Reactive oxygen species and nitric oxide in cutaneous leishmaniasis

Live Leishmania tarentolae secreting HNP1 as an immunotherapeutic tool against Leishmania infection in BALB/c mice

AIM

Several disadvantages about chemotherapy for leishmaniasis has reinforced discovery of novel therapeutic agents especially immunotherapeutics. HNP1, as a member of the mammalian antimicrobial peptides family, is an attractive molecule due to its broad functional spectrum. Here, the in vivo potency of HNP1 in transgenic Leishmania tarentolae as an immunotherapy tool against Leishmania major-infected BALB/c mice was examined.

METHODS & RESULTS

3 weeks after infection with L. major, the treatment effect of L. tarentolae-HNP1-EGFP was pursued. The results were promising in respect to parasite load control and Th1 immune response polarization compared with controls.

CONCLUSION

Immunotherapy by live L. tarentolae secreting HNP1 can elicit cellular immune response in a susceptible mouse model in order to control L. major infection.

Leishmania donovani Activates Hypoxia Inducible Factor-1α and miR-210 for Survival in Macrophages by Downregulation of NF-κB Mediated Pro-inflammatory Immune Response

Micro RNAs (miRNAs) have emerged as a critical regulator of several biological processes in both animals and plants. They have also been associated with regulation of immune responses in many human diseases during recent years. Visceral leishmaniasis (VL) is the most severe form of leishmaniasis, which is characterized by impairment of both innate and adaptive immune responses. In the present study, we observed that Leishmania establishes hypoxic environment in host macrophages that induces the expression of hypoxia inducible factor-1α (HIF-1α) and miRNA-210. Further, the expression of miRNA-210 was found to be dependent on activation of HIF-1α expression. The HIF-1α silencing by siRNA resulted in significantly (p < 0.001) decreased expression of miR-210 in parasites infected macrophages. We also observed that in siHIF-1α or antagomir-210 treated L. donovani infected macrophages, the parasitic load and percentage infectivity were significantly (p < 0.001) decreased. Furthermore, we found that inhibition of miR-210 leads to activation of NF-κB subunit p50, and it forms heterodimer with p65 and translocates into the nucleus from the cytoplasm. This significantly (p < 0.05) induced the transcription of pro-inflammatory cytokines genes such as TNF-α and IL-12 in miRNA-210 inhibited macrophages compared to uninhibited macrophages whereas the level of IL-10, an anti-inflammatory cytokine, was found to be significantly decreased (p < 0.001). These findings suggested that L. donovani infection induces hypoxic environment inside the macrophages that activates HIF-1α. Further, HIF-1α upregulates miR-210, which eventually establishes a suitable environment for the survival of parasite inside the host macrophages by downregulating NF-κB mediated pro-inflammatory immune responses.

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.

Human Neutrophil Peptide 1 as immunotherapeutic agent against Leishmania infected BALB/c mice

Human Neutrophil Peptide 1 (HNP1) produced by neutrophils, is a well-known antimicrobial peptide which plays a role both in innate as well as in adaptive immunity and is under intensive investigation as a potential therapeutic agent. Previous in vitro experiments have indicated the leishmaniacidal effect of recombinant HNP1 on Leishmania major (L. major) promastigotes and amastigotes. In the current study, we further extended the idea to explore the remedial effect of HNP1 in the two modalities of peptide therapy (folded HNP1) and gene therapy in L. major infected BALB/c mice. To this end, mice in five different groups received synthetic folded HNP1 (G1), pcDNA-HNP1-EGFP (G2), pcDNA-EGFP (G3), Amphotericin B (G4) and PBS (G5), which was started three weeks after infection for three consecutive weeks. Footpad swelling was monitored weekly and a day after the therapy ended, IFN-γ, IL-4, IL-10, IL-6 and nitric oxide produced by splenocytes were analyzed together with the parasite load in draining lymph nodes. Arginase activity and dermal histopathological changes were also analyzed in the infected footpads. We demonstrated that both therapeutic approaches effectively induced Th1 polarization and restricted parasite burden. It can control disease progression in contrast to non-treated groups. However, pcDNA-HNP1-EGFP is more promising in respect to parasite control than folded HNP1, but less effective than AmB treatment. We concluded with the call for a future approach, that is, a DNA-based expression of HNP1 combined with AmB as it can improve the leishmaniacidal efficacy.

The outbreak level of cutaneous leishmaniasis is approximated between one and 1.5 million individuals per year. Owning to several disadvantages of current therapies, special attention to expand novel and efficient therapies has been demanded. Among Anti-Microbial Peptides (AMPs), Human Neutrophil Peptide 1 (HNP1) is one of the most potential defensins. Our promising in vitro experiments have shown the leishmaniacidal effect of recombinant HNP1. Here, we displayed the remedial effect of HNP1 in two approaches including peptide therapy and gene therapy in susceptible mice infected with L. major. Our investigation showed that although both approaches could decrease the parasite load and induce Th1 immune response compared to the control group, pcDNA-HNP1-EGFP has a better effect compared to the folded HNP1. Hence, immunotherapy by HNP1 can help elicit proper immunity despite the direct effect on promastigotes and amastigotes forms of parasite.

Moroccan strains of Leishmania major and Leishmania tropica differentially impact on nitric oxide production by macrophages

BACKGROUND

Cutaneous leishmaniasis (CL) is a vector-borne parasitic disease caused by protozoa of the genus Leishmania. In Morocco, CL is a public health problem mainly caused by Leishmania major and Leishmania tropica, which are responsible for zoonotic and anthroponotic CL, respectively. Macrophages are the primary cells infected by Leishmania parasites and their capacity to produce nitric oxide (NO) is of critical importance for parasite elimination. To our knowledge, the role of NO on autochthonous infections has never been investigated before. In this study, we evaluated in vitro the capacity of autochthonous primary dermotropic strains of L. major and L. tropica to modulate NO production by J774-macrophages and determine the sensitivity of both species to exogenous NO.

METHODS

The infectivity of the J774 cell line was analyzed by optical microscopy. NO production by macrophages was measured by the Griess method. The sensitivity to NO by the two strains was assessed by the MTT assay using NO donors.

RESULTS

Our results show that the percentage of infected macrophages and the average number of parasites per macrophage were similar for L. major and L. tropica strains. While L. tropica significantly inhibited NO production induced by LPS and IFN-γ stimulation in J774 macrophages, L. major did not affect it. However, soluble Leishmania antigens (SLAs) from both autochthonous primary strains significantly inhibited the production of NO by J774-macrophages in a dose-dependent manner. Finally, our results demonstrated that promastigotes and amastigotes from both strains are sensitive to SNAP NO donor in a dose-dependent manner, although L. tropica demonstrated an increased sensitivity.

CONCLUSIONS

Our results suggest a differential ability of L. major and L. tropica strains to modulate the capacity of macrophages to produce NO. The increased ability of L. tropica to inhibit NO production by macrophages might come as a necessity due to its higher sensitivity to NO donor. Our results provide one explanation for the tendency of L. tropica to cause chronic lesions and may contribute to the different physiopathology of CL in Morocco.

Insights into the sand fly saliva: Blood-feeding and immune interactions between sand flies, hosts, and Leishmania

Background

Leishmaniases are parasitic diseases present worldwide that are transmitted to the vertebrate host by the bite of an infected sand fly during a blood feeding. Phlebotomine sand flies inoculate into the mammalian host Leishmania parasites embedded in promastigote secretory gel (PSG) with saliva, which is composed of a diverse group of molecules with pharmacological and immunomodulatory properties.

Methods and findings

In this review, we focus on 3 main aspects of sand fly salivary molecules: (1) structure and composition of salivary glands, including the properties of salivary molecules related to hemostasis and blood feeding, (2) immunomodulatory properties of salivary molecules and the diverse impacts of these molecules on leishmaniasis, ranging from disease exacerbation to vaccine development, and (3) use of salivary molecules for field applications, including monitoring host exposure to sand flies and the risk of Leishmania transmission. Studies showed interesting differences between salivary proteins of Phlebotomus and Lutzomyia species, however, no data were ever published on salivary proteins of Sergentomyia species.

Conclusions

In the last 15 years, numerous studies have characterized sand fly salivary proteins and, in parallel, have addressed the impact of such molecules on the biology of the host–sand fly–parasite interaction. The results obtained shall pave the way for the development of field-application tools that could contribute to the management of leishmaniasis in endemic areas.

Redox biology of Leishmania and macrophage targeted nanoparticles for therapy

Intramacrophage parasite ‘Leishmania’ has developed various mechanisms for proficient uptake into macrophages and phagosome regulation to avoid macrophage's oxidative burst induced by peroxide, hydroxyl radical, hypochlorous acid and peroxynitrite production. One major barrier for impairing the accession of old fashioned anti-Leishmanial drugs is intrinsic incapability to pass through cell membranes and limiting their abilities to ultimately destroy intracellular pathogens. Receptor-mediated targeted drug delivery to the macrophages by using nanoparticles emerges as promising strategy to improve therapeutic efficacy of old-fashioned drug. Receptor-mediated targeted nanoparticles can migrate across the cell membrane barriers and release enclosed drug cargo at sites of infection. This review is focusing on Leishmania-macrophage signaling alterations, its association with drug resistance and role of nanoparticles for receptor mediated macrophage targeting.

Antileishmanial Activity and Inducible Nitric Oxide Synthase Activation by RuNO Complex

Parasites of the genus Leishmania are capable of inhibiting effector functions of macrophages. These parasites have developed the adaptive ability to escape host defenses; for example, they inactivate the NF-κB complex and suppress iNOS expression in infected macrophages, which are responsible for the production of the major antileishmanial substance nitric oxide (NO), favoring then its replication and successful infection. Metal complexes with NO have been studied as potential compounds for the treatment of certain tropical diseases, such as ruthenium compounds, known to be exogenous NO donors. In the present work, the compound cis-[Ru(bpy)₂SO₃(NO)]PF₆, or RuNO, showed leishmanicidal activity directly and indirectly on promastigote forms of Leishmania (Leishmania) amazonensis. In addition, treatment with RuNO increased NO production by reversing the depletion of NO caused by Leishmania. We also found increased expression of Akt, iNOS, and NF-κB in infected and treated macrophages. These results demonstrated that RuNO was able to kill the parasite by NO release and modulate the transcriptional capacity of the cell.

Neutrophils Contribute to the Protection Conferred by ArtinM against Intracellular Pathogens: A Study on Leishmania major

ArtinM, a D-mannose binding lectin from Artocarpus heterophyllus, has immunomodulatory activities through its interaction with N-glycans of immune cells, culminating with the establishment of T helper type 1 (Th1) immunity. This interaction protects mice against intracellular pathogens, including Leishmania major and Leishmania amazonensis. ArtinM induces neutrophils activation, which is known to account for both resistance to pathogens and host tissue injury. Although exacerbated inflammation was not observed in ArtinM-treated animals, assessment of neutrophil responses to ArtinM is required to envisage its possible application to design a novel immunomodulatory agent based on carbohydrate recognition. Herein, we focus on the mechanisms through which neutrophils contribute to ArtinM-induced protection against Leishmania, without exacerbating inflammation. For this purpose, human neutrophils treated with ArtinM and infected with Leishmania major were analyzed together with untreated and uninfected controls, based on their ability to eliminate the parasite, release cytokines, degranulate, produce reactive oxygen species (ROS), form neutrophil extracellular traps (NETs) and change life span. We demonstrate that ArtinM-stimulated neutrophils enhanced L. major clearance and at least duplicated tumor necrosis factor (TNF) and interleukin-1beta (IL-1β) release; otherwise, transforming growth factor-beta (TGF-β) production was reduced by half. Furthermore, ROS production and cell degranulation were augmented. The life span of ArtinM-stimulated neutrophils decreased and they did not form NETs when infected with L. major. We postulate that the enhanced leishmanicidal ability of ArtinM-stimulated neutrophils is due to augmented release of inflammatory cytokines, ROS production, and cell degranulation, whereas host tissue integrity is favored by their shortened life span and the absence of NET formation. Our results reinforce the idea that ArtinM may be considered an appropriate molecular template for the construction of an efficient anti-infective agent.

Vaccination is a successful way to eliminate infectious diseases. The generated antibodies neutralize the invading microbe and avoid the establishment of infection. Vaccines are efficient to prevent infections by pathogens living outside rather than inside the host`s cells. This occurs because protection against intracellular pathogens requires the engagement of T lymphocytes. The discovery of receptors on innate immunity cells opened new perspectives in trying manners to stimulate effective response against intracellular pathogens. Frequently the microbial sensing by Toll-like receptors (TLRs) besides triggering immediate defense also orchestrates adaptative immunity towards T-cell response. Therefore, TLR ligands started to be assayed in new anti-infective approaches. Our laboratory has been investigating the immunomodulation induced by lectins, which are ubiquitous sugar-binding proteins. Our primary model is ArtinM, from the seeds of jackfruit, a lectin that binds to TLR2 sugar chains on macrophages and dendritic cells and promotes production of cytokines that engages T lymphocytes in a process that culminate with elimination of intracellular pathogens. Concomitantly, ArtinM activates other immune cells, including neutrophils, which contributes to the pathogen elimination, but may also account for tissue damage. This last possibility led us to investigate the lectin effects on neutrophils deeply. We analyzed neutrophils treated with ArtinM and infected with Leishmania major. We concluded that the leishmanicidal ability of ArtinM-stimulated neutrophils was due to augmented release of inflammatory cytokines, ROS production, and cell degranulation. Otherwise, host tissue integrity is favored by shortened cells lifespan and absence of NET formation. This work reinforces the idea that ArtinM can be an appropriate molecular template for the construction of an efficient anti-infective agent.

Impact of reactive oxygen species (ROS) on the control of parasite loads and inflammation in Leishmania amazonensis infection

Background

Reactive oxygen species (ROS) protect the host against a large number of pathogenic microorganisms. ROS have different effects on parasites of the genus Leishmania: some parasites are susceptible to their action, while others seem to be resistant. The role of ROS in L. amazonensis infection in vivo has not been addressed to date.

Methods

In this study, C57BL/6 wild-type mice (WT) and mice genetically deficient in ROS production by phagocytes (gp91^phox−/−) were infected with metacyclic promastigotes of L. amazonensis to address the effect of ROS in parasite control. Inflammatory cytokines, parasite loads and myeloperoxidase (MPO) activity were evaluated. In parallel, in vitro infection of peritoneal macrophages was assessed to determine parasite killing, cytokine, NO and ROS production.

Results

In vitro results show induction of ROS production by infected peritoneal macrophages, but no effect in parasite killing. Also, ROS do not seem to be important to parasite killing in vivo, but they control lesion sizes at early stages of infection. IFN-γ, TNF-α and IL-10 production did not differ among mouse strains. Myeloperoxidase assay showed augmented neutrophils influx 6 h and 72 h post - infection in gp91^phox−/− mice, indicating a larger inflammatory response in gp91^phox−/− even at early time points. At later time points, neutrophil numbers in lesions correlated with lesion size: larger lesions in gp91^phox−/− at earlier times of infection corresponded to larger neutrophil infiltrates, while larger lesions in WT mice at the later points of infection also displayed larger numbers of neutrophils.

Conclusion

ROS do not seem to be important in L. amazonensis killing, but they regulate the inflammatory response probably by controlling neutrophils numbers in lesions.

Macrophage Bactericidal Activities against Staphylococcus aureus Are Enhanced In Vivo by Selenium Supplementation in a Dose-Dependent Manner

Background

Dietary selenium is of fundamental importance to maintain optimal immune function and enhance immunity during infection. To this end, we examined the effect of selenium on macrophage bactericidal activities against Staphylococcus aureus.

Methods

Assays were performed in golden Syrian hamsters and peritoneal macrophages cultured with S. aureus and different concentrations of selenium.

Results

Infected and selenium-supplemented animals have significantly decreased levels of serum nitric oxide (NO) production when compared with infected but non-selenium-supplemented animals at day 7 post-infection (p < 0.05). A low dose of 5 ng/mL selenium induced a significant decrease in macrophage NO production, but significant increase in hydrogen peroxide (H₂O₂) levels (respectively, p = 0.009, p < 0.001). The NO production and H₂O₂ levels were significantly increased with increasing concentrations of selenium; the optimal macrophage activity levels were reached at 20 ng/mL. The concentration of 5 ng/mL of selenium induced a significant decrease in the bacterial arginase activity but a significant increase in the macrophage arginase activity. The dose of 20 ng/mL selenium induced a significant decrease of bacterial growth (p < 0.0001) and a significant increase in macrophage phagocytic activity, NO production/arginase balance and S. aureus killing (for all comparisons, p < 0.001).

Conclusions

Selenium acts in a dose-dependent manner on macrophage activation, phagocytosis and bacterial killing suggesting that inadequate doses may cause a loss of macrophage bactericidal activities and that selenium supplementation could enhance the in vivo control of immune response to S. aureus.

Phlebotomus papatasi exposure cross-protects mice against Leishmania major co-inoculated with Phlebotomus duboscqi salivary gland homogenate

Leishmania parasites are inoculated into host skin together with sand fly saliva and multiple exposures to uninfected sand fly bites protect mice against Leishmania infection. However, sand fly vectors differ in composition of the saliva and therefore the protection elicited by their salivary proteins was shown to be species-specific. On the other hand, the optimal vaccine based on sand fly salivary proteins should be based on conserved salivary proteins conferring cross-reactivity. In the present study we therefore focused on cross-protective properties of saliva from Phlebotomus papatasi and Phlebotomus duboscqi, the two natural vectors of Leishmania major. Two groups of mice exposed to bites of P. papatasi and two control, non-immunized groups were infected with L. major promastigotes along with either P. papatasi or P. duboscqi salivary gland homogenate. All mice were followed for the development of Leishmania lesions, parasite burdens, specific antibodies, and for production of NO, urea, or cytokines by peritoneal macrophages. Protection against Leishmania infection was observed not only in exposed mice challenged with homologous saliva but also in the group challenged with P. duboscqi saliva. Comparing both exposed groups, no significant differences were observed in parasite load, macrophage activity, or in the levels of anti-L. major and anti-P. papatasi/P. duboscqi antibodies. This is the first study showing cross-protection caused by salivary antigens of two Phlebotomus species. The cross-protective effect suggests that the anti-Leishmania vaccine based on P. papatasi salivary proteins might be applicable also in areas where L. major is transmitted by P. duboscqi.

Leishmaniasis in the middle East: incidence and epidemiology

Leishmaniasis is a major health problem worldwide, with several countries reporting cases of leishmaniasis resulting in loss of human life or a lifelong stigma because of bodily scars. The Middle East is endemic for cutaneous leishmaniasis, with countries like Syria reporting very high incidence of the disease. Despite several countries establishing national control programs for containing the sandfly vector and treatment of infection, the disease continues to spread. In addition to the endemicity of the region for leishmaniasis, the Middle East has seen a great deal of human migration either for earning of livelihood or due to political upheaval in the region. These factors contribute to the spread and proliferation of the causative species Leishmania and its sandfly host. This review discusses the current epidemiological scenario in Iraq, Syria, Saudi Arabia, and Jordan, emphasizing the number of cases reported, vector species, Leishmania species, and treatment available. The data is primarily from WHO reports for each country and current and old literature.

A defective TLR4 signaling for IFN-β expression is responsible for the innately lower ability of BALB/c macrophages to produce NO in response to LPS as compared to C57BL/6

C57BL/6 mice macrophages innately produce higher levels of NO than BALB/c cells when stimulated with LPS. Here, we investigated the molecular events that account for this intrinsic differential production of NO. We found that the lower production of NO in BALB/c is not due to a subtraction of L-arginine by arginase, and correlates with a lower iNOS accumulation, which is independent of its degradation rate. Instead, the lower accumulation of iNOS is due to the lower levels of iNOS mRNA, previously shown to be also independent of its stability, suggesting that iNOS transcription is less efficient in BALB/c than in C57BL/6 macrophages. Activation of NFκB is more efficient in BALB/c, thus not correlating with iNOS expression. Conversely, activation of STAT-1 does correlate with iNOS expression, being more prominent in C57BL/6 than in BALB/c macrophages. IFN-β and IL-10 are more highly expressed in C57BL/6 than in BALB/c macrophages, and the opposite is true for TNF-α. Whereas IL-10 and TNF-α do not seem to participate in their differential production of NO, IFN-β has a determinant role since 1) anti-IFN-β neutralizing antibodies abolish STAT-1 activation reducing NO production in C57BL/6 macrophages to levels as low as in BALB/c cells and 2) exogenous rIFN-β confers to LPS-stimulated BALB/c macrophages the ability to phosphorylate STAT-1 and to produce NO as efficiently as C57BL/6 cells. We demonstrate, for the first time, that BALB/c macrophages are innately lower NO producers than C57BL/6 cells because they are defective in the TLR-4-induced IFN-β-mediated STAT-1 activation pathway.

Nanoparticles as multifunctional devices for the topical treatment of cutaneous leishmaniasis

INTRODUCTION

Cutaneous and mucocutaneous leishmaniasis are major tropical skin diseases. Topical treatment is currently limited to the least severe forms of cutaneous leishmaniasis (CL) without risk of dissemination. It is also recommended in combination with systemic therapy for more severe forms. Progresses in this modality of treatment are hindered by the heterogeneity of the disease and shortcomings in the clinical trials.

AREAS COVERED

This review overlooks three major modalities of topical therapies in use or under investigation against CL: chemotherapy, photodynamic therapy and immunotherapy; either with older compounds such as paramomycin or more recent nitric oxide donors, antimicrobial peptides or silver derivatives. The advantages and limitations of their administration with newer formulation strategies such as nanoparticles (NPs) are discussed.

EXPERT OPINION

The efficacy of a topical treatment against CL depends not only on the intrinsic antileishmanial activity of the drug but also on the amount of drug available in the dermis. NPs as sustained release systems and permeation enhancers could favour the creation of a drug reservoir in the dermis. Additionally, certain NPs have immunomodulatory properties or wound healing capabilities of benefit in CL treatment. Pending task is the selective delivery of active compounds to intracellular amastigotes, because even small NPs are unable to penetrate deeply into the skin to encounter infected macrophages (except in ulcerative lesions).

Leishmania donovani prevents oxidative burst-mediated apoptosis of host macrophages through selective induction of suppressors of cytokine signaling (SOCS) proteins

One of the mechanisms for establishment of infection employed by intra-macrophage pathogen-like Leishmania is inhibition of oxidative burst-mediated macrophage apoptosis to protect their niche for survival and replication. We tried to elucidate the underlying mechanism for this by using H2O2 for induction of apoptosis. Leishmania donovani-infected macrophages were much more resistant to H2O2-mediated apoptosis compared with control. Although infected cells were capable of comparable reactive oxygen species production, there was less activation of the downstream cascade consisting of caspase-3 and -7 and cleaved poly(ADP)-ribose polymerase. Suppressors of cytokine signaling (SOCS) 1 and 3 proteins and reactive oxygen species scavenging enzyme thioredoxin, known to be involved in stabilization of protein-tyrosine phosphatases, were found to be induced during infection. Induction of SOCS proteins may be mediated by Egr1, and silencing of Socs1 and -3 either alone or in combination resulted in reduced thioredoxin levels, enhanced activation of caspases, and increased apoptosis of infected macrophages. The induction of protein-tyrosine phosphatases, thioredoxin, SOCS, and Egr1 in L. donovani-infected macrophages was found to be unaffected by H2O2 treatment. SOCS knocked down cells also displayed decreased parasite survival thus marking reduction in disease progression. Taken together, these results suggest that L. donovani may exploit SOCS for subverting macrophage apoptotic machinery toward establishing its replicative niche inside the host.

Leishmania amazonensis amastigotes trigger neutrophil activation but resist neutrophil microbicidal mechanisms

Neutrophils are the first cells to infiltrate to the site of Leishmania promastigote infection, and these cells help to reduce parasite burden shortly after infection is initiated. Several clinical reports indicate that neutrophil recruitment is sustained over the course of leishmaniasis, and amastigote-laden neutrophils have been isolated from chronically infected patients and experimentally infected animals. The goal of this study was to compare how thioglycolate-elicited murine neutrophils respond to L. amazonensis metacyclic promastigotes and amastigotes derived from axenic cultures or from the lesions of infected mice. Neutrophils efficiently internalized both amastigote and promastigote forms of the parasite, and phagocytosis was enhanced in lipopolysaccharide (LPS)-activated neutrophils or when parasites were opsonized in serum from infected mice. Parasite uptake resulted in neutrophil activation, oxidative burst, and accelerated neutrophil death. While promastigotes triggered the release of tumor necrosis factor alpha (TNF-α), uptake of amastigotes preferentially resulted in the secretion of interleukin-10 (IL-10) from neutrophils. Finally, the majority of promastigotes were killed by neutrophils, while axenic culture- and lesion-derived amastigotes were highly resistant to neutrophil microbicidal mechanisms. This study indicates that neutrophils exhibit distinct responses to promastigote and amastigote infection. Our findings have important implications for determining the impact of sustained neutrophil recruitment and amastigote-neutrophil interactions during the late phase of cutaneous leishmaniasis.

Oxidative status and the response to pegylated-interferon alpha2a plus ribavirin in chronic genotype 4 HCV hepatitis

Oxidative stress may play a pathogenic role in chronic hepatitis C (CHC). The present study examined the oxidative status in plasma of patients with CHC who received pegylated interferon and ribavirin therapy. The following groups were included: (1) sustained virological response (28 patients), (2) null response (26 patients), (3) breakthrough (24 patients), (4) relapse (24 patients), (5) spontaneous cure (23 patients) and (6) twenty five normal subjects as a control group. Markers of oxidative stress including plasma malondialdehyde, nitric oxide, reduced glutathione, total antioxidant capacity and uric acid as well as serum ALT, AST, alkaline phosphatase, total bilirubin, albumin, prothrombin time were studied. The study indicated significant decline in reduced glutathione and total antioxidant capacity and markedly elevated levels of malondialdehyde and nitric oxide in all groups compared with the controls. Null response group had the highest levels of malondialdehyde and nitric oxide. Nitric oxide was significantly higher in those with null response compared with all other groups and with control subjects. Uric acid was significantly higher in spontaneous cure group compared with all other groups and with the controls. We concluded that CHC patients had increased oxidative stress. The oxidative status in plasma of these patients was not changed by antiviral therapy. The study also showed an important contribution of nitric oxide in null response patients. High serum uric acid did not interfere with the response and/or did not predict the response to antiviral therapy.

UCP2 deficiency helps to restrict the pathogenesis of experimental cutaneous and visceral leishmaniosis in mice

BACKGROUND

Uncoupling protein 2 (UCP2) is a mitochondrial transporter that has been shown to lower the production of reactive oxygen species (ROS). Intracellular pathogens such as Leishmania upregulate UCP2 and thereby suppress ROS production in infected host tissues, allowing the multiplication of parasites within murine phagocytes. This makes host UCP2 and ROS production potential targets in the development of antileishmanial therapies. Here we explore how UCP2 affects the outcome of cutaneous leishmaniosis (CL) and visceral leishmaniosis (VL) in wild-type (WT) C57BL/6 mice and in C57BL/6 mice lacking the UCP2 gene (UCP2KO).

METHODOLOGY AND FINDINGS

To investigate the effects of host UCP2 deficiency on Leishmania infection, we evaluated parasite loads and cytokine production in target organs. Parasite loads were significantly lower in infected UCP2KO mice than in infected WT mice. We also found that UCP2KO mice produced significantly more interferon-γ (IFN-γ), IL-17 and IL-13 than WT mice (P<0.05), suggesting that UCP2KO mice are resistant to Leishmania infection.

CONCLUSIONS

In this way, UCP2KO mice were better able than their WT counterparts to overcome L. major and L. infantum infections. These findings suggest that upregulating host ROS levels, perhaps by inhibiting UPC2, may be an effective approach to preventing leishmaniosis.

Leishmania donovani-specific 25- and 28-kDa urinary proteins activate macrophage effector functions, lymphocyte proliferation and Th1 cytokines production

Growing incidence of drug resistance against leishmaniasis in endemic areas and limited drug options necessitates the need for a vaccine. Notwithstanding significant leishmanial research in the past decades, a vaccine candidate is far from reality. In this study, we report the potential of two urinary leishmanial proteins to induce macrophage effector functions, inflammatory cytokines production and human lymphocytes proliferation. A total four proteins of molecular mass 25, 28, 54 and 60 kDa were identified in human urine samples. The 25 and 28 kDa proteins significantly induced NADPH oxidase (p<0.001), superoxide dismutase (p<0.001) and inducible nitric oxide synthase (p<0.001) activities in stimulated RAW264.7 macrophages. The release of nitric oxide, tumor necrosis factor-alpha and interleukin (IL)-12 was also significantly (p<0.001) higher in 25 and 28 kDa activated macrophages as compared with cells activated with other two proteins. These two proteins also induced significant (p<0.001) proliferation and release of IFN-γ and IL-12 in human peripheral blood mononuclear cells.