Type 1 interferon (IFNalpha/beta) and type 2 nitric oxide synthase regulate the innate immune response to a protozoan parasite

Bacteria colonization and gene expression related to immune function in colon mucosa is associated with growth in neonatal calves regardless of live yeast supplementation

BACKGROUND

As Holstein calves are susceptible to gastrointestinal disorders during the first week of life, understanding how intestinal immune function develops in neonatal calves is important to promote better intestinal health. Feeding probiotics in early life may contribute to host intestinal health by facilitating beneficial bacteria colonization and developing intestinal immune function. The objective of this study was to characterize the impact of early life yeast supplementation and growth on colon mucosa-attached bacteria and host immune function.

RESULTS

Twenty Holstein bull calves received no supplementation (CON) or Saccharomyces cerevisiae boulardii (SCB) from birth to 5 d of life. Colon tissue biopsies were taken within 2 h of life (D0) before the first colostrum feeding and 3 h after the morning feeding at d 5 of age (D5) to analyze mucosa-attached bacteria and colon transcriptome. Metagenome sequencing showed that there was no difference in α and β diversity of mucosa-attached bacteria between day and treatment, but bacteria related to diarrhea were more abundant in the colon mucosa on D0 compared to D5. In addition, qPCR indicated that the absolute abundance of Escherichia coli (E. coli) decreased in the colon mucosa on D5 compared to D0; however, that of Bifidobacterium, Lactobacillus, and Faecalibacterium prausnitzii, which could competitively exclude E. coli, increased in the colon mucosa on D5 compared to D0. RNA-sequencing showed that there were no differentially expressed genes between CON and SCB, but suggested that pathways related to viral infection such as "Interferon Signaling" were activated in the colon mucosa of D5 compared to D0.

CONCLUSIONS

Growth affected mucosa-attached bacteria and host immune function in the colon mucosa during the first 5 d of life in dairy calves independently of SCB supplementation. During early life, opportunistic pathogens may decrease due to intestinal environmental changes by beneficial bacteria and/or host immune function. Predicted activation of immune function-related pathways may be the result of host immune function development or suggest other antigens in the intestine during early life. Further studies focusing on the other antigens and host immune function in the colon mucosa are required to better understand intestinal immune function development.

Innate biosignature of treatment failure in human cutaneous leishmaniasis

The quality and magnitude of the immune and inflammatory responses determine the clinical outcome of Leishmania infection, and contribute to the efficacy of antileishmanial treatments. However, the precise immune mechanisms involved in healing or in chronic immunopathology of human cutaneous leishmaniasis (CL) are not completely understood. Through sequential transcriptomic profiling of blood monocytes (Mo), neutrophils (Nφ), and eosinophils (Eφ) over the course of systemic treatment with meglumine antimoniate, we discovered that a heightened and sustained Type I interferon (IFN) response signature is a hallmark of treatment failure (TF) in CL patients. The transcriptomes of pre-treatment, mid-treatment and end-of-treatment samples were interrogated to identify predictive and prognostic biomarkers of TF. A composite score derived from the expression of 9 differentially expressed genes (common between Mo, Nφ and Eφ) was predictive of TF in this patient cohort for biomarker discovery. Similarly, machine learning models constructed using data from pre-treatment as well as post-treatment samples, accurately classified treatment outcome between cure and TF. Results from this study instigate the evaluation of Type-I IFN responses as new immunological targets for host-directed therapies for treatment of CL, and highlight the feasibility of using transcriptional signatures as predictive biomarkers of outcome for therapeutic decision making.

IFN-γ-mediated control of SARS-CoV-2 infection through nitric oxide

Introduction

The COVID-19 pandemic has highlighted the need to identify mechanisms of antiviral host defense against SARS-CoV-2. One such mediator is interferon-g (IFN-γ), which, when administered to infected patients, is reported to result in viral clearance and resolution of pulmonary symptoms. IFN-γ treatment of a human lung epithelial cell line triggered an antiviral activity against SARS-CoV-2, yet the mechanism for this antiviral response was not identified.

Methods

Given that IFN-γ has been shown to trigger antiviral activity via the generation of nitric oxide (NO), we investigated whether IFN-γ induction of antiviral activity against SARS-CoV-2 infection is dependent upon the generation of NO in human pulmonary epithelial cells. We treated the simian epithelial cell line Vero E6 and human pulmonary epithelial cell lines, including A549-ACE2, and Calu-3, with IFN-γ and observed the resulting induction of NO and its effects on SARS-CoV-2 replication. Pharmacological inhibition of inducible nitric oxide synthase (iNOS) was employed to assess the dependency on NO production. Additionally, the study examined the effect of interleukin-1b (IL-1β) on the IFN-g-induced NO production and its antiviral efficacy.

Results

Treatment of Vero E6 cells with IFN-γ resulted in a dose-responsive induction of NO and an inhibitory effect on SARS-CoV-2 replication. This antiviral activity was blocked by pharmacologic inhibition of iNOS. IFN-γ also triggered a NO-mediated antiviral activity in SARS-CoV-2 infected human lung epithelial cell lines A549-ACE2 and Calu-3. IL-1β enhanced IFN-γ induction of NO, but it had little effect on antiviral activity.

Discussion

Given that IFN-g has been shown to be produced by CD8+ T cells in the early response to SARS-CoV-2, our findings in human lung epithelial cell lines, of an IFN-γ-triggered, NO-dependent, links the adaptive immune response to an innate antiviral pathway in host defense against SARS-CoV-2. These results underscore the importance of IFN-γ and NO in the antiviral response and provide insights into potential therapeutic strategies for COVID-19.

Influence of standard culture conditions and effect of oleoresin from the microalga Haematococcus pluvialis on splenic cells from healthy Balb/c mice - a pilot study

In this work, we used splenocytes from healthy mice to study the effects of the two most commonly used cell culture media (A, B) with different compositions of redox reagents. The incubation of cells for 24 h resulted in a significant decrease in viability and metabolic activity of splenocytes, and the negative effects of incubation in medium B were more pronounced. In standard conditions, oxidative stress in cells was manifested by reduced mitochondrial potential, and this effect correlated with the transition of 58.3% of cells to the early stage of apoptosis under reducing conditions of medium A and up to 66.1% of cells under super-reducing conditions in medium B, suggesting altered cell physiology. High levels of ROS/RNS activated transcription factor Nrf2, superoxide dismutase 1, and catalase. The higher mRNA levels of these genes were under the conditions of medium B, whose super-reducing environment in combination with the environment of conventional incubators proved to be less suitable for the cells compared to medium A. Treatment of the cells with a lower concentration (10 µg/ml) of oleoresin obtained from the microalga H. pluvialis partially eliminated the negative effects of cultivation. Higher concentration of oleoresin (40 µg/ml) was slightly cytotoxic, due to the significant antioxidant effect of astaxanthin, the main bioactive component of the extract, which eliminated most of the ROS/RNS acting as signalling molecules. This study shows that the standard culture conditions do not reflect the physiological in vivo cell conditions; therefore, they are not generally suitable for incubation of all cell types.

Ligand Control of Dinitrosyl Iron Complexes for Selective Superoxide-Mediated Nitric Oxide Monooxygenation and Superoxide-Dioxygen Interconversion

Through nitrosylation of [Fe-S] proteins, or the chelatable iron pool, a dinitrosyl iron unit (DNIU) [Fe(NO)2] embedded in the form of low-molecular-weight/protein-bound dinitrosyl iron complexes (DNICs) was discovered as a metallocofactor assembled under inflammatory conditions with elevated levels of nitric oxide (NO) and superoxide (O2-). In an attempt to gain biomimetic insights into the unexplored transformations of the DNIU under inflammation, we investigated the reactivity toward O2- by a series of DNICs [(NO)2Fe(μ-MePyr)2Fe(NO)2] (1) and [(NO)2Fe(μ-SEt)2Fe(NO)2] (3). During the superoxide-induced conversion of DNIC 1 into DNIC [(K-18-crown-6-ether)2(NO2)][Fe(μ-MePyr)4(μ-O)2(Fe(NO)2)4] (2-K-crown) and a [Fe3+(MePyr)x(NO2)y(O)z]n adduct, stoichiometric NO monooxygenation yielding NO2- occurs without the transient formation of peroxynitrite-derived •OH/•NO2 species. To study the isoelectronic reaction of O2(g) and one-electron-reduced DNIC 1, a DNIC featuring an electronically localized {Fe(NO)2}9-{Fe(NO)2}10 electronic structure, [K-18-crown-6-ether][(NO)2Fe(μ-MePyr)2Fe(NO)2] (1-red), was successfully synthesized and characterized. Oxygenation of DNIC 1-red leads to the similar assembly of DNIC 2-K-crown, of which the electronic structure is best described as paramagnetic with weak antiferromagnetic coupling among the four S = 1/2 {FeIII(NO-)2}9 units and S = 5/2 Fe3+ center. In contrast to DNICs 1 and 1-red, DNICs 3 and [K-18-crown-6-ether][(NO)2Fe(μ-SEt)2Fe(NO)2] (3-red) display a reversible equilibrium of "3 + O2- ⇋ 3-red + O2(g)", which is ascribed to the covalent [Fe(μ-SEt)2Fe] core and redox-active [Fe(NO)2] unit. Based on this study, the supporting/bridging ligands in dinuclear DNIC 1/3 (or 1-red/3-red) control the selective monooxygenation of NO and redox interconversion between O2- and O2 during reaction with O2- (or O2).

Astaxanthin Extract from Haematococcus pluvialis and Its Fractions of Astaxanthin Mono- and Diesters Obtained by CCC Show Differential Antioxidant and Cytoprotective Effects on Naïve-Mouse Spleen Cells

Carotenoids are the most abundant lipid-soluble phytochemicals and are used as dietary supplements to protect against diseases caused by oxidative stress. Astaxanthin, a xanthophyll carotenoid, is a very potent antioxidant with numerous beneficial effects on cellular functions and signaling pathways. In this study, using spleen cells from healthy Balb/c mice, we report the bio-functional effects of an astaxanthin-rich extract (EXT) prepared from the microalga Haematococcus pluvialis and its astaxanthin monoesters-rich fraction (ME) and astaxanthin diesters-rich fraction (DE) obtained by fractionation of EXT using countercurrent chromatography (CCC). After incubation under standard culture conditions (humidity, 37 °C, 5% CO₂, atmospheric oxygen), the viability of untreated splenocytes, as determined by the trypan blue exclusion assay, the MTT assay, and the neutral red assay, decreases to approximately 75% after 24 h compared with naïve splenocytes. This effect correlated with the decrease in mitochondrial membrane potential and the transition of ~59% of cells to the early stage of apoptosis, as well as with the decreased ROS production, indicating that hyperoxia in cell-culture deteriorates cell functions. They are restored or stimulated by co-cultivation with EXT, ME, and DE up to 10 µg/mL in the order EXT > DE > ME, suggesting that esterification increases bioavailability to cells in vitro. ROS and H₂O₂ concentrations reflect mRNA transcriptional activity of Nrf2, superoxide dismutase 1 (SOD1), catalase, and glutathione peroxidase 1, as well as SOD-mediated ROS conversion, whereas they inversely correlate with iNOS-mediated NO production. The highest-tested concentration of EXT, ME, and DE (40 µg/mL) is detrimental to cells, probably because of the overwhelming scavenging activity of astaxanthin and its esters for the reactive oxygen/nitrogen species required for cellular functions and signal transduction at low physiological concentrations. In this study, we demonstrate that differential activities of ME and DE contribute to the final antioxidant and cytoprotective effects of astaxanthin extract, which is beneficial in preventing a wide range of ROS-induced adverse effects, with DE being more effective. In addition, the selection of physioxia-like conditions for pharmacological research is highlighted.

The Complexity of Interferon Signaling in Host Defense against Protozoan Parasite Infection

Protozoan parasites, such as Plasmodium, Leishmania, Toxoplasma, Cryptosporidium, and Trypanosoma, are causative agents of health-threatening diseases in both humans and animals, leading to significant health risks and socioeconomic losses globally. The development of effective therapeutic and prevention strategies for protozoan-caused diseases requires a full understanding of the pathogenesis and protective events occurring in infected hosts. Interferons (IFNs) are a family of cytokines with diverse biological effects in host antimicrobial defense and disease pathogenesis, including protozoan parasite infection. Type II IFN (IFN-γ) has been widely recognized as the essential defense cytokine in intracellular protozoan parasite infection, whereas recent studies also revealed the production and distinct function of type I and III IFNs in host defense against these parasites. Decoding the complex network of the IFN family in host-parasite interaction is critical for exploring potential new therapeutic strategies against intracellular protozoan parasite infection. Here, we review the complex effects of IFNs on the host defense against intracellular protozoan parasites and the crosstalk between distinct types of IFN signaling during infections.

Anti-leishmanial therapy: Caught between drugs and immune targets

Leishmaniasis is an enigmatic disease that has very restricted options for chemotherapy and none for prophylaxis. As a result, deriving therapeutic principles for curing the disease has been a major objective in Leishmania research for a long time. Leishmania is a protozoan parasite that lives within macrophages by subverting or switching cell signaling to the pathways that ensure its intracellular survival. Therefore, three groups of molecules aimed at blocking or eliminating the parasite, at least, in principle, include blockers of macrophage receptor- Leishmania ligand interaction, macrophage-activating small molecules, peptides and cytokines, and signaling inhibitors or activators. Macrophages also act as an antigen-presenting cell, presenting antigen to the antigen-specific T cells to induce activation and differentiation of the effector T cell subsets that either execute or suppress anti-leishmanial functions. Three groups of therapeutic principles targeting this sphere of Leishmania-macrophage interaction include antibodies that block pro-leishmanial response of T cells, ligands that activate anti-leishmanial T cells and the antigens for therapeutic vaccines. Besides these, prophylactic vaccines have been in clinical trials but none has succeeded so far. Herein, we have attempted to encompass all these principles and compose a comprehensive review to analyze the feasibility and adoptability of different therapeutics for leishmaniasis.

Macrophage Mitochondrial Biogenesis and Metabolic Reprogramming Induced by Leishmania donovani Require Lipophosphoglycan and Type I Interferon Signaling

Pathogen-specific rewiring of host cell metabolism creates the metabolically adapted microenvironment required for pathogen replication. Here, we investigated the mechanisms governing the modulation of macrophage mitochondrial properties by the vacuolar pathogen Leishmania. We report that induction of oxidative phosphorylation and mitochondrial biogenesis by Leishmania donovani requires the virulence glycolipid lipophosphoglycan, which stimulates the expression of key transcriptional regulators and structural genes associated with the electron transport chain. Leishmania-induced mitochondriogenesis also requires a lipophosphoglycan-independent pathway involving type I interferon (IFN) receptor signaling. The observation that pharmacological induction of mitochondrial biogenesis enables an avirulent lipophosphoglycan-defective L. donovani mutant to survive in macrophages supports the notion that mitochondrial biogenesis contributes to the creation of a metabolically adapted environment propitious to the colonization of host cells by the parasite. This study provides novel insight into the complex mechanism by which Leishmania metacyclic promastigotes alter host cell mitochondrial biogenesis and metabolism during the colonization process. IMPORTANCE To colonize host phagocytes, Leishmania metacyclic promastigotes subvert host defense mechanisms and create a specialized intracellular niche adapted to their replication. This is accomplished through the action of virulence factors, including the surface coat glycoconjugate lipophosphoglycan. In addition, Leishmania induces proliferation of host cell mitochondria as well as metabolic reprogramming of macrophages. These metabolic alterations are crucial to the colonization process of macrophages, as they may provide metabolites required for parasite growth. In this study, we describe a new key role for lipophosphoglycan in the stimulation of oxidative phosphorylation and mitochondrial biogenesis. We also demonstrate that host cell pattern recognition receptors Toll-like receptor 4 (TLR4) and endosomal TLRs mediate these Leishmania-induced alterations of host cell mitochondrial biology, which also require type I IFN signaling. These findings provide new insight into how Leishmania creates a metabolically adapted environment favorable to their replication.

Leishmania guyanensis suppressed inducible nitric oxide synthase provoked by its viral endosymbiont

Inducible nitric oxide synthase (iNOS) is essential to the production of nitric oxide (NO), an efficient effector molecule against intracellular human pathogens such as Leishmania protozoan parasites. Some strains of Leishmania are known to bear a viral endosymbiont termed Leishmania RNA virus 1 (LRV1). Recognition of LRV1 by the innate immune sensor Toll-like receptor-3 (TLR3) leads to conditions worsening the disease severity in mice. This process is governed by type I interferon (type I IFNs) arising downstream of TLR3 stimulation and favoring the formation of secondary metastatic lesions. The formation of these lesions is mediated by the inflammatory cytokine IL-17A and occurs in the absence, or low level of, protective cytokine IFN-γ. Here, we described that the presence of LRV1 led to the initial expression of iNOS and low production of NO that failed to control infection. We subsequently showed that LRV1-triggered type I IFN was essential but insufficient to induce robust iNOS induction, which requires strong activation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB). Leishmania guyanensis carrying LRV1 (LgyLRV1+) parasites mitigated strong iNOS production by limiting NF-kB activation via the induction of tumor necrosis factor-alpha-induced protein 3 (TNFAIP3), also known as A20. Moreover, our data suggested that production of LRV1-induced iNOS could be correlated with parasite dissemination and metastasis via elevated secretion of IL-17A in the draining lymph nodes. Our findings support an additional strategy by which LRV1-bearing Leishmania guyanensis evaded killing by nitric oxide and suggest that low levels of LRV1-induced NO might contribute to parasite metastasis.

Tissue tropism: Is it an intrinsic characteristic of Leishmania species?

The genus Leishmania comprises a wide range of species, some of which are pathogenic to humans and each of which has a different tissue preference, resulting in one of the three clinical forms of human leishmaniasis: visceral, cutaneous, or mucocutaneous. Although, all pathogenic species are deposited intradermally in the mammalian host upon an infectious sand fly bite, only the viscerotropic strains can leave the skin and reach the internal organs. We assume that Leishmania tissue tropism is not only the result of Leishmania genetic determinism but is also governed by the interaction of the parasite with different vectorial and human host elements. To shed light on these elements and key steps determining the course of the infection, we describe throughout this review the disease's progression from the early stages of infection taking place in the skin to the late stages succeeding in the parasite's visceral dissemination. Hence, we address the question of Leishmania tropism, through providing relevant hypotheses and answers gathered from the literature.

Expression Profile of Genes Related to the Th17 Pathway in Macrophages Infected by Leishmania major and Leishmania amazonensis: The Use of Gene Regulatory Networks in Modeling This Pathway

Leishmania amazonensis and Leishmania major are the causative agents of cutaneous and mucocutaneous diseases. The infections‘ outcome depends on host–parasite interactions and Th1/Th2 response, and in cutaneous form, regulation of Th17 cytokines has been reported to maintain inflammation in lesions. Despite that, the Th17 regulatory scenario remains unclear. With the aim to gain a better understanding of the transcription factors (TFs) and genes involved in Th17 induction, in this study, the role of inducing factors of the Th17 pathway in Leishmania–macrophage infection was addressed through computational modeling of gene regulatory networks (GRNs). The Th17 GRN modeling integrated experimentally validated data available in the literature and gene expression data from a time-series RNA-seq experiment (4, 24, 48, and 72 h post-infection). The generated model comprises a total of 10 TFs, 22 coding genes, and 16 cytokines related to the Th17 immune modulation. Addressing the Th17 induction in infected and uninfected macrophages, an increase of 2- to 3-fold in 4–24 h was observed in the former. However, there was a decrease in basal levels at 48–72 h for both groups. In order to evaluate the possible outcomes triggered by GRN component modulation in the Th17 pathway. The generated GRN models promoted an integrative and dynamic view of Leishmania–macrophage interaction over time that extends beyond the analysis of single-gene expression.

Toll-Like Receptor- and Protein Kinase R-Induced Type I Interferon Sustains Infection of Leishmania donovani in Macrophages

Leishmania donovani is a protozoan parasite that causes visceral leishmaniasis, provoking liver and spleen tissue destruction that is lethal unless treated. The parasite replicates in macrophages and modulates host microbicidal responses. We have previously reported that neutrophil elastase (NE) is required to sustain L. donovani intracellular growth in macrophages through the induction of interferon beta (IFN-β). Here, we show that the gene expression of IFN-β by infected macrophages was reduced by half when TLR4 was blocked by pre-treatment with neutralizing antibodies or in macrophages from tlr2^-/- mice, while the levels in macrophages from myd88^-/- mice were comparable to those from wild-type C57BL/6 mice. The neutralization of TLR4 in tlr2^-/- macrophages completely abolished induction of IFN-β gene expression upon parasite infection, indicating an additive role for both TLRs. Induction of type I interferon (IFN-I), OASL2, SOD1, and IL10 gene expression by L. donovani was completely abolished in macrophages from NE knock-out mice (ela2^-/-) or from protein kinase R (PKR) knock-out mice (pkr^-/-), and in C57BL/6 macrophages infected with transgenic L. donovani expressing the inhibitor of serine peptidase 2 (ISP2). Parasite intracellular growth was impaired in pkr^-/- macrophages but was fully restored by the addition of exogenous IFN-β, and parasite burdens were reduced in the spleen of pkr^-/- mice at 7 days, as compared to the 129Sv/Ev background mice. Furthermore, parasites were unable to grow in macrophages lacking TLR3, which correlated with lack of IFN-I gene expression. Thus, L. donovani engages innate responses in infected macrophages via TLR2, TLR4, and TLR3, via downstream PKR, to induce the expression of pro-survival genes in the host cell, and guarantee parasite intracellular development.

TLR9 signalling inhibits Plasmodium liver infection by macrophage activation

Recognition of pathogen-associated molecular patterns (PAMPs) through Toll-like receptors (TLRs) plays a pivotal role in first-line pathogen defense. TLRs are also likely triggered during a Plasmodium infection in vivo by parasite-derived components. However, the contribution of innate responses to liver infection and to the subsequent clinical outcome of a blood infection is not well understood. To assess the potential effects of enhanced TLR-signalling on Plasmodium infection, we systematically examined the effect of agonist-primed immune responses to sporozoite inoculation in the P. berghei/C57Bl/6 murine malaria model. We could identify distinct stage-specific effects on the course of infection after stimulation with two out of four TLR-ligands tested. Priming with a TLR9 agonist induced killing of pre-erythrocytic stages in the liver that depended on macrophages and the expression of inducible nitric oxide synthase (iNOS). These factors have previously not been recognized as antigen-independent effector mechanisms against Plasmodium liver stages. Priming with TLR4 and -9 agonists also translated into blood stage-specific protection against experimental cerebral malaria (ECM). These insights are relevant to the activation of TLR signalling pathways by adjuvant systems of antimalaria vaccine strategies. The protective role of TLR4-activation against ECM might also explain some unexpected clinical effects observed with pre-erythrocytic vaccine approaches.

The Paradox of a Phagosomal Lifestyle: How Innate Host Cell-Leishmania amazonensis Interactions Lead to a Progressive Chronic Disease

Intracellular phagosomal pathogens represent a formidable challenge for innate immune cells, as, paradoxically, these phagocytic cells can act as both host cells that support pathogen replication and, when properly activated, are the critical cells that mediate pathogen elimination. Infection by parasites of the Leishmania genus provides an excellent model organism to investigate this complex host-pathogen interaction. In this review we focus on the dynamics of Leishmania amazonensis infection and the host innate immune response, including the impact of the adaptive immune response on phagocytic host cell recruitment and activation. L. amazonensis infection represents an important public health problem in South America where, distinct from other Leishmania parasites, it has been associated with all three clinical forms of leishmaniasis in humans: cutaneous, muco-cutaneous and visceral. Experimental observations demonstrate that most experimental mouse strains are susceptible to L. amazonensis infection, including the C57BL/6 mouse, which is resistant to other species such as Leishmania major, Leishmania braziliensis and Leishmania infantum. In general, the CD4⁺ T helper (Th)1/Th2 paradigm does not sufficiently explain the progressive chronic disease established by L. amazonensis, as strong cell-mediated Th1 immunity, or a lack of Th2 immunity, does not provide protection as would be predicted. Recent findings in which the balance between Th1/Th2 immunity was found to influence permissive host cell availability via recruitment of inflammatory monocytes has also added to the complexity of the Th1/Th2 paradigm. In this review we discuss the roles played by innate cells starting from parasite recognition through to priming of the adaptive immune response. We highlight the relative importance of neutrophils, monocytes, dendritic cells and resident macrophages for the establishment and progressive nature of disease following L. amazonensis infection.

Nitric Oxide and Immune Responses in Cancer: Searching for New Therapeutic Strategies

In recent years, there has been an increasing interest in understanding the mysterious functions of nitric oxide (NO) and how this pleiotropic signaling molecule contributes to tumorigenesis. This review attempts to expose and discuss the information available on the immunomodulatory role of NO in cancer and recent approaches to the role of NO donors in the area of immunotherapy. To address the goal, the following databases were searched to identify relevant literature concerning empirical evidence: The Cochrane Library, Pubmed, Medline, EMBASE from 1980 through March 2020. Valuable attempts have been made to develop distinctive NO-based cancer therapy. Although the data do not allow generalization, the evidence seems to indicate that low / moderate levels may favor tumorigenesis while higher levels would exert anti-tumor effects. In this sense, the use of NO donors could have an important therapeutic potential within immunotherapy, although there are still no clinical trials. The emerging understanding of NO-regulated immune responses in cancer may help unravel the recent features of this "double-edged sword" in cancer physiological and pathologic processes and its potential use as a therapeutic agent for cancer treatment. In short, in this review, we discuss the complex cellular mechanism in which NO, as a pleiotropic signaling molecule, participates in cancer pathophysiology. We also debate the dual role of NO in cancer and tumor progression, and clinical approaches for inducible nitric oxide synthase (iNOS) based therapy against cancer.

Potential biomarkers of immune protection in human leishmaniasis

Leishmaniasis is a vector-borne neglected tropical disease endemic in over 100 countries around the world. Available control measures are not always successful, therapeutic options are limited, and there is no vaccine available against human leishmaniasis, although several candidate antigens have been evaluated over the last decades. Plenty of studies have aimed to evaluate the immune response development and a diverse range of host immune factors have been described to be associated with protection or disease progression in leishmaniasis; however, to date, no comprehensive biomarker(s) have been identified as surrogate marker of protection or exacerbation, and lack of enough information remains a barrier for vaccine development. Most of the current understanding of the role of different markers of immune response in leishmaniasis has been collected from experimental animal models. Although the data generated from the animal models are crucial, it might not always be extrapolated to humans. Here, we briefly review the events during Leishmania invasion of host cells and the immune responses induced against Leishmania in animal models and humans and their potential role as a biomarker of protection against human leishmaniasis.

Novais F, Nguyen BT, Nascimento MT, Lago J, Lago AS, Carvalho LP, Beiting DP, Scott P. Localized skin inflammation during cutaneous leishmaniasis drives a chronic, systemic IFN-γ signature

Cutaneous leishmaniasis is a localized infection controlled by CD4+ T cells that produce IFN-γ within lesions. Phagocytic cells recruited to lesions, such as monocytes, are then exposed to IFN-γ which triggers their ability to kill the intracellular parasites. Consistent with this, transcriptional analysis of patient lesions identified an interferon stimulated gene (ISG) signature. To determine whether localized L. braziliensis infection triggers a systemic immune response that may influence the disease, we performed RNA sequencing (RNA-seq) on the blood of L. braziliensis-infected patients and healthy controls. Functional enrichment analysis identified an ISG signature as the dominant transcriptional response in the blood of patients. This ISG signature was associated with an increase in monocyte- and macrophage-specific marker genes in the blood and elevated serum levels IFN-γ. A cytotoxicity signature, which is a dominant feature in the lesions, was also observed in the blood and correlated with an increased abundance of cytolytic cells. Thus, two transcriptional signatures present in lesions were found systemically, although with a substantially reduced number of differentially expressed genes (DEGs). Finally, we found that the number of DEGs and ISGs in leishmaniasis was similar to tuberculosis-another localized infection-but significantly less than observed in malaria. In contrast, the cytolytic signature and increased cytolytic cell abundance was not found in tuberculosis or malaria. Our results indicate that systemic signatures can reflect what is occurring in leishmanial lesions. Furthermore, the presence of an ISG signature in blood monocytes and macrophages suggests a mechanism to limit systemic spread of the parasite, as well as enhance parasite control by pre-activating cells prior to lesion entry.

Immunotherapy in treatment of leishmaniasis

Leishmaniasis caused by various species of protozoan transmitted by sand fly vectors occurs as a spectrum of clinical features including cutaneous, mucocutaneous and visceral forms. It is a geographically distributed parasitic disease and a major public health problem in the world. The clinical syndromes are highly variable depending on the parasite species, host genetics, vectors and environment. To date, there is no effective vaccine and traditional treatments are toxic, expensive with long administration duration and many adverse side effects and/or drug resistance. Instead of treatments based on chemotherapy, certain strategies aim to recover leishmaniasis and reduce the parasitic burden. Immunotherapy has focused on the induction of effective immune response to rapidly control the disease. Recent studies have indicated that a single dose of a suitable therapeutic vaccine induces a quick and lasting recovery in patients. Immunotherapy reduces the toxicity of drug and the emergence of resistance dramatically. It could be an effective addition to chemotherapy with a safe and potent drug compared with monotherapy, resulting in a prophylactic and therapeutic cure of leishmaniasis. This review has focused on treatment of leishmaniasis with particular emphasis on immunotherapy as an alternative to conventional drug treatment.

Perspectives on the Genetic Associations of Ankylosing Spondylitis

Ankylosing spondylitis (AS) is a common form of inflammatory spinal arthritis with a complex polygenic aetiology. Genome-wide association studies have identified more than 100 loci, including some involved in antigen presentation (HLA-B27, ERAP1, and ERAP2), some in Th17 responses (IL6R, IL23R, TYK2, and STAT3), and others in macrophages and T-cells (IL7R, CSF2, RUNX3, and GPR65). Such observations have already helped identify potential new therapies targeting IL-17 and GM-CSF. Most AS genetic associations are not in protein-coding sequences but lie in intergenic regions where their direct relationship to particular genes is difficult to assess. They most likely reflect functional polymorphisms concerned with cell type-specific regulation of gene expression. Clarifying the nature of these associations should help to understand the pathogenic pathways involved in AS better and suggest potential cellular and molecular targets for drug therapy. However, even identifying the precise mechanisms behind the extremely strong HLA-B27 association with AS has so far proved elusive. Polygenic risk scores (using all the known genetic associations with AS) can be effective for the diagnosis of AS, particularly where there is a relatively high pre-test probability of AS. Genetic prediction of disease outcomes and response to biologics is not currently practicable.

A primer on cytokines

Cytokines are pleiotropic polypeptides that control the development of and responses mediated by immune cells. Cytokine classification predominantly relies on [1] the target receptor(s), [2] the primary structural features of the extracellular domains of their receptors, and [3] their receptor composition. Functionally, cytokines are either pro-inflammatory or anti-inflammatory, hematopoietic colony-stimulating factors, developmental and would healing maintaining immune homeostasis. When the balance in C can form complex networks amongst themselves that may affect the homeostasis and diseases. Cytokines can affect resistance and susceptibility for many diseases and their availability in the host cytokine production and interaction is disturbed, immunopathogenesis sets in. Therefore, cytokine-targeting bispecific, and chimeric antibodies form a significant mode of immnuo-therapeutics Although the field has grown deep and wide, many areas of cytokine biology remain unknown. Here, we have reviewed these cytokines along with the organization, signaling, and functions through respective cytokine-receptor-families. Being part of the special issue on the Role of Cytokines in Leishmaniasis, this review is intended to be used as an organized primer on cytokines and not a resource for detailed discussion- for which a two-volume Handbook of cytokines is available- on each of the cytokines. Priming the readers on cytokines, we next brief the role of cytokines in Leishmaniasis. In the brief, we do not provide an account of each of the involved cytokines known to date, instead, we offer a temporal relationship between the cytokines and the progress of the infection towards the alternate outcomes- healing or non-healing- of the infection.

Macrophages as host, effector and immunoregulatory cells in leishmaniasis: Impact of tissue micro-environment and metabolism

Leishmania are protozoan parasites that predominantly reside in myeloid cells within their mammalian hosts. Monocytes and macrophages play a central role in the pathogenesis of all forms of leishmaniasis, including cutaneous and visceral leishmaniasis. The present review will highlight the diverse roles of macrophages in leishmaniasis as initial replicative niche, antimicrobial effectors, immunoregulators and as safe hideaway for parasites persisting after clinical cure. These multiplex activities are either ascribed to defined subpopulations of macrophages (e.g., Ly6C^highCCR2⁺ inflammatory monocytes/monocyte-derived dendritic cells) or result from different activation statuses of tissue macrophages (e.g., macrophages carrying markers of of classical [M1] or alternative activation [M2]). The latter are shaped by immune- and stromal cell-derived cytokines (e.g., IFN-γ, IL-4, IL-10, TGF-β), micro milieu factors (e.g., hypoxia, tonicity, amino acid availability), host cell-derived enzymes, secretory products and metabolites (e.g., heme oxygenase-1, arginase 1, indoleamine 2,3-dioxygenase, NOS2/NO, NOX2/ROS, lipids) as well as by parasite products (e.g., leishmanolysin/gp63, lipophosphoglycan). Exciting avenues of current research address the transcriptional, epigenetic and translational reprogramming of macrophages in a Leishmania species- and tissue context-dependent manner.

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.

Purified Splenic amastigotes of Leishmania donovani-Immunoproteomic approach for exploring Th1 stimulatory polyproteins

Visceral leishmaniasis (VL) represents one of the most challenging infectious diseases worldwide. The reason that once infected, patient develops immunity against Leishmania parasite has paved way to develop prophylactic vaccines against disease, but only some of these have moved ahead for clinical trials. Herein, the study to explore novel and potential vaccine candidates was extended to pathogenic form of parasite, that is, amastigote form which is less explored due to complexity of its purification process. Methods and results. Classical protocol of purification of splenic amastigotes was modified to obtain highly pure amastigotes which was confirmed by Western blotting in support with proteomics studies. Fractionation and sub-fractionation of purified splenic amastigotes revealed four sub-fractions, belonging to 97 to 68 kDa and 68 to 43 kDa ranges, which showed long-lasting protection with remarkable Th1-type cellular responses in hamsters vaccinated with these sub-fractions (LTT, NO, QRT-PCR). Further proteomics analysis, to identify and understand the precise nature and function of these protective protein sub-fractions, identified a total of 47 proteins including twenty-five hypothetical proteins/unknowns. Amastigote stage has potential Th1-stimulatory vaccine candidates, notably, among identified proteins, major were uncharacterized proteins/hypothetical proteins, which once characterized may serve as novel and potential vaccine candidates/drug targets.

Modulation of Cytokines and Extracellular Matrix Proteins Expression by Leishmania amazonensis in Susceptible and Resistant Mice

Leishmaniases are a complex of diseases with a broad spectrum of clinical forms, which depend on the parasite species, immunological status, and genetic background of the host. In the Leishmania major model, susceptibility is associated with the Th2 pattern of cytokines production, while resistance is associated with Th1 response. However, the same dichotomy does not occur in L. amazonensis-infected mice. Cytokines are key players in these diseases progression, while the extracellular matrix (ECM) components participate in the process of parasite invasion as well as lesion healing. In this article, we analyzed the influence of host genetics on the expression of cytokines, inducible nitric oxide synthase (iNOS), and ECM proteins, as well as the parasite load in mice with different genetic backgrounds infected by L. amazonensis. C57BL/10 and C3H/He mice were subcutaneously infected with 10⁶L. amazonensis promastigotes. Lesion kinetics, parasite load, cytokines, iNOS, and ECM proteins expression were measured by quantitative PCR (qPCR) in the footpad, draining lymph nodes, liver, and spleen at early (24 h and 30 days) and late phase (120 and 180 days) of infection. Analysis of lesion kinetics showed that C57BL/10 mice developed ulcerative lesions at the inoculation site after L. amazonensis infection, while C3H/He showed slight swelling in the footpad 180 days after infection. C57BL/10 showed progressive enhancement of parasite load in all analyzed organs, while C3H/He mice showed extremely low parasite loads. Susceptible C57BL/10 mice showed high levels of TGF-β mRNA in the footpad early in infection and high levels of proinflammatory cytokines mRNA (IL-12, TNF-α, and IFN-γ) and iNOS in the late phase of the infection. There is an association between increased expression of fibronectin, laminin, collagen III and IV, and TGF-β. On the other hand, resistant C3H/He mice presented a lower repertory of cytokines mRNA expression when compared with susceptible C57BL/10 mice, basically producing TNF-α, collagen IV, and laminin early in infection. The findings of our study indicate that L. amazonensis infection induces different cytokine expression in resistant and susceptible mice but not like the L. major model. An organ-compartmentalized cytokine response was observed in our model. Host genetics determine this response, which modulates ECM proteins expression.

Susceptibility to Intracellular Infections: Contributions of TNF to Immune Defense

An interesting puzzle is the fact that an infection of a tumor necrosis factor α (TNF)-deficient host with pathogens such as bacteria or parasites that reside intracellularly inevitably ends fatally. Is this due to one specific role of TNF in the immune defense or are different functions responsible for this outcome? In this review we provide an update of the functions of TNF in the defense against the intracellular pathogens Listeria monocytogenes, Mycobacterium tuberculosis, and Leishmania major. Furthermore, we discuss the role of TNF in the generation of proinflammatory macrophages in mouse models of infection and summarize briefly the potential consequences of anti-TNF treatment for infectious diseases.

CpG ODN D35 improves the response to abbreviated low-dose pentavalent antimonial treatment in non-human primate model of cutaneous leishmaniasis

Cutaneous leishmaniasis (CL) affects the lives of 0.7–1 million people every year causing lesions that take months to heal. These lesions can result in disfiguring scars with psychological, social and economic consequences. Antimonials are the first line of therapy for CL, however the treatment is lengthy and linked to significant toxicities; further, its efficacy is variable and resistant parasites are emerging. Shorter or lower dose antimonial treatment regimens, which would decrease the risk of adverse events and improve patient compliance, have shown reduced efficacy and further increase the risk emergence of antimonial-resistant strains. The progression of lesions in CL is partly determined by the immune response it elicits, and previous studies showed that administration of immunomodulatory type D CpG ODNs, magnifies the immune response to Leishmania and reduces lesion severity in nonhuman primates (NHP) challenged with Leishmania major or Leishmania amazonensis. Here we explored whether the addition of a single dose of immunomodulating CpG ODN D35 augments the efficacy of a short-course, low-dose pentavalent antimonial treatment regimen. Results show that macaques treated with D35 plus 5mg/kg sodium stibogluconate (Sb^V) for 10 days had smaller lesions and reduced time to re-epithelization after infection with Leishmania major. No toxicities were evident during the studies, even at doses of D35 10 times higher than those used in treatment. Critically, pentavalent antimonial treatment did not modify the ability of D35 to induce type I IFNs. The findings support the efficacy of D35 as adjuvant therapy for shorter, low dose pentavalent antimonial treatment.

Cutaneous leishmaniasis is a devastating disease that affects close to a million people every year. Its clinical presentation ranges from small uncomplicated lesions that heal over a few months to debilitating large chronic or recurring lesions that result in disfigurement, stigma, and economic loss. Antimonials are the first line treatment for cutaneous leishmaniasis in most countries, but the lengthy treatment schedules, significant associated toxicities, and the emergence of resistant strains, require the development of alternative strategies. As the immune response is a key determinant of disease course, immunomodulatory therapies could be harnessed to act in concert with antimonials to improve the safety and efficacy of CL treatment. Synthetic oligonucleotide D35 selectively activates plasmacytoid dendritic cells and was previously shown to reduce the severity of L. major and L. amazonensis lesions in rhesus macaques, but its activity in combination with antimonials was unknown. Our studies show that a single subcutaneous dose of innate immune modulator D35 improved the response to a low-dose abbreviated antimonial course, reducing the severity of the lesions and accelerating healing in primates. No toxicities were evident with D35 at doses ten-fold higher than the effective dose. The studies suggest that the combined therapy strategy shows clinical promise.

Interferon α in cancer immunoediting: From elimination to escape

Interferon α (IFNα) is a cytokine that mediates diverse immune responses to tumours. It is the oldest immune-based oncologic drug and has been widely used to treat various malignancies in humans. Yet, the use of IFNα in cancer therapy has only resulted in limited success and even led to worse clinical outcomes under certain instances. The emergence of the cancer immunoediting concept-which implicates the host immune system in promoting tumour growth-recapitulates the need to evaluate the immune functions of IFNα. This review proposes that IFNα has dual opposing roles in cancer development based on the mutational status of its signalling components, which determines the expression of anti- or pro-tumorigenic IFN-stimulated genes (ISGs). This duality may translate into new applications of IFNα in cancer immunotherapy.

Upregulation of intratumoral HLA class I and peritumoral Mx1 in ulcerated melanomas

Before the era of immune checkpoint blockade, a meta-analysis encompassing fifteen trials reported that adjuvant IFN-α significantly reduces the risk of relapse and improves survival of ulcerated melanoma (UM) with no benefit for higher doses compared to lower doses. IFNa2b affects many cell intrinsic features of tumor cells and modulates the host innate and cognate immune responses. To better understand the biological traits associated with ulceration that could explain the efficacy of prophylactic type 1 IFN, we performed immunohistochemical analysis of various molecules (major histocompatibility complex class I and class II, MX Dynamin Like GTPase 1 (MX1), inducible Nitric-Oxide Synthase (iNOS) or CD47) in two retrospective cohorts of melanoma patients, one diagnosed with a primary cutaneous melanoma (1995-2013, N = 172, among whom 49% were ulcerated melanoma (UM)) and a second one diagnosed with metastatic melanoma amenable to lymph node resection (EORTC 18952 and 18991 trials, N = 98, among whom 44% were UM). We found that primary and metastatic UM exhibit higher basal expression of MHC class I molecules, independently of Breslow thickness, histology and lymphocytic infiltration compared with NUM and that primary UM harbored higher constitutive levels of the antiviral protein Mx1 at the border of tumor beds than NUM. These findings suggest that UM expand in a tumor microenvironment where chronic exposure to type 1 IFN could favor a response to exogenous IFNs.

Sustained Type I interferon signaling as a mechanism of resistance to PD-1 blockade

PD-1 blockade represents a major therapeutic avenue in anticancer immunotherapy. Delineating mechanisms of secondary resistance to this strategy is increasingly important. Here, we identified the deleterious role of signaling via the type I interferon (IFN) receptor in tumor and antigen presenting cells, that induced the expression of nitric oxide synthase 2 (NOS2), associated with intratumor accumulation of regulatory T cells (Treg) and myeloid cells and acquired resistance to anti-PD-1 monoclonal antibody (mAb). Sustained IFNβ transcription was observed in resistant tumors, in turn inducing PD-L1 and NOS2 expression in both tumor and dendritic cells (DC). Whereas PD-L1 was not involved in secondary resistance to anti-PD-1 mAb, pharmacological or genetic inhibition of NOS2 maintained long-term control of tumors by PD-1 blockade, through reduction of Treg and DC activation. Resistance to immunotherapies, including anti-PD-1 mAb in melanoma patients, was also correlated with the induction of a type I IFN signature. Hence, the role of type I IFN in response to PD-1 blockade should be revisited as sustained type I IFN signaling may contribute to resistance to therapy.

Modulation of NKG2D, KIR2DL and Cytokine Production by Pleurotus ostreatus Glucan Enhances Natural Killer Cell Cytotoxicity Toward Cancer Cells

Medicinal mushrooms have been used for centuries against cancer and infectious diseases. These positive biological effects of mushrooms are due in part to the indirect action of stimulating immune cells. The objective of the current study is to investigate the possible immunomodulatory effects of mushroom polysaccharides on NK cells against different cancer cells. In this current study, fruiting bodies isolated from cultured Pleurotus ostreatus were extracted and partially purified using DEAE ion-exchange chromatography. The activation action of the collected fractions on Natural Killer cells was quantified against three different cancer cell lines in the presence or absence of human recombinant IL2 using three different activation and co-culture conditions. The possible modes of action of mushroom polysaccharides against cancer cells were evaluated at the cellular and molecular levels. Our results indicate that P. ostreatus polysaccharides induced NK-cells cytotoxic effects against lung and breast cancer cells with the largest effect being against breast cancer cells (81.2%). NK cells activation for cytokine secretion was associated with upregulation of KIR2DL genes while the cytotoxic activation effect of NK cells against cancer cells correlated with NKG2D upregulation and induction of IFNγ and NO production. These cytotoxic effects were enhanced in the presence of IL2. Analysis of the most active partially purified fraction indicates that it is predominantly composed of glucans. These results indicate bioactive 6-linked glucans present in P. ostreatus extracts activate NK-cell cytotoxicity via regulation of activation and induction of IFNγ and NO. These studies establish a positive role for bioactive P. ostreatus polysaccharides in NK-cells activation and induction of an innate immune response against breast and lung cancer cells.

Nucleic acid sensing activates the innate cytosolic surveillance pathway and promotes parasite survival in visceral leishmaniasis

Microbial pattern recognition critically contributes to innate response, both at extracellular and intracellular cytosolic surveillance pathway (CSP) interface. However, the role of pattern recognition by host innate receptors in CSP is poorly understood in Leishmania donovani infection. Here, we have demonstrated that cytosolic targeting of L.donovani DNA (Ld-DNA) inhibits macrophage responsiveness to IFNɣ, through decreased MHC-II expression and lowered pSTAT1 (Y701) levels, involving host three-prime repair exonuclease-1 (TREX-1). The Ld-DNA potently induced type-1 IFNs, i.e. significant over-production of IFNβ through activation of the IRF pathway. Interestingly, knockdown of TRIF or MyD88 expression in macrophages had no effect on cytosolic Ld-DNA transfection-mediated IFN-β production, indicating involvement of a TLR independent pathway. Contrastingly, Ld-DNA failed to induce IFNβ in both TBK-1 and IRF3KO knockout macrophages. Although IFNβ was not induced by Ld-DNA in STING- knockout macrophages, STING alone was not enough for the induction. Evidently, besides STING, Ld-DNA recognition for induction of IFNβ critically required cytosolic cyclic GMP-AMP synthase (cGAS). Furthermore, the cGAS dependent targeting of Ld-DNA induced IFNβ over-production that contributed to antimony resistance in L.donovani infection. We provide the first evidence that enhanced cytosolic sensing of Ld-DNA in infection by antimony resistant (SBR-LD), but not antimony sensitive L.donovani strains (SBS-LD), was critically regulated by host MDRs, multi drug resistant associated protein 1 (MRP 1) and permeability glycoprotein (P-gp) in macrophages. Collectively, our results disclose Ld-DNA as a vital pathogen associated molecular pattern (PAMP) driving host Type-I IFN responses and antimony resistance. The findings may help in future development of policies for novel anti-leishmanial therapeutics.

Sources of Type I Interferons in Infectious Immunity: Plasmacytoid Dendritic Cells Not Always in the Driver's Seat

Type I Interferons (IFNs) are hallmark cytokines produced in immune responses to all classes of pathogens. Type I IFNs can influence dendritic cell (DC) activation, maturation, migration, and survival, but also directly enhance natural killer (NK) and T/B cell activity, thus orchestrating various innate and adaptive immune effector functions. Therefore, type I IFNs have long been considered essential in the host defense against virus infections. More recently, it has become clear that depending on the type of virus and the course of infection, production of type I IFN can also lead to immunopathology or immunosuppression. Similarly, in bacterial infections type I IFN production is often associated with detrimental effects for the host. Although most cells in the body are thought to be able to produce type I IFN, plasmacytoid DCs (pDCs) have been termed the natural "IFN producing cells" due to their unique molecular adaptations to nucleic acid sensing and ability to produce high amounts of type I IFN. Findings from mouse reporter strains and depletion experiments in in vivo infection models have brought new insights and established that the role of pDCs in type I IFN production in vivo is less important than assumed. Production of type I IFN, especially the early synthesized IFNβ, is rather realized by a variety of cell types and cannot be mainly attributed to pDCs. Indeed, the cell populations responsible for type I IFN production vary with the type of pathogen, its tissue tropism, and the route of infection. In this review, we summarize recent findings from in vivo models on the cellular source of type I IFN in different infectious settings, ranging from virus, bacteria, and fungi to eukaryotic parasites. The implications from these findings for the development of new vaccination and therapeutic designs targeting the respectively defined cell types are discussed.

Interleukin-18 in Health and Disease

Interleukin (IL)-18 was originally discovered as a factor that enhanced IFN-γ production from anti-CD3-stimulated Th1 cells, especially in the presence of IL-12. Upon stimulation with Ag plus IL-12, naïve T cells develop into IL-18 receptor (IL-18R) expressing Th1 cells, which increase IFN-γ production in response to IL-18 stimulation. Therefore, IL-12 is a commitment factor that induces the development of Th1 cells. In contrast, IL-18 is a proinflammatory cytokine that facilitates type 1 responses. However, IL-18 without IL-12 but with IL-2, stimulates NK cells, CD4⁺ NKT cells, and established Th1 cells, to produce IL-3, IL-9, and IL-13. Furthermore, together with IL-3, IL-18 stimulates mast cells and basophils to produce IL-4, IL-13, and chemical mediators such as histamine. Therefore, IL-18 is a cytokine that stimulates various cell types and has pleiotropic functions. IL-18 is a member of the IL-1 family of cytokines. IL-18 demonstrates a unique function by binding to a specific receptor expressed on various types of cells. In this review article, we will focus on the unique features of IL-18 in health and disease in experimental animals and humans.

Resolution of Cutaneous Leishmaniasis and Persistence of Leishmania major in the Absence of Arginase 1

Arginase (Arg) 1 is expressed by hematopoietic (e.g., macrophages) and nonhematopoietic cells (e.g., endothelial cells) and converts l-arginine into ornithine and urea. The enzyme is implicated in tissue repair but also antagonizes the production of NO by type 2 NO synthase in myeloid cells and thereby impedes the control of intracellular parasites such as Leishmania major In this study, we tested whether Arg1 is required for spontaneous healing of acute cutaneous leishmaniasis in C57BL/6 mice and for lifelong parasite persistence in draining lymph nodes (dLNs) of healed mice. In vitro, bone marrow-derived macrophages and lymphoid endothelial cells readily expressed Arg1 in response to IL-4 and/or IL-13, whereas skin or dLN fibroblasts failed to do so, even during hypoxia. In vivo, Arg1 was found in skin lesions and, to a much lower extent, also in dLNs of acutely infected C57BL/6 mice but became undetectable at both sites after healing. Deletion of Arg1 in hematopoietic and endothelial cells using Tie2Cre^+/-Arg1^fl/fl C57BL/6 mice abolished the expression of Arg1 in skin lesions and dLNs but did not affect development and resolution of skin lesions, parasite burden, NO production, or host cell tropism of L. major during the acute or persistent phase of infection. Similar to wild-type controls, parasites persisting in Arg1-deficient mice favored NO synthase 2-negative areas and mainly resided in myeloid cells and fibroblasts. We conclude that Arg1 expression by hematopoietic and endothelial cells is completely dispensable for clinical resolution of cutaneous leishmaniasis and for long-term persistence of L. major.

Natural Products Mediated Targeting of Virally Infected Cancer

The role of viral infection in developing cancer was determined in the start of 20th century. Until now, 8 different virus-associated cancers have been discovered and most of them progressed in immunosuppressed individuals. The aim of the present study is to look into the benefits of natural products in treating virally infected cancers. The study focuses on bioactive compounds derived from natural sources. Numerous pharmaceutical agents have been identified from plants (vincristine, vinblastine, stilbenes, combretastatin, and silymarin), marine organisms (bryostatins, cephalostatin, ecteinascidins, didemnin, and dolastatin), insects (cantharidin, mastoparan, parectadial, and cecropins), and microorganisms (vancomycin, rhizoxin, ansamitocins, mitomycin, and rapamycin). Beside these, various compounds have been observed from fruits and vegetables which can be utilized in anticancer therapy. These include curcumin in turmeric, resveratrol in red grapes, S-allyl cysteine in allium, allicin in garlic, catechins in green tea, and β-carotene in carrots. The present study addresses various types of virally infected cancers, their mechanism of action, and the role of different cell surface molecules elicited during viral binding and entry into the target cell along with the anticancer drugs derived from natural products by targeting screening of bioactive compounds from natural sources.

Understanding the tumour micro-environment communication network from an NOS2/COX2 perspective

Recent findings suggest that co-expression of NOS2 and COX2 is a strong prognostic indicator in triple-negative breast cancer patients. These two key inflammation-associated enzymes are responsible for the biosynthesis of NO and PGE2 , respectively, and can exert their effect in both an autocrine and paracrine manner. Impairment of their physiological regulation leads to critical changes in both intra-tumoural and intercellular communication with the immune system and their adaptation to the hypoxic tumour micro-environment. Recent studies have also established a key role of NOS2-COX2 in causing metabolic shift. This review provides an extensive overview of the role of NO and PGE2 in shaping communication between the tumour micro-environment composed of tumour and immune cells that in turn favours tumour progression and metastasis. LINKED ARTICLES: This article is part of a themed section on Nitric Oxide 20 Years from the 1998 Nobel Prize. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.2/issuetoc.

In Search of Biomarkers for Pathogenesis and Control of Leishmaniasis by Global Analyses of Leishmania-Infected Macrophages

Leishmaniasis is a vector-borne, neglected tropical disease with a worldwide distribution that can present in a variety of clinical forms, depending on the parasite species and host genetic background. The pathogenesis of this disease remains far from being elucidated because the involvement of a complex immune response orchestrated by host cells significantly affects the clinical outcome. Among these cells, macrophages are the main host cells, produce cytokines and chemokines, thereby triggering events that contribute to the mediation of the host immune response and, subsequently, to the establishment of infection or, alternatively, disease control. There has been relatively limited commercial interest in developing new pharmaceutical compounds to treat leishmaniasis. Moreover, advances in the understanding of the underlying biology of Leishmania spp. have not translated into the development of effective new chemotherapeutic compounds. As a result, biomarkers as surrogate disease endpoints present several potential advantages to be used in the identification of targets capable of facilitating therapeutic interventions considered to ameliorate disease outcome. More recently, large-scale genomic and proteomic analyses have allowed the identification and characterization of the pathways involved in the infection process in both parasites and the host, and these analyses have been shown to be more effective than studying individual molecules to elucidate disease pathogenesis. RNA-seq and proteomics are large-scale approaches that characterize genes or proteins in a given cell line, tissue, or organism to provide a global and more integrated view of the myriad biological processes that occur within a cell than focusing on an individual gene or protein. Bioinformatics provides us with the means to computationally analyze and integrate the large volumes of data generated by high-throughput sequencing approaches. The integration of genomic expression and proteomic data offers a rich multi-dimensional analysis, despite the inherent technical and statistical challenges. We propose that these types of global analyses facilitate the identification, among a large number of genes and proteins, those that hold potential as biomarkers. The present review focuses on large-scale studies that have identified and evaluated relevant biomarkers in macrophages in response to Leishmania infection.

Impact of primary mouse macrophage cell types on Leishmania infection and in vitro drug susceptibility

Primary mouse macrophages are frequently used to provide an in vitro intracellular model to evaluate antileishmanial drug efficacy. The present study compared the phenotypic characteristics of Swiss, BALB/c, and C57BL/6 mouse bone marrow-derived macrophages and peritoneal exudate cells using different stimulation and adherence protocols upon infection with a Leishmania infantum laboratory strain and two clinical isolates. Evaluation parameters were susceptibility to infection, permissiveness to amastigote multiplication, and impact on drug efficacy. Observed variations in infection of peritoneal exudate cells can mostly be linked to changes in the inflammatory cytokine profiles (IL-6, TNF-α, KC/GRO) rather than to differences in initial production of nitric oxide and reactive oxygen species. Optimization of the cell stimulation and adherence conditions resulted in comparable infection indices among peritoneal exudate cells and the various types of bone marrow-derived macrophages. BALB/c-derived bone marrow-derived macrophages were slightly more permissive to intracellular amastigote replication. Evaluation of antileishmanial drug potency in the various cell systems revealed minimal variation for antimonials and paromomycin, and no differences for miltefosine and amphotericin B. The study results allow to conclude that drug evaluation can be performed in all tested primary macrophages as only marginal differences are observed in terms of susceptibility to infection and impact of drug exposure. Combined with some practical considerations, the use of 24-h starch-stimulated, 48-h adhered, Swiss-derived peritoneal exudate cells can be advocated as an efficient, reliable, relatively quick, and cost-effective tool for routine drug susceptibility testing in vitro whenever the use of primary cells is feasible.

Foxp3+ T reg cells control psoriasiform inflammation by restraining an IFN-I-driven CD8+ T cell response

Psoriasis is a complex inflammatory skin disease affecting ∼3% of the population worldwide. Although type I interferons (IFN-I) are thought to be involved in its pathogenesis, the details of this relationship remain elusive. Here we show that in a murine model of imiquimod-driven psoriatic skin inflammation, Foxp3+ regulatory T cells (T reg cells) control inflammation severity by restraining IFN-I. Depletion of T reg cells induces IFN-I and IFN-stimulated gene expression, and leads to accumulation of CD8+ T cells in lesional skin. Mononuclear phagocytes (MNPs) were the source of IFN-I, and their depletion reversed the effect of T reg cell depletion. Blockade of IFN-I signaling abolished CD8+ T cell infiltration and excess inflammation in the skin of T reg cell-depleted mice. Depletion of CD8+ T cells attenuated pathology, confirming their role as critical effector cells downstream of IFN-I. Our results describe an unexpected role for T reg cells in restraint of an MNP-IFN-I-driven CD8+ T cell response during psoriasiform skin inflammation. These findings highlight a pathway with potential relevance for the treatment of early-stage disease.

Type-1 interferons prolong the lifespan of neutrophils by interfering with members of the apoptotic cascade

Polymorphonuclear Neutrophils (PMNs) are metabolically highly active phagocytes, present in abundant numbers in the circulation. These active cells take the onus of clearing invading pathogens by crowding at inflammatory sites in huge numbers. Though PMNs are extremely short living and die upon spontaneous apoptosis, extended lifespan has been observed among those cells arrive at the inflammation sites or tackle intracellular infections or face any microbial challenges. The delay/inhibition of spontaneous apoptosis of these short-living cells at the inflammatory core rather helps in combating pathogens. Like many candidates, type-1 interferons (type-1 IFNs) is a group of cytokines predominant at the inflammation site. Although there are some isolated reports, a systematic study is still lacking which addresses the impact of the predominant type of interferon on the spontaneous apoptosis of neutrophils. Here in, we have observed that exposure of these IFNs (IFN-β, IFN-α & IFN-ω etc) on human neutrophils prevents the degradation of the Bfl1, an important anti-apoptotic partner in the apoptotic cascade. Treatment showed a significant reduction in the release of cytochrome-C in the cytosol, a critical regulator in the intrinsic apoptotic pathway. We also noticed a reduction in the conversion of procaspase -3 to active caspase-3, a crucial executioner caspase towards initiation of apoptosis. Taken together our results show that exposure to interferon interferes with apoptotic pathways of neutrophils and thereby delay its spontaneous apoptosis. These findings would help us further deciphering specific roles if these inflammatory agents are causing any immune-metabolomic changes on PMNs at the inflammatory and infection core.

Leishmania amazonensis downregulates macrophage iNOS expression via Histone Deacetylase 1 (HDAC1): a novel parasite evasion mechanism

The induced expression of nitric oxide synthase (iNOS) controls the intracellular growth of Leishmania in infected macrophages. Histones deacetylases (HDACs) negatively regulate gene expression through the formation of complexes containing transcription factors such as NF-κB p50/50. Herein, we demonstrated the occupancy of p50/p50_HDAC1 to iNOS promoter associated with reduced levels of H3K9Ac. Remarkably, we found increased levels of HDAC1 in L. amazonensis-infected macrophages. HDAC1 upregulation was not found in L. major-infected macrophages. The parasite intracellular load was reduced in HDAC1 knocked-down macrophages, which presented increased nitric oxide levels. HDAC1 silencing led to the occupancy of CBP/p300 to iNOS promoter and the rise of H3K9Ac modification. Importantly, the immunostaining of skin samples from hiporeactive cutaneous leishmaniasis patients infected with L. amazonensis, revealed high levels of HDAC1. In brief, L. amazonensis induces HDAC1 in infected macrophages, which contribute to parasite survival and is associated to hiporeactive stage found in L. amazonensis infected patients.

Exogenous Stimulation of Type I Interferon Protects Mice with Chronic Granulomatous Disease from Aspergillosis through Early Recruitment of Host-Protective Neutrophils into the Lung

Invasive aspergillosis (IA) remains the primary cause of morbidity and mortality in chronic granulomatous disease (CGD) patients, often due to infection by Aspergillus species refractory to antifungals. This motivates the search for alternative treatments, including immunotherapy. We investigated the effect of exogenous type I interferon (IFN) activation on the outcome of IA caused by three Aspergillus species, A. fumigatus, A. nidulans, and A. tanneri, in CGD mice. The animals were treated with poly(I):poly(C) carboxymethyl cellulose poly-l-lysine (PICLC), a mimetic of double-stranded RNA, 24 h preinfection and postinfection. The survival rates and lung fungal burdens were markedly improved by PICLC immunotherapy in animals infected with any one of the three Aspergillus species. While protection from IA was remarkable, PICLC induction of type I IFN in the lungs surged 24 h posttreatment and returned to baseline levels by 48 h, suggesting that PICLC altered early events in protection against IA. Immunophenotyping of recruited leukocytes and histopathological examination of tissue sections showed that PICLC induced similar cellular infiltrates as those in untreated-infected mice, in both cases dominated by monocytic cells and neutrophils. However, the PICLC immunotherapy resulted in a marked earlier recruitment of the leukocytes. Unlike with conidia, infection with A. nidulans germlings reduced the protective effect of PICLC immunotherapy. Additionally, antibody depletion of neutrophils totally reversed the protection, suggesting that neutrophils are crucial for PICLC-mediated protection. Together, these data show that prophylactic PICLC immunotherapy prerecruits these cells, enabling them to attack the conidia and thus resulting in a profound protection from IA.IMPORTANCE Patients with chronic granulomatous disease (CGD) are highly susceptible to invasive aspergillosis (IA). While Aspergillus fumigatus is the most-studied Aspergillus species, CGD patients often suffer IA caused by A. nidulans, A. tanneri, and other rare species. These non-fumigatus Aspergillus species are more resistant to antifungal drugs and cause higher fatality rates than A. fumigatus Therefore, alternative therapies are needed to protect CGD patients. We report an effective immunotherapy of mice infected with three Aspergillus species via PICLC dosing. While protection from IA was long lasting, PICLC induction of type I IFN surged but quickly returned to baseline levels, suggesting that PICLC was altering early events in IA. Interestingly, we found responding immune cells to be similar between PICLC-treated and untreated-infected mice. However, PICLC immunotherapy resulted in an earlier recruitment of the leukocytes and suppressed fungal growth. This study highlights the value of type I IFN induction in CGD patients.

Hypoxia, Hypoxia-Inducible Factor-1α, and Innate Antileishmanial Immune Responses

Low oxygen environments and accumulation of hypoxia-inducible factors (HIFs) are features of infected and inflamed tissues. Here, we summarize our current knowledge on oxygen levels found in Leishmania-infected tissues and discuss which mechanisms potentially contribute to local tissue oxygenation in leishmanial lesions. Moreover, we review the role of hypoxia and HIF-1 on innate antileishmanial immune responses.

Type I Interferon Signaling Is Required for CpG-Oligodesoxynucleotide-Induced Control of Leishmania major, but Not for Spontaneous Cure of Subcutaneous Primary or Secondary L. major Infection

We previously showed that in mice infected with Leishmania major type I interferons (IFNs) initiate the innate immune response to the parasite at day 1 and 2 of infection. Here, we investigated which type I IFN subtypes are expressed during the first 8 weeks of L. major infection and whether type I IFNs are essential for a protective immune response and clinical cure of the disease. In self-healing C57BL/6 mice infected with a high dose of L. major, IFN-α4, IFN-α5, IFN-α11, IFN-α13, and IFN-β mRNA were most prominently regulated during the course of infection. In C57BL/6 mice deficient for IFN-β or the IFN-α/β-receptor chain 1 (IFNAR1), development of skin lesions and parasite loads in skin, draining lymph node, and spleen was indistinguishable from wild-type (WT) mice. In line with the clinical findings, C57BL/6 IFN-β^−/−, IFNAR1^−/−, and WT mice exhibited similar mRNA expression levels of IFN-γ, interleukin (IL)-4, IL-12, IL-13, inducible nitric oxide synthase, and arginase 1 during the acute and late phase of the infection. Also, myeloid dendritic cells from WT and IFNAR1^−/− mice produced comparable amounts of IL-12p40/p70 protein upon exposure to L. major in vitro. In non-healing BALB/c WT mice, the mRNAs of IFN-α subtypes (α2, α4, α5, α6, and α9) were rapidly induced after high-dose L. major infection. However, genetic deletion of IFNAR1 or IFN-β did not alter the progressive course of infection seen in WT BALB/c mice. Finally, we tested whether type I IFNs and/or IL-12 are required for the prophylactic effect of CpG-oligodesoxynucleotides (ODN) in BALB/c mice. Local and systemic administration of CpG-ODN 1668 protected WT and IFN-β^−/− mice equally well from progressive leishmaniasis. By contrast, the protective effect of CpG-ODN 1668 was lost in BALB/c IFNAR1^−/− (despite a sustained suppression of IL-4) and in BALB/c IL-12p35^−/− mice. From these data, we conclude that IFN-β and IFNAR1 signaling are dispensable for a curative immune response to L. major in C57BL/6 mice and irrelevant for disease development in BALB/c mice, whereas IL-12 and IFN-α subtypes are essential for the disease prevention by CpG-ODNs in this mouse strain.

Monocyte-Derived Signals Activate Human Natural Killer Cells in Response to Leishmania Parasites

Activated natural killer (NK) cells release interferon (IFN)-γ, which is crucial for the control of intracellular pathogens such as Leishmania. In contrast to experimental murine leishmaniasis, the human NK cell response to Leishmania is still poorly characterized. Here, we investigated the interaction of human blood NK cells with promastigotes of different Leishmania species (Leishmania major, Leishmania mexicana, Leishmania infantum, and Leishmania donovani). When peripheral blood mononuclear cells or purified NK cells and monocytes (all derived from healthy blood donors from Germany without a history of leishmaniasis) were exposed to promastigotes, NK cells showed increased surface expression of the activation marker CD69. The extent of this effect varied depending on the Leishmania species; differences between dermotropic and viscerotropic L. infantum strains were not observed. Upregulation of CD69 required direct contact between monocytes and Leishmania and was partly inhibitable by anti-interleukin (IL)-18. Unexpectedly, IL-18 was undetectable in most of the supernatants (SNs) of monocyte/parasite cocultures. Confocal fluorescence microscopy of non-permeabilized cells revealed that Leishmania-infected monocytes trans-presented IL-18 to NK cells. Native, but not heat-treated SNs of monocyte/Leishmania cocultures also induced CD69 on NK cells, indicating the involvement of a soluble heat-labile factor other than IL-18. A role for the NK cell-activating cytokines IL-1β, IL-2, IL-12, IL-15, IL-21, and IFN-α/β was excluded. The increase of CD69 was not paralleled by NK cell IFN-γ production or enhanced cytotoxicity. However, prior exposure of NK cells to Leishmania parasites synergistically increased their IFN-γ release in response to IL-12, which was dependent on endogenous IL-18. CD1c+ dendritic cells were identified as possible source of Leishmania-induced IL-12. Finally, we observed that direct contact between Leishmania and NK cells reduced the expression of CD56 mRNA and protein on NK cells. We conclude that Leishmania activate NK cells via trans-presentation of IL-18 by monocytes and by a monocyte-derived soluble factor. IL-12 is needed to elicit the IFN-γ-response of NK cells, which is likely to be an important component of the innate control of the parasite.

Role of Mast Cells in clearance of Leishmania through extracellular trap formation

Mast Cells (MCs) are one of the first immune cells encountered by invading pathogens. Their presence in large numbers in the superficial dermis, where Leishmania is encountered, suggests that they may play a critical role in immune responses to Leishmania. In this study the interactions of Leishmania donovani, the causative agent of visceral Leishmaniasis, and Leishmania tropica, the causative agent of cutaneous Leishmaniasis with MCs were studied. Co-culture of Leishmania with Peritoneal Mast Cells (PMCs) from BALB/c mice and Rat Basophilic Leukaemia (RBL-2H3) MCs led to significant killing of L. tropica and to a lesser extent of L. donovani. Also, while there was significant uptake of L. tropica by MCs, L. donovani was not phagocytosed. There was significant generation of Reactive Oxygen Species (ROS) by MCs on co-culture with these species of Leishmania which may contribute to their clearance. Interactions of MCs with Leishmania led to generation of MC extracellular traps comprising of DNA, histones and tryptase probably to ensnare these pathogens. These results clearly establish that MCs may contribute to host defences to Leishmania in a differential manner, by actively taking up these pathogens, and also by mounting effector responses for their clearance by extracellular means.

Type I Interferon Supports Inducible Nitric Oxide Synthase in Murine Hepatoma Cells and Hepatocytes and during Experimental Acetaminophen-Induced Liver Damage

Cytokine regulation of high-output nitric oxide (NO) derived from inducible NO synthase (iNOS) is critically involved in inflammation biology and host defense. Herein, we set out to characterize the role of type I interferon (IFN) as potential regulator of hepatic iNOS in vitro and in vivo. In this regard, we identified in murine Hepa1-6 hepatoma cells a potent synergism between pro-inflammatory interleukin-β/tumor necrosis factor-α and immunoregulatory IFNβ as detected by analysis of iNOS expression and nitrite release. Upregulation of iNOS by IFNβ coincided with enhanced binding of signal transducer and activator of transcription-1 to a regulatory region at the murine iNOS promoter known to support target gene expression in response to this signaling pathway. Synergistic iNOS induction under the influence of IFNβ was confirmed in alternate murine Hepa56.1D hepatoma cells and primary hepatocytes. To assess iNOS regulation by type I IFN in vivo, murine acetaminophen (APAP)-induced sterile liver inflammation was investigated. In this model of acute liver injury, excessive necroinflammation drives iNOS expression in diverse liver cell types, among others hepatocytes. Herein, we demonstrate impaired iNOS expression in type I IFN receptor-deficient mice which associated with diminished APAP-induced liver damage. Data presented indicate a vital role of type I IFN within the inflamed liver for fine-tuning pathological processes such as overt iNOS expression.