IL-1 signalling is dispensable for protective immunity in Leishmania-resistant mice

Exploring the impact of epidemiological and clinical factors on the progression of canine leishmaniosis by statistical and whole genome analyses: from breed predisposition to comorbidities

Canine leishmaniosis (CanL), caused by Leishmania infantum, is a complex disease of growing importance in Europe. Clinical manifestations result from the down-modulation of the host immune response through multiple host-parasite interactions. Although several factors might influence CanL progression, this is the first known study evaluating risk factors for its different clinical stages in a large referral hospital population (n = 35.669) from an endemic area, over a 20 year period. Genome-wide scans for selection signatures were also conducted to explore the genomic component of clinical susceptibility to L. infantum infection. The prevalence of CanL was 3.2% (16.7% stage I; 43.6% stage II; 32.1% stage III; 7.6% stage IV). Dog breed (crossbreed), bodyweight (<10 kg), living conditions (indoors), regular deworming treatment, and being vaccinated against Leishmania significantly decreased the transmission risk and the risk for developing severe clinical forms. Conversely, the detection of comorbidities was associated with advanced clinical forms, particularly chronic kidney disease, neoplasia, cryptorchidism, infectious tracheobronchitis and urate urolithiasis, although those did not impact the clinical outcome. Significant associations between an increased risk of severe clinical stages and findings in the anamnesis (renal or skin-related manifestations) and physical examination (ocular findings) were also detected, highlighting their diagnostic value in referred cases of CanL. Sixteen breeds were found to be significantly more susceptible to developing severe stages of leishmaniosis (e.g. Great Dane, Rottweiler, English Springer Spaniel, Boxer, American Staffordshire Terrier, Golden Retriever), while 20 breeds displayed a clinical resistantance phenotype and, thus, are more likely to mount an efficient immune response against L. infantum (e.g. Pointer, Samoyed, Spanish Mastiff, Spanish Greyhound, English Setter, Siberian Husky). Genomic analyses of these breeds retrieved 12 regions under selection, 63 candidate genes and pinpointed multiple biological pathways such as the IRE1 branch of the unfolded protein response, which could play a critical role in clinical susceptibility to L. infantum infection.

Microfluidics Technology for the Design and Formulation of Nanomedicines

In conventional drug administration, drug molecules cross multiple biological barriers, distribute randomly in the tissues, and can release insufficient concentrations at the desired pathological site. Controlling the delivery of the molecules can increase the concentration of the drug in the desired location, leading to improved efficacy, and reducing the unwanted effects of the molecules under investigation. Nanoparticles (NPs), have shown a distinctive potential in targeting drugs due to their unique properties, such as large surface area and quantum properties. A variety of NPs have been used over the years for the encapsulation of different drugs and biologics, acting as drug carriers, including lipid-based and polymeric NPs. Applying NP platforms in medicines significantly improves the disease diagnosis and therapy. Several conventional methods have been used for the manufacturing of drug loaded NPs, with conventional manufacturing methods having several limitations, leading to multiple drawbacks, including NPs with large particle size and broad size distribution (high polydispersity index), besides the unreproducible formulation and high batch-to-batch variability. Therefore, new methods such as microfluidics (MFs) need to be investigated more thoroughly. MFs, is a novel manufacturing method that uses microchannels to produce a size-controlled and monodispersed NP formulation. In this review, different formulation methods of polymeric and lipid-based NPs will be discussed, emphasizing the different manufacturing methods and their advantages and limitations and how microfluidics has the capacity to overcome these limitations and improve the role of NPs as an effective drug delivery system.

Role of host genetics and cytokines in Leishmania infection

Cytokines and chemokines are important regulators of innate and specific responses in leishmaniasis, a disease that currently affects 12 million people. We overviewed the current information about influences of genetically engineered mouse models of cytokine and chemokine on leishmaniasis. We found that genetic background of the host, parasite species and sub-strain, as well as experimental design often modify effects of genetically engineered cytokine genes. Next we analyzed genes and QTLs (quantitative trait loci) that control response to Leishmania species in mouse in order to establish relationship between genetic control of cytokine expression and organ pathology. These studies revealed a network-like complexity of the combined effects of the multiple functionally diverse QTLs and their individual specificity. Genetic control of organ pathology and systemic immune response overlap only partially. Some QTLs control both organ pathology and systemic immune response, but the effects of genes and loci with the strongest impact on disease are cytokine-independent, whereas several loci modify cytokines levels in serum without influencing organ pathology. Understanding this genetic control might be important in development of vaccines designed to stimulate certain cytokine spectrum.

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.

Leishmania infantum infection reduces the amyloid β42-stimulated NLRP3 inflammasome activation

Activation of the NLRP3 inflammasome has been shown to play a major role in the neuroinflammation that accompanies Alzheimer's disease (AD); interventions that down regulate the NLRP3 inflammasome could thus be beneficial in AD. Parasite infections were recently shown to be associated with improved cognitive functions in Apolipoprotein E4 (ApoE4)-expressing members of an Amazonian tribe. We verified in an in vitro model whether Leishmania infantum infection could reduce NLRP3. Results obtained in an initial experimental model in which PBMC were LPS primed and nigericin-stimulated showed that L. infantum infection significantly reduced ASC-speck formation (i.e. intracellular inflammasome proteins assembly), as well as the production of activated caspase 5 and IL-1β, but increased that of activated caspase 1 and IL-18. Moreover, L. infantum infection induced the generation of an anti-inflammatory milieu by suppressing the production of TNFα and increasing that of IL-10. These results were replicated when cells that had been LPS-primed were stimulated with Aβ₄₂ and infected with L. infantum. Results herein indicate that Leishmania infection favors an anti-inflammatory milieu, which includes the down-regulation of NLRP3 inflammasome activation, possibly to facilitate its survival inside host cells. A side effect of Leishmaniasis would be the hampering of neuroinflammation; this could play a protective role against AD development.

Identification of gene expression profiles in Leishmania major infection by integrated bioinformatics analyses

Gene expression profiling in mouse models of leishmaniasis has given useful information to understand the molecular pathways active in lesions and to discover new diagnostic/therapeutic targets. Although the host response plays a critical role in protection from leishmaniasis and promoting disease severity, there are still unexplained aspects in the mechanism of non-healing cutaneous lesions, which need biomarkers for both targeted- therapy and diagnosis. To address this, transcriptional profiling of the skin lesions obtained from BALB/c mice infected with Leishmania major and healthy skin from naïve mice were evaluated by bioinformatics analysis, and then the results were validated by Revers Transcriptase-PCR. Five genes among the up-regulated differentially expressed genes named FCGR4, CCL4, CXCL9, Arg1 and IL-1β were found to have relatively high diagnostic value for CL due to L. major. Pathway analysis revealed that Triggering Receptor Expressed On Myeloid Cells 1 (TREM1) signaling pathways are active in cutaneous lesions, providing new insights for the understanding and treatment of leishmaniasis.

Inflammasome Activation in Response to Intracellular Protozoan Parasites

Inflammasomes are cytosolic complexes that assemble in response to cellular stress or upon sensing microbial molecules, culminating in cytokine processing and an inflammatory form of cell death called pyroptosis. Inflammasomes are usually composed of a sensor molecule, an adaptor protein, and an inflammatory caspase, such as Caspase-1, which cleaves and activates multiple substrates, including Gasdermin-D, pro-IL-1β, and pro-IL-18. Ultimately, inflammasome activation promotes inflammation and restriction of the microbial infection. In recent years, many studies have addressed the role of inflammasomes during fungal, bacterial, viral, and parasitic diseases, revealing sophisticated aspects of the host-pathogen interaction. In this review, we summarize recent advances on inflammasome activation in response to intracellular parasites, including Leishmania spp., Plasmodium spp., Trypanosoma cruzi, and Toxoplasma gondii.

Variable gene expression and parasite load predict treatment outcome in cutaneous leishmaniasis

Patients infected with Leishmania braziliensis develop chronic lesions that often fail to respond to treatment with antiparasite drugs. To determine whether genes whose expression is highly variable in lesions between patients might influence disease outcome, we obtained biopsies of lesions from patients before treatment with pentavalent antimony and performed transcriptomic profiling on these clinical samples. We identified genes that were highly variably expressed between patients, and the variable expression of these genes correlated with treatment outcome. Among the most variable genes in all the patients were components of the cytolytic pathway, and the expression of these genes correlated with parasite load in the skin. We demonstrated that treatment failure was linked to the cytolytic pathway activated during infection. Using a host-pathogen marker profile of as few as three genes, we showed that eventual treatment outcome could be predicted before the start of treatment in two separate cohorts of patients with cutaneous leishmaniasis (n = 21 and n = 25). These findings raise the possibility of point-of-care diagnostic screening to identify patients at high risk of treatment failure and provide a rationale for a precision medicine approach to drug selection in cutaneous leishmaniasis. This work more broadly demonstrates the value of identifying genes of high variability in other diseases to better understand and predict diverse clinical outcomes.

A polymorphism in the IL1B gene (rs16944 T/C) is associated with cutaneous leishmaniasis caused by Leishmania guyanensis and plasma cytokine interleukin receptor antagonist

Nod-like Receptor Protein3 (NLRP3) inflammasome in macrophages infected with Leishmania sp. enhances the secretion of IL-1β. Excess IL-1β production is linked to disease severity in patients with cutaneous leishmaniasis (CL) caused by L. mexicana. Blockade of the NLRP3 inflammasome in cell cultures from skin biopsies of patients with CL caused by L. braziliensis inhibited the release of IL-1β. We hypothesized that common single nucleotide polymorphisms in the IL1B and in its receptor antagonist IL1RN genes may be predictive of CL caused by L. guyanensis. The SNPs -511T/C (rs16944) and +3954C/T (rs1143634) of the IL1B and IL1RN VNTR (rs2234663) were assessed in 881 patients with CL and 837 healthy controls by PCR-RFLP and direct PCR respectively. Plasma cytokines levels were also assayed. The plasma levels of IL-1β were higher in patients compared to control subjects. In contrast, increased plasma levels of IL-1Ra were observed in controls. The rs16944 C/C genotype was more common among the patients (OR = 1.5 [95%CI 1.1-2.0]; P = 0.004) and the C allele suggests susceptibility to CL (OR = 1.2 [95%CI 1.1-1.4]; P = 0.003). The rs16944 C/C genotype shows a tendency to correlate with lower levels of the IL-1Ra cytokine. Low levels of IL-1Ra cytokine and rs16944 C/C genotype seem to confer susceptibility to L. guyanensis-infection in the Amazonas.

Intracellular Pathogens: Host Immunity and Microbial Persistence Strategies

Infectious diseases caused by pathogens including viruses, bacteria, fungi, and parasites are ranked as the second leading cause of death worldwide by the World Health Organization. Despite tremendous improvements in global public health since 1950, a number of challenges remain to either prevent or eradicate infectious diseases. Many pathogens can cause acute infections that are effectively cleared by the host immunity, but a subcategory of these pathogens called "intracellular pathogens" can establish persistent and sometimes lifelong infections. Several of these intracellular pathogens manage to evade the host immune monitoring and cause disease by replicating inside the host cells. These pathogens have evolved diverse immune escape strategies and overcome immune responses by residing and multiplying inside host immune cells, primarily macrophages. While these intracellular pathogens that cause persistent infections are phylogenetically diverse and engage in diverse immune evasion and persistence strategies, they share common pathogen type-specific mechanisms during host-pathogen interaction inside host cells. Likewise, the host immune system is also equipped with a diverse range of effector functions to fight against the establishment of pathogen persistence and subsequent host damage. This article provides an overview of the immune effector functions used by the host to counter pathogens and various persistence strategies used by intracellular pathogens to counter host immunity, which enables their extended period of colonization in the host. The improved understanding of persistent intracellular pathogen-derived infections will contribute to develop improved disease diagnostics, therapeutics, and prophylactics.

CD8+ T cell cytotoxicity mediates pathology in the skin by inflammasome activation and IL-1β production

Deregulated CD8+ T cell cytotoxicity plays a central role in enhancing disease severity in several conditions. However, we have little understanding of the mechanisms by which immunopathology develops as a consequence of cytotoxicity. Using murine models of inflammation induced by the protozoan parasite leishmania, and data obtained from patients with cutaneous leishmaniasis, we uncovered a previously unrecognized role for NLRP3 inflammasome activation and IL-1β release as a detrimental consequence of CD8+ T cell-mediated cytotoxicity, ultimately resulting in chronic inflammation. Critically, pharmacological blockade of NLRP3 or IL-1β significantly ameliorated the CD8+ T cell-driven immunopathology in leishmania-infected mice. Confirming the relevance of these findings to human leishmaniasis, blockade of the NLRP3 inflammasome in skin biopsies from leishmania-infected patients prevented IL-1β release. Thus, these studies link CD8+ T cell cytotoxicity with inflammasome activation and reveal novel avenues of treatment for cutaneous leishmaniasis, as well as other of diseases where CD8+ T cell-mediated cytotoxicity induces pathology.

Leishmaniasis is a neglected tropical disease endemic in 98 countries and approximately 1 million new cases occur each year. Disease caused by Leishmania braziliensis, the main causative agent of leishmaniasis in South America, leads to skin ulcers that are difficult to heal with drugs that target the parasites. This is because disease severity seen in patients infected with L. braziliensis is largely due to the immune response that develops, rather than the number of parasites in the skin. CD8+ T cells induce cell death in the lesions of L. braziliensis-infected mice, as well as in the lesions from L. braziliensis-infected patients, which promotes disease. However, the mechanism mediating CD8+ T cell dependent pathology is unknown. Here, using studies in mice and experiments with L. braziliensis patients’ samples we show that increased disease severity is due to inflammasome activation, and furthermore that therapies that block either inflammasome activation or IL-1β ameliorate disease in mouse models of severe leishmaniasis. Based on these studies we propose a novel strategy of therapy for L. braziliensis infection and other diseases in which cytotoxicity plays a central role in promoting disease severity.

Pro- and anti-inflammatory cytokines in cutaneous leishmaniasis: a review

Cutaneous leishmaniasis (CL) is caused by different species of the genus Leishmania. Pro- and anti-inflammatory cytokines play different roles in resistance/susceptibility and the immunopathogenesis of Leishmania infection. The balance and dynamic changes in cytokines may control or predict clinical outcome. T helper 1 (Th1) inflammatory cytokines (especially interferon-γ, tumor necrosis factor-α and interleukin-12) are the crucial factors in the initiation of protective immunity against L. major infection, whereas T helper 2 cytokines including IL-5, IL-4, and IL-13 facilitate the persistence of parasites by downregulating the Th1 immune response. On the other hand, aggravation of inflammatory reactions leads to collateral tissue damage and formation of ulcer. For this reason, immunity system such as T regulatory cells produce regulatory cytokines such as transforming growth factor-β and IL-10 to inhibit possible injures caused by increased inflammatory responses in infection site. In this article, we review the role of pro- and anti-inflammatory cytokines in the immunoprotection and immunopathology of CL.

Immune responses against protozoan parasites: a focus on the emerging role of Nod-like receptors

Nod-like receptors (NLRs) have gained attention in recent years because of the ability of some family members to assemble into a multimeric protein complex known as the inflammasome. The role of NLRs and the inflammasome in regulating innate immunity against bacterial pathogens has been well studied. However, recent studies show that NLRs and inflammasomes also play a role during infections caused by protozoan parasites, which pose a significant global health burden. Herein, we review the diseases caused by the most common protozoan parasites in the world and discuss the roles of NLRs and inflammasomes in host immunity against these parasites.

The Nlrp3 inflammasome, IL-1β, and neutrophil recruitment are required for susceptibility to a nonhealing strain of Leishmania major in C57BL/6 mice

Infection of C57BL/6 mice with most Leishmania major strains results in a healing lesion and clearance of parasites from the skin. Infection of C57BL/6 mice with the L. major Seidman strain (LmSd), isolated from a patient with chronic lesions, despite eliciting a strong Th1 response, results in a nonhealing lesion, poor parasite clearance, and complete destruction of the ear dermis. We show here that in comparison to a healing strain, LmSd elicited early upregulation of IL-1β mRNA and IL-1β-producing dermal cells and prominent neutrophil recruitment to the infected skin. Mice deficient in Nlrp3, apoptosis-associated speck-like protein containing a caspase recruitment domain, or caspase-1/11, or lacking IL-1β or IL-1 receptor signaling, developed healing lesions and cleared LmSd from the infection site. Mice resistant to LmSd had a stronger antigen-specific Th1 response. The possibility that IL-1β might act through neutrophil recruitment to locally suppress immunity was supported by the healing observed in neutropenic Genista mice. Secretion of mature IL-1β by LmSd-infected macrophages in vitro was dependent on activation of the Nlrp3 inflammasome and caspase-1. These data reveal that Nlrp3 inflammasome-dependent IL-1β, associated with localized neutrophil recruitment, plays a crucial role in the development of a nonhealing form of cutaneous leishmaniasis in conventionally resistant mice.

Innate immunity against Leishmania infections

Leishmaniasis is a major health problem that affects more than 300 million people throughout the world. The morbidity associated with the disease causes serious economic burden in Leishmania endemic regions. Despite the morbidity and economic burden associated with Leishmaniasis, this disease rarely gets noticed and is still categorized under neglected tropical diseases. The lack of research combined with the ability of Leishmania to evade immune recognition has rendered our efforts to design therapeutic treatments or vaccines challenging. Herein, we review the literature on Leishmania from innate immune perspective and discuss potential problems as well as solutions and future directions that could aid in identifying novel therapeutic targets to eliminate this parasite.

PKC/ROS-Mediated NLRP3 Inflammasome Activation Is Attenuated by Leishmania Zinc-Metalloprotease during Infection

Parasites of the Leishmania genus infect and survive within macrophages by inhibiting several microbicidal molecules, such as nitric oxide and pro-inflammatory cytokines. In this context, various species of Leishmania have been reported to inhibit or reduce the production of IL-1β both in vitro and in vivo. However, the mechanism whereby Leishmania parasites are able to affect IL-1β production and secretion by macrophages is still not fully understood. Dependent on the stimulus at hand, the maturation of IL-1β is facilitated by different inflammasome complexes. The NLRP3 inflammasome has been shown to be of pivotal importance in the detection of danger molecules such as inorganic crystals like asbestos, silica and malarial hemozoin, (HZ) as well as infectious agents. In the present work, we investigated whether Leishmania parasites modulate NLRP3 inflammasome activation. Using PMA-differentiated THP-1 cells, we demonstrate that Leishmania infection effectively inhibits macrophage IL-1β production upon stimulation. In this context, the expression and activity of the metalloprotease GP63 - a critical virulence factor expressed by all infectious Leishmania species - is a prerequisite for a Leishmania-mediated reduction of IL-1β secretion. Accordingly, L. mexicana, purified GP63 and GP63-containing exosomes, caused the inhibition of macrophage IL-1β production. Leishmania-dependent suppression of IL-1β secretion is accompanied by an inhibition of reactive oxygen species (ROS) production that has previously been shown to be associated with NLRP3 inflammasome activation. The observed loss of ROS production was due to an impaired PKC-mediated protein phosphorylation. Furthermore, ROS-independent inflammasome activation was inhibited, possibly due to an observed GP63-dependent cleavage of inflammasome and inflammasome-related proteins. Collectively for the first time, we herein provide evidence that the protozoan parasite Leishmania, through its surface metalloprotease GP63, can significantly inhibit NLRP3 inflammasome function and IL-1β production.

Leishmania parasites are the causative agent of leishmaniasis, a wide spread disease in tropical and subtropical areas. The microorganisms have been shown to be well-adapted to their hosts and are able to enter their target cells where they replicate themselves. To ensure these processes, Leishmania disrupts a multitude of cellular signals and protective mechanisms, which overall attenuates immune responses against the parasites. A key factor for inflammatory processes, also during infections, is IL-1β. As previous studies suggested a dysregulation of IL-1β levels after infection with Leishmania parasites, we herein investigated the underlying mechanisms. Our work reveals that Leishmania suppressing IL-1β production through its virulence factor GP63. Furthermore, our data suggests that the parasites can dampen the maturation of IL-1β after different stimuli. In this regard we established a role for the suppression of the kinase PKC and the generation of reactive oxygen species, as well as the cleavage of cellular proteins that are important for IL-1β-generation. Thus, we here present a novel aspect for how Leishmania parasites can counteract host protective mechanisms.

NLR proteins and parasitic disease

Parasitic diseases are a serious global health concern. Many of the most common and most severe parasitic diseases, including Chagas' disease, leishmaniasis, and schistosomiasis, are also classified as neglected tropical diseases and are comparatively less studied than infectious diseases prevalent in high income nations. The NLRs (nucleotide-binding domain leucine-rich-repeat-containing proteins) are cytosolic proteins known to be involved in pathogen detection and host response. The role of NLRs in the host response to parasitic infection is just beginning to be understood. The NLR proteins NOD1 and NOD2 have been shown to contribute to immune responses during Trypanosoma cruzi infection, Toxoplasma gondii infection, and murine cerebral malaria. The NLRP3 inflammasome is activated by T. cruzi and Leishmania amazonensis but also induces pathology during infection with schistosomes or malaria. Both the NLRP1 and NLRP3 inflammasomes respond to T. gondii infection. The NLRs may play crucial roles in human immune responses during parasitic infection, usually acting as innate immune sensors and driving the inflammatory response against invading parasites. However, this inflammatory response can either kill the invading parasite or be responsible for destructive pathology. Therefore, understanding the role of the NLR proteins will be critical to understanding the host defense against parasites as well as the fine balance between homeostasis and parasitic disease.

Role of hemodialysis with high cut-off membranes in a patient with a non-recognized leishmaniasis

BACKGROUND

We report here a case of a woman affected by fever, weight loss, splenomegaly, and leucopenia associated with trombocytopenia, transferred to the intensive care unit with acute kidney injury and septic shock.

METHODS

Patient was treated with high cut-off continuous veno-venous hemodialysis (HCO-CVVHD).

RESULTS

During treatment, the patient experienced a stable improvement in the hemodynamic, pulmonary function and tissue perfusion parameters. After 48 h of treatment, significant reductions in SOFA score (from 12, before starting the procedure, to 6) and in serum inflammatory mediators (as IL-6, from 599-568 pg/ml) were observed. Leishmania infection was identified as responsible of the septic condition only 48 h after removing hemodialysis. Antiprotozoal therapy was begun and the patient discharged.

CONCLUSIONS

By supporting the renal function and reducing systemic inflammation, HCO-CVVHD could be a useful bridge therapy. This procedure allowed the medical team to gain sufficient time to diagnose the type of infection and begin an etiological therapy.

Infection with Leishmania major induces a cellular stress response in macrophages

We investigated early cellular responses induced by infection with Leishmania major in macrophages from resistant C57/BL6 mice. Infection increased production of reactive oxygen species by resident, but not inflammatory peritoneal macrophages. In addition, infection increased activation of stress-activated protein kinases/c-Jun N-terminal kinases (SAPK/JNK) in resident, but not in inflammatory peritoneal macrophages. Infection also increased expression of membrane and soluble FasL, but infected macrophages remained viable after 48 h. Infection increased secretion of cytokines/chemokines TNF-α, IL-6, TIMP-1, IL-1RA, G-CSF, TREM, KC, MIP-1α, MIP-1β, MCP-1, and MIP-2 in resident macrophages. Addition of antioxidants deferoxamine and N-acetylcysteine reduced ROS generation and JNK activation. Addition of antioxidants or JNK inhibitor SP600125 reduced secretion of KC. Furthermore, treatment with antioxidants or JNK inhibitor also reduced intracellular parasite replication. These results indicated that infection triggers a rapid cellular stress response in resident macrophages which induces proinflammatory signals, but is also involved in parasite survival and replication in host macrophages.

Old World cutaneous leishmaniasis: diagnosis and treatment

Cutaneous leishmaniasis is a major world health problem. Diagnosis is suspected on evocative clinical presentation in patients living in or coming from endemic areas. Several methods have been used. The smear is a simple investigation used in endemic regions. The culture enables to identify the specimen. PCR has a high sensitivity. Montenegro's reaction is used in the epidemiological study. Pentavalent antimony derivatives remain the mainstay of systemic treatment. Their efficiency is well established. Their toxicity should be researched. Other treatments can be utilized, such as miltefosine. Local therapy is used in uncomplicated lesions. Injections of the pentavalent antimony derivate, cryotherapy and paromomycin ointmentsis are important options and should be used more frequently in Old World leishmaniasis.

IL-17 mediates immunopathology in the absence of IL-10 following Leishmania major infection

Leishmaniasis, resulting from infection with the protozoan parasite Leishmania, consists of a wide spectrum of clinical manifestations, from healing cutaneous lesions to fatal visceral infections. A particularly severe form of cutaneous leishmaniasis, termed mucosal leishmaniasis, exhibits decreased IL-10 levels and an exaggerated inflammatory response that perpetuates the disease. Using a mouse model of leishmaniasis, we investigated what cytokines contribute to increased pathology when IL-10-mediated regulation is absent. Leishmania major infected C57BL/6 mice lacking IL-10 regulation developed larger lesions than controls, but fewer parasites. Both IFN-γ and IL-17 levels were substantially elevated in mice lacking the capacity to respond to IL-10. IFN-γ promoted an increased infiltration of monocytes, while IL-17 contributed to an increase in neutrophils. Surprisingly, however, we found that IFN-γ did not contribute to increased pathology, but instead regulated the IL-17 response. Thus, blocking IFN-γ led to a significant increase in IL-17, neutrophils and disease. Similarly, the production of IL-17 by cells from leishmaniasis patients was also regulated by IL-10 and IFN-γ. Additional studies found that the IL-1 receptor was required for both the IL-17 response and increased pathology. Therefore, we propose that regulating IL-17, possibly by downregulating IL-1β, may be a useful approach for controlling immunopathology in leishmaniasis.

Leishmaniasis is a tropical disease transmitted by sand flies that causes visceral and cutaneous lesions. In humans, the most severe form of cutaneous leishmaniasis is the mucosal form, causing disfiguring lesions in the nasal and oral mucosa. Why these patients develop severe disease is not clear. It is known, however, that the severe disease is not due to an overwhelming number of parasites, but rather appears to be due to an uncontrolled inflammatory response that includes elevated production of IFN-γ and IL-17. Here, we used a murine model of leishmaniasis to identify the factors involved in this pathology, and found that mice infected with Leishmania major developed severe lesions in the absence of IL-10 or IL-10 signaling, and similar to patients, contained high levels of IFN-γ and IL-17. While both of these cytokines have the potential to induce pathology, we found that IL-17 was responsible for the severe pathology seen in the absence of IL-10 regulation, and furthermore that IL-17 levels were higher and pathology greater in the absence of IFN-γ. Thus, our study suggests that IL-17, but not the IFN-γ, is a strong candidate to be targeted in strategies to control the severe immunopathology observed in mucosal leishmaniasis patients.

Immunopathogenesis of non-healing American cutaneous leishmaniasis and progressive visceral leishmaniasis

The outcomes of Leishmania infection are determined by host immune and nutrition status, parasite species, and co-infection with other pathogens. While subclinical infection and self-healing cutaneous leishmaniasis (CL) are common, uncontrolled parasite replication can lead to non-healing local lesions or visceral leishmaniasis (VL). It is known that infection control requires Th1-differentiation cytokines (IL-12, IL-18, and IL-27) and Th1 cell and macrophage activation. However, there is no generalized consensus for the mechanisms of host susceptibility. The recent studies on regulatory T cells and IL-17-producing cells help explain the effector T cell responses that occur independently of the known Th1/Th2 cell signaling pathways. This review focuses on the immunopathogenesis of non-healing American CL and progressive VL. We summarize recent evidence from human and animal studies that reveals the mechanisms of dysregulated, hyper-responses to Leishmania braziliensis, as well as the presence of disease-promoting or the absence of protective responses to Leishmania amazonensis and Leishmania donovani. We highlight immune-mediated parasite growth and immunopathogenesis, with an emphasis on the putative roles of IL-17 and its related cytokines as well as arginase. A better understanding of the quality and regulation of innate immunity and T cell responses triggered by Leishmania will aid in the rational control of pathology and the infection.

Disease severity in patients infected with Leishmania mexicana relates to IL-1β

Leishmania mexicana can cause both localized (LCL) and diffuse (DCL) cutaneous leishmaniasis, yet little is known about factors regulating disease severity in these patients. We analyzed if the disease was associated with single nucleotide polymorphisms (SNPs) in IL-1β (−511), CXCL8 (−251) and/or the inhibitor IL-1RA (+2018) in 58 Mexican mestizo patients with LCL, 6 with DCL and 123 control cases. Additionally, we analyzed the in vitro production of IL-1β by monocytes, the expression of this cytokine in sera of these patients, as well as the tissue distribution of IL-1β and the number of parasites in lesions of LCL and DCL patients. Our results show a significant difference in the distribution of IL-1β (−511 C/T) genotypes between patients and controls (heterozygous OR), with respect to the reference group CC, which was estimated with a value of 3.23, 95% CI = (1.2, 8.7) and p-value = 0.0167), indicating that IL-1β (−511 C/T) represents a variable influencing the risk to develop the disease in patients infected with Leishmania mexicana. Additionally, an increased in vitro production of IL-1β by monocytes and an increased serum expression of the cytokine correlated with the severity of the disease, since it was significantly higher in DCL patients heavily infected with Leishmania mexicana. The distribution of IL-1β in lesions also varied according to the number of parasites harbored in the tissues: in heavily infected LCL patients and in all DCL patients, the cytokine was scattered diffusely throughout the lesion. In contrast, in LCL patients with lower numbers of parasites in the lesions, IL-1β was confined to the cells. These data suggest that IL-1β possibly is a key player determining the severity of the disease in DCL patients. The analysis of polymorphisms in CXCL8 and IL-1RA showed no differences between patients with different disease severities or between patients and controls.

Leishmania mexicana is an intracellular parasite that causes two polarly opposed diseases: One is a self-limited disease, characterized by ulcerative lesions associated with a low infectious load, as found in patients with localized cutaneous leishmaniasis (LCL). And the other pole is characterized by a progressive disease where abundant parasites spread uncontrollably throughout the skin inside heavily infected phagocytic cells, as occurs in patients with diffuse cutaneous leishmaniasis (DCL). The cause of this severe form of the disease is unknown, although the early encounter between the parasite and the inflammatory response of the host possibly plays a decisive role in the disease outcome. We here show that polymorphism in the gene encoding IL-1β (−511 C/T) represents a variable influencing the risk to develop the disease for patients infected with Leishmania mexicana. In vitro experiments showed that monocytes of DCL patients secreted significantly higher levels of the proinflammatory cytokine IL-1β as compared to LCL patients. DCL patients also had augmented levels of IL-1β in serum, and the cytokine was diffusely distributed throughout lesions, which was correlated with the numbers of parasites in the lesions. We propose that IL-1β possibly plays a key role in establishing the disease severity in patients infected with Leishmania mexicana.