A comparative study of human glomerular basement membrane thickness using direct measurement and orthogonal intercept methods.

INTRODUCTION: Here we report estimates of glomerular basement membrane (GBM) thickness in the Brazilian population performed using direct (DM) and orthogonal interception methods (OIM), and comment on potential sources of variation among estimates made by different laboratories. METHODOLOGY: A total of 38 patients, ranging from 3 to 78 years of age, 26 (68%) males and 12 (32%) females, were submitted to kidney biopsy procedures for renal disease diagnosis. Glomeruli were diagnosed with minor histological changes by conventional, immunofluorescence and electron microscopy. GBM thickness was estimated using both DM and OIM methods. RESULTS: Estimates of GBM thickness obtained using DM were higher than those obtained by OIM. However, the application of a correction for non-perpendicular membrane sectioning to DM estimates yielded similar results to those obtained under OIM. The estimated GMB thickness using DM after correction was 289 + 44 nm, versus 287 + 48 nm by OIM. No statistically significant differences were detected in GMB thickness, nor with respect to patient age or sex. CONCLUSIONS: GBM thickness in the studied Brazilian population measured approximately 290 nm. The application of criteria for estimating the shortest distance between the endothelial and podocyte cell membranes with correction for non-perpendicular membrane sectioning can increase the accuracy of GBM thickness estimates using DM and OIM.

Splenic Transcriptional Responses in Severe Visceral Leishmaniasis: Impaired Leukocyte Chemotaxis and Cell Cycle Arrest.

Structural changes in the spleen have been reported in several infectious diseases. In visceral leishmaniasis (VL), a severe parasitic disease caused by Leishmania spp., the loss of white pulp accompanies a severe clinical presentation. Hamster model reproduces aspects of human VL progression. In the early stages, a transcriptomic signature of leukocyte recruitment was associated with white pulp hyperplasia. Subsequently, impaired leukocyte chemotaxis with loss of T lymphocytes in the periarteriolar lymphoid sheath occurred. This differential gene expression was subsequently corroborated by transcriptomic profiling of spleens in severe human VL. At the latest stage, spleen disorganization was associated with increasing clinical signs of VL. White pulp disruption was accompanied by decreased DLK1 expression. The expression of CXCL13, CCR5, CCL19, CCR6, CCR7 and LTA decreased, likely regulated by CDKN2A overexpression. Our findings enlighten a pathway implying cell cycle arrest and decreased gene expression involved in spleen organization.

Urinary cytology: a potential tool for differential diagnosis of acute kidney injury in patients with nephrotic syndrome.

OBJECTIVE: Acute tubular necrosis (ATN) is a frequent cause of acute kidney injury (AKI). In patients with nephrotic syndrome (NS), AKI demands the differential diagnosis between ATN and rapidly progressive glomerulonephritis. In some cases, conclusive diagnosis is possible only by kidney biopsy. We aimed to study the potential use of urine cytology in the differential diagnosis between ATN and proliferative glomerular lesion in patients with NS. RESULTS: Cell size analysis showed a higher proportion of small cells and a lower proportion of large cells in the urine of patients with AKI. Cells phenotypes were easily defined using cytological preparations. Leukocytes were found to be a primary classifier of NS groups, with higher number in patients with AKI and patients with proliferative glomerular lesions. Although renal biopsy is still required for confirmative diagnosis, our data suggests that urinary cytology can be readily performed and support the differential diagnosis between proliferative glomerular lesion and ATN in patients with NS and AKI.

Phenotypical Characterization of Spleen Remodeling in Murine Experimental Visceral Leishmaniasis.

Background: Visceral leishmaniasis (VL) is caused by Leishmania infantum or L. donovani infection. One of the main problems related to this disease is the emergence of severe clinical forms with a lethality of 5-20%, even while under specific treatment. In humans and other species susceptible to fatal VL, such as dogs and hamsters, the disruption of splenic white pulp (WP) is accompanied by disease progression. Control of VL progression is seen in BALB/c mice, as evidenced by a mild clinical presentation and controlled parasite replication in the liver and spleen. In this study, we investigated the features involved in the morphological remodeling of splenic compartments associated with the control of VL progression to death. Methods: We evaluated cohorts of BALB/c mice after 30, 60, and 90 days of infection by L. infantum. Spleen morphology, cell population subsets and cytokine production were studied in the spleen using flow- and histo-cytometry. Results: Intraperitoneal infection with 108 promastigotes of L. infantum led to progressive increases in spleen size at 60 and 90 days after infection. Splenomegaly was the only clinical sign of disease observed. At 30 days after infection, hyperplasia in the WP and decreased numbers of plasmacytoid dendritic cells were observed. The WP hyperplasia subsided at 60 days post-infection. However, the splenomegaly remained in association with increased numbers of macrophages, B and T lymphocytes and plasma cells. An increased number of lymphoid tissue inducer (LTi) cells was observed; these were distributed around the periarteriolar lymphoid sheath in control mice and scattered throughout the red pulp in the Leishmania-infected mice. After 90 days of infection, increased IL-6 and IFN-γ production was seen in the spleen, as well as higher frequencies of follicular and plasmacytoid dendritic cells. Conclusion: The data presented herein emphasizes the potential role of spleen remodeling in the control of severe forms of VL and highlights features potentially involved in this process.

Classification of glomerular hypercellularity using convolutional features and support vector machine.

Glomeruli are histological structures of the kidney cortex formed by interwoven blood capillaries, and are responsible for blood filtration. Glomerular lesions impair kidney filtration capability, leading to protein loss and metabolic waste retention. An example of lesion is the glomerular hypercellularity, which is characterized by an increase in the number of cell nuclei in different areas of the glomeruli. Glomerular hypercellularity is a frequent lesion present in different kidney diseases. Automatic detection of glomerular hypercellularity would accelerate the screening of scanned histological slides for the lesion, enhancing clinical diagnosis. Having this in mind, we propose a new approach for classification of hypercellularity in human kidney images. Our proposed method introduces a novel architecture of a convolutional neural network (CNN) along with a support vector machine, achieving near perfect average results on FIOCRUZ data set in a binary classification (lesion or normal). Additionally, classification of hypercellularity sub-lesions was also evaluated, considering mesangial, endocapilar and both lesions, reaching an average accuracy of 82%. Either in binary task or in the multi-classification one, our proposed method outperformed Xception, ResNet50 and InceptionV3 networks, as well as a traditional handcrafted-based method. To the best of our knowledge, this is the first study on deep learning over a data set of glomerular hypercellularity images of human kidney.

Assessment of histological liver alterations in dogs naturally infected with Leishmania infantum.

BACKGROUND: The liver plays a central role in the development of canine visceral leishmaniasis. Studies of natural infection in animals and humans indicate a direct relationship between resolution of infection and the formation and maturation of granulomas in the liver. However, in contrast to other reports in the literature, the present study found no differences in the characteristics of hepatic granulomas that could be related to resistance or susceptibility to Leishmania. Here, we describe the hepatic alterations observed in dogs with differing clinical manifestations of visceral leishmaniasis in an endemic area in the state of Bahia, Brazil. METHODS: We examined 148 animals in an endemic area. The animals were clinically examined, and the infection was determined by ELISA, spleen aspirate culture and quantitative PCR. The animals were grouped into asymptomatic or symptomatic based on the number of signs of LV. The histological liver evaluation was performed in a blinded way. RESULTS: Our results indicated no association between the characteristics of granulomas and clinical presentation. We found an association between the intensity of this inflammatory response and parasite load in the animals' spleens. It is important to note that while hepatic alterations, such as portal and perivascular inflammation and the presence of larger amounts of granulomas, were linked with higher parasite loads, we found the inverse to be true with respect to intrasinusoidal lymphocytosis, the formation of intrasinusoidal inflammatory cell aggregates and Kupffer cell hypertrophy. CONCLUSIONS: Our findings suggest that the presence of mononuclear inflammatory cells inside the sinusoids is more important than that of organized granulomas in terms of the containment of parasitism by the host. We suggest that the presence of granulomas indicates the failure of a first line of defense mechanism in the control of parasite infection, which could be related to the presence of inflammatory cells and Kupffer cell hypertrophy inside the sinusoids. We further demonstrated that dogs with active Leishmania spp. infection present a higher frequency of inflammatory changes in the liver. In addition to being correlated with the severity of clinical manifestation, these hepatic alterations were also associated with changes in hematological and biochemical parameters.

Parasitic load and histological aspects in different regions of the spleen of dogs with visceral leishmaniasis.

Leishmania infantum causes from subclinical infection to severe disease in humans and dogs. The spleen is one of the organs most affected by the infection. Although evidence exists that the parasitic load distribution and histological alterations may not be homogeneous in the affected organs of naturally infected individuals, it has not been formally demonstrated using the current techniques used for studying the disease. In six dogs naturally infected with Leishmania, parasitic load and histological changes were compared in samples collected from the lower, middle and upper third of the spleen. Parasitic load in the spleen of the group of dogs was variable, revealing a difference of 61 times between animals with the lowest and the highest parasitism. The set of parasitic load values of each dog showed a cluster trend, when compared to the other animals. Nevertheless, the parasitic load values of each dog showed a variation ranging from 3.2 to 34.7 times between lowest and highest value. Histological changes showed recognizable variation in frequency (granulomas) or intensity (perisplenitis) in the spleen of 2 out of the 6 dogs. The agreement of histological findings between samples collected from the different thirds of the spleen was good (kappa coeficient, 0.61-0.80) very good (0.81-0.99) or perfect (1.00), for most of the parameters analyzed. Variability of parasitic load and, to a lesser extent, histological changes in spleen of dogs with visceral leishmaniasis is observed. Such variability may be taken in account in the design of studies on pathogenesis, vaccine and therapeutic drug development.

Selecting the right gate to identify relevant cells for your assay: a study of thioglycollate-elicited peritoneal exudate cells in mice.

OBJECTIVE: In this study, we investigate the diversity and modulation of leukocyte populations represented in the gates defined by size and granularity at different time points of thioglycollate-induced peritonitis in mouse. RESULTS: The inflammatory cells were distributed into four regions (R1-R4) of a data plot graph defined by cell size and granularity. R1 and R2 contained agranular cells that were small in size and predominately included T (CD3+) lymphocytes along with B (B220+) lymphocytes. Macrophages (F4/80+) were the predominant cells found in the R3 region. However, these cells were present in all regions, albeit at a lower frequency in R1 and R2. Granulocytes (Gr1+) were mainly distributed in R3 and R4. The wide distribution of F4/80+ and Gr1+ cells may reflect the recruitment and activation state of the different macrophage and granulocyte populations. Based on these observations, size and granularity may contribute to an initial step in the analysis and sorting of thioglycollate-elicited peritoneal exudate cells. However, the developmental stage and cell activation state may interfere with cell segregation using size and granularity as parameters.

Sera from Visceral Leishmaniasis Patients Display Oxidative Activity and Affect the TNF-α Production by Macrophages In Vitro.

Mammalian protection against leishmanial infection depends on the development of an effective immune response. Zoonotic visceral leishmaniasis (ZVL) patients are usually unable to mount an effective immune response against the parasite and indeed appear to be severely immunosuppressed. This suppression has strong nonspecific and specific components mediated by serum factors and leishmanicidal activity of infected macrophages, respectively. The lipid profile has been shown to be altered in ZVL patients' sera. This work aimed at (i) determining the HDL, Apo A1, LDL, and VLDL concentrations in ZVL patients' sera; (ii) investigating the oxidative effect of ZVL patients' sera on the ß-carotene matrix; (iii) measuring IL-10, IL-6, IL-12p40, and tumour necrosis factor-α (TNF-α) concentrations in the macrophage cultures, to which 10% of ZVL patients' serum had been added. Levels of HDL, LDL fraction, and apolipoprotein A1 in ZVL patients' sera were lower than those of healthy individuals' sera, except for the mean level of VLDL. The matrix of ß-carotene and linoleic acid system was oxidized in the presence of ZLV patients' sera. The presence of ZVL patients' sera did not modify the cytokine production of IL-6, IL-12p40, and IL-10 by human macrophages in vitro but TNF-α production was altered, probably due to lack of macrophage stimulation by lipoprotein.

Evaluation of a new set of recombinant antigens for the serological diagnosis of human and canine visceral leishmaniasis.

Current strategies for the control of zoonotic visceral leishmaniasis (VL) rely on its efficient diagnosis in both human and canine hosts. The most promising and cost effective approach is based on serologic assays with recombinant proteins. However, no single antigen has been found so far which can be effectively used to detect the disease in both dogs and humans. In previous works, we identified Leishmania infantum antigens with potential for the serodiagnosis of VL. Here, we aimed to expand the panel of the available antigens for VL diagnosis through another screening of a genomic expression library. Seven different protein-coding gene fragments were identified, five of which encoding proteins which have not been previously studied in Leishmania and rich in repetitive motifs. Poly-histidine tagged polypeptides were generated from six genes and evaluated for their potential for diagnosis of VL by ELISA (Enzyme Linked ImmunoSorbent Assay) with sera from infected humans and dogs. None of those was valid for the detection of human VL (26-52% sensitivity) although their performance was increased in the canine sera (48-91% sensitivity), with one polypeptide useful for the diagnosis of canine leishmaniasis. Next, we assayed a mixture of three antigens, found to be best for human or canine VL, among 13 identified through different screenings. This "Mix" resulted in similar levels of sensitivity for both human (84%) and canine (88%) sera. With improvements, this validates the use of multiple proteins, including antigens identified here, as components of a single system for the diagnosis of both forms of leishmaniasis.

A minimally invasive approach to spleen histopathology in dogs: A new method for follow-up studies of spleen changes in the course of Leishmania infantum infection.

Severe forms of zoonotic visceral leishmaniosis (ZVL) are associated with disruption of the spleen structure. However, the study of spleen histology requires splenectomy or necropsy. In this work, we present a minimally invasive cell-block technique for studying spleen tissue histology in dogs with ZVL. We examined 13 dogs with and seven dogs without Leishmania infantum infection. The dogs with Leishmania infection had a lower frequency of lymphoid follicles (2/13, Fisher's test, P<0.02) and a higher density of plasma cells (score 3, Fisher's test, P<0.02) than uninfected dogs (5/7 exhibiting lymphoid follicles and a plasma cell score of 1). The dogs with Leishmania infection also presented with granulomas (8/13) and infected macrophages (5/13). These differences in the histological presentations of spleen tissue from infected and uninfected dogs corresponded to changes observed in conventional histology. Hence, the cell-block technique described here may be used in the follow-up care and study of dogs with ZVL and other diseases in both clinical practice and research.

Disruption of Splenic Lymphoid Tissue and Plasmacytosis in Canine Visceral Leishmaniasis: Changes in Homing and Survival of Plasma Cells.

Visceral leishmaniasis (VL) is a disease caused by Leishmania infantum, which is transmitted by phlebotomine sandflies. Dogs are the main urban reservoir of this parasite and the disease presents similar characteristics in both humans and dogs. In this paper, we investigated the potential pathways involved in plasma cell replacement of normal cell populations in the spleen, with respect to disease severity in dogs from an endemic area for visceral leishmaniasis. To this end, canine spleen samples were grouped into three categories: TYPE1SC- (non-infected dogs or without active infection with organized white pulp), TYPE1SC+ (infected dogs with organized white pulp) or TYPE3SC+ (infected animals with disorganized white pulp). We analyzed the distribution of different plasma cell isotypes (IgA, IgG and IgM) in the spleen. The expression of cytokines and chemokines involved in plasma cell homing and survival were assessed by real time RT-PCR. Polyclonal B cell activation and hypergammaglobulinemia were also evaluated. The proportion of animals with moderate or intense plasmacytosis was higher in the TYPE3SC+ group than in the other groups (Fisher test, P<0.05). This was mainly due to a higher density of IgG+ plasma cells in the red pulp of this group. The albumin/globulin ratio was lower in the TYPE3SC+ animals than in the TYPE1SC- or TYPE1SC+ animals, which evidences VL-associated dysproteinemia. Interestingly, TYPE3SC+ animals showed increased expression of the BAFF and APRIL cytokines, as well as chemokine CXCL12. Aberrant expression of BAFF, APRIL and CXCL12, together with amplified extrafollicular B cell activation, lead to plasma cell homing and the extended survival of these cells in the splenic red pulp compartment. These changes in the distribution of immunocompetent cells in the spleen may contribute to the progression of VL, and impair the spleen's ability to protect against blood borne pathogens.

Arginase I, polyamine, and prostaglandin E2 pathways suppress the inflammatory response and contribute to diffuse cutaneous leishmaniasis.

Diffuse cutaneous leishmaniasis (DCL) is a rare clinical manifestation of tegumentary leishmaniasis. The molecular mechanisms underlying DCL pathogenesis remain unclear, and there is no efficient treatment available. This study investigated the systemic and in situ expression of the inflammatory response that might contribute to suppression in DCL. The plasma levels of arginase I, ornithine decarboxylase (ODC), transforming growth factor ß (TGF-ß), and prostaglandin E2 (PGE2) were higher in patients with DCL, compared with patients with localized cutaneous leishmaniasis (LCL) or with controls from an area of endemicity. In situ transcriptomic analyses reinforced the association between arginase I expression and enzymes involved in prostaglandin and polyamine synthesis. Immunohistochemistry confirmed that arginase I, ODC, and cyclooxygenase2 expression was higher in lesion biopsy specimens from patients with DCL than in those from patients with LCL. Inhibition of arginase I or ODC abrogates L. amazonensis replication in infected human macrophages. Our data implicate arginase I, ODC, PGE2, and TGF-ß in the failure to mount an efficient immune response and suggest perspectives in the development of new strategies for therapeutic intervention for patients with DCL.

A case of conventional treatment failure in visceral leishmaniasis: leukocyte distribution and cytokine expression in splenic compartments.

BACKGROUND: In this paper we study the distribution of leukocyte populations and of cytokine-producing cells in the spleen of a patient with visceral leishmaniasis resistant to clinical treatment. It is the first attempt to compare the distribution of leukocyte populations and cytokine-producing cells in the splenic compartments of a patient with visceral leishmaniasis with those observed in patients without the disease. CASE PRESENTATION: A 25-year-old male, farmer, was hospitalized on several occasions with diagnosis of visceral leishmaniasis and received all recommended treatments for the disease with only transient improvement followed by relapse. He was eventually subjected to splenectomy in order to control the effects of hypersplenism and to potentially overcome infection. After surgery and combined chemotherapy, the disease evolved to cure. In comparison with the spleens of the other two patients without visceral leishmaniasis, an increase was observed in the CD4/CD8 ratio and in the number of IL-10- and FoxP3-producing cells, while the number of IL-17-producing cells was lower in the spleen of the patient with visceral leishmaniasis. CONCLUSION: This report confirms previous data on changes in the CD4/CD8 ratio in the spleens of patients with visceral leishmaniasis. Additionally the data presented herein suggests that splenic FoxP3- and IL-17-producing cells are involved in the chronicity of visceral leishmaniasis.

Leishmania amazonensis infection impairs dendritic cell migration from the inflammatory site to the draining lymph node.

BACKGROUND: In vitro studies show that Leishmania infection decreases the adhesion of inflammatory phagocytes to connective tissue by a mechanism dependent on the modulation of integrin function. However, we know little about the influence of this reduction in leukocyte adhesion on parasite dissemination from the infection site. METHODS: In this work, we used a model of chronic peritonitis induced by thioglycollate to study the effect of L. amazonensis infection on the ability of inflammatory phagocyte populations to migrate from an inflammatory site to the draining lymph node. Uninfected or Leishmania-infected thioglycollate-elicited peritoneal exudate cells were transferred from C57BL/6 to BALB/c mice or from Ly5.1+ to Ly5.1- mice. The transferred cells were injected into the peritoneal cavity and tracked to the draining lymph node. RESULTS: Migrating cells corresponded to approximately 1% of the injected leukocytes. The proportion of migrating CD11b+CD11c+ (myeloid dendritic cell) was lower after incubation with Leishmania (1.3 to 2.6 times lower in the experiments using C57BL/6 to BALB/c animals and 2.7 to 3.4 times lower in the experiments using Ly5.1+ to Ly5.1- animals) than after leukocyte incubation with medium alone (P < 0.01). There was no consistent decrease in the migration of CD11b+F4/80+ (macrophage) or SSChi GR-1+ (neutrophil) populations. CONCLUSIONS: Coincubation with Leishmania changes the migratory pattern of dendritic cells in vivo. Such changes in dendritic cell migration may be associated with immunological events that maintain inflammation at the sites of infection.

Human mucosal leishmaniasis: neutrophils infiltrate areas of tissue damage that express high levels of Th17-related cytokines.

Mucosal leishmaniasis (ML) is characterised by severe tissue destruction. Herein, we evaluated the involvement of the IL-17-type response in the inflammatory infiltrate of biopsy specimens from 17 ML patients. IL-17 and IL-17-inducing cytokines (IL-1ß, IL-23, IL-6 and TGF-ß) were detected by immunohistochemistry in ML patients. IL-17(+) cells exhibited CD4(+), CD8(+) or CD14(+) phenotypes, and numerous IL-17(+) cells co-expressed the CC chemokine receptor 6 (CCR6). Neutrophils, a hallmark of Th17-mediated inflammation, were regularly detected in necrotic and perinecrotic areas and stained positive for neutrophil elastase, myeloperoxidase and MMP-9. Taken together, these observations demonstrate the existence of Th17 cells in ML lesions associated with neutrophils in areas of tissue injury and suggest that IL-17 is involved in ML pathogenesis.

Activity of physalins purified from Physalis angulata in in vitro and in vivo models of cutaneous leishmaniasis.

OBJECTIVES: We have previously demonstrated the immunomodulatory effects of physalins, secosteroids purified from Physalis angulata. Here we investigate the antileishmanial activity of physalins in vitro and in vivo in a model of cutaneous leishmaniasis. METHODS: The antileishmanial activity of physalins B, D and F was tested in Leishmania-infected macrophage cultures. For the in vivo studies, BALB/c mice were infected with Leishmania amazonensis subcutaneously in the ear pinna and treated with physalin F by topical administration. RESULTS: Physalins B and F were able to reduce the percentage of Leishmania-infected macrophages and the intracellular parasite number in vitro at concentrations non-cytotoxic to macrophages. More importantly, topical treatment with physalin F significantly reduced the lesion size, the parasite load and histopathological alterations in BALB/c mice infected with L. amazonensis. CONCLUSIONS: Our results demonstrate the potent antileishmanial activity of physalins, especially physalin F, and suggest these molecules as the basis for the development of new therapeutic options for cutaneous leishmaniasis.

Effect of nicotine treatment and withdrawal on random-pattern skin flaps in rats.

BACKGROUND: Tobacco use is associated with a high incidence of skin necrosis after surgery. The ideal timing for the cessation of tobacco use before plastic surgery has not, however, been precisely determined. The aim of this work was to define the ideal duration of nicotine withdrawal prior to random-pattern skin flap surgery in rats. METHODS: Groups of 11 animals were subcutaneously injected with saline or nicotine (2mg/kg) twice a day and subjected to random-pattern skin flap surgery according to the following protocol: Group I: continuously injected with saline 4 weeks before and 1 week after the surgery; Group II: injected with nicotine for 4 weeks until the day of the surgery; Group III: injected with nicotine for 4 weeks until one day before the surgery; Group IV: injected with nicotine for 4 weeks until 5 days before the surgery; Group V: injected with nicotine for 4 weeks until 10 days before the surgery; Group VI: continuously injected with nicotine for 4 weeks before and 1 week after the surgery. McFARLANE skin flaps were performed on the dorsal skin, and the rats were sacrificed 1 week after the surgery. RESULTS: The necrotic area was smaller in group I (8.85cm2) than in group II (12.15cm2), III (12.88cm2) and VI (14.84cm2) (ANOVA p<0.0001). There was no difference between groups I, IV (10.13cm2) and V (9.27cm2). CONCLUSIONS: In conclusion, 5 days before surgery was considered the ideal time for nicotine withdrawal in this experimental model.

Association between skin parasitism and a granulomatous inflammatory pattern in canine visceral leishmaniosis.

In this work we examined 76 stray dogs from an area of endemic visceral leishmaniosis, in order to determine whether the presence of skin inflammation or a specific inflammatory pattern could be taken as indicative of infection with Leishmania chagasi, and whether the parasite burden in the skin could be associated with the intensity or the nature of the inflammatory process. Inflammatory infiltrates were observed in the skin of 51 out of 55 animals with diagnosis of leishmaniosis, and in 17 out of 21 animals without signs of infection. Amastigotes were identified in the skin of 29 out of the 55 animals with diagnosis of leishmaniosis. Granuloma and a monomorphic macrophage inflammatory infiltrate, and not a mixed focal or mixed diffuse inflammation, were significantly associated with skin parasitism, both in terms of frequency ( P=0.015 in the Chi-square test) and intensity ( P=0.005 in the Kruskal-Wallis test). A low parasite burden was associated with a multifocal inflammatory pattern.

Skin reactions to thimerosal and Leishmania in dogs from a leishmaniasis endemic area: it is better to keep them apart

Positive Montenegro's skin test is a delayed type hypersensitivity reaction widely used as indicative of previous infection with Leishmania in both humans and dogs. Montenegro's antigen consists of a crude Leishmania antigen solution, usually containing thimerosal as preserving agent. In this work it is shown that a large proportion of dogs (11 out of 56) examined in an endemic area of leishmaniasis presented induration at the site of injection of a diluent containing thimerosal alone. This clearly demonstrates that thimerosal leads to a high number of false positive skin reactions in dogs and that its use in Montenegro's skin test antigenic preparations should be avoided