Modulation des radeaux lipidiques et des propriétés de fusion des phagosomes par le lipophosphoglycane du parasite intracellulaire Leishmania donovani

Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal.

Presence of antibodies against Leishmania chagasi in haemodialysed patients

SOUZA,Roberto Mascarenhas et al.Presence of antibodies against Leishmania chagasi in haemodialysed patients.Transactions of the Royal Society of Tropical Medicine and Hygiene,v. 103, p.749-751, 2009.

Presence of antibodies against Leishmania chagasi in haemodialysed patients

SOUZA, R. M. et al. Presence of antibodies against Leishmania chagasi in haemodialysed patients. Transactions of the Royal Society of Tropical Medicine and Hygiene, v. 103, n.7, p. 749—751. ISSN 0035-9203.

iNOS-producing inflammatory dendritic cells constitute the major infected cell type during the chronic Leishmania major infection phase of C57BL/6 resistant mice.

Leishmania major parasites reside and multiply in late endosomal compartments of host phagocytic cells. Immune control of Leishmania growth absolutely requires expression of inducible Nitric Oxide Synthase (iNOS/NOS2) and subsequent production of NO. Here, we show that CD11b+ CD11c+ Ly-6C+ MHC-II+ cells are the main iNOS-producing cells in the footpad lesion and in the draining lymph node of Leishmania major-infected C57BL/6 mice. These cells are phenotypically similar to iNOS-producing inflammatory DC (iNOS-DC) observed in the mouse models of Listeria monocytogenes and Brucella melitensis infection. The use of DsRed-expressing parasites demonstrated that these iNOS-producing cells are the major infected population in the lesions and the draining lymph nodes. Analysis of various genetically deficient mouse strains revealed the requirement of CCR2 expression for the recruitment of iNOS-DC in the draining lymph nodes, whereas their activation is strongly dependent on CD40, IL-12, IFN-gamma and MyD88 molecules with a partial contribution of TNF-alpha and TLR9. In contrast, STAT-6 deficiency enhanced iNOS-DC recruitment and activation in susceptible BALB/c mice, demonstrating a key role for IL-4 and IL-13 as negative regulators. Taken together, our results suggest that iNOS-DC represent a major class of Th1-regulated effector cell population and constitute the most frequent infected cell type during chronic Leishmania major infection phase of C57BL/6 resistant mice.

Presence of antibodies against Leishmania chagasi in haemodialysed patients

SOUZA,Roberto Mascarenhas et al.Presence of antibodies against Leishmania chagasi in haemodialysed patients.Transactions of the Royal Society of Tropical Medicine and Hygiene,v. 103, p.749-751, 2009.

Presence of antibodies against Leishmania chagasi in haemodialysed patients

SOUZA, R. M. et al. Presence of antibodies against Leishmania chagasi in haemodialysed patients. Transactions of the Royal Society of Tropical Medicine and Hygiene, v. 103, n.7, p. 749—751. ISSN 0035-9203.

Unravelling metabolism of Leishmania by metabolomics

The leishmaniases are neglected tropical diseases with an urgent need for effective drugs. Better understanding of the metabolism of the causative parasites will hopefully lead to development of new compounds targeted at critical points of the parasite’s biochemical pathways. In my work I focused on the pentose phosphate pathway of Leishmania, specifically on transketolase, sugar utilisation, and comparison between insect and mammalian infective stages of the parasites. The pentose phosphate pathway (PPP) is the major cellular source of NADPH, an agent critical for oxidative stress defence. The PPP uses glucose, reduces the NADP+ cofactor and produces various sugar phosphates by mutual interconversions. One of the enzymes involved in this latter part is transketolase (TKT). A Leishmania mexicana cell line deleted in transketolase (Δtkt) was assessed regarding viability, sensitivity to a range of drugs, changes in metabolism, and infectivity. The Δtkt cell line had no obvious growth defect in the promastigote stage, but it was more sensitive to an oxidative stress inducing agent and most of the drugs tested. Most importantly, the Δtkt cells were not infective to mice, establishing TKT as a new potential drug target. Metabolomic analyses revealed multiple changes as a consequence of TKT deletion. Levels of the PPP intermediates upstream of TKT increased substantially, and were diverted into additional reactions. The perturbation triggered further changes in metabolism, resembling the ‘stringent metabolic response’ of amastigotes. The Δtkt cells consumed less glucose and glycolytic intermediates were decreased indicating a decrease in flux, and metabolic end products were diminished in production. The decrease in glycolysis was possibly caused by inhibition of fructose-1,6-bisphosphate aldolase by accumulation of the PPP intermediates 6-phosphogluconate and ribose 5-phosphate. The TCA cycle was fuelled by alternative carbon sources, most likely amino acids, instead of glucose. It remains unclear why deletion of TKT is lethal for amastigotes, increased sensitivity to oxidative stress or drop in mannogen levels may contribute, but no definite conclusions can be made. TKT localisation indicated interesting trends too. The WT enzyme is present in the cytosol and glycosomes, whereas a mutant version, truncated by ten amino acids, but retaining a C-terminal targeting sequence, localised solely to glycosomes. Surprisingly, cells expressing purely cytosolic or glycosomal TKT did not have different phenotypes regarding growth, oxidative stress sensitivity or any detected changes in metabolism. Hence, control of the subcellular localisation remains unclear as well as its function. However, these data are in agreement with the presumed semipermeable nature of the glycosome. Further, L. mexicana promastigote cultures were grown in media with different combinations of labelled glucose and ribose and their incorporation into metabolism was followed. Glucose was the preferred carbon source, but when not available, it could be fully replaced with ribose. I also compared metabolic profiles from splenic amastigotes, axenic amastigotes and promastigotes of L. donovani. Metabolomic analysis revealed a substantial drop in amino acids and other indications coherent with a stringent metabolic response in amastigotes. Despite some notable differences, axenic and splenic amastigotes demonstrated fairly similar results both regarding the total metabolic profile and specific metabolites of interest.

Influência do vírus da hepatite G (GBV-C) na resposta imune frente à infecção por Leishmania chagasi

GB virus type C (GBV-C) appears to promote a Th1 response and is associated with prolonged survival in HIV-infected people. L. chagasi causes a spectrum of illness that varies from severe visceral leishmaniasis, a disease that in the majority of cases is fatal if not treated, to self resolution of infection and development of positive DTH response that is protective against symptomatic disease. To determine if GBV-C viremia might influence the outcome of Leishmania infection, we characterized GBV-C status in a cohort of subjects residing in a L. chagasi endemic area in Brazil. GBV-C viremia was more prevalent in blood donors from urban than in periurban regions of Natal, Brazil (16% and 7.5% respectively). Evidence of prior GBV-C (anti-E2 antibodies) was detected in 24% and 12%of these groups respectively. Anti-E2 increased with age (p= 0.0121). No difference in GBV-C viremia was found in the DTH+ and VL groups (p= 0.269); however, subjects with visceral leishmaniasis were more likely to have anti-E2 than DTH+ subjects (p=0.0012), and DTH induration was smaller in subjects with E2 antibodies (4.5 mm) compared those without (7.12 mm) (p= 0.002). Furthermore, the size of the Leishmania DTH response was greater in GBV-C viremica subjects (6.8 mm) compared to non-viremic subjects (3.3 mm; p= 0.0054). There findings suggest that GBV-C virus may promote a type 1 immune response that could influence the outcome of Leishmania infection

Estudo sobre a participação de roedores na cadeia de transmissão de Leishmania infantum (Protozoa: Trypanosomatidae) no Rio Grande do Norte

American visceral leishmaniasis is a zoonosis caused by Leishmania infantum and transmitted by the bite of the sand flies Lutzomia longipalpis.The main domestic reservoir is the dog, while foxes and opposums are the known wild reservoirs. However, identification of natural infections with L. infantum in rodents appears for need of investigating the participation of these rodents how source of infection of the parasite. In the present work the Leishmania infantum infection was investigated in rodents captured in Rio Grande do Norte, aiming at to offer subsidies to the understanding of the epidemic chains of LVA in the State. Thirteen Galea spixii were distributed in four groups, being G1 the group control with four animals and the others, G2, G3 and G4, with three animals each. Those animals were intraperitoneally inoculated with 107 promastigotas of L. infantum and accompanied for, respectively, 30, 90 and 180 days. Weekly the animals were monitored as for the corporal weight and rectal temperature. At the end of each stipulated period the animals were killed. Blood were used for determination of the parameters biochemical and haematological, PCR, ELISA, microscopic examination and cultivation in NNN medium. Liver, spleen and lymph node were used in Giemsa-stained impression and cultivation in NNN medium. Liver and spleen fragments were still used in PCR and histopathological, respectively. At the same time 79 rodents of the species Rattus rattus, Bolomys lasiurus, Oligoryzomys nigripis, Oryzomys subflavus and Trichomys apereoides were captured in the Municipal districts of Brejinho, Campo Grande, Coronel Ezequiel, Passa e Fica and Vázea for identification of natural infection with L. infantum. Evidence of infection was checked by direct examination of Giemsa-stained impression of liver, spleen and blood and culture of these tissues in NNN medium. Antibodies were researched by ELISA. They were not found differences among the weigh corporal final, rectal temperature and biochemical and haematological parameters of the Galea spixii controls and infected. The rectal temperature of the animals varied from 36OC to 40OC. For the first time values of the haematocrit (33,6% to 42,8%), hemoglobin (10,2 to 14,5g/dl), erythrocyts number (4,67x106 to 6,90x106/mm3), total leukocytes (0,9x103 to 9,2x103/mm3), platelets (49x103 to 509x103/mm3) total proteins (1,56 to 6,06 g/dl), albumin (1,34 to 3,05 g/dl) and globulins (0,20 to 3,01 g/dl) of the Galea spixii were determined. The lymphocytes were the most abundant leucocytes. Infection for L. infantum was diagnosed in two animals euthanasied 180 days after the infection. In one of the animals was also identified antibodies anti-Leishmania. The parasite was not found in none of the five other species of rodents captured. Galea spixii are resistant to the infection for L. infantum and they are not good models for the study for visceral leishmaniose, although they can act as infection sources. More studies are necessary to determine the paper of the rodents in the epidemic chain of transmission of the visceral leishmaniose in the State of Rio Grande do Norte

Uma Lectina D-lactose específica da esponja marinha Cinachyrella apion: purificação, caracterização e interação com Leishmania chagasi

Four different sponge species were screened using Ouchterlony agarose gel and immunodiffusion tests to identify cross-reactivity with the polyclonal antibody IgG anti-deglicosilated CvL, a lectin from Cliona varians. Crude extract from the sponge Cinachyrella apion showed cross-reactivity and also a strong haemmaglutinating activity towards human erythrocytes of all ABO groups. Thus, it was submitted to acetone fractionation, IgG anti-deglicosilated CvL Sepharose affinity chromatography, and Fast Protein Liquid Chromatography (FPLC-AKTA) gel filtration on a Superose 6 10 300 column to purify a novel lectin. C. apion lectin (CaL) agglutinated all types of human erythrocytes with preference for papainized type A and O erythrocytes. The haemagglutinating activity is independent of Ca2+, Mg2+ and Mn2+ ions, and it was strongly inhibited by the disaccharide D-lactose, up to a minimum concentration of 6.25 mM. CaL molecular mass determined by FPLC-AKTA gel filtration on a Superose 12 10 300 column and SDS gel electrophoresis was approximately 124 kDa, consisting of eight subunits of 15.5 kDa, assembled by hydrophobic interactions. The lectin was relatively heat- and pH-stable. Leishmania chagasi romastigotes were agglutinated by CaL, indicating that lactose receptors could be presented in this parasite stage. These findings are indicative of the physiological defense roles of CaL and its possible use in the antibiosis of pathogenic protozoa

Estado nutricional e efeito da vitamina A na resposta imune frente à infecção por Leishmania Infantum

Nutritional status is an important determinant to the response against Leishmania infection, although few studies have characterized the molecular basis for the association found between malnutrition and the disease. Vitamin A supplementation has long been used in developing countries to prevent mortality by diarrheal and respiratory diseases, but there are no studies on the role of vitamin A in Leishmania infection, although we and others have found vitamin A deficiency in visceral Leishmaniasis (VL). Regulatory T cells are induced in vitro by vitamin A metabolites and are considered important cells implicated T CD4+ cell suppression in human VL. This work aimed to examine the correlation of nutritional status and the effect of vitamin A in the response against Leishmania infantum infection. A total of 179 children were studied: 31 had active VL, 33 VL history, 44 were DTH+ and 71 were DTH- and had negative antibody to Leishmania (DTH-/Ac-). Peripheral blood monuclear cells were isolated in a subgroup of 10 active VL and 16 DTH-/Ac- children and cultivated for 20h under 5 different conditions: 1) Medium, 2) Soluble promastigote L. infantum antigens (SLA), 3) All-trans retinoic acid (ATRA), 4) SLA + ATRA and 5) Concanavalin A. T CD4+CD25highFoxp3+, T CD4+CD25-Foxp3- and CD14+ monocytes were stained and studied by flow cytometry for IL-10, TGF-β and IL-17 production. Nutritional status was compromised in VL children, which presented lower BMI/Age and retinol concentrations when compared to healthy controls. We found a negative correlation between nutritional status (measured by BMI/Age and serum retinol) and anti-Leishmania antibodies and acute phase proteins. There was no correlation between nutritional status and parasite load. ATRA presented a dual effect in Treg cells and monocytes: In healthy children (DTH-/Ac-), it induced a regulatory response, increasing IL-10 and TGF-β production; in VL children it modulated the immune response, preventing increased IL-10 production after SLA stimulation. Furthermore, we found a positive correlation between BMI/Age and IL-17 production and negative correlation between serum retinol and IL-10 and TGF-β production in T CD4+CD25highFoxp3+ cells after SLA stimulus. Our results show a potential dual role of vitamin A in the immune system: improvement of regulatory profile during homeostasis and down modulation of IL-10 in Treg cells and monocytes during symptomatic VL. Therefore, the use of vitamin A concomitant to VL therapy might improve recovery from disease status in Leishmania infantum infection

A infecção por Leishmania infantum chagasi altera o metabolismo lipídico do hospedeiro

American visceral leishmaniasis (AVL), caused by Leishmania infantum chagasi (L.i.chagasi), stands as a public health problem in Brazil, with human and canine cases related in all states..Lipid metabolism can be modified in several status of infection. For example, experimental studies show that the cholesterol is necessary to internalization and replication of L.i.chagasi in macrophages through caveolar domains. Patients with AVL present low levels of cholesterol and a visible triglycerides increase. This work aimed to evaluate the lipid metabolism in several post-infection status by L.i.chagasi, including individuals with symptomatic infection (AVL), and asymptomatic. The levels of cholesterol, triglycerides, HDL and reactive C protein, were measured. Individuals with AVL were compared with individuals with assymptomatic infection and presented low levels of total cholesterol (128 ± 6.180 mg/dL vs. 158 ±5.733 mg/dL, p=0.0001), HDL (29 ± 1.746 mg/dL vs. 37 ± 1.647 mg/dL, p=0.0001), increased levels of triglycerides (149.5 mg/dL ± 12.72 vs. 78.00 ± 10.43 mg/dL, p=0.0095) and higher levels of reactive C protein (1.750± 0.4939 mg/dL vs. 0.40 ± 0.1707 mg/dL; p=0.0001). The expression of genes related to lipid metabolism, such as LXR-a, LXR-b, PPAR-a, PPAR-d, PPAR-g and APOE was evaluated by real time PCR. A reduction in the expression of those genes was found in the group of AVL patients corroborating the serum levels of the metabolites earlier quantified. Our findings suggest a modulation of metabolism of lipids, in the chronic phase of AVL, this could facilitate the survival of leishmania, due to the known reduction on the ability of macrophages in presenting antigens efficiently to the T cells due to the reduction in the cholesterol available, it results in a subversion of the host immunity.

Anticorpos anti-trypanosoma cruzi como preditivos de infecção por leishmania infantum

Leishmania infantum and Trypanosoma cruzi are trypanosomatids of medical importance and are, respectively, the etiologic agents of visceral leishmaniasis (VL) and Chagas disease (CD) in Brazil. People infected with L. infantum or T. cruzi may develop asymptomatically, enabling the transmission of pathogens through blood transfusion and / or organs. The assessment of the infection by T. cruzi is included among the tests performed for screening blood donors in Brazil, however, there is no availability of tests for Leishmania. Serological tests for T. cruzi are very sensitive, but not specific, and may have cross-reactions with other microorganisms. Thus, the aim of this study was to determine the prevalence of Leishmania infection in blood donors and assess whether the serological test for T. cruzi detect L. infantum. Among the 300 blood samples from donors, discarded in 2011, 61 were T. cruzi positive, 203 were from donors with other infections and 36 were from handbags with low blood volume, but without infection. We also assessed 144 samples from donors without infections and able to donate blood, totaling 444 subjects. DNA was extracted from blood samples of all to perform quantitative PCR (qPCR) to detect Leishmania DNA. The buffy coat obtained from all samples was grown in Schneider medium supplemented and NNN. All samples were evaluated for the presence of anti-Leishmania antibody. The serological results indicate a percentage of 22% of Leishmania infection in blood samples obtained from discarded bags. A total of 60% of samples positive in ELISA for T. cruzi were negative by IFI, used as confirmatory test, ie 60% false positive for Chagas. Among these samples false positive for Chagas, 72% were positive by ELISA for Leishmania characterizing the occurrence of cross reaction between serologic assays. Of the 300 cultures performed, 18 grew parasites that were typed by qPCR and specific isoenzymes, found the species Leishmania infantum crops. Among the 18 cultures, 4 were purged from scholarships for low volume and all negative serology blood bank, thus demonstrating that there is a real risk of Leishmania transmission via transfusion. It is concluded that in an area endemic for leishmaniasis in Brazil, serological diagnosis performed to detect infection by T. cruzi among blood donors can identify infection by L. infantum and although cause false positive for Chagas, this cross-reactivity reduces the risk of Leishmania infection via blood transfusion, since tests are not applied specific detection of the parasite. In this way, there remains the need to discuss the implementation of a specific serological screening test for Leishmania in endemic countries such as Brazil