Parasitic helminths infect millions of people and animals worldwide. A key feature of their lifecycle is the longevity of survival within a single host, which is often attributed to the ability of the parasite to divert or modulate the immune response against it. The excretory-secretory (ES) products released by helminths are of interest as the mediators of such immunomodulation. Heligmosomoides polygyrus is an excellent model of gastrointestinal (GI) helminth infection in rodents, and has been used here to investigate several aspects of the immune response, and the manipulation of these, in mice. Firstly, the roles of B cells and antibodies in infection with H. polygyrus and towards the adult ES (HES) were investigated. Using several B cell-deficient mouse strains, a minimal effect on immunity to primary infection with H. polygyrus was demonstrated. However, primary infection serum binds to a select set of highly immunodominant components of the complex protein mixture of HES, which were identified as venom allergen-like proteins (VALs). Utilising four strains of mice that vary in their resistance phenotype to H. polygyrus, several aspects of immunity towards the worm were investigated. Increased levels of markers of alternatively activated macrophages, which are a key component of the granulomatous inflammatory response around invading H. polygyrus larvae, were found in the most resistant strains, SJL and BALB/c. Depletion of macrophages, by administration of clodronate, severely disrupted the granuloma and parasite clearance. Numbers of innate lymphoid cells and the subsequent Th2 response, specificity range and titre of antibody, and activation of regulatory T cells all correlate with a resistant phenotype. A deficiency in the cytokine macrophage migration inhibitory factor (MIF) renders a resistant BALB/c mouse completely susceptible to infections with H. polygyrus, and Nippostronygylus brasiliensis, an acute model of GI helminth infection. This is accompanied by a failure to induce both ILCs and an early myeloid-derived cell population upon infection. The influx of alternatively activated macrophages around larvae in the mucosa of the small intestine is delayed in MIF-/- mice, although all immunological parameters are comparable to wild-type by day 14 post-infection. The susceptible phenotype of MIF-/- mice can be replicated using a chemical inhibitor of MIF in BALB/c mice. Finally, the previously documented transforming growth factor-β (TGF-β) activity of HES was dissected out further using two methods of fractionation. Distinct fractions with TGF-β activity were subjected to mass spectrometry to identify protein components that could be potential candidates for this activity.

ABSTRACT Alzheimer's disease (AD) is the most common progressive age related dementia and the fourth major cause of mortality in the elderly in the United States. AD is pathologically characterized by deposition of amyloid beta (Aβ) plaques in the brain parenchyma and neurofibrillary tangles (NFTs) within the neuronal soma. While pharmacological targets have been discovered, current strategies for the symptomatic or disease-modifying treatment of AD do not significantly slow or halt the underlying pathological progression of the disease. Consequently, more effective treatment is needed. One possibility for amelioration is using human umbilical cord blood cell (HUCBC) therapy. HUCBCs comprise a population of hematopoietic stem and progenitor cells. During recent years, functional recovery has been observed from the use of HUCBCs in pre-clinical animal models of brain and spinal cord injuries. Thus, modulation by cell therapy, specifically HUCBCs, may be a suitable treatment for AD and other models because of the observed cognitive and behavioral improvements. The studies presented in this dissertation centers on the suitability of using HUBCs as a potential treatment for AD. Expanding on this, the aims of the study sought to: (I) Investigate bio-distribution of HUCBC transplantation in PSAPP mice, (II) Characterize efficacy and determine therapeutic outcome of HUCBC following short and long term multi injections at early and late disease stages in PSAPP mice and (III) Determine AD-like pathological and cognitive changes associated with multiple HUCBC-derived monocyte (CD14) injections in PSAPP mice. Thus the findings of this work evolved from experiments that characterized the effects of low-dose infusions of HUCBC and HUCBC-derived monocytes into 6 month old Presenilin 1/Amyloid Precursor Protein (PSAPP) plaque-developing transgenic AD mice. Treated mice were studied using standard behavioral tests to determine the effects of infusion on the multiple cognitive domains affected by AD, followed by biochemical and histological analyses that included Aβ load and amyloid precursor protein (APP) processing. Specifically, PSAPP mice and their wild-type (WT) littermates were treated monthly with a peripheral HUCBC infusion over a period of 6 and 10 months, followed by cognitive and motor evaluation. Additionally, based on reports that tumor cells can originate from stem cells present in HUCB, we further examined whether monocytes purified from HUCBCs would have a similar significant effect on the reduction of AD-like pathology in PSAPP mice. HUCB cells homed into tissues including the brain. The principal finding was significant reduction in Aβ levels and β–amyloid plaques following low-dose infusions of both HUCBC– derived mononuclear cells as well as HUCBC-derived monocytes, with the monocytes providing a stronger effect. Results further demonstrated that HUCBC and HUCBC– derived monocyte infusion could improve memory function and locomotor ability in treated PSAPP mice. A possible reason for behavioral improvements in these animals may be the significant reduction in both Aβ levels and plaque load. This study also identified significant reduction in microglial activation and astrocytosis, both of which can contribute to AD pathology. In conclusion, our data suggest that it might be the HUCBC–derived monocytic population rather than stem cells that are responsible for the reduction in AD pathology.

In Pseudomonas aeruginosa, which causes severe secondary infections in immunocompromised patients, virulence factor expression is regulated by quorum sensing signal molecules known as acyl homoserine lactones (AHLs). One of the major AHLs produced by P. aeruginosa, N-(3-oxododecanoyl)-L-homoserine lactone (OdDHL), has also been shown to alter the function of a range of mammalian cells. The goals of experiments reported in this thesis were to use murine models to investigate the effects of in vivo exposure to OdDHL on TH responses, define the direct effects of OdDHL on TH cells and to explore the mechanism by which OdDHL alters the function of TH cells. It was found that in vivo exposure to OdDHL led to changes in cytokine and antibody subclass production indicative of a shift towards the underlying TH bias of the mouse strain studied. Such shifts may play a role in infections with P. aeruginosa, as strong TH1 or TH2 responses have been associated with worsening prognosis for the host, while more balanced responses have been associated with decreases in both infection and pathology. These results suggest that treatments targeting the immunomodulatory activities of OdDHL may be of benefit in the clinical setting in the future. Direct analysis of TH cells in defined in vitro systems revealed that exposure to OdDHL led to uniform decreases in cytokine production and proliferation. These decreases in cytokine production were found to be the result of OdDHL acting on both TH cells and the antigen presenting cells (APCs) that activate them, and only occurred when cells were exposed to OdDHL within 4 hours of stimulation. These findings suggest that OdDHL is acting on a molecular target common to several cells types, and that in TH cells and APCs, this target is involved in the early stages of TH cell activation. Experiments in which T cells were activated with mitogens that bypass the cell membrane revealed that OdDHL is not acting on the cell membrane or membrane-associated activation factors, suggesting that OdDHL is instead inhibiting TH cell function through interactions with one or more intracellular signalling molecules.

Poxviruses are renowned for encoding proteins that modulate virtually every aspect of the host immune system. One effective barrier against virus infection is apoptosis, a form of programmed cell death. Apoptosis is controlled at the mitochondria by pro- and anti-apoptotic members of the highly conserved Bcl-2 family of proteins, and two members in particular, Bak and Bax, are absolutely critical to the induction of cell death. Although poxviruses encode an array of effective inhibitors of apoptosis, only members of the Avipoxvirus genus, of which fowlpox virus is the prototypical member, encode proteins with obvious, albeit limited, sequence identity to cellular Bcl-2 proteins. Fowlpox virus, the prototypical avipoxvirus, encodes FPV039, a protein that possesses two of the four highly conserved Bcl-2 homology (BH) domains that characterise the Bcl-2 family. Here we demonstrate that, like cellular Bcl-2 proteins, FPV039 localised to the mitochondria where it prevented apoptosis induced by a variety of cytotoxic stimuli, including virus infection itself. FPV039 inhibited apoptosis induced by Bak and Bax through an interaction with Bak and activated Bax. FPV039 also interacted with a discrete subset of BH3-only proteins, the upstream activators of Bak and Bax, to prevent Bax activation in the first place. Additionally, we have characterised the function and mechanism of action of a novel deerpox virus protein, DPV022. Intriguingly, DPV022 lacks obvious homology to cellular Bcl-2 proteins but shares limited regions of amino acid identity with two other poxviral inhibitors of apoptosis, vaccinia virus F1L and myxoma virus M11L, which are themselves unrelated. Here we demonstrate that DPV022 localised to the mitochondria where it interacted directly with Bak and Bax to inhibit apoptosis, even in the absence all cellular anti-apoptotic Bcl-2 proteins. We have also embarked on a preliminary analysis of the apical events that initially trigger apoptosis during infection with vaccinia virus, the prototypical poxvirus. Accordingly, we demonstrate that the BH3-only protein Noxa contributed to the vaccinia virus-induced apoptotic response, possibly through an involvement with dsRNA. Together, this study represents a comprehensive analysis of the ways in which poxviruses manipulate the cellular Bcl-2 family of proteins, the arbiters of cell death. / Virology

A new paradigm for the treatment of infectious disease is through the modulation of innate immune responses. In this capacity, host defense peptides (HDPs) and synthetic Toll-like receptor 9 (TLR9) ligands have the greatest demonstrated potentials. The work presented here considers mechanisms for the improvement of these treatments through optimization, or in the case of HDPs the minimization, of the interactions of these ligands with sensory receptors.<p>Toll-like Receptor 9 activates the innate immune system in response to microbial DNA or immune-modulating oligodeoxynucleotides. While cell stimulation experiments demonstrate the preferential activating ability of CpG-containing nucleic acids, direct binding investigations have reached contradictory conclusions regarding the sequence-specificity of TLR9 ligand binding. To address this discrepancy the characterization of human TLR9 ligand binding properties is reported. TLR9 has a high degree of ligand specificity in being able to discriminate not only CpG dinucleotides, but also higher order six nucleotide motifs that mediate species-specific activation. However, TLR9 ligand binding is also functionally influenced by nucleic acids in a sequence-independent manner both in vitro and in cell proliferation experiments. A model is proposed in which TLR9 activation is mediated specifically by CpG-containing ligands while sensitivity of the receptor is modulated by the absolute concentration of nucleic acids in a sequence-independent fashion. <p>Host defense peptides are among the leading candidates to combat antibiotic resistant bacterial strains. Recently, HDPs have been demonstrated to function as ligands for the bacterial sensory kinase PhoQ resulting in the induction of virulence and adaptive responses. Thus, concerns have been raised regarding therapeutic applications of HDPs. Here a methodology is described that permits discrimination and quantification of the distinct, but related, peptide behaviors of direct antimicrobial activity and PhoQ ligand potential. Utilizing peptide derivatives of the model HDP Bac2A it is demonstrated that antimicrobial efficiency is significantly, and inversely, related to PhoQ ligand efficacy. This provides a rational basis for HDP selection with greater therapeutic potential and minimized potential for initiation of bacterial resistance.

Les objectifs de ce projet étaient d'identifier les propriétés immunomodulatrices de produits obtenus par la fermentation du lactosérum à l'aide de souches sélectionnées de Lactobacillus kefiranofaciens développées par la compagnie Technologies BiolActis lnc. Différentes préparations d'une matrice protéique malléable (MPM), contenant des substances solubles et des bactéries ont été générées par fermentation et leurs effets sur les macrophages et les cellules épithéliales intestinales ont été évalués in vitro par analyse de la production de cytokines inflammatoires ainsi que l'étude des voies de signalisation intracellulaire impliquées. Nous avons aussi vérifié l'efficacité anti-inflammatoire in vivo des MPMs et de la souche bactérienne lors de colites expérimentales aigues chez des animaux afin d'identifier les cytokines et cellules suppressives impliquées. Des groupes de souris ont été traitées simultanément ou de façon préventive avec des produits choisis afin d'en vérifier les effets anti-inflammatoires lors de l'induction de la colite expérimentale par le sulfate de dextran. De nombreux paramètres biologiques et immunologiques ont été évalués, tels que le poids, le taux d'hématocrite, la densité du côlon, les niveaux de production de cytokines par des tests ELISA ou par RT-PCR en temps réel ainsi que plusieurs immunomarquages des diverses populations lymphocytaires dans les tissus intestinaux analysés par cytofluorométrie. Les résultats obtenus in vitro indiquent que les produits de fermentation du lactosérum modulent la production de cytokines macrophagiques pro-inflammatoires et anti-inflammatoires. Certains produits de fermentation augmentent la production de l'IL-6 induite par le PEP ou diminuent la production de la PGE2 sans affecter significativement la production de l'IL-10. Ces produits exercent leurs effets surtout par l'activation des voies dépendant des MAPK p38 et ERK1/2 ainsi que de la COX-2. La souche bactérienne R2C2 induit aussi bien la production d'IL-6 que celle de l'IL-10 chez les macrophages. Tous les produits de fermentation ont diminué la production de la chimiokine IL-8 par les cellules épithéliales intestinales impliquées dans l'induction de la réponse inflammatoire. Lors de la colite expérimentale induite par le DSS, l'administration simultanée de MPM a corrigé la perte de poids des animaux et rétablit la perte de lymphocytes B dans les tissus épithéliaux. L'utilisation préventive du MPM et de la bactérie R2C2 a empêché l'anémie induite par le DSS mais a aggravé la perte de poids et l'inflammation du côlon malgré la production accrue d'IL-10 et la stimulation de lymphocytes T suppresseurs. Ces effets ont été accompagnés de l'activation d'une nouvelle classe de lymphocytes, les Th17. Les effets anti-inflammatoires semblent plus intéressants lors d'une utilisation simultanée, suggérant la prise de ces produits lors de troubles gastro-intestinaux légers. D'autre part, les modifications dans les conditions de production pourraient expliquer les différences observées dans l'efficacité anti-inflammatoire des produits. ______________________________________________________________________________ MOTS-CLÉS DE L’AUTEUR : Colite, DSS, Inflammation, Intestin, Lactobacilles, Lactobacillus kefiranofaciens, Lactosérum, IL-6, IL-10, IL-17, IL-23, Macrophages, PGE-2, TNP-α.

A new paradigm for the treatment of infectious disease is through the modulation of innate immune responses. In this capacity, host defense peptides (HDPs) and synthetic Toll-like receptor 9 (TLR9) ligands have the greatest demonstrated potentials. The work presented here considers mechanisms for the improvement of these treatments through optimization, or in the case of HDPs the minimization, of the interactions of these ligands with sensory receptors.<p>Toll-like Receptor 9 activates the innate immune system in response to microbial DNA or immune-modulating oligodeoxynucleotides. While cell stimulation experiments demonstrate the preferential activating ability of CpG-containing nucleic acids, direct binding investigations have reached contradictory conclusions regarding the sequence-specificity of TLR9 ligand binding. To address this discrepancy the characterization of human TLR9 ligand binding properties is reported. TLR9 has a high degree of ligand specificity in being able to discriminate not only CpG dinucleotides, but also higher order six nucleotide motifs that mediate species-specific activation. However, TLR9 ligand binding is also functionally influenced by nucleic acids in a sequence-independent manner both in vitro and in cell proliferation experiments. A model is proposed in which TLR9 activation is mediated specifically by CpG-containing ligands while sensitivity of the receptor is modulated by the absolute concentration of nucleic acids in a sequence-independent fashion. <p>Host defense peptides are among the leading candidates to combat antibiotic resistant bacterial strains. Recently, HDPs have been demonstrated to function as ligands for the bacterial sensory kinase PhoQ resulting in the induction of virulence and adaptive responses. Thus, concerns have been raised regarding therapeutic applications of HDPs. Here a methodology is described that permits discrimination and quantification of the distinct, but related, peptide behaviors of direct antimicrobial activity and PhoQ ligand potential. Utilizing peptide derivatives of the model HDP Bac2A it is demonstrated that antimicrobial efficiency is significantly, and inversely, related to PhoQ ligand efficacy. This provides a rational basis for HDP selection with greater therapeutic potential and minimized potential for initiation of bacterial resistance.

No description available.

Στόχος της παρούσας ερευνητικής εργασίας είναι να διερευνηθεί η επίδραση της ιμικουϊμόδης, ενός τοπικώς εφαρμοζόμενου στο δέρμα αγωνιστού των Toll-like 7 υποδοχέων (Τoll-like receptors, ΤLRs), στην συστηματική ανοσία σε ασθενείς με δερματικές HSV και HPV λοιμώξεις. Πιο αναλυτικά θέλουμε να διερευνήσουμε μήπως η τοπική χορήγηση ιμικουϊμόδης μπορεί να επηρεάσει τις κυτταροκίνες που συμμετέχουν στους μηχανισμούς φυσικής και επίκτητης ανοσίας και τους κυτταρικούς πληθυσμούς και όπως είναι τα Τ κύτταρα (βοηθητικά, κυτταροτοξικά, παρθενικά, μνήμης, ενεργοποιημένα και ρυθμιστικά), τα Β κύτταρα και τα φυσικά φονικά κύτταρα (ΝΚ). Οι TLRs είναι ο συνδετικός κρίκος μεταξύ φυσικής και επίκτητης ανοσίας εφόσον είναι οι υποδοχείς που αναγνωρίζουν και προσδένουν μοριακές δομές των παθογόνων (pathogen associated molecular patterns-PAMPs). Η έκφραση TLRs έχει εντοπιστεί σε πολλούς κυτταρικούς όπως ουδετερόφιλα, μακροφάγα, δεντριτικά κύτταρα, ενδοθηλιακά κύτταρα της δερμίδας, επιθηλιακά κύτταρα των βλεννογόνων, Β και Τ κύτταρα. Η ενεργοποίηση των TLRs οδηγεί σε έκκριση κυτταροκινών και χημειοκινών που έχουν σαν στόχο την ενεργοποίηση της φυσικής ανοσίας, που προκαλεί τελικά την δημιουργία της επίκτητης ανοσίας. Οι ιμιδαζοκινολίνες συνιστούν μία κατηγορία νουκλεοσιδικών αναλόγων που αναπτύχθηκαν σαν αντιϊκοί παράγοντες. Η ιμικουϊμόδη είναι ένας εκπρόσωπος των ιμιδαζοκινολινών που χρησιμοποιείται για την θεραπεία των κονδυλωμάτων και των επιθηλιακών καρκίνων του δέρματος. Η ιμικουϊμόδη (imiquimod) είναι προσδέτης των TLRs - πιο ειδικά του TLR-7 και χορηγείται τοπικά υπό την μορφή αλοιφής. Έχει χαρακτηριστεί σαν ανοσορρυθμιστικός παράγοντας, γιατί μέσω της πρόσδεσης της στον TLR-7 προκαλεί ένα σύνολο αντιδράσεων όπως η αύξηση της κυτταροτοξικότητας των φυσικών φονικών κυττάρων (ΝΚ), η ενεργοποίηση των μακροφάγων να εκκρίνουν κυτταροκίνες, η ενεργοποίηση και η μετανάστευση των κυττάρων του Langerhans από το δέρμα στους λεμφαδένες και η επαγωγή του πολλαπλασιασμού και της διαφοροποίησης των Τ και Β κυττάρων. Επί του παρόντος παραμένει άγνωστο αν η τοπικώς εφαρμοζόμενη ιμικουϊμόδη είναι σε θέση να εξασκεί επιπλέον της τοπικής και συστηματική ανοσοτροποποιητική δράση. Για τον λόγο αυτό στην παρούσα εργασία μελετήσαμε την επίδραση της ιμικουϊμόδης στο ανοσοποιητικό σύστημα υγιών μαρτύρων και ασθενών με HSV και HPV λοιμώξεις τόσο σε επίπεδο κυτταροκινών με την μέθοδο Cytometric bead array (CBA) όσο και σε επίπεδο κυκλοφορούντων κυτταρικών πληθυσμών στο περιφερειακό αίμα με κυτταρομετρία ροής (FACS). Τα αποτελέσματα μας υποδεικνύουν ότι η τοπική εφαρμογή της ιμικουϊμόδης είναι ικανή να προκαλέσει συστηματική ανοσοτροποποίηση και αυτό αποτελεί μια νέα και αποτελεσματική εναλλακτική θεραπεία. / In this study we investigate the influence of imiquimod, a topical applicable agonist of Toll-like receptor 7 (TLR7) in skin, on systemic immunity of patients with herpes simplex virus (HSV) and human papilloma virus (HPV) infections. We investigated whether the topical application of imiquimod affects cytokines which participate in mechanisms of innate and adaptive immune responses and cell populations, such as T-cells (helper, cytotoxic, naïve, memory, activated and regulatory), B-cells and natural killer cells (NK cells). TLRs help to bridge the gap between innate and adaptive immunity, since they recognize and bind pathogen associated molecular patterns of pathogens. The expression of TLRs has been detected on neutrophils, macrophages, dendritic cells, dermal endothelial cells, mucosal epithelial cells, T and B cells. Activation of TLRs mediates the release of cytokines and chemokines that recruit innate immune responses, which lead to the formation of adaptive immunity. Imidazoquinolines represent a group of nucleoside analogues that have been used as antiviral agents. Imiquimod belongs to imidazoquinolines and it has been used for the treatment of genital warts (caused by HPV) and cutaneous cancers. Imiquimod is a ligand of TLR7 and a patient-applied cream. It has been characterized as an immune response modifier, because through its binding to TLR7 it generates a cascade of reactions such as upregulation of cytotoxicity in NK cells, activation of macrophages to secrete cytokines, activation and migration of Langerhans cells from skin to lymph nodes and induction of proliferation and differentiation of T and B cells. Currently it is unknown if the topical application of imiquimod is able to exert, apart from a local, also a systemic immunomodulatory action. For this reason we tried to elucidate the effects of imiquimod on the immune system of patients with HSV and HPV infections at two levels. First we have measured the circulating cell populations in whole blood using flow cytometry and secondly we have determined the serum levels of IL-2, IL-4, IL-6, IL-10, TNF-α, IFN-α and IFN-γ with cytometric bead array. The results demonstrate that our hypothesis is correct and imiquimod could be an alternative and effective treatment of cutaneous HSV and HPV infections.

Os antimoniais pentavalentes, tais como o Glucantime, são geralmente usados como fármacos de primeira escolha para o tratamento das leishmanioses, no entanto seu mecanismo de ação não é completamente esclarecido. Atua contra formas amastigotas intracelulares de Leishmania sp, comprometendo o potencial redox levando danos ao DNA do parasito. Alguns trabalhos sugerem que o Glucantime aumenta a capacidade fagocítica e a produção de TNF-alfa por fagócitos. O objetivo deste estudo foi avaliar a capacidade do Glucantime modular a atividade do macrófago, a principal célula hospedeira da Leishmania. Inicialmente, a toxicidade do Glucantime foi testada sobre macrófagos peritoneais de camundongos BALB/c, tratando as monocamadas in vitro por 48 horas. A viabilidade celular foi avaliada pelo método do MTT. A capacidade do Glucantime (0,1, 1 e 10 mg/ml) modular os macrófagos foi avaliada tratando as monocamadas de macrófagos peritoneais por 24 horas antes da infecção com Leishmania braziliensis. Após 48 horas de incubação com meio de cultura foi avaliado o índice de infecção por contagem. Antes e após a infecção foram analisados a produção de óxido nítrico (NO) pelo método de Griess, espécies reativas de oxigênio (EROS) por fluorimetria usando a sonda H2DCFDA e a produção de citocinas por ELISA. Para avaliar se o Glucantime seria capaz de modular macrófagos in vivo, camundongos suíços foram tratados por 5 dias consecutivos com 8 mg de Glucantime pela via intraperitoneal. Macrófagos peritôneais foram avaliados quanto a sua capacidade de controlar a infecção in vitro com L. braziliensis. Os resultados mostraram que nas concentrações até 10 mg/ml, o Glucantime não alterou a viabilidade dos macrófagos in vitro. O pré-tratamento dos macrófagos com Glucantime nas concentrações de 0.1mg/mL, 1mg/mL e 10mg/mL, foi capaz de reduzir o índice de infecção em 49%, 74% e 85%, respectivamente. Em macrófagos não infectados a produção de NO foi aumentada na concentração de 10mg/ml de Glucantime. O tratamento com 1 e 10 mg/ml de Glucantime foi capaz de aumentar significativamente a produção de EROs (p<0,05 e p<0.01, respectivamente) e a produção IL-12 (p<0,05), mas a IL-10 não foi alterada. Não houve alterações significativas desses parâmetros em relação ao controle após a infecção com L. braziliensis. Os macrófagos oriundos dos animais tratados com Glucantime foram capazes de reduzir o índice de infecção por L. braziliensis (p<0,05). Esses resultados sugerem que o Glucantime é capaz de ativar os macrófagos e esse efeito pode contribuir para o mecanismo de ação desse fármaco. / The pentavalent antimonial drugs, such as Glucantime, are generally used as first choice for the treatment of leishmaniasis, however its mechanism is not fully understood. It has activity against intracellular amastigotes of Leishmania sp, compromising the redox potential and causing damage to the DNA of the parasite. Some studies suggesting that Glucantime enhances phagocytosis and TNF-&#945; production by phagocytes. The aim of this study is to evaluate the modulation of Glucantime on macrophages, the major host cell of Leishmania. Initially, Glucantimes toxicity was tested on peritoneal macrophages from BALB/c mice, by treating the monolayers in vitro for 48 hours. Cell viability was evaluated by MTT method. The capacity of Glucantime (0,1, 1 and 10 mg/ml) of modulate macrophages was evaluated by treating the monolayers of peritoneal macrophages for 24 hours before the infection with Leishmania braziliensis. After 48 hours of incubation with culture medium the infection index was evaluated by counting. Before and after the infection were analyzed the production of nitric oxide (NO) by Griess method, reactive oxygen species (ROS) by fluorimetry using the H2DCFDA dye and cytokines by ELISA. To evaluate if Glucantime could modulate macrophages in vivo, Swiss Webster mice were treated for 5 consecutive days with 8 mg Glucantime by intraperitoneal route. Peritoneal macrophages were evaluated about its capacity of control the in vitro infection with L. braziliensis. Results showed that until the concentration of 10 mg/ml, Glucantime did not alter the macrophages viability in vitro. The pre-treatment of macrophages with Glucantime at 0.1mg/mL, 1mg/mL and 10mg/mL was able to reduce the infection index in 49%, 74% and 85%, respectively. On non-infected macrophages the NO production was increased at 10mg/ml of Glucantime. The treatment with 1 and 10 mg/ml de Glucantime was able to significantly increase the ROS production (p<0,05 and p<0.01, respectively) and IL-12 production (p<0,05), however the IL-10 production was not altered. There were no significant changes of these parameters comparing to control after the L. braziliensis infection. The macrophages from the treated mice were capable of reduce the infection index by L. braziliensis (p<0,05). These results suggest that Glucantime is capable of activate macrophages and this effect could contribute to the mechanism of action of this drug.