibit increased resistin and MCP1 secretion and reduced adiponectin secretion into cell culture supernatants, while TLR9 ligands (ODNs) show differential effects in Tlr9-/- vs Tlr9wt/wt primary murine adipocytes. TLR9 expression is significantly increased in visceral compared to subcutaneous adipose tissue depots in non-diabetic obese patients and correlates with systemic resistin levels in a compartment-specific manner. Thus, adipocytic TLR9 is a putative, new protective factor during (obesity-associated) adipose tissue inflammation.

Brain Endothelium: The "Innate Immunity Response Hypothesis" in Cerebral Malaria Pathogenesis.

Cerebral malaria (CM) is a life-threatening neurological syndrome caused by Plasmodium falciparum infection afflicting mainly children in Africa. Current pathogenesis models implicate parasite and host-derived factors in impairing brain vascular endothelium (BVE) integrity. Sequestration of Plasmodium-infected red blood cells (iRBCs) in brain microvessels is a hallmark of CM pathology. However, the precise mechanisms driving loss of blood-brain barrier (BBB) function with consequent brain injury are still unsettled and it is plausible that distinct pathophysiology trajectories are involved. Studies in humans and in the mouse model of CM indicate that inflammatory reactions intertwined with microcirculatory and coagulation disturbances induce alterations in vascular permeability and impair BBB integrity. Yet, the role of BVE as initiator of immune responses against parasite molecules and iRBCs is largely unexplored. Brain endothelial cells express pattern recognition receptors (PRR) and are privileged sensors of blood-borne infections. Here, we focus on the hypothesis that innate responses initiated by BVE and subsequent interactions with immune cells are critical to trigger local effector immune functions and induce BBB damage. Uncovering mechanisms of BVE involvement in sensing Plasmodium infection, recruiting of immune cells and directing immune effector functions could reveal pharmacological targets to promote BBB protection with potential applications in CM clinical management.