Conserved histone methyltransferases of the DOT1 family are involved in replication regulation, cell cycle progression, stage differentiation, and gene regulation in trypanosomatids. However, the specific functions of these enzymes depend on the host evasion strategies of the parasites. In this study, we investigated the role of DOT1B in Leishmania mexicana, focusing on life cycle progression and infectivity. In contrast to Trypanosoma brucei, in which DOT1B is essential for the differentiation of mammal-infective bloodstream forms to insect procyclic forms, L. mexicana DOT1B (LmxDOT1B) is not critical for the differentiation of promastigotes to amastigotes in vitro. Additionally, there are no significant differences in the ability to infect or differentiate in macrophages or sand fly vectors between the LmxDOT1B-depleted and control strains. These findings highlight the divergence of the function of DOT1B in these related parasites, suggesting genus-specific adaptations in the use of histone modifications for life cycle progression and host adaptation processes.

Leishmania (L.) mexicana -induced cutaneous leishmaniasis (CL) is a neglected tropical disease characterized by localized chronic ulcers (LCL) and, in rare cases, by disseminated skin lesions (DCL). The therapeutic options for CL are currently limited, and the immune dysregulation leading to chronicity of disease is poorly understood. Here, we identified interleukin (IL)-10-dependent upregulation of arginase 1 (ARG1) in cutaneous CX3CR1+ myeloid cells as central immunometabolic determinant of chronic CL in L. mexicana -infected C57BL/6 wild-type (WT) mice. Deletion of Arg1 in myeloid cells ( Arg1ΔCx3cr1 ) enabled parasite control and clinical healing. Single-cell RNA sequencing revealed that ARG1, together with interferon-γ produced by T-helper 1 (Th1) cells, caused pathologic differentiation of Ly6Chigh monocytes into inflammatory macrophages (iMACs) that simultaneously expressed ARG1, nitric oxide synthase type 2 (NOS2) and the chemokines CXCL9/10. These Arg1+Nos2+Cxcl9/10+ iMACs induced a lasting depletion of L-arginine in the skin, served as parasite niche, and maintained a self-perpetuating cycle of host cell recruitment. In Arg1ΔCx3cr1 mice, the ARG1+NOS2+ host cell niche for the parasite was diminished. Prophylactic or therapeutic oral L-arginine supplementation restored tissue arginine levels, reduced parasite burden, and prevented or resolved chronic disease. L-arginine-treated mice showed enhanced T cell expansion and Th1 differentiation, remained free of clinical relapses, and were resistant to reinfection. As skin lesion biopsies from L. mexicana -infected LCL and DCL patients demonstrated a similar pattern of Th1/Th2 cytokine, Arg1 and Nos 2 mRNA expression as seen in mice, we suggest metabolic reprogramming by oral L-arginine as a promising and easy-to-apply host-directed therapy for human L. mexicana CL. ONE SENTENCE SUMMARY Arginase 1-mediated arginine depletion accounts for chronic cutaneous leishmaniasis, which can be prevented and even cured by oral L-arginine therapy. ### Competing Interest Statement The authors have declared no competing interest. * Arg1 /ARG1 : arginase 1 CLSFM : confocal laser scanning fluorescence microscopy DC : dendritic cell dLN : draining (popliteal) lymph node dpi : days post infection IFN : interferon IL : interleukin KO : knockout LD : limiting dilution NK : natural killer cell NO : nitric oxide Nos2 /NOS2 : type 2 (or inducible) nitric oxide synthase p.i., post infection scRNA-seq : single-cell RNA sequencing Th : T helper lymphocytes WT : wild-type. RTG 2740 ImmunoMicroTope, DFG CRC1181, DFG SPP1937 Innate lymphoid cells Interdisciplinary Center for Clinical Research (IZKF), Erlangen Staedtler (Germany), https://ror.org/04088fk89 Programa de Apoyo a Proyectos de Investigación e Innovación Tecnológica of the Universidad Nacional Autónoma de Méico

Interleukin (IL)-4 plays a central role in the initiation of a type 2 T helper cell (Th2) response, which leads to non-healing and progressive infections with the protozoan parasite Leishmania (L.) major. Here, we tested the hypothesis that type 2 innate lymphoid cells (ILC2), which promote the development of Th2 cells, form an important source of IL-4 early after intradermal or subcutaneous L. major infection. Lineage-marker negative CD90.2+CD127+PD1− ILC2 were readily detectable in the ear or foot skin, but hardly in the draining lymph nodes of both naïve and L. major-infected self-healing C57BL/6 and non-healing BALB/c mice and made up approximately 20% to 30% of all CD45+SiglecF− cells. Dermal ILC2 of C57BL/6 mice expressed the inducible T cell-costimulator (ICOS, CD278), whereas BALB/C ILC2 were positive for the stem cell antigen (Sca)-1. Within the first 5 days of infection, the absolute numbers of ILC2 did not significantly change in the dermis, which is in line with the unaltered expression of cytokines activating (IL-18, IL-25, IL-33, TSLP) or inhibiting ILC2 (IL-27, IFN-γ). At day 5 to 6 post infection, we observed an upregulation of IL-4, but not of IL-5, IL-10 or IL-13 mRNA. Using IL-4-reporter (4get) mice, we found that the production of IL-4 by C57BL/6 or BALB/c mice was largely restricted to CD45+SiglecF+ cells of high granularity, i.e., eosinophils. From these data, we conclude that eosinophils, but not ILC2, are a major innate source of IL-4 at the skin site of L. major infection.

Cutaneous leishmaniasis (CL) frequently entails chronic skin lesions that heal only slowly. Until now, the available therapeutic options are very limited. Here, we present a case of a 5½-year-old Syrian refugee with two progressive lower-leg skin ulcers caused by Leishmania tropica . The patient received topical treatment with LeiProtect ® , a newly developed, hydroxypropylcellulose-based, filmogenic gel containing nontoxic concentrations of pharmaceutical sodium chlorite. The skin lesions completely healed within 8 weeks and did not relapse during 1 year of follow-up, underlining the efficacy of this novel local therapy of CL.

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.

Experimental cutaneous leishmaniasis of mice is a valuable model to study the immune response to the protozoan pathogen Leishmania and to define mechanisms of parasite control and resolution of inflammation as well as of parasite evasion and chronicity of disease. In addition, over many years Leishmania-infected mice have been successfully used to analyze the function of newly discovered immune cell types, transcription factors, cytokines, and effector mechanisms in vivo. In this chapter we present detailed protocols for the culture, propagation, and inoculation of Leishmania promastigotes, the monitoring of the course of cutaneous infection, the determination of the tissue parasite burden and for the phenotyping of the ensuing immune response. The focus lies on the L. major mouse model, but an overview on other established models of murine cutaneous leishmaniasis is also provided.

AbstractArginase (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+/−Arg1fl/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.

Neutralization or deletion of tumor necrosis factor (TNF) causes loss of control of intracellular pathogens in mice and humans, but the underlying mechanisms are incompletely understood. Here, we found that TNF antagonized alternative activation of macrophages and dendritic cells by IL-4. TNF inhibited IL-4-induced arginase 1 (Arg1) expression by decreasing histone acetylation, without affecting STAT6 phosphorylation and nuclear translocation. In Leishmania major-infected C57BL/6 wild-type mice, type 2 nitric oxide (NO) synthase (NOS2) was detected in inflammatory dendritic cells or macrophages, some of which co-expressed Arg1. In TNF-deficient mice, Arg1 was hyperexpressed, causing an impaired production of NO in situ. A similar phenotype was seen in L. major-infected BALB/c mice. Arg1 deletion in hematopoietic cells protected these mice from an otherwise lethal disease, although their disease-mediating T cell response (Th2, Treg) was maintained. Thus, deletion or TNF-mediated restriction of Arg1 unleashes the production of NO by NOS2, which is critical for pathogen control.

The protozoan parasite Leishmania (Viannia) braziliensis is one of the main causes of cutaneous and mucocutaneous leishmaniasis in South America. Here, we describe three cases of L. (V) braziliensis infection which were acquired during travelling in Bolivia, Peru or Paraguay and illustrate the phenotypic heterogeneity and therapeutic complexity of the disease. Two patients presented with unusual clinical manifestations, i.e. with prominent regional lymphadenopathy ("bubonic leishmaniasis") and with simultaneously emerged skin and mucosal lesions, respectively. Both patients insufficiently responded to oral treatment with miltefosine; resolution of the lesions was only achieved after a course of intravenous liposomal amphotericin B.

JDDG: Journal der Deutschen Dermatologischen GesellschaftVolume 11, Issue 1 p. 83-85 Clinical Letters Two cases of successful treatment of multilesional cutaneous leishmaniasis with liposomal amphotericin B Florian Butsch, Florian Butsch Department of Dermatology, University Medical Center of the Johannes Gutenberg University Mainz, GermanySearch for more papers by this authorMichael Faulde, Michael Faulde Department of Medical Entomology/Zoology, Central Institute of the Bundeswehr Medical Service, Koblenz, Germany, and Institute of Immunology, Medical Microbiology and Parasitology, University Clinics, Bonn, GermanySearch for more papers by this authorAndrea Debus, Andrea Debus Medical Microbiology and Immunology of Infectious Diseases, Microbiology Institute - Clinical Microbiology, Immunology and Hygiene, Friedrich-Alexander-University Erlangen-Nuremberg and University Clinic of Erlangen, GermanySearch for more papers by this authorChristian Bogdan, Christian Bogdan Medical Microbiology and Immunology of Infectious Diseases, Microbiology Institute - Clinical Microbiology, Immunology and Hygiene, Friedrich-Alexander-University Erlangen-Nuremberg and University Clinic of Erlangen, GermanySearch for more papers by this authorEsther von Stebut, Esther von Stebut Department of Dermatology, University Medical Center of the Johannes Gutenberg University Mainz, GermanySearch for more papers by this author Florian Butsch, Florian Butsch Department of Dermatology, University Medical Center of the Johannes Gutenberg University Mainz, GermanySearch for more papers by this authorMichael Faulde, Michael Faulde Department of Medical Entomology/Zoology, Central Institute of the Bundeswehr Medical Service, Koblenz, Germany, and Institute of Immunology, Medical Microbiology and Parasitology, University Clinics, Bonn, GermanySearch for more papers by this authorAndrea Debus, Andrea Debus Medical Microbiology and Immunology of Infectious Diseases, Microbiology Institute - Clinical Microbiology, Immunology and Hygiene, Friedrich-Alexander-University Erlangen-Nuremberg and University Clinic of Erlangen, GermanySearch for more papers by this authorChristian Bogdan, Christian Bogdan Medical Microbiology and Immunology of Infectious Diseases, Microbiology Institute - Clinical Microbiology, Immunology and Hygiene, Friedrich-Alexander-University Erlangen-Nuremberg and University Clinic of Erlangen, GermanySearch for more papers by this authorEsther von Stebut, Esther von Stebut Department of Dermatology, University Medical Center of the Johannes Gutenberg University Mainz, GermanySearch for more papers by this author First published: 26 November 2012 https://doi.org/10.1111/j.1610-0387.2012.08072.x Prof. Dr. Esther von Stebut, Department of Dermatology, University Medical Center of the Johannes Gutenberg University Mainz, Langenbeckstraße 1, 55131 Mainz, Germany. E-mail: vonstebu@mail.uni-mainz.de AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Volume11, Issue1January 2013Pages 83-85 RelatedInformation

JDDG: Journal der Deutschen Dermatologischen GesellschaftVolume 11, Issue 1 p. 83-85 Clinical Letters Erfolgreiche Behandlung von zwei Patienten mit multiläsionaler kutaner Leishmaniasis mit liposomalem Amphotericin Florian Butsch, Florian Butsch Hautklinik und Poliklinik, Universitätsmedizin der Johannes Gutenberg-Universität MainzSearch for more papers by this authorMichael Faulde, Michael Faulde Abteilung für Entomologie/Zoologie, Zentrales Institut des Sanitätsdienstes der Bundeswehr Koblenz und Institut für Medizinische Mikrobiologie, Immunologie und Parasitologie, Universitätsklinik BonnSearch for more papers by this authorAndrea Debus, Andrea Debus Mikrobiologisches Institut – Klinische Mikrobiologie, Immunologie und Hygiene, Friedrich-Alexander-Universität Erlangen-Nürnberg und Universitätsklinik ErlangenSearch for more papers by this authorChristian Bogdan, Christian Bogdan Mikrobiologisches Institut – Klinische Mikrobiologie, Immunologie und Hygiene, Friedrich-Alexander-Universität Erlangen-Nürnberg und Universitätsklinik ErlangenSearch for more papers by this authorEsther von Stebut, Esther von Stebut Hautklinik und Poliklinik, Universitätsmedizin der Johannes Gutenberg-Universität MainzSearch for more papers by this author Florian Butsch, Florian Butsch Hautklinik und Poliklinik, Universitätsmedizin der Johannes Gutenberg-Universität MainzSearch for more papers by this authorMichael Faulde, Michael Faulde Abteilung für Entomologie/Zoologie, Zentrales Institut des Sanitätsdienstes der Bundeswehr Koblenz und Institut für Medizinische Mikrobiologie, Immunologie und Parasitologie, Universitätsklinik BonnSearch for more papers by this authorAndrea Debus, Andrea Debus Mikrobiologisches Institut – Klinische Mikrobiologie, Immunologie und Hygiene, Friedrich-Alexander-Universität Erlangen-Nürnberg und Universitätsklinik ErlangenSearch for more papers by this authorChristian Bogdan, Christian Bogdan Mikrobiologisches Institut – Klinische Mikrobiologie, Immunologie und Hygiene, Friedrich-Alexander-Universität Erlangen-Nürnberg und Universitätsklinik ErlangenSearch for more papers by this authorEsther von Stebut, Esther von Stebut Hautklinik und Poliklinik, Universitätsmedizin der Johannes Gutenberg-Universität MainzSearch for more papers by this author First published: 03 January 2013 https://doi.org/10.1111/j.1610-0387.2012.08072_suppl.xAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Volume11, Issue1January 2013Pages 83-85 RelatedInformation

Removing cytotoxics: A MnII–pentaazamacrocycle removes NO., O2.−, and their ONOO− product as shown by real-time amperometry at single cells (see picture). This is the first compound able to completely abolish the cytotoxic effects of reactive oxygen (ROS) and reactive nitrogen species (RNS) in inflammation.

Myeloid differentiation protein 88 (MyD88) is a general adaptor for the signaling cascade through receptors of the Toll/IL-1R family. When infected with Leishmania major parasites, MyD88-deficient mice displayed a dramatically enhanced parasite burden in their tissues similar to that found in susceptible BALB/c mice. In contrast, MyD88 knockout mice did not develop ulcerating lesions despite a lack of interleukin-12 (IL-12) production and a predominant T helper 2 cell response. Blockade of IL-4 produced early (day 1) after infection restored a protective T helper 1 response in MyD88 knockout mice.