Monocyte chemotactic protein-1 stimulates the killing of leishmania major by human monocytes, acts synergistically with IFN-gamma and is antagonized by IL-4

Chemokines: A key driver for inflammation in protozoan infection

Chemokines belong to the group of small proteins within the cytokine family having strong chemo-attractant properties. In most cases, the strong immuno-modulatory role of chemokines is crucial for generating the immune response against pathogens in various protozoan diseases. In this review, we have given a brief update on the classification, characterization, homeostasis, transcellular migration, and immuno-modulatory role of chemokines. Here we will evaluate the potential role of chemokines and their regulation in various protozoan diseases. There is a significant direct relationship between parasitic infection and the recruitment of effector cells of the immune response. Chemokines play an indispensable role in mediating several defense mechanisms against infection, such as leukocyte recruitment and the generation of innate and cell-mediated immunity that aids in controlling/eliminating the pathogen. This process is controlled by the chemotactic movement of chemokines induced as a primary host immune response. We have also addressed that chemokine expressions during infection are time-dependent and orchestrated in a systematic pattern that ultimately assists in generating a protective immune response. Taken together, this review provides a systematic understanding of the complexity of chemokines profiles during protozoan disease conditions and the rationale of targeting chemokines for the development of therapeutic strategies.

The cytokine/chemokine response in Leishmania/HIV infection and co-infection

HIV infection progressively weakens the immune system by infecting and destroying cells involved in host defense. Viral infection symptoms are generated and aggravated as immunosuppression progresses, triggered by the presence of opportunistic infections: among these is leishmaniasis, a disease caused by the intracellular parasite Leishmania. The incidence of this co-infection is growing progressively due to the geographic distribution overlap. Both pathogens infect monocytes/macrophages and dendritic cells, although they can also modulate the activity of other cells without co-infecting, such as T and B lymphocytes. Leishmania/HIV co-infection could be described as a system comprising modulations of cell surface molecule expression, production of soluble factors, and intracellular death activities, leading ultimately to the potentiation of infectivity, replication, and spread of both pathogens. This review describes the cytokine/chemokine response in Leishmania/HIV infection and co-infection, discussing how these molecules modulate the course of the disease and analyzing the therapeutic potential of targeting this network.

MCP-1/IL-12 ratio expressions correlated with adventitial collagen depositions in renal vessels and IL-4/IFN-γ expression correlated with interstitial collagen depositions in the kidneys of dogs with canine leishmaniasis

Collagen deposition is a common event in chronic inflammation, and canine Leishmaniosis (CanL) is generally associated with a long and chronic evolution. Considering that the kidney shows fibrinogenic changes during CanL, and the balance of cytokines/chemokines regulates the profibrinogenic and antifibrinogenic immune responses differently, it can be hypothesized that the balance of cytokines/chemokines can be differentially expressed in the renal tissue in order to determine the expression of collagen depositions in the kidneys. This study aimed to measure collagen deposition and to evaluate cytokine/chemokine expressions in the kidney by means of qRT-PCR in sixteen Leishmania-infected dogs and six uninfected controls. Kidney fragments were stained with hematoxylin & eosin (H&E), Masson's Trichrome, Picrosirius Red, and Gomori's reticulin. Intertubular and adventitial collagen depositions were evaluated by the morphometric approach. Cytokine RNA expressions were measured by means of qRT-PCR to identify molecules involved in chronic collagen depositions in kidneys with CanL. Collagen depositions were related to the presence of clinical signs, and more intense intertubular collagen depositions occurred in infected dogs. Adventitial collagen deposition, as morphometrically measured by the average area of the collagen, was more intense in clinically affected dogs than in subclinically infected dogs. TNF-α/TGF-β, MCP1/IL-12, CCL5/IL-12, IL-4/IFN-γ, and IL-12/TGF-β expressions were associated with clinical manifestations in dogs with CanL. The IL-4/IFN-α ratio was more commonly expressed and upregulated in clinically affected dogs, and downregulated in subclinically infected dogs. Furthermore, MCP-1/IL-12 and CCL5/IL-12 were more commonly expressed in subclinically infected dogs. Strong positive correlations were detected between morphometric values of interstitial collagen depositions and MCP-1/IL-12, IL-12, and IL-4 mRNA expression levels in the renal tissues. Adventitial collagen deposition was correlated with TGF-β, IL-4/IFN-γ, and TNF-α/TGF-β. In conclusion, our results showed the association of MCP-1/IL-12 and CCL5/IL-12 ratios with an absence of clinical signs, as well as an IL-4/IFN-α ratio with adventitial and intertubular collagen depositions in dogs with visceral leishmaniosis.

Single nucleotide polymorphisms in genes involved in immune responses and outcome of tegumentary leishmaniasis

Leishmaniases are neglected tropical diseases with a broad clinical spectrum. Tegumentary leishmaniasis (TL) is a disease caused by different Leishmania species, transmitted by phlebotomine sand flies and distributed worldwide. TL can present a cutaneous (CL) or mucocutaneous (MCL) clinical form depending on factors inherent to the parasite, the host and the vector. Polymorphisms in the immune response genes are host genetic factors that influence the pathogenesis or control of leishmaniasis. Single nucleotide polymorphisms (SNPs) in immune genes have been evaluated in several countries where leishmaniasis is endemic. In this review, we report studies on SNPs in several immune genes that might be associated with susceptibility or resistance to TL. We summarize studies from around the world and in Brazil, highlight the difficulties of these studies and future analyses needed to enhance our knowledge regarding host genetic factors in TL. Understanding the genetic characteristics of the host that facilitate resistance or susceptibility to leishmaniasis can contribute to the development of immunotherapy schedules for this disease. The current treatment methods are toxic, and no human vaccine is available.

Role of Chemokines in the Pathogenesis of Visceral Leishmaniasis

Abstract:

Visceral leishmaniasis (VL; also known as kala-azar), caused by the protozoan parasite Leishmania donovani is characterized by the inability of the host to generate an effective immune response. The manifestations of the disease depends on involvement of various immune components such as activation of macrophages, cell mediated immunity, secretion of cytokines and chemokines, etc. Macrophages are the final host cells for Leishmania parasites to multiply, and they are the key to a controlled or aggravated response that leads to clinical symptoms. The two most common macrophage phenotypes are M1 and M2. The pro-inflammatory microenvironment (mainly by IL-1β, IL-6, IL-12, IL-23, and TNF-α cytokines) and tissue injury driven by classically activated macrophages (M1-like) and wound healing driven by alternatively activated macrophages (M2-like) in an anti-inflammatory environment (mainly by IL-10, TGF-β, chemokine ligand (CCL)1, CCL2, CCL17, CCL18, and CCL22). Moreover, on polarized Th cells, chemokine receptors are expressed differently. Typically, CXCR3 and CCR5 are preferentially expressed on polarized Th1 cells, whereas CCR3, CCR4 and CCR8 have been associated with the Th2 phenotype. Further, the ability of the host to produce a cell-mediated immune response capable of regulating and/or eliminating the parasite is critical in the fight against the disease. Here, we review the interactions between parasites and chemokines and chemokines receptors in the pathogenesis of VL.

miR-548d-3p Is Up-Regulated in Human Visceral Leishmaniasis and Suppresses Parasite Growth in Macrophages

Visceral leishmaniasis caused by Leishmania (Leishmania) infantum in Latin America progress with hepatosplenomegaly, pancytopenia, hypergammaglobulinemia, and weight loss and maybe lethal mainly in untreated cases. miRNAs are important regulators of immune and inflammatory gene expression, but their mechanisms of action and their relationship to pathogenesis in leishmaniasis are not well understood. In the present study, we sought to quantify changes in miRNAs associated with immune and inflammatory pathways using the L. (L.) infantum promastigote infected- human monocytic THP-1 cell model and plasma from patients with visceral leishmaniasis. We identified differentially expressed miRNAs in infected THP-1 cells compared with non-infected cells using qPCR arrays. These miRNAs were submitted to in silico analysis, revealing targets within functional pathways associated with TGF-β, chemokines, glucose metabolism, inflammation, apoptosis, and cell signaling. In parallel, we identified differentially expressed miRNAs in active visceral leishmaniasis patient plasma compared with endemic healthy controls. In silico analysis of these data indicated different predicted targets within the TGF-β, TLR4, IGF-I, chemokine, and HIF1α pathways. Only a small number of miRNAs were commonly identified in these two datasets, notably with miR-548d-3p being up-regulated in both conditions. To evaluate the potential biological role of miR-548d-3p, we transiently transfected a miR-548d-3p inhibitor into L. (L.) infantum infected-THP-1 cells, finding that inhibition of miR-548d-3p enhanced parasite growth, likely mediated through reduced levels of MCP-1/CCL2 and nitric oxide production. Further work will be required to determine how miR-548d-3p plays a role in vivo and whether it serves as a potential biomarker of progressive leishmaniasis.

Quantitative analysis of proteins secreted by Leishmania (Viannia) braziliensis strains associated to distinct clinical manifestations of American Tegumentary Leishmaniasis

The role of Leishmania braziliensis in the development of different clinical forms of American Tegumentary Leishmaniasis (ATL) is unclear, but it has been suggested that molecules secreted/released by parasites could modulate the clinical outcome. Here, we analyzed the infection rate and cytokine profile of macrophages pretreated with the secretome of two L. braziliensis strains associated with polar clinical forms of ATL: one associated with localized self-healing cutaneous leishmaniasis (LCL) and other associated with the disseminated form (DL). Besides, we use an iTRAQ-based quantitative proteomics approach to compare the abundance of proteins secreted by those strains. In vitro infection demonstrated that pretreatment with secretome resulted in higher number of infected macrophages, as well as higher number of amastigotes per cell. Additionally, macrophages pretreated with LCL secretome exhibited a proinflammatory profile, whereas those pretreated with the DL one did not. These findings suggest that secretomes made macrophages more susceptible to infection and that molecules secreted by each strain modulate, differentially, the macrophages' cytokine profile. Indeed, proteomics analysis showed that the DL secretome is rich in molecules involved in macrophage deactivation, while is poor in proteins that activate proinflammatory pathways. Together, our results reveal new molecules that may contribute to the infection, persistence and dissemination of the parasite. SIGNIFICANCE: Leishmania braziliensis is associated to localized self-healing cutaneous lesions (LCL), disseminated leishmaniasis (DL), and mucocutaneous lesions (MCL). To understand the role of the parasite in those distinct clinical manifestations we evaluated infection rates and cytokine profiles of macrophages pre-treated with secretomes of two L. braziliensis strains associated with DL and LCL, and quantitatively compared these secretomes. The infection index of macrophages pretreated with the DL secretome was significantly higher than that exhibited by non-treated cells. Interestingly, whereas the LCL secretome stimulated a proinflammatory setting, favoring an effector cell response that would explain the proper resolution of the disease caused by this strain, the DL strain was not able to elicit such response or has mechanisms to prevent this activation. Indeed, DL secretome is rich in peptidases that may deactivate cell pathways crucial for parasite elimination, while is poor in proteins that could activate proinflammatory pathways, favoring parasite infection and persistence.

Immunotherapeutic Potential of Interleukin-32 and Trained Immunity for Leishmaniasis Treatment

Neglected tropical diseases annually account for several million infections worldwide. Efficacious treatment for these poorly understood infectious diseases is often limited to ineffective, expensive, and toxic therapies such as the SbV used for leishmaniasis patients. Here, we review the latest discoveries and literature on the molecular pathways, cell types, and immune mediators involved in the immune response to infection with New World Leishmania spp. in humans and their interaction with the adaptive and innate immune system. Novel developments in the field of trained innate immunity and the recently described role of IL-32 are emphasized as potential immunotherapeutic treatments for the management of leishmaniasis.

Enhanced production of pro-inflammatory cytokines and chemokines in Ethiopian cutaneous leishmaniasis upon exposure to Leishmania aethiopica

The clinical course and outcome of cutaneous leishmaniasis (CL) vary due to the infecting Leishmania species and host genetic makeup that result in different immune responses against the parasites. The host immune response to Leishmania aethiopica (L.aethiopica), the causative agent of CL in Ethiopia, is poorly understood. To contribute to the understanding of the protective immune response in CL due to L.aethiopica, we characterized the cytokine response to L. aethiopica in patients with the localized form of CL (LCL) and age-and sex-matched apparently healthy controls. By applying a whole blood based in vitro culture we found enhanced release of TNF, IL-6, MCP-1 or CCL2, IP-10 or CXCL10, MIP-1β or CCL4 and IL-8 or CXCL8- but not of IL-10CL patients in response to L. aethiopica compared to the controls. No difference was observed between LCL cases and controls in the secretion of these cytokines and chemokines in whole blood cultures treated with the TLR-ligands LPS, MALP-2 or polyI: C. The observed increased secretion of the pro-inflammatory cytokines/chemokines reflects an enhanced response against the parasites by LCL patients as compared to healthy controls rather than a generally enhanced ability of blood leukocytes from LCL patients to respond to microbial constituents. Our findings suggest that the enhanced production of pro-inflammatory cytokines/chemokines is associated with localized cutaneous leishmaniasis caused by L.aethiopica.

Nucleotides and AHCC Enhance Th1 Responses In Vitro in Leishmania-Stimulated/Infected Murine Cells

A stronger Th1 (cellular) immune response in canine leishmaniosis (CanL) leads to a better prognosis. Dietary nucleotides plus AHCC^® have shown beneficial effects in dogs with clinical leishmaniosis and in clinically healthy Leishmania-infected dogs. The potential leishmanicidal activity of nucleotides and AHCC was assessed by quantifying nitric oxide (NO) production and replication of parasites. Their effects on lymphocyte proliferation were studied with and without soluble Leishmania infantum antigen (SLA) stimulation. Cytokine level variations were assessed using naïve and L. infantum-infected macrophages/lymphocytes cocultures. Promastigotes and amastigotes proliferation and NO macrophage production were not directly affected. Lymphocyte proliferation was significantly enhanced by nucleotides, AHCC, and their combinations only after SLA stimulation. Nucleotides and AHCC significantly increased the production of IL-1β, IL-2, IL-5, IL-9, IL-10, and IL-12 by naïve immune cells. In naïve and L. infantum-infected macrophage/lymphocyte cocultures, nucleotides with or without AHCC led to significant increases in IFN-γ and TNF-α. Given that these cytokines are involved in the effective Th1 immune response against Leishmania parasites, these mechanisms of action could explain the previously reported in vivo clinical efficacy of such combination and further support the use of nucleotides with or without AHCC in the management of CanL patients.

The role of monocytes/macrophages in Leishmania infection: A glance at the human response

Leishmania are obligate intracellular parasites of mononuclear phagocytes transmitted by Phlebotomine sandflies. Monocytes are one of the main cell types recruited to the site of the bite having an important role in the defense against Leishmania parasites in the first hours of infection. In the tissue, macrophages play a pivotal role as both the primary replication sites and the major effector cells responsible for parasite elimination. Many authors have reviewed the monocyte/macrophage-Leishmania interactions from results derived in mice, however, given the important differences between mice an humans we considered vital to discuss the role of these cells in human leishmaniasis. In this review, we recapitulated the most important studies carried out to understand the different roles of human monocyte/macrophages in Leishmania infection and how they can participate in both control and the immunopathogenesis of the disease.

Profiles of Local and Systemic Inflammation in the Outcome of Treatment of Human Cutaneous Leishmaniasis Caused by Leishmania (Viannia)

The immune mechanisms that contribute to the efficacy of treatment of cutaneous leishmaniasis (CL) are not fully understood. The aim of this study was to define immune correlates of the outcome of treatment of CL caused by Leishmania (Viannia) species during standard of care treatment with pentavalent antimonials. We conducted a comparative expression profiling of immune response genes in peripheral blood mononuclear cells (PBMCs) and lesion biopsy specimens obtained from CL patients before and at the end of treatment (EoT) with meglumine antimoniate. The ex vivo response of PBMCs to L (V) panamensis partially reflected that of lesion microenvironments. Significant downregulation of gene expression profiles consistent with local innate immune responses (monocyte and neutrophil activation and chemoattractant molecules) was observed at EoT in biopsy specimens of patients who cured (n = 8), compared to those from patients with treatment failure (n = 8). Among differentially expressed genes, pretreatment expression of CCL2 was significantly predictive of the therapeutic response (receiver operating characteristic [ROC] curve, area under the curve [AUC] = 0.82, P = 0.02). Polymorphisms in regulatory regions of the CCL2 promoter were analyzed in a pilot cohort of DNA samples from CL patients (cures, n = 20, and treatment failure, n = 20), showing putative association of polymorphisms rs13900(C/T) and rs2857656(G/C) with treatment outcome. Our data indicate that dampening gene expression profiles of monocyte and neutrophil activation characterize clinical cure after treatment of CL, supporting participation of parasite-sustained inflammation or deregulated innate immune responses in treatment failure.

In-situ immune profile of polymorphic vs. macular Indian Post Kala-azar dermal leishmaniasis

Post Kala-azar Dermal Leishmaniasis (PKDL), a sequel of apparently cured Visceral Leishmaniasis presents in South Asia with papulonodular (polymorphic) or hypomelanotic lesions (macular). Till date, the polymorphic variant was considered predominant, constituting 85–90%. However, following active-case surveillance, the proportion of macular PKDL has increased substantially to nearly 50%, necessitating an in-depth analysis of this variant. Accordingly, this study aimed to delineate the cellular infiltrate in macular vis-à-vis polymorphic PKDL. To study the overall histopathology, hematoxylin and eosin staining was performed on lesional sections and phenotyping by immunohistochemistry done in terms of dendritic cells (CD1a), macrophages (CD68), HLA-DR, T-cells (CD8, CD4), B-cells (CD20) and Ki67 along with assessment of the status of circulating homing markers CCL2, CCL7 and CXCL13. In polymorphic cases (n = 20), the cellular infiltration was substantial, whereas in macular lesions (n = 20) it was mild and patchy with relative sparing of the reticular dermis. Although parasite DNA was identified in both variants by ITS-1 PCR, the parasite load was significantly higher in the polymorphic variant and Leishman-Donovan bodies were notably minimally present in macular cases. Both variants demonstrated a decrease in CD1a⁺ dendritic cells, HLA-DR expression and CD4⁺ T-cells. In macular cases, the proportion of CD68⁺ macrophages, CD8⁺ T-cells and CD20⁺ B-cells was 4.6 fold, 17.0 fold and 1.6 fold lower than polymorphic cases. The absence of Ki67 positivity and increased levels of chemoattractants suggested dermal homing of these cellular subsets. Taken together, as compared to the polymorphic variant, patients with macular PKDL demonstrated a lower parasite load along with a lesser degree of cellular infiltration, suggesting differences in host-pathogen interactions, which in turn can impact on their disease transmitting potential and responses to chemotherapy.

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Comparative analysis of immunopathology of polymorphic vs. macular PKDL.

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Dense lymphohistiocytic infiltrate in polymorphic PKDL.

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Mild and patchy cellular infiltration in macular PKDL with minimal Leishman Donovan bodies.

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Decreased presence of CD1a, HLA-DR and CD4⁺ T-cells in both variants.

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The presence of CD8⁺, CD68⁺and CD20⁺ cells in polymorphic>>>macular PKDL.

Histological and immunological differences between zoonotic cutaneous leishmaniasis due to Leishmania major and sporadic cutaneous leishmaniasis due to Leishmania infantum

Lesion features in cutaneous leishmaniasis (CL) depend on the infecting Leishmania species as well as on host immune reponse. In this study, we evaluated the histological and immunological differences between two forms of CL described in Tunisia: zoonotic cutaneous leishmaniasis (ZCL) caused by L. major and sporadic cutaneous leishmaniasis (SCL) caused by L. infantum. Histological analysis showed a mild to moderate infiltrate within ZCL lesions. In contrast, massive infiltration of the dermis was observed within SCL lesions. Contrary to ZCL, infiltrates within SCL lesions were organized and showed granuloma composed of macrophages and lymphocytes. In addition, immunohistochemical analysis showed a predominance of CD4⁺ T cells within both CL forms. Furthermore, expression of interferon-γ, interleukin (IL)-10, IL-8, IL-13 and monocyte chemotactic protein (MCP)-1 was evaluated using real-time quantitative polymerase chain reaction (RT-qPCR). MCP-1 and IL-10 were expressed at comparable levels in ZCL and SCL lesions. Interestingly, IL-8 mRNA levels were significantly higher in ZCL lesions compared to SCL lesions, but interferon-γ was significantly higher in SCL lesions than in ZCL lesions.

Protection mediated by chemokine CXCL10 in BALB/c mice infected by Leishmania infantum

BACKGROUND

Visceral leishmaniasis (VL) caused by Leishmania infantum is characterised by the loss of the ability of the host to generate an effective immune response. Chemokines have a direct involvement in the pathogenesis of leishmaniasis, causing a rapid change in the expression of these molecules during infection by Leishmania.

OBJECTIVES

Herein, it was investigated the role of CXCL10 in controlling infection by L. infantum.

METHODS

RAW 264.7 macrophages were infected with L. infantum in vitro and treated or not with CXCL10 (25, 50 and 100 ng/mL). Parasite load, as well as nitric oxide (NO), IL-4 and IL-10 production were assessed at 24 and 48 h after infection. In vivo, BALB/c mice were infected and treated or not with CXCL10 (5 μg/kg) at one, three and seven days of infection. Parasite load, IFN-g, IL-4, TGF-β and IL-10 were evaluated one, seven and 23 days post treatment.

FINDINGS

In vitro, CXCL10 reduced parasitic load, not dependent on NO, and inhibited IL-10 and IL-4 secretion. In vivo, CXCL10 was able to reduce the parasite load in both liver and spleen, four weeks after infection, representing a higher decrease in the number of parasites in these organs, also induced IFN-γ at day 23 after treatment, correlating with the decrease in parasite load, and reduced IL-10 and TGF-β.

MAIN CONCLUSIONS

This study suggests a partial protective role of CXCL10 against L. infantum, mediated by IFN-g, not dependent on NO, and with suppression of IL-10 and TGF-β. These data may provide information for the development of new approaches for future therapeutic interventions for VL.

Local Delivery of the Toll-Like Receptor 9 Ligand CpG Downregulates Host Immune and Inflammatory Responses, Ameliorating Established Leishmania (Viannia) panamensis Chronic Infection

Infection by Leishmania (Viannia) panamensis, the predominant etiologic agent for cutaneous leishmaniasis in Colombia, is characterized by a chronic mixed inflammatory response. Current treatment options are plagued by toxicity, lengthy treatment regimens, and growing evidence of drug resistance. Immunotherapy, modulating the immune system to mount a protective response, may provide an alternate therapeutic approach. We investigated the ability of the Toll-like receptor 9 (TLR9) ligand CpG to modulate established disease in the L (V) panamensis mouse model. Treatment of established infection with a high dose (50 μg) of CpG ameliorated disease and lowered parasite burden. Interestingly, immediately after treatment there was a significant increase in transforming growth factor β (TGF-β) and concomitantly an increase in T regulatory cell (Treg) function. Although a general reduction in cell-mediated immune cytokine and chemokine (gamma interferon [IFN-γ], interleukin 10 [IL-10], IL-13, IL-6, granulocyte-macrophage colony-stimulating factor [GM-CSF], IL-4, and MIP-1α) responses of the treated mice was observed, certain chemokines (RANTES, monocyte chemoattractant protein 1[MCP-1], and IP-10) were increased. Further, in peripheral blood mononuclear cells (PBMCs) from patients with cutaneous leishmaniasis, CpG treatment similarly exhibited a dose-response effect on the production of IFN-γ, IL-17, IL-10, and IL-13, with reductions observed at higher doses. To further understand the underlying mechanisms and cell populations driving the CpG mediated response, we examined the ex vivo dose effects mediated by the TLR9⁺ cell populations (dendritic cells, macrophages, and B cells) found to accumulate labeled CpG in vivo Notably, B cells altered the production of IL-17, IL-13, and IFN-γ, supporting a role for B cells functioning as antigen-presenting cells (APCs) and/or regulatory cells during infection. Interestingly, B cells have been previously demonstrated as a primary type of APC in patients infected with L (V) panamensis and thus may be useful targets of immunotherapy. Collectively, our results show that CpG-induced immune regulation leads to a dampening of the host immune response and healing in the mouse model, and it may provide an alternate approach to treatment of cutaneous leishmaniasis caused by L (V) panamensis.

Similar Fecal Microbiota Signatures in Patients With Diarrhea-Predominant Irritable Bowel Syndrome and Patients With Depression

BACKGROUND & AIMS

Patients with irritable bowel syndrome (IBS) often have psychiatric comorbidities. Alterations in the intestinal microbiota have been associated with IBS and depression, but it is not clear if there is a microbial relationship between these disorders. We studied the profiles of fecal microbiota samples from patients with IBS, depression, or comorbidities of IBS and depression; we determined the relationships among these profiles and clinical and pathophysiological features of these disorders.

METHODS

We used 454 pyrosequencing to analyze fecal microbiota samples from 100 subjects (40 with diarrhea-predominant IBS [IBS-D], 15 with depression, 25 with comorbidities of IBS and depression, and 20 healthy individuals [controls]), recruited at Peking University. Abdominal and psychological symptoms were evaluated with validated questionnaires. Visceral sensitivity was evaluated using a barostat. Colonic mucosal inflammation was assayed by immunohistochemical analyses of sigmoid tissue biopsy specimens.

RESULTS

Fecal microbiota signatures were similar between patients with IBS-D and depression in that they were less diverse than samples from controls and had similar abundances of alterations. They were characterized by high proportions of Bacteroides (type I), Prevotella (type II), or nondominant microbiota (type III). Most patients with IBS-D or depression had type I or type II profiles (IBS-D had 85% type I and type II profiles, depression had 80% type I and type II profiles). Colon tissues from patients with type I or type II profiles had higher levels of inflammatory markers than colon tissues from patients with type III profiles. The level of colon inflammation correlated with the severity of IBS symptoms.

CONCLUSIONS

Patients with IBS-D and depression have similar alterations in fecal microbiota; these might be related to the pathogenesis of these disorders. We identified 3 microbial profiles in patients that could indicate different subtypes of IBS and depression or be used as diagnostic biomarkers.

Immunopathology of Leishmaniasis: An Update

Leishmaniasis represents a severe, increasing, public health problem. The perspective of its control is highly dependent on research progress, on therapeutic manipulations of the immune system, and on vaccine development. There is a correlation between the clinical outcome of Leishmania infection and the cytokine response profile. While a protective immune response against Leishmania has been clearly identified to be related to the influence of a type-1 response and IFN-γ production, the precise role of T helper (TH) 2 cytokines in non-healing infections requires further exploration. IL-4 and IL-13 (TH2 cytokines) can promote disease progression in cutaneous leishmaniasis, whereas IL-4 would appear to enhance protective type-1 responses in visceral leishmaniasis. Thus, the TH1/TH2 paradigm of resistance/susceptibility to intracellular parasites is probably an oversimplification of a more complicated network of regulatory/counter regulatory interactions. Moreover, the presence of antigen specific regulatory T cell subsets may provide an environment that contributes to the balance between TH1 and TH2 cells. Finally, the involvement of CD8+ T cells has been described, but the modality of their function in this kind of infection has not been so far elucidated.

The adult murine heart has a sparse, phagocytically active macrophage population that expands through monocyte recruitment and adopts an 'M2' phenotype in response to Th2 immunologic challenge

Tissue resident macrophages have vital homeostatic roles in many tissues but their roles are less well defined in the heart. The present study aimed to identify the density, polarisation status and distribution of macrophages in the healthy murine heart and to investigate their ability to respond to immune challenge. Histological analysis of hearts from CSF-1 receptor (csf1-GFP; MacGreen) and CX3CR1 (Cx3cr1(GFP/+)) reporter mice revealed a sparse population of GFP positive macrophages that were evenly distributed throughout the left and right ventricular free walls and septum. F4/80+CD11b+ cardiac macrophages, sorted from myocardial homogenates, were able to phagocytose fluorescent beads in vitro and expressed markers typical of both 'M1' (IL-1β, TNF and CCR2) and 'M2' activation (Ym1, Arg 1, RELMα and IL-10), suggesting no specific polarisation in healthy myocardium. Exposure to Th2 challenge by infection of mice with helminth parasites Schistosoma mansoni, or Heligmosomoides polygyrus, resulted in an increase in cardiac macrophage density, adoption of a stellate morphology and increased expression of Ym1, RELMα and CD206 (mannose receptor), indicative of 'M2' polarisation. This was dependent on recruitment of Ly6ChighCCR2+ monocytes and was accompanied by an increase in collagen content. In conclusion, in the healthy heart resident macrophages are relatively sparse and have a phagocytic role. Following Th2 challenge this population expands due to monocyte recruitment and adopts an 'M2' phenotype associated with increased tissue fibrosis.

Rapid Sequestration of Leishmania mexicana by Neutrophils Contributes to the Development of Chronic Lesion

The protozoan Leishmania mexicana parasite causes chronic non-healing cutaneous lesions in humans and mice with poor parasite control. The mechanisms preventing the development of a protective immune response against this parasite are unclear. Here we provide data demonstrating that parasite sequestration by neutrophils is responsible for disease progression in mice. Within hours of infection L. mexicana induced the local recruitment of neutrophils, which ingested parasites and formed extracellular traps without markedly impairing parasite survival. We further showed that the L. mexicana-induced recruitment of neutrophils impaired the early recruitment of dendritic cells at the site of infection as observed by intravital 2-photon microscopy and flow cytometry analysis. Indeed, infection of neutropenic Genista mice and of mice depleted of neutrophils at the onset of infection demonstrated a prominent role for neutrophils in this process. Furthermore, an increase in monocyte-derived dendritic cells was also observed in draining lymph nodes of neutropenic mice, correlating with subsequent increased frequency of IFNγ-secreting T helper cells, and better parasite control leading ultimately to complete healing of the lesion. Altogether, these findings show that L. mexicana exploits neutrophils to block the induction of a protective immune response and impairs the control of lesion development. Our data thus demonstrate an unanticipated negative role for these innate immune cells in host defense, suggesting that in certain forms of cutaneous leishmaniasis, regulating neutrophil recruitment could be a strategy to promote lesion healing.

Infection with the protozoan Leishmania parasites causes a spectrum of diseases ranging from cutaneous to visceral forms that are fatal if left untreated. Among the different Leishmania species, Leishmania mexicana causes chronic cutaneous lesions in humans. To study this disease, we used a murine model. Following infection with Leishmania mexicana, most mouse species including C57BL/6 develop chronic non-healing lesion. Within hours of infection, neutrophils are recruited locally and they ingest the parasites. Although neutrophils are leukocytes that are able to rapidly kill pathogens using an arsenal of molecules, several microorganisms including some, but not all, Leishmania species are able to survive within these cells. Here, we show that L. mexicana elicits the rapid recruitment of neutrophils at the site of infection, survives within these cells and uses them to its advantage. Furthermore, transient parasite sequestration by neutrophils delays recruitment of other leukocytes such as monocytes, contributing to the impaired development of a protective immune response against the parasite and chronic lesion development. Thus, we describe a previously unanticipated pathogenic role for neutrophils in chronic lesion development. More importantly, our data suggest that in certain forms of cutaneous leishmaniasis, regulating neutrophil recruitment could be a strategy to promote lesion healing.

Menstrual blood-derived stromal stem cells from women with and without endometriosis reveal different phenotypic and functional characteristics

Retrograde flow of menstrual blood cells during menstruation is considered as the dominant theory for the development of endometriosis. Moreover, current evidence suggests that endometrial-derived stem cells are key players in the pathogenesis of endometriosis. In particular, endometrial stromal stem cells have been suggested to be involved in the pathogenesis of this disease. Here, we aimed to use menstrual blood, as a novel source of endometrial stem cells, to investigate whether stromal stem cells from endometriosis (E-MenSCs) and non-endometriosis (NE-MenSCs) women differed regarding their morphology, CD marker expression pattern, proliferation, invasion and adhesion capacities and their ability to express certain immunomodulatory molecules. E-MenSCs were morphologically different from NE-MenSCs and showed higher expression of CD9, CD10 and CD29. Furthermore, E-MenSCs had higher proliferation and invasion potentials compared with NE-MenSCs. The amount of indoleamine 2,3-dioxygenase-1 (IDO1) and cyclooxygenase-2 (COX-2) in E-MenSCs co-cultured with allogenic peripheral blood mononuclear cells (PBMCs) was shown to be higher both at the gene and protein levels, and higher IDO1 activity was detected in the endometriosis group. However, NE-MenSCs revealed increased concentrations of forkhead transcription factor-3 (FOXP3) when compared with E-MenSCs. Nonetheless, interferon (IFN)-γ, Interleukin (IL)-10 and monocyte chemoattractant protein-1 (MCP-1) levels were higher in the supernatant of E-MenSCs-PBMC co-cultures. Here, we showed that there are inherent differences between E-MenSCs and NE-MenSCs. These findings propose the key role MenSCs could play in the pathogenesis of endometriosis and further support the retrograde and stem cell theories of endometriosis. Hence, considering its renewable and easily available nature, menstrual blood could be viewed as a reliable and inexpensive material for studies addressing the cellular and molecular aspects of endometriosis.

Immunotherapy and Immunochemotherapy in Visceral Leishmaniasis: Promising Treatments for this Neglected Disease

Leishmaniasis has several clinical forms: self-healing or chronic cutaneous leishmaniasis or post-kala-azar dermal leishmaniasis; mucosal leishmaniasis; visceral leishmaniasis (VL), which is fatal if left untreated. The epidemiology and clinical features of VL vary greatly due to the interaction of multiple factors including parasite strains, vectors, host genetics, and the environment. Human immunodeficiency virus infection augments the severity of VL increasing the risk of developing active disease by 100–2320 times. An effective vaccine for humans is not yet available. Resistance to chemotherapy is a growing problem in many regions, and the costs associated with drug identification and development, make commercial production for leishmaniasis, unattractive. The toxicity of currently drugs, their long treatment course, and limited efficacy are significant concerns. For cutaneous disease, many studies have shown promising results with immunotherapy/immunochemotherapy, aimed to modulate and activate the immune response to obtain a therapeutic cure. Nowadays, the focus of many groups centers on treating canine VL by using vaccines and immunomodulators with or without chemotherapy. In human disease, the use of cytokines like interferon-γ associated with pentavalent antimonials demonstrated promising results in patients that did not respond to conventional treatment. In mice, immunomodulation based on monoclonal antibodies to remove endogenous immunosuppressive cytokines (interleukin-10) or block their receptors, antigen-pulsed syngeneic dendritic cells, or biological products like Pam3Cys (TLR ligand) has already been shown as a prospective treatment of the disease. This review addresses VL treatment, particularly immunotherapy and/or immunochemotherapy as an alternative to conventional drug treatment in experimental models, canine VL, and human disease.

Host genetic factors in American cutaneous leishmaniasis: a critical appraisal of studies conducted in an endemic area of Brazil

American cutaneous leishmaniasis (ACL) is a vector-transmitted infectious disease with an estimated 1.5 million new cases per year. In Brazil, ACL represents a significant public health problem, with approximately 30,000 new reported cases annually, representing an incidence of 18.5 cases per 100,000 inhabitants. Corte de Pedra is in a region endemic for ACL in the state of Bahia (BA), northeastern Brazil, with 500-1,300 patients treated annually. Over the last decade, population and family-based candidate gene studies were conducted in Corte de Pedra, founded on previous knowledge from studies on mice and humans. Notwithstanding limitations related to sample size and power, these studies contribute important genetic biomarkers that identify novel pathways of disease pathogenesis and possible new therapeutic targets. The present paper is a narrative review about ACL immunogenetics in BA, highlighting in particular the interacting roles of the wound healing gene FLI1 with interleukin-6 and genes SMAD2 and SMAD3 of the transforming growth factor beta signalling pathway. This research highlights the need for well-powered genetic and functional studies on Leishmania braziliensis infection as essential to define and validate the role of host genes in determining resistance/susceptibility regarding this disease.

Chronicity of dermal leishmaniasis caused by Leishmania panamensis is associated with parasite-mediated induction of chemokine gene expression

Chronic tegumentary leishmaniasis is characterized by a scarcity of parasites in lesions and a heightened inflammatory response. Deregulated and hyperactive inflammation contributes to tissue damage and parasite persistence. The mechanisms by which immune cells are recruited to the lesion and their relationship to clinical outcomes remain elusive. We examined the expression levels of chemokines and their receptors in relation to clinical outcome in dermal leishmaniasis caused by Leishmania (Viannia) panamensis. Primary macrophages from healthy donors were infected with L. panamensis strains isolated from self-healing patients (n = 4) and those presenting chronic disease (n = 5). A consistent pattern of upregulation of neutrophil (cxcl1, cxcl2, cxcl5, and cxcl8/il-8) and monocyte (ccl2, ccl7, ccl8, cxcl3, and cxcl10) chemotactic chemokines and ccr1 and ccr5 receptor genes, evaluated by reverse transcription-quantitative PCR (qRT-PCR), was observed upon infection with strains from patients with chronic dermal leishmaniasis; induction of CXCL5 and CCL8 was corroborated at the protein level. No apparent upregulation was elicited in macrophages infected with strains from self-healing patients. Expression levels of ccl8, cxcl2, cxcl3, and cxcl5 in lesion biopsy specimens from patients with chronic cutaneous leishmaniasis (CL) were compared to those in biopsy specimens from Montenegro skin tests of individuals with asymptomatic infection. Increased expression levels of cxcl5 (P < 0.05), ccl8, and cxcl3 were corroborated in chronic CL lesions. Our study revealed a dichotomy in macrophage chemokine gene expression elicited by L. panamensis strains from patients with self-healing disease and those presenting chronic disease, consistent with parasite-mediated hyperactivation of the inflammatory response driving chronicity. The predominant upregulation of neutrophil and monocyte chemoattractants indicates novel mechanisms of sustained inflammatory activation and may provide new therapeutic targets against chronic dermal leishmaniasis.

STAT4 is critical for immunity but not for antileishmanial activity of antimonials in experimental visceral leishmaniasis

We and others have previously shown that IL-12 is indispensable for immunity and is required for the optimal antiparasitic activity of antimonials in experimental visceral leishmaniasis caused by Leishmania donovani. Here we investigated the role of STAT4 in immunity against L. donovani using STAT4 knockout mice and also determined the effect of STAT4 deficiency in response to antimonial therapy. Upon infection with L. donovani, stat4⁻/⁻ BALB/c and C57BL/6 mice showed enhanced susceptibility to Leishmania during late time points of infection which was associated with a marked reduction in Th1 responses and hepatic immunopathology. Interestingly, these defects in Th1 responses in stat4⁻/⁻ did not impair the antimonial chemotherapy as both stat4⁻/⁻ and WT mice showed comparable levels of parasite clearance from the liver and spleen. These findings highlight the role of STAT4 in immunity to L. donovani infection and also provide evidence that STAT4 is dispensable for antimonial-based chemotherapy.

MicroRNA expression profile in human macrophages in response to Leishmania major infection

Background

Leishmania (L.) are intracellular protozoan parasites able to survive and replicate in the hostile phagolysosomal environment of infected macrophages. They cause leishmaniasis, a heterogeneous group of worldwide-distributed affections, representing a paradigm of neglected diseases that are mainly embedded in impoverished populations. To establish successful infection and ensure their own survival, Leishmania have developed sophisticated strategies to subvert the host macrophage responses. Despite a wealth of gained crucial information, these strategies still remain poorly understood. MicroRNAs (miRNAs), an evolutionarily conserved class of endogenous 22-nucleotide non-coding RNAs, are described to participate in the regulation of almost every cellular process investigated so far. They regulate the expression of target genes both at the levels of mRNA stability and translation; changes in their expression have a profound effect on their target transcripts.

Methodology/Principal Findings

We report in this study a comprehensive analysis of miRNA expression profiles in L. major-infected human primary macrophages of three healthy donors assessed at different time-points post-infection (three to 24 h). We show that expression of 64 out of 365 analyzed miRNAs was consistently deregulated upon infection with the same trends in all donors. Among these, several are known to be induced by TLR-dependent responses. GO enrichment analysis of experimentally validated miRNA-targeted genes revealed that several pathways and molecular functions were disturbed upon parasite infection. Finally, following parasite infection, miR-210 abundance was enhanced in HIF-1α-dependent manner, though it did not contribute to inhibiting anti-apoptotic pathways through pro-apoptotic caspase-3 regulation.

Conclusions/Significance

Our data suggest that alteration in miRNA levels likely plays an important role in regulating macrophage functions following L. major infection. These results could contribute to better understanding of the dynamics of gene expression in host cells during leishmaniasis.

Leishmania parasites belong to different species, each one characterized by specific vectors and reservoirs, and causes cutaneous or visceral disease(s) of variable clinical presentation and severity. In its mammalian host, the parasite is an obligate intracellular pathogen infecting the monocyte/macrophage lineage. Leishmania have developed ambiguous relationships with macrophages. Indeed, these cells are the shelter of invading parasites, where they will grow and eventually will reside in a silent state for life. But macrophages are also the cells that participate, through the induction of several pro-inflammatory mediators and antigen presentation, to shape the host immune response and ultimately kill the invader. To subvert these anti-parasite responses, Leishmania manipulate the host machinery for their own differentiation and survival. We aimed to evaluate the impact of L. major (the causative agent of zoonotic cutaneous leishmaniasis) infection on deregulation of non-coding miRNAs, a class of important regulators of gene expression. Our results revealed the implication of several miRNAs on macrophage fate upon parasite infection through regulation of different pathways, including cell death. Our findings provided a new insight for understanding mechanisms governing this miRNA deregulation by parasite infection and will help to provide clues for the development of control strategies for this disease.

Gene expression profile of cytokines and chemokines in skin lesions from Brazilian Indians with localized cutaneous leishmaniasis

Cutaneous leishmaniasis (CL) is a chronic inflammatory disease caused by dermotropic Leishmania species belonging to the Viannia subgenera, with Leishmania (V.) braziliensis considered the main agent in Brazil. After infection, a local inflammatory process is initiated, inducing the expression of several cytokine/chemokine genes. We evaluated the immunity to CL of patients living in the indigenous community Xakriabá, Minas Gerais state, Brazil, by performing detailed analyses of the mRNA expression of different cytokines and chemokines in CL lesions, considering the time evolution (recent or late). We also studied the profile of the inflammatory infiltrate by histopathological analysis. The histopathological features of recent CL lesions showed an intense inflammatory reaction, characterized by the presence of both mononuclear and polymorphonuclear cells, whereas late CL lesions exhibited a predominance of mononuclear leukocytes. The gene expression of cytokines/chemokines in skin biopsies from the CL group showed higher transcript levels of modulatory (IL10 and TGFB1), anti-inflammatory (IL4), and pro-inflammatory (TNF, IFNG, IL12B, CCL2, CCL3, CCL5, CXCL10) biomarkers in recent lesions than in late lesions. Our findings suggest that differential gene expression of cytokines and chemokines found in skin lesions from CL patients is associated with time evolution of lesions.

PLGA nanoparticles loaded with KMP-11 stimulate innate immunity and induce the killing of Leishmania

We recently demonstrated that immunization with polyester poly(lactide-co-glycolide acid) (PLGA) nanoparticles loaded with the 11-kDa Leishmania vaccine candidate kinetoplastid membrane protein 11 (KMP-11) significantly reduced parasite load in vivo. Presently, we explored the ability of the recombinant PLGA nanoparticles to stimulate innate responses in macrophages and the outcome of infection with Leishmania braziliensis in vitro. Incubation of macrophages with KMP-11-loaded PLGA nanoparticles significantly decreased parasite load. In parallel, we observed the augmented production of nitric oxide, superoxide, TNF-α and IL-6. An increased release of CCL2/MCP-1 and CXCL1/KC was also observed, resulting in macrophage and neutrophil recruitment in vitro. Lastly, the incubation of macrophages with KMP-11-loaded PLGA nanoparticles triggered the activation of caspase-1 and the secretion of IL-1β and IL-18, suggesting inflammasome participation. Inhibition of caspase-1 significantly increased the parasite load. We conclude that KMP-11-loaded PLGA nanoparticles promote the killing of intracellular Leishmania parasites through the induction of potent innate responses.

FROM THE CLINICAL EDITOR

In this novel study, KMP-11-loaded PLGA nanoparticles are demonstrated to promote the killing of intracellular Leishmania parasites through enhanced innate immune responses by multiple mechanisms. Future clinical applications would have a major effect on our efforts to address parasitic infections.

Human macrophage response to L. (Viannia) panamensis: microarray evidence for an early inflammatory response

Background

Previous findings indicate that susceptibility to Leishmania (Viannia) panamensis infection of monocyte-derived macrophages from patients and asymptomatically infected individuals were associated with the adaptive immune response and clinical outcome.

Methodology/Principal Findings

To understand the basis for this difference we examined differential gene expression of human monocyte-derived macrophages following exposure to L. (V.) panamensis. Gene activation profiles were determined using macrophages from healthy volunteers cultured with or without stationary phase promastigotes of L. (V.) panamensis. Significant changes in expression (>1.5-fold change; p<0.05; up- or down-regulated) were identified at 0.5, 4 and 24 hours. mRNA abundance profiles varied over time, with the highest level of activation occurring at earlier time points (0.5 and 4 hrs). In contrast to observations for other Leishmania species, most significantly changed mRNAs were up- rather than down-regulated, especially at early time points. Up-regulated transcripts over the first 24 hours belonged to pathways involving eicosanoid metabolism, oxidative stress, activation of PKC through G protein coupled receptors, or mechanism of gene regulation by peroxisome proliferators via PPARα. Additionally, a marked activation of Toll-receptor mediated pathways was observed. Comparison with published microarray data from macrophages infected with L. (Leishmania) chagasi indicate differences in the regulation of genes involved in signaling, motility and the immune response.

Conclusions

Results show that the early (0.5 to 24 hours) human monocyte-derived macrophage response to L. (Viannia) panamensis is not quiescent, in contrast to published reports examining later response times (48–96 hours). Early macrophage responses are important for the developing cellular response at the site of infection. The kinetics and the mRNA abundance profiles induced by L. (Viannia) panamensis illustrate the dynamics of these interactions and the distinct biologic responses to different Leishmania species from the outset of infection within their primary host cell.

Leishmania parasites cause a spectrum of diseases (cutaneous, visceral and the deforming forms—chronic cutaneous and mucocutaneous) known as leishmaniasis. The macrophage, a key cell in the immune system, is the cellular target of Leishmania parasites in the mammalian host. Previous studies showed the responses of monocytederived macrophages from naturally infected humans to infection with Leishmania (Viannia) panamensis were key to adaptive immune responses and clinical outcome. Consequently, an mRNA microarray approach was employed to assess the changes in macrophage gene expression over time (0.5 to 24 hours) induced by L. panamensis. The highest level of gene expression induction occurred early (0.5–4 hours); the early pathways (groups of genes) activated included those involved in the innate immune response (signaling, phagocytosis, TLR activation, and inflammatory). Early gene activation is presumed to be important for the developing cellular milieu at the site of infection. By 24 hours post-infection the dominant pathways involved metabolic functions. However, a comparison of the macrophage response to L. (V.) panamensis to that of L. (L.) chagasi (causative agent of visceral leishmaniasis) at 24 hours revealed a differential up-regulation of genes (cell adhesion, signaling, and inflammation) in response to these species. These observations underscore the distinct biology of different Leishmania species from the outset of infection.

Leishmania major infection in humanized mice induces systemic infection and provokes a nonprotective human immune response

Background

Leishmania (L.) species are the causative agent of leishmaniasis. Due to the lack of efficient vaccine candidates, drug therapies are the only option to deal with cutaneous leishmaniasis. Unfortunately, chemotherapeutic interventions show high toxicity in addition to an increased risk of dissemination of drug-resistant parasites. An appropriate laboratory animal based model is still missing which allows testing of new drug strategies in the context of human immune cells in vivo.

Methodology/Principal Findings

Humanized mice were infected subcutaneously with stationary phase promastigote L. major into the footpad. The human immune response against the pathogen and the parasite host interactions were analyzed. In addition we proved the versatility of this new model to conduct drug research studies by the inclusion of orally given Miltefosine. We show that inflammatory human macrophages get infected with Leishmania parasites at the site of infection. Furthermore, a Leishmania-specific human-derived T cell response is initiated. However, the human immune system is not able to prevent systemic infection. Thus, we treated the mice with Miltefosine to reduce the parasitic load. Notably, this chemotherapy resulted in a reduction of the parasite load in distinct organs. Comparable to some Miltefosine treated patients, humanized mice developed severe side effects, which are not detectable in the classical murine model of experimental leishmaniasis.

Conclusions/Significance

This study describes for the first time L. major infection in humanized mice, characterizes the disease development, the induction of human adaptive and innate immune response including cytokine production and the efficiency of Miltefosine treatment in these animals. In summary, humanized mice might be beneficial for future preclinical chemotherapeutic studies in systemic (visceral) leishmaniasis allowing the investigation of human immune response, side effects of the drug due to cytokine production of activated humane immune cells and the efficiency of the treatment to eliminate also not replicating (“hiding”) parasites.

As many as 12 million people suffer from Leishmania (L.) infection worldwide with about one to two million newly infected people every year. Due to the lack of vaccine strategies, the only option is chemotherapeutic intervention which can cause serious side effects. Therefore, new prevention or treatment strategies are urgently needed in addition to an appropriate animal model for testing. We infected humanized mice in the footpad with stationary phase promastigote L. major and analyzed the human innate and adaptive immune response by flow cytometry, histology, and quantitative PCR. Infected macrophages were detectable at the site of infection and in lymphoid organs. Additionally, we were able to measure Leishmania-specific T cell priming in humanized mice. However, these human immune defense mechanisms were not sufficient to prevent systemic spreading and lethality. By the inclusion of Miltefosine, we tested this novel model for its versatility in conducting drug studies. The oral treatment was able to reduce parasitic load but also revealed side effects which are described in humans but not in mice. Therefore, we propose humanized mice as a novel model, which offers the opportunity to study new therapy strategies in chronic leishmaniasis in the context of a human immune system.

Characteristics of "Tip-DCs and MDSCs" and Their Potential Role in Leishmaniasis

Since the first description of dendritic cells (DCs) by Steinman and Cohn (1973), the myeloid lineage of leukocytes was investigated intensively. Nowadays it is obvious that myeloid cells, especially DCs, are crucial for the adaptive and innate immune response against intracellular pathogens such as Leishmania major parasites. Based on the overlapping expression of molecules that were commonly used to classify myeloid cells, it becomes difficult to denominate those cell types precisely. Of note, most of these markers used for myeloid cell identification are expressed on a broad range of myeloid cells, and should therefore be handled with care if used for subtyping of myeloid cells. In this mini-review we aim to discuss the relative impact of DCs that release TNF and nitric oxide (Tip-DCs) and myeloid cells with suppressive capacities (myeloid-derived suppressor cells, MDSCs) in infectious diseases such as experimental leishmaniasis. In our point of view it cannot be excluded that the novel subsets that were denominated as “Tip-DCs” and “MDSCs” might not be classical “subsets” but rather represent myeloid cells in a transient maturation stage expressing different genes, in response to the surrounding environment.

Macrophages in cancer and infectious diseases: the 'good' and the 'bad'

Macrophages are crucial orchestrators of host defence and tissue homeostasis. Macrophages are heterogeneous and plastic cells that in response to different microenvironmental signals can mount a broad spectrum of different programs of polarized activation. In different pathological contexts including cancer and infectious diseases, macrophages diversity and plasticity may act as a double-edged sword. The elucidation of the molecular mechanisms underlying macrophages recruitment and functional activation allows the identification of valuable targets for the development of innovative therapeutic approaches.

Characterization of chronic cutaneous lesions from TNF-receptor-1-deficient mice infected by Leishmania major

Leishmania major-infected TNF receptor 1 deficient (TNFR1 KO) mice resolve parasitism but fail to resolve lesions, while wild-type mice completely heal. We investigated the cell composition, cytokine production, and apoptosis in lesions from L. major-infected TNFR1 KO and wild-type (WT) mice. Chronic lesions from L. major-infected TNFR1 KO mice presented larger number of CD8+ T and Ly6G+ cells. In addition, higher concentrations of mRNA for IFN-γ CCL2 and CCL5, as well as protein, but lower numbers of apoptotic cells, were found in lesions from TNFR1 KO mice than in WT, at late time points of infection. Our studies showed that persistent lesions in L. major-infected TNFR1 KO mice may be mediated by continuous migration of cells to the site of inflammation due to the presence of chemokines and also by lower levels of apoptosis. We suggest that this model has some striking similarities to the mucocutaneous clinical form of leishmaniasis.

Measuring the killing of intracellular pathogens: Leishmania

Macrophages are professional phagocytes serving as a first line of defence against pathogenic organisms. Macrophages are equipped with efficient effector functions to kill invading microorganisms. The first important mechanism of macrophage host-defence is phagocytosis of pathogens. Subsequently, internalized pathogens are targeted for destruction in maturating phagolysosomal compartments. This process is mediated by lysosomal proteases and an acidified compartment. To investigate macrophages' killing potential in this chapter, we describe an assay based on human primary cells infected with the obligatory intracellular parasite Leishmania. For this pathogen the macrophage has a dual role. The parasite can use macrophages for its intracellular multiplication, but at the same time host macrophages, upon stimulation, can kill the parasite.

Murine immune response induced by Leishmania major during the implantation of paraffin tablets

We carried out a model of chronic inflammation using a subcutaneous paraffin tablet in mice experimentally infected with Leishmania major. It was previously reported that the parasite load following paraffin implantation occurred at a peak of 21 days in both BALB/c and C57BL/6 mice. At the present study, we have investigated what cytokines and chemokines are directly related to the parasite load in C57BL/6 mice. All mice were divided in four groups: mice implanted with paraffin tablets; mice experimentally infected with L. major; mice implanted with paraffin tablets and experimentally infected with L. major; and mice submitted only to the surgery were used for the Real-Time Polymerase Chain Reaction (RT-PCR) controls. Fragments of skin tissue and the tissue surrounding the paraffin tablets (inflammatory capsule) were collected for histopathology and RT-PCR studies. By 21 days, a diffuse chronic inflammatory reaction was mainly observed in the deep dermis where macrophages parasitized with Leishmania amastigotes were also found. RT-PCR analysis has shown that BALB/c mice showed strong IL-4 and IL-10 mRNA expression than controls with very little expression of IFN-γ. In contrast, both IFN-γ and IL-10 mRNA was found in higher levels in C57BL/6 animals. Moreover, in C57BL/6 mice the expression of chemokines mRNA of CCL3/MIP-1α was more highly expressed than CCL2/MCP-1. We conclude that the Th1 immune response C57BL/6 did not change to a Th2 response, even though C57BL/6 animals presented higher parasitism than BALB/c mice 21 days after infection and paraffin implantation.

The -2518bp promoter polymorphism at CCL2/MCP1 influences susceptibility to mucosal but not localized cutaneous leishmaniasis in Brazil

Mucosal leishmaniasis (ML) follows localized cutaneous leishmaniasis (CL) caused by Leishmania braziliensis. Proinflammatory responses mediate CL self-healing but are exaggerated in ML. Proinflammatory monocyte chemoattractant protein 1 (MCP-1; encoded by CCL2) is associated with CL. We explore its role in CL/ML through analysis of the regulatory CCL2 -2518bp promoter polymorphism in CL/ML population samples and families from Brazil. Genotype frequencies were compared among ML/CL cases and control groups using logistic regression and the family-based association test (FBAT). MCP-1 was measured in plasma and macrophages. The GG recessive genotype at CCL2 -2518bp was more common in patients with ML (N=67) than in neighborhood control (NC; N=60) subjects (OR 1.78; 95% CI 1.01-3.14; P=0.045), than in NC combined with leishmanin skin-test positive (N=60) controls (OR 4.40; 95% CI 1.42-13.65; P=0.010), and than in controls combined with CL (N=60) patients (OR 2.78; 95% CI 1.13-6.85; P=0.045). No associations were observed for CL compared to any groups. FBAT (91 ML and 223 CL cases in families) confirmed recessive association of ML with allele G (Z=2.679; P=0.007). Higher levels of MCP-1 occurred in plasma (P=0.03) and macrophages (P<0.0001) from GG compared to AA individuals. These results suggest that high MCP-1 increases risk of ML.

Role of chemokines in regulation of immunity against leishmaniasis

Successful immunity to Leishmania depends on recruitment of appropriate immune effector cells to the site of infection and chemokines play a crucial role in the process. At the same time, Leishmania parasites possess the ability to modify the chemokine profiles of their host thereby facilitating establishment of progressive infection. Therapeutic and prophylactic strategies targeted at chemokines and their receptors provide a promising area for further research. This review highlights our current knowledge concerning the role of chemokines and their receptors in modulating leishmaniasis in both clinical settings and experimental disease models.

Evaluation of localized and systemic immune responses in cutaneous leishmaniasis caused by Leishmania tropica: interleukin-8, monocyte chemotactic protein-1 and nitric oxide are major regulatory factors

We have established Leishmania tropica as the causative agent of cutaneous leishmaniasis (CL) in the region of India where the disease is endemic. The association between localized and circulating levels of immune-determinants in CL patients was evaluated. Reverse transcription-polymerase chain reaction analysis revealed up-regulation of interferon-gamma (IFN-gamma), interleukin (IL)-1beta, IL-8, tumour necrosis factor-alpha (TNF-alpha), IL-10 and IL-4 in dermal lesions at the pretreatment stage (n = 31) compared with healthy controls (P < 0.001) and a significant down-regulation after treatment (n = 14, P < 0.05). The results indicated that an unfavourable clinical outcome in CL was not related to an inadequate T helper 1 (Th1) cell response, but rather to impairment in multiple immune functions. Comparative assessment of treatment regimes with rifampicin (RFM) or sodium antimony gluconate (SAG) revealed tissue cytokine levels to be significantly reduced after treatment with RFM (P < 0.005), while no significant decrease was evident in the levels of IFN-gamma, TNF-alpha and IL-10 (P > 0.05) as a result of treatment with SAG. Increased transcripts of monocyte chemoattractant protein-1 (MCP-1) (P < 0.001) and inducible nitric oxide synthase (iNOS) (P < 0.05) were evident before treatment in tissue lesions and remained high after treatment. Immunohistochemistry demonstrated strong expression of myeloperoxidase (MPO) and IL-8, and moderate expression of iNOS in dermal lesions. The expression levels of IL-8, MCP-1 and nitric oxide (NO) were high in patient sera before treatment, as determined using cytokine bead array and enzyme-linked immunosorbent assay (ELISA). At the post-treatment stage, the serum IL-8 levels had decreased; however, the levels of MCP-1 and NO remained high. These data suggest that IL-8 is an effector immune-determinant in the progression of CL, whereas NO facilitates the parasite killing by macrophages via MCP-1-mediated stimulation.

CEACAM1+ myeloid cells control angiogenesis in inflammation

Local inflammation during cutaneous leishmaniasis is accompanied by accumulation of CD11b+ cells at the site of the infection. A functional role for these monocytic cells in local angiogenesis in leishmaniasis has not been described so far. Here, we show that CD11b+ cells express high levels of the myeloid differentiation antigen carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1). In experimental cutaneous leishmaniasis in C57BL/6 wild-type (B6.WT) and B6.Ceacam1−/− mice, we found that only B6.Ceacam1−/− mice develop edemas and exhibit impairment of both hemangiogenesis and lymphangiogenesis. Because CEACAM1 expression correlates with functional angiogenesis, we further analyzed the role of the CD11b+ population. In B6.Ceacam1−/− mice, we found systemic reduction of Ly-6Chigh/CD11bhigh monocyte precursors. To investigate whether CEACAM1+ myeloid cells are causally related to efficient angiogenesis, we used reverse bone marrow transplants (BMTs) to restore CEACAM1+ or CEACAM1− bone marrow in B6.Ceacam1−/− or B6.WT recipients, respectively. We found that angiogenesis was restored by CEACAM1+ BMT only. In addition, we observed reduced morphogenic potential of inflammatory cells in Matrigel implants in CEACAM1− backgrounds or after systemic depletion of CD11bhigh macrophages. Taken together, we show for the first time that CEACAM1+ myeloid cells are crucial for angiogenesis in inflammation.

Alveolar macrophage recruitment and activation by chronic second hand smoke exposure in mice

Approximately 15% of cases of COPD occur in non-smokers. Among the potential risk factors for COPD in non-smokers is second-hand smoke (SHS) exposure. However, the Surgeon General reported in 2006 that the evidence linking second hand smoke and COPD is insufficient to infer a causal relationship, largely because current evidence does not establish a biological link. The goal of this study was to determine whether SHS exposure can induce alveolar macrophage recruitment and expression of activation markers that we have previously demonstrated in human smokers and in mouse models of emphysema. To achieve these goals, we studied mice exposed to an ambient mixture of predominantly [89%] sidestream smoke at increasing doses over 3 months. We found that second hand smoke exposure induced a dose-dependent increase in alveolar macrophage recruitment (mean +/- sd; 224,511 +/- 52,330 vs 166,152 +/- 47,989 macrophages/ml of bronchoalveolar lavage in smoke-exposed vs air-exposed controls at 3 months, p = 0.003). We also found increased expression of several markers of alveolar macrophage activation (PLA2g7, dkfzp434l142, Trem-2, and pirin, all p < 0.01 at 3 months) and increased lavage levels of two inflammatory mediators associated with COPD (CCL2 [MCP-1], 58 +/- 12 vs. 43 +/- 22 pg/ml, p = 0.03; and TNFalpha, 138 +/- 43 vs 88 +/- 78 pg/ml, p = 0.04 at 3 months). These findings indicate that second smoke exposure can cause macrophage recruitment and activation, providing a biological link between second-hand smoke exposure and the development of inflammatory processes linked to COPD.

Alternative activation of macrophages: immune function and cellular biology

Macrophages are the first line of defense of the organism against pathogens and, in response to the microenvironment, become differentially activated. In the presence of IL-4 and IL-13, cytokines that are produced in a Th-2 type response, particularly during allergy and parasitic infections, macrophages become differentially activated. Alternative activated macrophages play an important role in the protection of the host by decreasing inflammation and promoting tissues repair. However, alternative activation of macrophages also downregulates host protection against selected pathogens. This defect is associated with an altered receptor expression pattern and extensive modulation of intracellular membrane trafficking. This review shows how alternative activation of macrophages induces extensive cellular remodelling of phagocytic, endocytic, signaling and secretory pathways which play an important, but unclear role in the pathogenesis of different disease.

Effects of tropism and virulence of Leishmania parasites on cytokine production by infected human monocytes

The nature of early interactions between Leishmania and macrophages which determine the outcome of infection can be related directly to parasite biological properties. Here we compared the capacity of L. major (Lm) strains, reported to be high (LmHV) and low virulent and (LmLV) in the mouse model and L. infantum (Li) strains, dermotropic (LiD) and viscerotropic (LiV), to infect and modulate cytokine production in human peripheral blood derived monocytes. Monocytes were infected with metacyclic promastigotes for 24, 48 and 72 h. Parasite burden was significantly higher in Lm- than in Li-infected monocytes. LmHV and LiD induced a significantly higher parasite burden than LmLV and LiV respectively. Cytokine production was evaluated in monocytes infected for 24 h. Contrary to interleukin (IL)-12p70, monocyte chemotactic protein-1 and transforming growth factor-beta production was increased significantly in infected monocytes with no differences between strains. Lm isolates induced significantly higher quantities of tumour necrosis factor (TNF)-alpha than Li isolates. Low levels of IL-10 were induced by all Leishmania strains and, interestingly, co-stimulation with lipopolysaccharide (LPS) was accompanied by a dramatic increase in IL-10 production by infected monocytes. In conclusion, Lm isolates displaying different levels of virulence in mice exhibited significant differences in parasite burden but similar abilities to modulate cytokine production in human monocytes. Li strains showed weaker infectivity and TNF-alpha inducing-capacity compared with Lm strains. The dramatic increase of IL-10 production in infected monocytes co-stimulated by LPS may play a role in disease progression considering the presence of LPS during bacterial superinfections observed during human leishmaniasis.

Early infection with Leishmania major restrains pathogenic response to Leishmania amazonensis and parasite growth

Experimental models of infection with Leishmania spp. have provided knowledge of several immunological events involved in the resistance mechanism used by the host to restrain parasite growth. It is well accepted that concomitant immunity exists, and there is some evidence that it would play a major role in long-lasting acquired resistance to infection. In this paper, the resistance to Leishmania amazonensis infection in C57BL/6 mice infected with Leishmania major was investigated. C57BL/6 mice, which spontaneously heal lesions caused by infection with L. major, were infected with L. amazonensis at different times before and after L. major. We demonstrated that C57BL/6 mice previously infected with L. major restrain pathogenic responses induced by L. amazonensis infection and decrease parasite burdens by one order of magnitude. Co-infected mice showed production of IFN-gamma in lesions similar to mice infected solely with L. major, but higher TNF-alpha and nitric oxide synthase (iNOS) mRNA expression was observed. Surprisingly, the restrained pathogenic response was not related to IL-10 production, as evidenced by lower levels of both mRNA, protein expression in lesions from co-infected mice and in co-infections in IL-10(-/-) mice. Examination of the inflammatory infiltrate at the site of infection showed a reduced number of monocytes and lymphocytes in L. amazonensis lesions. Additionally, differential production of the CCL3/MIP-1 alpha and CCL5/RANTES was observed. We suggest that the control of lesion progression caused by L. amazonensis in C57BL/6 mice pre-infected with L. major is related to the induction of a down-regulatory environment at the site of infection with L. amazonensis.

In vitro antihydatic action of IFN-gamma is dependent on the nitric oxide pathway

Hydatidosis is a widely endemic helminthic disease vectored in human by the larval stage of the metacestode Echinococcus granulosus. It is characterized by the long-term coexistence of chronic infection with detectable humoral and cellular responses against the macroparasite. Previous studies demonstrated interferon-gamma (IFN-gamma) and nitric oxide (NO) production (in vivo and in vitro) during hydatidosis. In this study, we tested the hypothesis that NO production after IFN-gamma induction may constitute a host defense against E. granulosus. We also investigated the IFN-gamma effect on protoscolices (larval form of the parasite) viability in coculture with hydatid patients' peripheral blood mononuclear cells (PBMC). PBMCs from hydatic patients incubated with IFN-gamma (100 U/mL) alone are effective in the killing of protoscolices. This scolicidal activity is concomitant with elevation of nitrite levels. NO release and cytotoxic activity are inhibited by N-monomethyl-L-arginine (L-NMMA), a specific inhibitor of the NO pathway and increased by L-arginine, an NO precursor, and tetrahydrobiopterin (BH4), a nitric oxide synthase (NOS) cofactor. Our results indicate that IFN-gamma mediated iNOS induction as one of host defense mechanism against human E. granulosus infection.

Listeria species escape from the phagosomes of interleukin-4-deactivated human macrophages independent of listeriolysin

Listeria monocytogenes is the causative agent of infections like sepsis and meningitis, especially in immunocompromised hosts. Human macrophages are able to phagocytose and digest L. monocytogenes but IL-4 prevents human macrophages from killing the bacteria, the mechanisms of which are unknown. In the present study, we examined various listeria species and strains including wild-type and deletion mutants in human macrophages pretreated with IL-4. To analyse the IL-4-mediated deactivation process, we combined quantitative infection assays with various morphologic methods. IL-4 facilitates survival and escape of the pathogenic L. monocytogenes wild-type strain 10403S from the macrophage phagosomes. In untreated macrophages, the isogenic listeriolysin deletion mutant strain DP-L2161 was killed and did not escape from the phagolysosomes. However, after macrophage deactivation with IL-4 DP-L2161 survived and escaped from the phagosomes. This was also the case, but to a lesser extent, even for the naturally avirulent L. innocua. As detected by confocal laser-scanning fluorescence microscopy and electron microscopy, IL-4 permitted the escape of all listeria species tested, including DP-L2161 and L. innocua from the phagosomal compartment of the macrophages. We conclude that escape from the phagosome and survival of the listeria species tested in IL-4-deactivated human macrophages is independent of the virulence factor listeriolysin.

Circulating nitric oxide and C-reactive protein levels in Indian kala azar patients: correlation with clinical outcome

Interferon gamma (IFN-gamma) and nitric oxide (NO) are the major players of the host defense against Leishmania. In the present study circulating levels of IFN-gamma, NO, interleukin (IL)-6 and C-reactive protein (CRP) were compared in kala azar (KA), post-kala azar dermal leishmaniasis (PKDL) and healthy controls. A significantly elevated level of these parameters was evident in KA compared to PKDL or control. Further, significantly elevated levels of IFN-gamma, NO and CRP were observed in sodium antimony gluconate (SAG) unresponsive cases compared to responsive cases. In PKDL cases, NO was significantly elevated while other parameters were comparable to control. At post-treatment stage, KA patients showed a significant decrement in all the parameters, however, IL-6 and CRP remained above control level. Hence, data implies that the parasites survive in spite of the presence of effector molecules, and the excessive release of IFN-gamma and NO could be associated with the progression of the disease.