Endoplasmic reticulum stress regulates immunosuppressive function of myeloid derived suppressor cells in leprosy

Myeloid derived suppressor cells (MDSC) are a heterogeneous population of immature myeloid cells defined by their phenotype along with the ability to suppress adaptive T cell responses. Although MDSC are expanded in response to microbial infection, the factors that regulate the suppressive function of MDSC in this context are not known. Here, we studied MDSC in patients with leprosy, a chronic infectious disease caused by Mycobacterium leprae, in which the clinical manifestations including bacterial load present on a spectrum that correlates with the type of immune response. We found cells with a granulocytic MDSC phenotype are increased in patients across the spectrum of leprosy. However, only MDSC from leprosy patients with disseminated multibacillary infection, not patients with localized paucibacillary disease or healthy controls, suppress M. leprae- specific T cell proliferation and IFN-γ production. An increase in an ER stress gene signature was seen in MDSC from multibacillary patients vs paucibacillary patients. Additionally, the immunosuppressive function of MDSC from multibacillary patients was reversed by either treatment with a free radical scavenger or blockade of interleukin (IL)-10. Conversely, induction of ER stress in MDSC-like cells from paucibacillary patients was sufficient to induce suppressor activity. These studies of human leprosy link multibacillary infection, ER stress and MDSC suppressive function.

IL-34 differentiation of immunosuppressive macrophage

Myeloid cells are necessary for effective immune responses in infection. Myeloid cells enter the skin differentiate into effector myeloid cells, such as macrophages (MΦ). The local and systemic factors responsible for this phenomena are poorly understood. Leprosy provides a human model to study myeloid cells in the skin as exposure of patients to the same pathogen, Mycobacterium leprae, results in distinct disease manifestations. In self-limited, tuberculoid leprosy (T-lep), appropriate monocyte activation results in differentiation into effector M1 MΦ that produce antimicrobial peptides and control M. leprae. In lepromatous leprosy (L-lep), inadequate immune responses fail to clear M. leprae. IL-15 and IL-10 were previously found to promote effector M1 MΦ in T-lep and immunosuppressive M2 MΦ in L-lep patients, respectively, but whether other immunologic factors affect MΦ differentiation in leprosy has not been investigated. Herein, we find IL-34, a cytokine known to drive M2 MΦ development in vitro, is increased in L-lep lesions. Differentiation of monocyte derived MΦ (MDM) with IL-34 results in increased IL-10 production following stimulation with M. leprae when compared to M-CSF derived MDM. Similar to IL-10 derived MDM, IL-34 derived MDM demonstrate increased phagocytic activity, but surprisingly, are able to activate a vitamin D dependent antimicrobial response similar to IL-15 derived MDM. These data indicate that IL-34 drives an alternative pathway of M2 MΦ development. IL-34 MDM produce anti-inflammatory cytokines, but retain the ability to induce antimicrobial responses. These findings raise the potential of IL-34 or IL-34 MDM to treat inflammatory skin disorders while retaining the ability to fight infection.

A phylogenomic study quantifies competing mechanisms for pseudogenization in prokaryotes-The Mycobacterium leprae case

BACKGROUND

Pseudogenes are non-functional sequences in the genome with homologous sequences that are functional (i.e. genes). They are abundant in eukaryotes where they have been extensively investigated, while in prokaryotes they are significantly scarcer and less well studied. Here we conduct a comprehensive analysis of the evolution of orthologs of Mycobacterium leprae pseudogenes in prokaryotes. The leprosy pathogen M. leprae is of particular interest since it contains an unusually large number of pseudogenes, comprising approximately 40% of its entire genome. The analysis is conducted in both broad and narrow phylogenetic ranges.

RESULTS

We have developed an informatics-based approach to characterize the evolution of pseudogenes. This approach combines tools from phylogenomics, genomics, and transcriptomics. The results we obtain are used to assess the contributions of two mechanisms for pseudogene formation: failed horizontal gene transfer events and disruption of native genes.

CONCLUSIONS

We conclude that, although it was reported that in most bacteria the former is most likely responsible for the majority of pseudogenization events, in mycobacteria, and in particular in M. leprae with its exceptionally high pseudogene numbers, the latter predominates. We believe that our study sheds new light on the evolution of pseudogenes in bacteria, by utilizing new methodologies that are applied to the unusually abundant M. leprae pseudogenes and their orthologs.

Generation of a Live Attenuated Influenza Vaccine that Elicits Broad Protection in Mice and Ferrets

New influenza vaccines that provide effective and broad protection are desperately needed. Live attenuated viruses are attractive vaccine candidates because they can elicit both humoral and cellular immune responses. However, recent formulations of live attenuated influenza vaccines (LAIVs) have not been protective. We combined high-coverage transposon mutagenesis of influenza virus with a rapid high-throughput screening for attenuation to generate W7-791, a live attenuated mutant virus strain. W7-791 produced only a transient asymptomatic infection in adult and neonatal mice even at doses 100-fold higher than the LD₅₀ of the parent strain. A single administration of W7-791 conferred full protection to mice against lethal challenge with H1N1, H3N2, and H5N1 strains, and improved viral clearance in ferrets. Adoptive transfer of T cells from W7-791-immunized mice conferred heterologous protection, indicating a role for T cell-mediated immunity. These studies present an LAIV development strategy to rapidly generate and screen entire libraries of viral clones.

Mycobacterium leprae infection disrupts the vitamin D-mediated antibacterial response (INM3P.362)

Leprosy is a debilitating disease caused by infection with Mycobacterium leprae (mLEP). Patients diagnosed with leprosy present on a spectrum of disease characterized by disseminated lepromatous leprosy (L-lep) at one end and self-limiting tuberculoid leprosy (T-lep) at the other end. Previous studies have demonstrated the role of the vitamin D (vit D) system in mediating the antibacterial response to mycobacterial infection; however, it is not understood how dysregulation of the vit D system contributes to disease outcomes. The present study investigates the factors that regulate vit D metabolism and activation in leprosy. Monocytes were infected with mLEP and analyzed for vit D system gene expression and metabolism. In contrast to stimulation with synthetic toll-like receptor 2 (TLR2) ligand, mLEP infection did not induce production of the biologically active form of vit D. Furthermore, gene expression of activating enzyme 1α-hydroxylase (CYP27B1) and vit D receptor (VDR) were not induced by infection. Conversely, treatment with irradiated mLEP induced expression of CYP27B1 and VDR. This suggests that infection does not stimulate the vit D intracrine system in the same manner described for TLR2-sensing of mycobacterial peptides. Instead, infection triggers mechanisms that repress vit D metabolism. Moreover, mLEP-infected T-lep-associated macrophages are resistant to this repression. This study highlights the role of the vit D system in the host response to mLEP infection.

Physiologic stress molecules activate an acute phase response and enhance macrophage antimicrobial activity to Mycobacterium leprae (INM3P.411)

Leprosy is a disease caused by the pathogen Mycobacterium leprae (mLEP). Patients can present with the progressive, lepromatous form of the disease or the self-limited, tuberculoid form of the disease. Physiologic stress is thought to inhibit host defense mediated by adrenergic catecholamines and neuroendocrine glucocorticoids. We hypothesize that acute treatment with adrenergic agents or glucocorticoids would inhibit in vitro macrophage mediated antimicrobial activity. Human monocyte-derived macrophages or mouse bone marrow-derived macrophages were treated with the adrenergic agonist metaproterenol hemisulfate (MPH, 1μM) or the glucocorticoid dexamethasone (Dex, 100nM) for two hours followed by LPS (100ng/ml) or mLEP (MOI 5). RNASeq was performed at various time points or an mLEP viability measurement was performed at 24 hours following infection. Unexpectedly, when compared to vehicle (DMSO), pretreatment with MPH resulted in greatly enhanced antimicrobial activity against mLEP, similar to interferon-γ pretreatment, whereas Dex resulted in a more modest induction of antimicrobial activity. Both Dex and MPH did not reduce the expression of the antimicrobial peptide cathelicidin, but did induce a dramatic increase in expression of genes involved in the acute phase response. Our findings suggest that molecules involved in the physiological stress response may be acutely beneficial during initial encounter with mLEP.

BCG-treated M2-macrophages enhance IFN-γ production of T cells (P3348)

M1- and M2-polarized Macrophage (MΦ) subtypes differentially regulate anti-mycobacterial defense. To examine their roles in human infection, we compared the gene expression profile of M1- vs. M2-MΦ to the expression profile of lesional skin from patients with restricted (tuberculoid, T-lep) vs. disseminated (lepromatous, L-lep) leprosy (a mycobacterial skin infection). Rank-Rank Hypergeometric Overlap (RRHO) is a novel algorithm for comparing full gene expression profiles from two independent microarray experiments that generates the most statistically significant overlapping gene list without requiring strict p-value/fold change cutoffs. RRHO analysis showed significant overlap of genes between M2-MΦ and L-lep lesions (n = 1559, max log hypergeometric p-value = 196), indicating a role for M2-MΦ in immune unresponsiveness. Bacillus Calmette-Guerin (BCG) is given to protect household contacts against leprosy. We hypothesized that BCG treatment may affect the function of M2-MΦ and investigated its effects in vitro. We found that BCG-treated M2-MΦ secreted less IL-10 (p < 0.05), with no effect on IL-12p40, compared to untreated M2-MΦ. In addition, BCG-treated M2-MΦ increased the frequency of IFN-γ producing cells in an antigen non-specific manner (p < 0.05), suggesting an adjuvant effect of BCG. Our data indicates M2-MΦ can be reprogrammed by BCG, resulting in increased IFN-γ production to enhance anti-mycobacterial immunity.

MicroRNAs induced during Mycobacterium leprae infection and their effects on immune response (P3019)

MicroRNAs have been shown to be crucial in regulation of immune cell development and cancer progression. Recently, it has become increasingly clear that their involvement in regulation of immune responses to infection is also important. Here we use Mycobacterium leprae, the causative agent of leprosy, as a model to determine the potential roles of microRNAs in infectious disease. The immune response to M. leprae has been well-characterized as presenting as a spectrum, ranging from a contained infection characterized by a Th1 response in tuberculoid (T-lep) patients to a disseminated infection reflecting a Th2 response in lepromatous (L-lep) patients. We performed mRNA and microRNA microarray analysis on 6 T-lep and 4 L-lep lesions and subsequently integrated this data using Ingenuity. Preliminary gene network analysis of differentially expressed microRNAs in L-lep versus T-lep yielded multiple networks potentially targeted, including antigen presentation. A supervised analysis of Th1 and Th2 gene targeting indicates that microRNAs more highly expressed in L-lep lesions, such as miR-21 and miR-146a, may preferentially target proinflammatory genes required for a Th1 immune response. Further analysis to determine the functional effects of these microRNAs and their involvement in skewing towards a Th2 immune response to infection could explain the bias in disease outcome.

Identification of PE/PPE epitopes of Mycobacterium leprae recognized by peripheral blood mononuclear cells in leprosy (P3332)

Leprosy, a chronic disease caused by the intracellular pathogen Mycobacterium leprae (M leprae), is a major health concern. Mycobacterial PE/PPE proteins may play a role in the interface of host-pathogen interaction and disease development. However, it remains unclear how the immune system recognizes those proteins and their components. Here, we have employed an Internet online-based tool called immune epitope database analysis resource (http://tools.iedb.org) to predict and analyze epitopes of M. leprae PE/PPE proteins. Thirteen candidate T cell epitopes were identified with a potential to bind a broad range of MHC class II haplotypes. Using ELISA, we found that 7/13 of predicted epitopes stimulated IFN-γ production in peripheral blood mononuclear cells (PBMCs) of tuberculoid or reversal reaction leprosy patients but not healthy donors. Among them, ML0588 (7-21) exhibited the broadest stimulatory capacity, eliciting IFN-γ production by PBMCs in 4/7 patients. Taken together, we have utilized the immune epitope database to identify seven peptides encoded by M. leprae PE/PPE proteins as strong candidate T cell epitopes for the induction of IFN-γ production in leprosy patients. These findings suggest that T cell recognition of these proteins may contribute to host defense against leprosy and be of potential use in a diagnostic test for leprosy.

Type I IFN suppresses Type II IFN triggered antimicrobial responses in humans (P1277)

The mechanism by which Type I IFNs contribute to immune suppression in bacterial infections in humans was investigated by studying leprosy as a model. The Type I IFN, IFN-β, as well as an inducible regulatory pathway involving sequential induction of IL-10 were differentially expressed in progressive lepromatous (L-lep) vs. the self-limited tuberculoid (T-lep) lesions. A common IFN-β gene signature was detected in the peripheral blood of active tuberculosis patients and the skin lesions of L-lep patients, with approximately half of the common IFN-β induced genes also induced by IL-10. Contrary to the expression of Type I IFNs and inducible genes, the Type II IFN, IFN-γ, and downstream genes that comprise antimicrobial pathways were differentially expressed in T-lep vs. L-lep lesions. The IFN-γ-induced macrophage antimicrobial response was inhibited by IFN-β and IL-10, by a mechanism involving blocking the generation of bioactive 1,25-dihyroxyvitamin D as well as inhibiting induction of antimicrobial peptides cathelicidin and DEFB4. Together, these data identify the ability of IFN-β to induce IL-10 as a mechanism by which Type I IFNs inhibit Type II IFN induced host defense pathways and thereby contribute to the pathogenesis of bacterial infections in humans.

DDX41 recognizes bacterial secondary messengers cyclic di-GMP and cyclic di-AMP to activate a type I interferon immune response (P1375)

Cytosolic detection of bacterially derived secondary messengers cyclic-di-GMP (c-di-GMP) or cyclic -di-AMP (c-di-AMP) by the host immune system activates an innate immune response characterized by the induction of type I interferons (IFNs). Induction of IFN by c-di-GMP or c-di-AMP has been shown to be dependent on a stimulator of IFN genes-TANK binding kinase 1-IFN regulatory factor 3 (STING-TBK1-IRF3) signaling axis. Although STING has been shown to interact with c-di-GMP, an upstream sensor of these cyclic dinucleotides is unknown. Here we identify the helicase, DEAD (Asp-Glu-Ala-Asp) box polypeptide 41 (DDX41) as the pattern recognition receptor (PRR) that senses both c-di-GMP and c-di-AMP. DDX41 specifically and directly interacts with c-di-GMP. Knockdown of DDX41 via shRNA in murine or human immune cells inhibits the induction of innate immune genes and results in defective STING, TBK1 and IRF3 activation in response to c-di-GMP or c-di-AMP. Our findings suggest a mechanism whereby c-di-GMP and c-di-AMP molecules are detected by the DDX41 PRR, which complexes with the STING adaptor to signal to TBK1-IRF3 and activate the IFN response.

Racial disparities in the vitamin D-mediated innate immune response following supplementation (P3379)

We have previously demonstrated that innate (Toll-like receptor 2/1) and adaptive (IFN-γ) immune signals converge on a common vitamin D-dependent antimicrobial pathway in the human macrophage against Mycobacterium tuberculosis, including activation of CYP27B1 which converts 25D into the active 1,25D hormone as well as expression of antimicrobial peptides cathelicidin and human beta defensin 4. This antimicrobial activity is dependent on the level of extracellular 25D in culture. Therefore, we asked if this antimicrobial response could be recapitulated using sera from 25D deficient subjects before and after vitamin D repletion of the host in vivo. Serum has been collected prospectively from 67 Hispanic/Latino, 12 black and 21 non-Hispanic white, vitamin D-insufficient/deficient (8-29 ng/ml) before and after treatment with 500,000 IU vitamin D3. The mean total serum 25D in all three ethnic groups was 20ng/ml before and rose significantly (p<0.001) after vitamin D3 repletion, with a mean fold-change of 2.0, 2.9 and 3.0 in white, Hispanic and blacks, respectively. Despite the most substantial rise in total 25D in the minority populations, the ability of the sera from white donors to increase IFN-γ-stimulated macrophage cathelicidin was 3-fold (p<0.01) and 2-fold greater (p<0.05) than in cells conditioned in African and Hispanic/Latino American sera, respectively. These data suggest an ethnic/racial disparity in response to vitamin D supplementation.

Investigating how bacteriophages influence the human immune response to Propionibacterium acnes (P3148)

Numerous lines of evidence implicate the Gram-positive skin commensal, Propionibacterium acnes, in the pathogenesis of acne vulgaris, in part by eliciting a host inflammatory response. The emergence of antibiotic resistance in up to 60% of P. acnes isolates, along with the adverse side effects of current treatments has highlighted the need for the development of safer and more effective anti-acne therapeutics. We have investigated the bacteriophages that infect and kill P. acnes and found that they have limited genetic diversity and broad host ranges against clinical isolates, pointing to the potential utility of a phage-based acne treatment. Here, we explored whether these phages, by lysing P. acnes, influence the human immune response to the bacteria. Human monocytes were cultured in the presence of phage-killed or live bacteria, and cytokine responses were measured. We found that monocytes cultured with phage-killed bacteria secrete lower levels of pro-inflammatory cytokines, such as TNFα, IL-1β and IL-12p40, as compared to those infected with live bacteria; phage alone did not stimulate a response. This pattern was also observed when phage and bacteria were added concurrently, that is, during active phage infection, and in all cases, this was consistent across multiple donors. These data suggest that bacteriophage-mediated killing of P. acnes bacteria could help to ameliorate the inflammation associated with acne as a therapeutic modality.

Viral Infection Triggers Rapid Differentiation of Human Blood Monocytes into Dendritic Cells (45.12)

Viruses post a constant threat of human existence. Although human immune system plays a central role in recognizing and eradicating pathogens, how it responds to virus infection remains unclear. Here we show that monocytes make up the majority of a wide variety of virus susceptible population in human peripheral blood mononuclear cells. Notably, infection with influenza virus, vesicular stomatitis virus and vaccinia virus promotes monocytes to differentiate within 18 hours into CD16-negative CD83-positive mature dendritic cells (DCs) with enhanced capacity to activate T cells. Virus-induced monocyte differentiation into DCs does not require cell division, and happens despite the synthesis of virus proteins, suggesting that monocytes thwart the capacity of these highly lytic viruses to hijack host cell biosynthesis pathway. Indeed, virus-induced DC differentiation from monocytes requires infectious virus and viral protein synthesis. Thus, our results demonstrate that monocytes are uniquely susceptible to virus infection among human peripheral blood mononuclear cells, with the likely purpose of differentiating into DCs with enhanced capacity to activate innate and acquired anti-virus immunity.

Role of microRNAs in immune response to infection (112.18)

Regulation of microRNAs has been shown to be critical in immune cell development as well as the progression of certain cancers. However, their role in immune response to microbial infection has remained elusive. We chose to use Mycobacterium leprae, the causative agent of leprosy, as a model to determine the potential roles of microRNA in pathogenesis. The immune response to M. leprae has been well-characterized as presenting as a spectrum, ranging from a more contained Th1 response in tuberculoid patients to a more disseminated Th2 response in lepromatous patients, providing a good system for examining the correlation of microRNAs and type of immune response. We performed mRNA and microRNA microarray analysis on 6 T-lep and 6 L-lep lesions to determine whether microRNA disregulation and subsequent downregulation of key immune genes contributes to the outcome and morbidity of infection. We discovered 7 microRNAs in T-lep and 28 microRNAs in L-lep lesions and cross-referenced them in MiRNA and Genes Integrated Analysis (MAGIA) web tool with mRNA gene transcripts that were significantly downregulated in the same lesions. Preliminary analysis of Th1 and Th2 gene targeting shows microRNAs more highly expressed in L-lep lesions may preferentially target proinflammatory genes, which could explain the bias in immune response to infection.

IFN-γ induced antimicrobial response against M. leprae in human macrophages (117.12)

The role of IFN-γ in inducing an antimicrobial response in macrophages was investigated in leprosy, a disease caused by intracellular bacterium M. leprae. Tuberculoid leprosy (T-lep) is characterized by few skin lesions with low bacterial numbers, whereas lepromatous leprosy (L-lep) is characterized by disseminated skin lesions and increased bacilli numbers. The host immune response in T-lep is characterized by Th1 cytokines and expression of the vitamin D dependent antimicrobial pathway, in contrast to L-lep, which is predominately Th2. We have linked expression of the Th1 cytokine IFN-γ and antimicrobial response in leprosy by induction of vitamin D dependent antimicrobial response genes CAMP and DEFB4. IFN-γ is present in T-lep patients, where the disease is self-limited, however, the role of IFN-γ in antimicrobial activity is unclear. IFN-γ mediates antimicrobial activity against M. tuberculosis, a related pathogen, in the presence of vitamin D sufficient serum, but not in the presence of vitamin D deficient serum. Our preliminary data shows that M. leprae infected macrophages pretreated with IFN-γ prior to infection in combination with post-infection IFN-γ treatment in vitamin D sufficient serum reduced bacterial viability by approximately 80% compared to media control. Our studies suggest that IFN-γ can trigger a vitamin D dependent antimicrobial response in human macrophages as well as antimicrobial activity against M. leprae.

Identification of novel small molecule inducers of endothelium-driven innate immunity (54.10)

The endothelium plays a critical role in promoting inflammation in cardiovascular disease and other chronic inflammatory conditions. Conversely, an augmented immune response can be protective against microbial pathogens and in cancer immunotherapy. Many small molecule screens have sought to identify agents that prevent endothelial cell activation. Yet, small molecule screens to identify agents that induce endothelial cell activation have not been reported. In this regard, a bioassay was developed which identifies activated endothelium by its capacity to trigger MIP1 beta from primary monocytes. Subsequently, a 642 compound library of 39 distinctive scaffolds generated by diversity oriented synthesis was screened for small molecules that activated the endothelium. From the identified inflammatory compounds, 96 analogs of one particular class of compounds were efficiently prepared by solid phase split-and-pool synthesis. Structure-function analysis combined with transcriptional profiling of active and inactive analogues identified inflammatory gene networks induced exclusively by the active compound. The identification of a family of chemical probes that augment innate immunity through endothelial cell activation provides a framework for understanding gene networks involved in endothelial inflammation as well as the development of novel endothelium-driven immunotherapeutic agents.

MicroRNA-21 targets the vitamin D-dependent antimicrobial pathway in leprosy (147.12)

Leprosy is a human disease in which the clinical manifestations correlate with the host immune response to the pathogen, Mycobacterium leprae. In tuberculoid (T-lep) patients the infection is localized and Th1 cytokines predominate in lesions; whereas, in lepromatous patients (L-lep) the infection is disseminated and Th2 cytokines predominate. Evidence also suggests a role for the vitamin D-dependent antimicrobial pathway in contributing to host defense in leprosy. By profiling miRNAs in leprosy lesions, we identified 13 miRNAs differentially expressed in L-lep vs. T lep lesions. Bioinformatic analysis revealed a significant enrichment of L-lep-specific miRNAs that preferentially target genes important in T-lep lesions, including twelve Th1 and antimicrobial pathway genes. The most differentially expressed miRNA in L-lep lesions, hsa-mir-21, was upregulated in M. leprae-infected monocytes and induced by the mycobacterial virulence factor phenolic glycolipid-I (PGL-I). Hsa-mir-21, by downregulating Toll-like receptor induced CYP27B1 and IL1B and upregulating IL-10, inhibited the vitamin D-dependent antimicrobial peptide gene expression. In contrast, knockdown of hsa-mir-21 in M. leprae-infected monocytes enhanced antimicrobial peptide gene expression. The ability of the pathogen to upregulate hsa-mir-21 which targets multiple genes associated with the immunologically localized disease form provides an effective mechanism to escape the vitamin D antimicrobial pathway.

Role of host lipid metabolism and tissue macrophages in psoriasis (147.30)

Epidemiologic studies and clinical co-morbidity suggests a link between psoriasis and atherosclerosis. These conditions share common inflammatory mediators, including macrophage (Mp) signaling and the presence of oxidized low-density lipoprotein (LDL). We examined the role of lipid metabolism and tissue Mp in psoriasis. Using immunohistochemistry on psoriatic tissue, we identified a subpopulation of CD209+/CD163+ dermal Mp which have phagocytic properties and are capable of engulfing oxidized lipids. Next, using gene-expression arrays, we examined the effect of oxidized lipids on Mp signaling. Treatment of THP-1 Mp with a component of minimally oxidized LDL induced the expression of interleukins-1, -6, -15, -17, -23, cathelicidin and vascular endothelial growth factor, all of which play a role is psoriasis. Lastly, we examined the properties of high-density lipoprotein (HDL) in serum from psoriatic patients. In healthy patients, HDL is capable of reverse cholesterol transport and has potent anti-inflammatory properties. In patients with systemic inflammatory disease, including atherosclerosis, HDL loses these properties and becomes dysfunctional. Using a well-established model of monocyte chemotaxis as well as an in-vitro model of IL-23 production, both as markers of inflammation, we demonstrated that HDL from psoriatic patients was dysfunctional and had pro-inflammatory properties. Taken together, these data provide a role for tissue Mp and host lipid metabolism in psoriasis

Activation of NOD2 induces an IL-32 regulated dendritic cell program in leprosy (111.22)

The ability of the innate immune system to recognize and respond to microbial pathogens is determined by the interaction of microbial ligands with host receptors located in specific cellular compartments. For Mycobacterium leprae, tricaylated lipoproteins are recognized by cell surface TLR2/1 and muramyl dipeptide (MDP) by intracellular NOD2. The association of NOD2 polymorphisms with susceptibility to leprosy led us to hypothesize that activation of NOD2 regulates key innate immune host defense pathways in leprosy. We first examined gene expression profiles of monocytes stimulated with NOD2 ligand (MDP) or TLR2/1 ligand (19kD) and compared them to those found in lesions of tuberculoid (T-lep) vs. lepromatous (L-lep) leprosy. NOD2 activation and T-lep lesions are both characterized by DC gene programs. NOD2 activation induces differentiation into CD1b+ DC that are potent antigen presenting cells compared to TLR2/1L-triggered DC. Gene expression analysis and gene knockdown experiments revealed that NOD2-induced DC differentiation is regulated by IL-32. Furthermore, NOD2L activation of monocytes from L-lep patients show reduced induction of IL-32 and CD1b+ DC; however, CD1b expression is rescued by the addition of exogenous IL-32. In conclusion, we provide evidence that NOD2L induces a IL-32-regulated DC program in monocytes, with relevance to the pathogenesis and therapeutic intervention in infectious diseases such as leprosy.

IL-17 is essential for host defense against cutaneous Staphylococcus aureus infection (37.50)

Although neutrophil recruitment is required for immunity against Staphylococcus aureus, a role for T cells has been suggested based on the increased susceptibility of humans who have altered T cell immune responses to S. aureus cutaneous infections. Here, the contribution of T cells to host defense was investigated in a mouse model of S. aureus cutaneous infection. Mice deficient in γδ but not αβ T cells had substantially larger skin lesions with higher bacterial counts and impaired neutrophil recruitment compared with wild-type mice. This neutrophil recruitment was dependent upon epidermal Vγ5+ γδ T cell production of IL-17 but not IL-21 and IL-22. Further, IL-17 induction required IL-1, TLR2 and IL-23 and was critical for host defense, since IL-17R-deficient mice had a similar phenotype as γδ T cell-deficient mice. Importantly, γδ T cell deficient mice treated with a single dose of recombinant IL-17 had lesion sizes and bacterial counts that resembled wild-type mice, demonstrating that IL-17 can restore the impaired immunity in γδ T cell deficient mice. This study defines a novel role for IL-17-producing epidermal γδ T cells in innate immunity against S. aureus.

Triggering human TLR2/1-induces distinct IL-1β- and VDR-dependent antimicrobial peptides required for host defense β (135.42)

Activation of Toll-like receptor 2/1 (TLR2/1) on human monocytes induces a vitamin D receptor (VDR) dependent antimicrobial pathway against intracellular mycobacteria, involving the induction of the antimicrobial peptide cathelicidin. Here, we demonstrate a novel TLR-induced antimicrobial pathway leading to induction of DEFB4, requiring synergy between IL-1β- and VDR- dependent transcriptional activation. Strikingly, TLR2/1 induction of DEFB4, but not cathelicidin required IL-1β activity despite both requiring VDR activation. TLR2/1L activation triggered the upregulation of both IL-1β and IL-1 receptor, and downregulation of the IL-1 receptor antagonist. The differential requirements for induction of DEFB4 and cathelicidin were reflected by differences in their respective promoter regions, the DEFB4 promoter had one vitamin D response element (VDRE) and two NF-κB sites, whereas the cathelicidin promoter had three VDREs and no NF-κB sites. Transfection of NF-κB into primary monocytes synergized with 1,25D3 in activating DEFB4 but not cathelicidin. Knockdown of either DEFB4 or cathelicidin resulted in the loss of TLR2/1-mediated antimicrobial activity against intracellular mycobacterial infection in primary monocytes. Therefore, these data identify a novel mechanism of host defense requiring the induction of IL-1β in synergy with vitamin D activation, for TLR-induced antimicrobial pathway against intracellular pathogens.

Characterization of foam cell formation in human macrophage subsets (95.17)

The hallmark of the human atherosclerotic plaque is the presence of lipid-laden macrophages, or foam cells. However, many macrophage subsets are found within atherosclerotic lesions and it is not well understood how monocytes differentiate into these subsets. We focused on characterizing macrophages derived in vitro from human peripheral blood monocytes treated with IL-15, IL-4 or IL-10. We show these macrophages to have differing phenotypes: CD209+CD64+, CD209+CD23+, or CD209+CD163+ for macrophages derived from IL-15, IL-4, or IL-10 respectively. To characterize the macrophage subsets ability to become foam cells we measured their uptake of fluorescently-labeled oxidized LDL (oxLDL). IL-10 derived macrophages had the greatest amount of oxLDL uptake. We then investigated the mechanism of uptake and found that fucoidan, a class-A scavenger receptor competitor, significantly inhibited uptake of oxLDL in IL-10 cells. On the other hand a blocking antibody against the class B scavenger receptor, CD36, did not inhibit uptake. Furthermore, we found IL-10 macrophages to express higher mRNA levels of the class A scavenger receptors macrophage receptor with collagenous structure (MARCO) and macrophage scavenger receptor (MSR) expression. These data suggests that IL-10 may promote foam cell formation and is dependent on class-A, but not class B scavenger receptors.

Granulysin crystal structure and a structure-derived lytic mechanism

Our crystal structure of granulysin suggests a mechanism for lysis of bacterial membranes by granulysin, a 74-residue basic protein from human cytolytic T lymphocyte and natural killer cells. We determined the initial crystal structure of selenomethionyl granulysin by MAD phasing at 2A resolution. We present the structure model refined using native diffraction data to 0.96A resolution. The five-helical bundle of granulysin resembles other "saposin folds" (such as NK-lysin). Positive charges distribute in a ring around the granulysin molecule, and one face has net positive charge. Sulfate ions bind near the segment of the molecule identified as most membrane-lytic and of highest hydrophobic moment. The ion locations may indicate granulysin's orientation of initial approach towards the membrane. The crystal packing reveals one way to pack a sheet of granulysin molecules at the cell surface for a concerted lysis effort. The energy of binding granulysin charges to the bacterial membrane could drive the subsequent lytic processes. The loosely packed core facilitates a hinge or scissors motion towards exposure of hydrophobic surface that we propose tunnels the granulysin into the fracturing target membrane.

IRF3 mediates a TLR3/TLR4-specific antiviral gene program

We have identified a subset of genes that is specifically induced by stimulation of TLR3 or TLR4 but not by TLR2 or TLR9. Further gene expression analyses established that upregulation of several primary response genes was dependent on NF-kappaB, commonly activated by several TLRs, and interferon regulatory factor 3 (IRF3), which was found to confer TLR3/TLR4 specificity. Also identified was a group of secondary response genes which are part of an autocrine/paracrine loop activated by the primary response gene product, interferon beta (IFNbeta). Selective activation of the TLR3/TLR4-IRF3 pathway potently inhibited viral replication. These results suggest that TLR3 and TLR4 have evolutionarily diverged from other TLRs to activate IRF3, which mediates a specific gene program responsible for innate antiviral responses.

The A' and F' pockets of human CD1b are both required for optimal presentation of lipid antigens to T cells

CD1 proteins are unique in their ability to present lipid Ags to T cells. Human CD1b shares significant amino acid homology with mouse CD1d1, which contains an unusual putative Ag-binding groove formed by two large hydrophobic pockets, A' and F'. We investigated the function of the amino acid residues that line the A' and F' pockets of CD1b by engineering 36 alanine-substitution mutants and analyzing their ability to present mycobacterial glycolipid Ags. Two lipid Ags presented by CD1b were studied, a naturally occurring glucose monomycolate (GMM) isolated from mycobacteria, which contains two long alkyl chains (C54-C62 and C22-C24) and synthetic GMM (sGMM), which includes two short alkyl chains (C18 and C14). We identified eight residues in both the A' and F' pockets that were involved in the presentation of both GMM and sGMM to T cells. Interestingly, four additional residues located in the distal portion of the A' pocket were required for the optimal presentation of GMM, but not sGMM. Conversely, nine residues located between the center of the groove and the F' pocket were necessary for the optimal presentation of sGMM, but not GMM. These data indicate that both the A' and F' pockets of human CD1b are required for the presentation of lipid Ags to T cells.

Overexpression of CD1d by keratinocytes in psoriasis and CD1d-dependent IFN-gamma production by NK-T cells

The MHC class I-like protein CD1d is a nonpolymorphic molecule that plays a central role in development and activation of a subset of T cells that coexpress receptors used by NK cells (NK-T cells). Recently, T cells bearing NK receptors were identified in acute and chronic lesions of psoriasis. To determine whether NK-T cells could interact with epidermal cells, we examined the pattern of expression of CD1d in normal skin, psoriasis, and related skin disorders, using a panel of CD1d-specific mAbs. CD1d was expressed by keratinocytes in normal skin, although expression was at a relatively low level and was generally confined to upper level keratinocytes immediately beneath the lipid-rich stratum corneum. In contrast, there was overexpression of CD1d in chronic, active psoriatic plaques. CD1d could be rapidly induced on keratinocytes in normal skin by physical trauma that disrupted barrier function or by application of a potent contact-sensitizing agent. Keratinocytes displayed enhanced CD1d following exposure to IFN-gamma. Combining CD1d-positive keratinocytes with human NK-T cell clones resulted in clustering of NK-T cells, and while no significant proliferation ensued, NK-T cells became activated to produce large amounts of IFN-gamma. We conclude that CD1d can be expressed in a functionally active form by keratinocytes and is up-regulated in psoriasis and other inflammatory dermatoses. The ability of IFN-gamma to enhance keratinocyte CD1d expression and the subsequent ability of CD1d-positive keratinocytes to activate NK-T cells to produce IFN-gamma, could provide a mechanism that contributes to the pathogenesis of psoriasis and other skin disorders.

Evidence of enhanced type 2 immune response and impaired upregulation of a type 1 response in frail elderly nursing home residents

Peripheral blood mononuclear cells (PBMC) of frail elderly nursing home residents had significantly higher PHA-induced interleukin-10 (IL-10) production compared to PBMC's from young control subjects. No correlation was observed between IL-10 production and interleukin-12 (IL-12) p40 production, proliferative response or with the proportion of CD28-negative T cells. To better characterize the host response to a ubiquitous pathogen, the dose response and time-dependent (kinetic) production of IL-10 and IL-12 p40 of PBMC stimulated with Staphylococcus aureus Cowan (SAC) was studied. IL-10 production continued to increase at 48 h, while IL-12 p40 levels declined or remained stable, in both young and elderly subjects. In analyzing how excessive IL-10 production might influence antigen presenting cell functions, IL-12 was markedly inhibited by recombinant IL-10 (rIL-10), while anti-IL-10 enhances IL-12 p40 production in cultures from young controls; but the PBMC cultured from an elderly cohort were not able to generate similar absolute levels of IL-12 p40 even in the presence of anti-IL-10. These preliminary data suggest that there may be both over production of IL-10 in some individuals, as well an an impaired ability to upregulate a T Helper 1 (type 1) reaction. These age-related changes could even be more dramatic at the tissue level and contribute to the impaired delayed type hypersensitivity (DTH) and failed host defense to infection, such as to primary and reactivation tuberculosis.

Human non-small cell lung cancer cells express a type 2 cytokine pattern

In addition to infiltrating inflammatory cells, tumors also produce cytokines and growth factors that may alter tumor growth, tumor immunogenicity, and the host immune response. To characterize the expression profile of human non-small cell lung cancer (NSCLC)-derived cytokines, the mRNA expression of type 1 and type 2 cytokines in five human NSCLC lines was analyzed by reverse transcriptase-PCR. Expression of interleukin 5 (IL-5) and IL-10 was demonstrated in all tumor lines evaluated, whereas IL-4 was present in three of five lines and IL-13 was present in two of five lines. In contrast, none of the tumor lines expressed IL-2 and IFN-gamma. Type 2 cytokine protein production by NSCLC lines was confirmed by immunoprecipitation and cytokine specific ELISA. Tumor-derived IL-10 secretion was significantly augmented by exogenous recombinant cytokines including IL-4 and tumor necrosis factor-alpha. To evaluate whether fresh NSCLC nodules also express a type 2 cytokine pattern, the content of type 1 and type 2 cytokines in tissue homogenates from 13 fresh NSCLC nodules and normal lung surgical specimens was assessed. Human NSCLC nodules contain significantly more type 2 cytokines than does normal lung tissue when corrected for total protein concentration. To identify the cellular source of type 2 cytokine production in tumor nodules, immunohistology was performed on sections from 5 lung squamous cell carcinomas and 5 adenocarcinomas. All of the specimens revealed positive staining for type 2 cytokines within tumor cells. In summary, we report that human NSCLC cells produce type 2 cytokines both in situ and in vitro, which may play an active immunoregulatory role in the lung cancer microenvironment.

A MYSID SHRIMP CARRYING A PAIR OF BINOCULARS

Like other mysid shrimps, the tropical shallow-water species Dioptromysis paucispinosa possesses compound eyes of the refracting superposition type. In the rear of each eye, pointing backwards, is a single conspicuous facet almost three times the diameter of those in the rest of the eye. Underlying the large facet is an equally enlarged single crystalline cone, projecting an upright image onto a specialized retina of 120 densely packed and extremely narrow rhabdoms. This peculiar arrangement constitutes an acute zone which operates as a simple eye within a compound eye. Calculations of spatial sampling frequency and photon catch indicate that the centre of the acute zone resolves more than six times better than the normal eye, but it requires intensities more than a log unit higher ­ figures not unlike those of modern compact binoculars. The fact that the acute zone covers a visual field of 15­20°, with a large binocular overlap, strengthens the analogy with a pair of binoculars. The resolution of the acute zone is also remarkable in absolute terms: a rhabdom axis separation of 0.64° rivals foveal vision in large insects, although the entire eye of Dioptromysis measures only 0.4 mm. With the normal posture of the shrimp, the acute zone points backwards, about 12° above the horizon. Difficulties in understanding the animal's use of such an acute zone were resolved by the discovery of large coordinated eye movements. The eyestalk can be rotated around its axis by at least 130°. This makes the acute zone aim forwards and upwards, which is a more sensible direction for spotting and pursuing prey. The acute zone is probably held in the rest position aiming backwards only to avoid having an important part of the forward visual field constantly occupied by an eye region of inferior sensitivity.

Expression of the thymus leukemia antigen in mouse intestinal epithelium

The Qa and Tla regions of the mouse major histocompatibility complex contain a series of genes encoding proteins with structural similarity to the class I transplantation antigens of the same complex. In contrast to the genes encoding the transplantation antigens, the Qa and Tla genes show very little polymorphism. Function(s) of the proteins encoded by the Qa and Tla loci remain an enigma. Recently, the protein products of the Qa and Tla loci, often referred to as class Ib major histocompatibility complex molecules, have been proposed to present antigen to gamma delta T cells. In mice, gamma delta T cells have been found concentrated in several epithelial barriers and in the skin; yet, expression of serologically detectable Tla antigens is believed restricted to thymocytes, activated T lymphocytes, and some T-cell leukemias. Here we report that luminal epithelial cells of the mouse small intestine express the thymus leukemia antigen (TLA). We also find that, unlike T cells in Peyer's patches, a significant fraction of intestinal epithelial lymphocytes also express TLA. RNA prepared from intestinal cells contains transcripts of the T18d gene, which encodes TLA. These data extend the known expression profile of TLA molecules to mature lymphocytes and to nonhematopoietic cells. These data also demonstrate the specific expression of TLA on antigen-presenting cells in a site enriched for T cells that express gamma delta T-cell antigen receptor.

On the mechanism of human T cell suppression

Previous evidence from several laboratories suggests that CD8+ T suppressor cells may be important regulatory elements governing specific unresponsiveness of lepromatous lepromatous leprosy patients to M.leprae. To analyse the mechanism of suppression, CD8+ Ts clones were established from lesions and peripheral blood of lepromatous patients and tested for ability to suppress antigen-responsive CD4+. Th clones or PBL. Suppression required induction by specific M.leprae antigen, but was effected in an antigen-non-specific fashion. The Ts clones failed to exhibit cytotoxicity of four antigen-exposed MHC-matched target cells: (i) an ori-SV40 transformed macrophage line; (ii) EBV transformed B cell lines; (iii) primary macrophages; and (iv) M.leprae responsive CD4+ cells. The possibility that Ts clones induce functional inactivation of CD4+ clones in vitro was investigated. M.leprae-responsive CD4+ clones were preincubated with Ts CD8+ clones, APC, and antigen for 16 h, after which the CD8+ cells were removed. The CD4+ clones with M.leprae and APC remained unresponsive to restimulation with APC and antigen for at least 10 days, although they responded to IL-2. Addition of IL-2 to the pre- or post-incubation cultures neither prevented the induction of unresponsiveness, nor reversed it. Earlier models of tolerance have suggested that receptor occupancy in the absence of second signals induces tolerance in B and T cells. Under conditions in which antigen responses of Th clones were HLA-DR-restricted, the Ts clones were able to suppress the response of DR mismatched Th clones. Thus, the effect of the Ts cells, like mechanisms requiring antigen presentation without a second signal, appears to be induction of clonal anergy in Th cells, perhaps by a novel mechanism.