American trypanosomiasis (Chagas' disease)

Chagas disease in the immunocompromised host

PURPOSE OF REVIEW

To highlight recent advances in our understanding of Trypanosoma cruzi infection in immunocompromised individuals, a condition that is increasingly recognized as populations shift and use of immunosuppressive medications becomes more commonplace.

RECENT FINDINGS

Chagas disease screening programs should include people at risk for both Chagas disease and immunocompromise, e.g. people who have resided for ≥6 months in endemic Latin America who have an immunocompromising condition such as HIV or who are planned to start an immunosuppressive medication regimen. The goal of identifying such individuals is to allow management strategies that will reduce their risk of T. cruzi reactivation disease. For people with HIV- T. cruzi coinfection, strict adherence to antiretroviral therapy is important and antitrypanosomal treatment is urgent in the setting of symptomatic reactivation. People at risk for T. cruzi reactivation due to immunosuppression caused by advanced hematologic conditions or postsolid organ transplantation should be monitored via T. cruzi qPCR and treated with preemptive antitrypanosomal therapy if rising parasite load on serial specimens indicates reactivation. Reduction of the immunosuppressive regimen, if possible, is important.

SUMMARY

Chronic Chagas disease can lead to severe disease in immunocompromised individuals, particularly those with advanced HIV (CD4 + < 200 cells/mm 3 ) or peri-transplantation.

Synthesis of new non-natural L-glycosidic flavonoid derivatives and their evaluation as inhibitors of Trypanosoma cruzi ecto-nucleoside triphosphate diphosphohydrolase 1 (TcNTPDase1)

Trypanosoma cruzi is the pathogen of Chagas disease, a neglected tropical disease that affects more than 6 million people worldwide. There are no vaccines to prevent infection, and the therapeutic arsenal is very minimal and toxic. The unique E-NTPDase of T. cruzi (TcNTPDase1) plays essential roles in adhesion and infection and is a virulence factor. Quercetin is a flavonoid with antimicrobial, antiviral, and antitumor activities. Its potential as a partial inhibitor of NTPDases has also been demonstrated. In this work, we synthesized the non-natural L-glycoside derivatives of quercetin and evaluated them as inhibitors of recombinant TcNTPDase1 (rTcNTPDase1). These compounds, and quercetin and miquelianin, a natural quercetin derivative, were also tested. Compound 16 showed the most significant inhibitory effect (94%). Quercetin, miquelianin, and compound 14 showed inhibition close to 50%. We thoroughly investigated the inhibitory effect of 16. Our data suggested a competitive inhibition with a Ki of 8.39 μM (± 0.90). To better understand the interaction of compound 16 and rTcNTPDase1, we performed molecular dynamics simulations of the enzyme and docking analyses with the compounds. Our predictions show that compound 16 binds to the enzyme's catalytic site and interacts with important residues for NTPDase activity. As an inhibitor of a critical T. cruzi enzyme, (16) could be helpful as a starting point in the developing of a future treatment for Chagas disease. Furthermore, the discovery of (16) as an inhibitor of TcNTPDase1 may open new avenues in the study and development of new inhibitors of E-NTPDases.

Chagas disease in immunocompromised patients

SUMMARYAs Chagas disease remains prevalent in the Americas, it is important that healthcare professionals and researchers are aware of the screening, diagnosis, monitoring, and treatment recommendations for the populations of patients they care for and study. Management of Trypanosoma cruzi infection in immunocompromised hosts is challenging, particularly because, regardless of antitrypanosomal treatment status, immunocompromised patients with Chagas disease are at risk for T. cruzi reactivation, which can be lethal. Evidence-based practices to prevent and manage T. cruzi reactivation vary depending on the type of immunocompromise. Here, we review available data describing Chagas disease epidemiology, testing, and management practices for various populations of immunocompromised individuals, including people with HIV and patients undergoing solid organ and hematopoietic stem cell transplantation.

Radiological findings in megaesophagus secondary to Chagas disease: chest X-ray and esophagogram

Objective

To identify and classify the radiographic patterns of megaesophagus in Chagas disease, as seen on esophagograms and chest X-rays.

Materials and Methods

This was a prospective study of 35 patients diagnosed with esophageal disease via manometry. The changes found on esophagograms were stratified according to Rezende's classification, divided into four categories (grades I through IV) determined by the degree of dilatation and impairement of esophageal motility. We subsequently correlated that ranking with the chest X-ray findings: gastric air bubble; air-fluid level; and mediastinal widening.

Results

Among the 35 patients, the esophageal disease was classified as grade I in 9 (25.7%), grade II in 3 (8.6%), grade III in 19 (54.3%), and grade IV in 4 (11.4%). None of the patients with grade I esophageal disease showed changes on chest X-rays. In two of the three patients with grade II disease, there was no gastric air-bubble, although there were no other findings in any of the grade II patients. Of the 19 patients with grade III disease, 15 had abnormal findings on X-rays. All four patients with grade IV disease showed abnormalities.

Conclusion

The use of Rezende's classification is feasible, encompassing findings ranging from the subtle changes that characterize the initial phases of esophageal disease to the complete akinesia seen in dolicomegaesophagus. Chest X-ray findings are more common in patients with advanced stages of the disease and indicate the degree of esophageal involvement in Chagas disease.

Effects of aspirin-triggered resolvin D1 on peripheral blood mononuclear cells from patients with Chagas' heart disease

Chagas disease is caused by Trypanosoma cruzi (T. cruzi). In some patients with Chagas disease, symptoms progress to chronic chagasic cardiomyopathy. Endogenously, inflammation is resolved in the presence of lipid mediators such as aspirin-triggered RvD1 (AT-RvD1) which has anti-inflammatory and pro-resolution effects. Here, we demonstrated, for the first time, the effects of AT-RvD1 on T. cruzi antigen-stimulated peripheral blood mononuclear cells (PBMCs) from patients with Chagas heart disease. The levels of IFN-γ, TNF-α, IL-10, and IL-13 increased in PBMCs from cardiac-form Chagas patients in stage B1 (patients with fewer heart abnormalities) stimulated with T. cruzi antigen compared to those in non-stimulated PBMCs. AT-RvD1 reduced the IFN-γ concentrations in PBMCs from patients with Chagas disease stimulated with T. cruzi antigen compared to stimulated with T. cruzi antigen cells. AT-RvD1 treatment resulted in no observable changes in TNF-α, IL-10, and IL-13 levels. AT-RvD1 significantly decreased the percentage of necrotic cells and caused a significant reduction in the proliferation rate of T. cruzi antigen-stimulated PBMCs from patients with Chagas disease. These findings demonstrate that AT-RvD1 modulates the immune response in Chagas disease patients and might have potential to be used as an alternative approach for slowing the development of further heart damage.

Pharmacophore modeling for anti-Chagas drug design using the fragment molecular orbital method

BACKGROUND

Chagas disease, caused by the parasite Trypanosoma cruzi, is a neglected tropical disease that causes severe human health problems. To develop a new chemotherapeutic agent for the treatment of Chagas disease, we predicted a pharmacophore model for T. cruzi dihydroorotate dehydrogenase (TcDHODH) by fragment molecular orbital (FMO) calculation for orotate, oxonate, and 43 orotate derivatives.

METHODOLOGY/PRINCIPAL FINDINGS

Intermolecular interactions in the complexes of TcDHODH with orotate, oxonate, and 43 orotate derivatives were analyzed by FMO calculation at the MP2/6-31G level. The results indicated that the orotate moiety, which is the base fragment of these compounds, interacts with the Lys43, Asn67, and Asn194 residues of TcDHODH and the cofactor flavin mononucleotide (FMN), whereas functional groups introduced at the orotate 5-position strongly interact with the Lys214 residue.

CONCLUSIONS/SIGNIFICANCE

FMO-based interaction energy analyses revealed a pharmacophore model for TcDHODH inhibitor. Hydrogen bond acceptor pharmacophores correspond to Lys43 and Lys214, hydrogen bond donor and acceptor pharmacophores correspond to Asn67 and Asn194, and the aromatic ring pharmacophore corresponds to FMN, which shows important characteristics of compounds that inhibit TcDHODH. In addition, the Lys214 residue is not conserved between TcDHODH and human DHODH. Our analysis suggests that these orotate derivatives should preferentially bind to TcDHODH, increasing their selectivity. Our results obtained by pharmacophore modeling provides insight into the structural requirements for the design of TcDHODH inhibitors and their development as new anti-Chagas drugs.

In vitro and in vivo studies of the trypanocidal properties of WRR-483 against Trypanosoma cruzi

Background

Cruzain, the major cysteine protease of Trypanosoma cruzi, is an essential enzyme for the parasite life cycle and has been validated as a viable target to treat Chagas' disease. As a proof-of-concept, K11777, a potent inhibitor of cruzain, was found to effectively eliminate T. cruzi infection and is currently a clinical candidate for treatment of Chagas' disease.

Methodology/Principal Findings

WRR-483, an analog of K11777, was synthesized and evaluated as an inhibitor of cruzain and against T. cruzi proliferation in cell culture. This compound demonstrates good potency against cruzain with sensitivity to pH conditions and high efficacy in the cell culture assay. Furthermore, WRR-483 also eradicates parasite infection in a mouse model of acute Chagas' disease. To determine the atomic-level details of the inhibitor interacting with cruzain, a 1.5 Å crystal structure of the protease in complex with WRR-483 was solved. The structure illustrates that WRR-483 binds covalently to the active site cysteine of the protease in a similar manner as other vinyl sulfone-based inhibitors. Details of the critical interactions within the specificity binding pocket are also reported.

Conclusions

We demonstrate that WRR-483 is an effective cysteine protease inhibitor with trypanocidal activity in cell culture and animal model with comparable efficacy to K11777. Crystallographic evidence confirms that the mode of action is by targeting the active site of cruzain. Taken together, these results suggest that WRR-483 has potential to be developed as a treatment for Chagas' disease.

Current drugs for Chagas' disease, caused by Trypanosoma cruzi infection, are limited in efficacy and are severely toxic. Hence the development of novel chemotherapeutic agents targeting T. cruzi infections is an important undertaking. In recent years, there has been considerable interest in cruzain, the major protease in T. cruzi, as a target to treat Chagas' disease. Herein, we present the synthesis of WRR-483, a small molecule designed as an irreversible cysteine protease inhibitor, and an assessment of its biological activity against cruzain and T. cruzi infection. This compound displays pH-dependent affinity for cruzain and highly effective trypanocidal activity in both cell cuture and a mouse model of acute Chagas' disease. The crystal structure of WRR-483 bound to cruzain elucidates the details of inhibitor binding to the enzyme. Based on these results, this inhibitor is a promising compound for the development of therapeutics for Chagas' disease.

The role of selenium in intestinal motility and morphology in a murine model of Typanosoma cruzi infection

Infection with Trypanosoma cruzi causes megasyndromes of the gastrointestinal (GI) tract in humans and animals. In the present study, we employed magnetic resonance imaging to non-invasively monitor the effect of selenium supplementation on alterations in the GI tract of T. cruzi-infected mice. CD1 mice infected with T. cruzi (Brazil strain) exhibited dilatation of the intestines similar to that we recently reported in infected C57Bl/6 mice. The average intestine lumen diameter increased by 65% and the increase was reduced to 29% in mice supplemented with 2 ppm selenium in the drinking water. When supplemented with 3 ppm selenium in chow the lumen diameter was also significantly reduced although the difference between the infected and infected supplemented mice was smaller. Intestinal motility in infected mice fed with selenium-enriched chow was increased compared with infected mice fed with normal unsupplemented chow and was not significantly different from intestinal motility in uninfected mice. We suggest that Se may be used to modulate the inflammatory, immunological, and/or antioxidant responses involved in intestinal disturbances caused by T. cruzi infection.

Imaging the Gastrointestinal Tract of Small Animals

Animal models of human diseases are increasingly available and are invaluable for studies of organ pathophysiology. Megacolon, abnormal dilatation of the colon not caused by mechanical obstruction, involves the destruction of the autonomic nervous system innervating the colon. Animal models of megacolon include mouse models of Chagas disease and Hirschprung's disease. Small animal imaging has become an important research tool and recent advances in preclinical imaging modalities have enhanced the information content available from longitudinal studies of animal models of human diseases. While numerous applications of imaging technologies have been reported to study the brain and heart of mouse models, fewer studies of the gastrointestinal system have been undertaken due to technical limitations caused by peristaltic and respiratory motion. Various imaging modalities relevant to study of the gastrointestinal tract of intact live animals are reviewed herein.

Perspectives on Trypanosoma cruzi-induced heart disease (Chagas disease)

Chagas disease is caused by the parasite Trypanosoma cruzi. It is a common cause of heart disease in endemic areas of Latin America. The year 2009 marks the 100th anniversary of the discovery of T cruzi infection and Chagas disease by the Brazilian physician Carlos Chagas. Chagasic cardiomyopathy develops in from 10% to 30% of persons who are chronically infected with this parasite. Echocardiography and magnetic resonance imaging (MRI) are important modalities in the evaluation and prognostication of individuals with chagasic heart disease. The etiology of chagasic heart disease likely is multifactorial. Parasite persistence, autoimmunity, and microvascular abnormalities have been studied extensively as possible pathogenic mechanisms. Experimental studies suggest that alterations in cardiac gap junctions may be etiologic in the pathogenesis of conduction abnormalities. The diagnosis of chronic Chagas disease is made by serology. The treatment of this infection has shortcomings that need to be addressed. Cardiac transplantation and bone marrow stem cell therapy for persons with Chagas disease have received increasing research attention in recent years.

Modulation of host cell mechanics by Trypanosoma cruzi

To investigate the effects of Trypanosoma cruzi on the mechanical properties of infected host cells, cytoskeletal stiffness and remodeling dynamics were measured in parasite-infected fibroblasts. We find that cell stiffness decreases in a time-dependent fashion in T. cruzi-infected human foreskin fibroblasts without a significant change in the dynamics of cytoskeletal remodeling. In contrast, cells exposed to T. cruzi secreted/released components become significantly stiffer within 2 h of exposure and exhibit increased remodeling dynamics. These findings represent the first direct mechanical data to suggest a physical picture in which an intact, stiff, and rapidly remodeling cytoskeleton facilitates early stages of T. cruzi invasion and parasite retention, followed by subsequent softening and disassembly of the cytoskeleton to accommodate intracellular replication of parasites. We further suggest that these changes occur through protein kinase A and inhibition of the Rho/Rho kinase signaling pathway. In the context of tissue infection, changes in host cell mechanics could adversely affect the function of the infected organs, and may play an important role on the pathophysiology of Chagas' disease.

Biological characterization of Trypanosoma cruzi stocks from domestic and sylvatic vectors in Sierra Nevada of Santa Marta, Colombia

Sierra Nevada of Santa Marta is one of the most endemic regions of Chagas disease in Colombia. In this study, we compared the biological behavior and genetic features of Trypanosoma cruzi stocks that were isolated from domestic and sylvatic insects in this area. Rhodnius prolixus (from domestic environments) and Triatoma dimidiata (from sylvatic, peridomestic and domestic environments) are the most important vectors in this region. Genetic characterization showed that all stocks corresponded to T. cruzi I, but LSSP-PCR analyses indicated that some genotypes were present in both environments. Biological characterization in vitro showed a low growth rate in sylvatic T. cruzi stocks and in some domestic T. cruzi stocks, possibly indicating the presence of stocks with similar behavior in both transmission cycles. In parallel, in vivo behavioral analysis also indicated that T. cruzi stocks are variable and this species did not show a correlation between the environments where they were isolated. In addition, all stocks demonstrated a low mortality rate and histopathological lesions in heart, skeletal muscle and colon tissue. Moreover, our data indicated that experimentally infected chagasic mice displayed a relation between their myocardial inflammation intensity, parasitism tissue and parasite load using the qPCR. In conclusion, our results indicate that the T. cruzi stocks present in SNSM have similar biological behavior and do not show a correlation with the different transmission cycles. This could be explained by the complex transmission dynamics of T. cruzi in Sierra Nevada of Santa Marta, where hosts, vectors (e.g., T. dimidiata) and reservoirs circulate in both environments due to the close contact between the two transmission cycles, favoring environment overlapping. This knowledge is an important key to understanding the epidemiology and pathology of Chagas disease in this Colombian region. Furthermore, our findings could be of significant use in the design of control strategies restricted to a specified endemic region.

Targeted screening strategies to detect Trypanosoma cruzi infection in children

BACKGROUND

Millions of people are infected with Trypanosoma cruzi, the causative agent of Chagas disease in Latin America. Anti-trypanosomal drug therapy can cure infected individuals, but treatment efficacy is highest early in infection. Vector control campaigns disrupt transmission of T. cruzi, but without timely diagnosis, children infected prior to vector control often miss the window of opportunity for effective chemotherapy.

METHODS AND FINDINGS

We performed a serological survey in children 2-18 years old living in a peri-urban community of Arequipa, Peru, and linked the results to entomologic, spatial and census data gathered during a vector control campaign. 23 of 433 (5.3% [95% CI 3.4-7.9]) children were confirmed seropositive for T. cruzi infection by two methods. Spatial analysis revealed that households with infected children were very tightly clustered within looser clusters of households with parasite-infected vectors. Bayesian hierarchical mixed models, which controlled for clustering of infection, showed that a child's risk of being seropositive increased by 20% per year of age and 4% per vector captured within the child's house. Receiver operator characteristic (ROC) plots of best-fit models suggest that more than 83% of infected children could be identified while testing only 22% of eligible children.

CONCLUSIONS

We found evidence of spatially-focal vector-borne T. cruzi transmission in peri-urban Arequipa. Ongoing vector control campaigns, in addition to preventing further parasite transmission, facilitate the collection of data essential to identifying children at high risk of T. cruzi infection. Targeted screening strategies could make integration of diagnosis and treatment of children into Chagas disease control programs feasible in lower-resource settings.

Serological diagnosis of Trypanosoma cruzi: evaluation of three enzyme immunoassays and an indirect immunofluorescent assay

Chagas' disease is an important cause of heart failure in Latin America, but is rare in the United States. The immigration of persons from endemic countries increases the potential of encountering patients with the disease. Concerns have also been raised about the introduction of Trypanosoma cruzi, the parasite that causes the disease, into the blood supply and during organ transplantation. To compare Chagas' antibody tests that are available in the United States, we evaluated three IgG ELISAs, CeLLabs T. cruzi ELISA, Hemagen Chagas' kit and IVD Research Chagas' Serum Microwell ELISA, and MarDx indirect immunofluorescent assays. The CeLLabs and Hemagen IgG ELISAs had 100 % agreement, sensitivity and specificity. The IVD Research IgG ELISA had 94·6 % agreement, 100 % sensitivity and 93 % specificity.

Sigmoid volvulus an update

Sigmoid volvulus is the third most common cause of colonic obstruction in the United States after cancer and diverticulitis. Etiologic factors include anatomic variation, chronic constipation, neurologic disease, and megacolon. Management of sigmoid volvulus involves relief of obstruction and the prevention of recurrent attacks; the outcome depends on the population and selection of patients. Although volvulus is uncommon, it may be encountered during pregnancy and is a condition that poses significant risk to both mother and fetus requiring a management strategy that varies with each trimester.

Trypanosoma cruzi infection disrupts vinculin costameres in cardiomyocytes

Chagas' disease cardiomyopathy is an important manifestation of Trypanosoma cruzi infection, leading to cardiac dysfunction and serious arrhythmias. We have here investigated by indirect immunofluorescence assay the distribution of vinculin, a focal adhesion protein with a major role in the transmission of contraction force, during the T. cruzi-cardiomyocyte infection in vitro and in vivo. No change in vinculin distribution was observed after 24 h of infection, where control and T. cruzi-infected cardiomyocytes displayed vinculin localized at costameres and intercalated discs. On the other hand, a clear disruption of vinculin costameric distribution was noted after 72 h of infection. A significant reduction in the levels of vinculin expression was observed at all times of infection. In murine experimental Chagas' disease, alteration in the vinculin distribution was also detected in the infected myocardium, with no costameric staining in infected myocytes and irregular alignment of intercalated discs in cardiac fibers. These data suggest that the disruption of costameric vinculin distribution and the enlargement of interstitial space due to inflammatory infiltration may contribute to the reduction of transmission of cardiac contraction force, leading to alterations in the heart function in Chagas' disease.

Inhibition of host connective tissue growth factor expression: a novel Trypanosoma cruzi ‐mediated response

Connective tissue growth factor (CTGF) is a secreted cytokine that plays a fundamental role in the development of tissue fibrosis by mediating many of the profibrotic effects of TGF-beta. We present the novel finding that the intracellular pathogen Trypanosoma cruzi elicits immediate and sustained repression of basal CTGF expression in dermal fibroblasts, followed by down-regulation of the extracellular matrix proteins, fibronectin, and collagen I alpha1. To address mechanisms underlying this response, the major CTGF-regulating pathways were investigated. We report that both T. cruzi trypomastigotes and secreted parasite factor(s) antagonize TGF-beta-dependent induction of CTGF in fibroblasts. Of the TGF-beta-dependent signaling pathways required for CTGF expression, we demonstrate that T. cruzi interferes with cellular Erk1/2 phosphorylation but not Smad3 signaling. While increased stimulation of Erk phosphorylation alone was insufficient to override the parasite-mediated repression of CTGF, stimulation of fibroblasts with increased concentrations of TGF-beta, which activates both Smad3 and Erk1/2, completely abrogated this inhibition. Together with the finding that T. cruzi-mediated down-regulation of CTGF expression requires de novo host cell protein synthesis, our data indicate that the unique ability of T. cruzi to interfere with the host fibrogenic response is a complex process requiring input from multiple host cell signaling pathways.

Trypanosoma cruzi carrying a targeted deletion of a Tc52 protein-encoding allele elicits attenuated Chagas' disease in mice

The intracellular protozoan parasite Trypanosoma cruzi is the etiological agent of Chagas' disease. We have previously characterized a T. cruzi virulence factor named Tc52 sharing structural and functional properties with the thioredoxin and glutaredoxin protein family. Single mutant parasite clones (Tc52(+/-)) exhibiting low virulence in vitro and in vivo were obtained by targeted Tc52 gene replacement. In this report, we have extended our study to analyze the immune response and the disease phenotype in Tc52(+/-)-infected BALB/c mice, during the acute and chronic phases of the disease. Significantly lower parasitemia were found in Tc52(+/-)-infected mice, as compared to wild-type parasite (WT)-infected ones. However, the expansion of all classes of lymphocytes and macrophages was similar for both clones. Furthermore, except for IgG2b levels which were higher in the case of WT-infected mice, all classes of Ig presented no significant difference for WT and Tc52(+/-)-infected animals. Interestingly, a lack of suppression of IL-2 production and of T-cell proliferation inhibition was observed in the case of spleen cells from Tc52(+/-)-infected mice. Finally, the pattern of inflammation process was different and characterized as diffused in the case of Tc52(+/-)-infected mice, or presenting numerous foci in the case of WT-infected mice. Localization of the Tc52 protein in tissue sections and infected heart cell primary cultures by immunofluorescence and immunogold labeling, respectively, revealed the presence of Tc52 at the amastigote surface and associated to aggregates within host cell vesicles. Taken together, these results reinforce the notion of Tc52 being a virulence factor playing a role in the phenotype of the immune response associated to the infection and on the course of the disease.

Neuromuscular diseases and disorders of the alimentary system

This review outlines the relationship and interaction between neuromuscular diseases and disorders of the alimentary system. Neuromuscular manifestations of gastrointestinal and hepatobiliary diseases are first considered. Such diseases may cause neuromuscular disorders by leading to nutritional deficiency or by more direct mechanisms. The pathogenesis, clinical features, and treatment of these various neuromuscular manifestations are discussed. The impact of disorders of nerve, neuromuscular transmission, and muscle on the alimentary system is then reviewed. The main sequelae are impaired deglutition and gastrointestinal dysmotility. The management of these complications is considered.

Trypanosoma cruzi infection and the rat central nervous system: proliferation of parasites in astrocytes and the brain reaction to parasitism

Chagas' disease, caused by the protozoan Trypanosoma cruzi, is characterized by an acute phase in which parasites circulate in the blood and proliferate in several cell types, especially muscle cells. A life-long chronic phase follows the acute phase. In young patients, the acute phase is more severe, and meningoencephalitis frequently occurs in children before 2 years of age. Parasites have been rarely observed in neurons but their presence inside glial cells has been reported without characterization of the glial cell type. The cells involved in the brain reaction to the parasites and the time course of this reaction remain to be studied. Therefore, using suckling and juvenile rats and different T. cruzi populations, we aimed at determining the brain target for parasite proliferation and the cells involved in the brain reaction. Around the middle of the acute phase, histological and ultrastructural findings indicated that T. cruzi proliferates in astrocytes, forming nests devoid of enclosing membrane as described for non-glial cells. The brain nodular reaction comprised astrocytes, microglia, macrophages and neutrophils. Resting microglia was devoid of parasites in contrast to macrophages and neutrophils that probably participate in parasite removal. Suckling animals were significantly more affected, the numbers of nests and nodules varying with inoculum size. Histoquantitative analysis showed higher number of nests at the parasitemic peak (day 13) and drastic fall at day 20 post-inoculation. The highest number of nodules occurred at day 20 with drastic reduction at day 30. Recovery from histopathological alterations occurred even in surviving younger animals.

The immune compromised host in the twenty-first century: management of mucocutaneous infections

Infectious diseases encountered in dermatology have changed tremendously during the past few decades with the emergence of the immunocompromised host. This change is a result of the human immunodeficiency virus epidemic, use of immunomodulating drugs, bone marrow transplantation, increasing prevalence of diabetes mellitus, and an aging population. New pathogens have been discovered and new disorders have occurred. In the compromised host, infection can be more aggressive and widespread locally, be caused by opportunistic pathogens, and be disseminated hematogenously from or to the skin. The prevalence of nonmelanoma skin cancer has increased, and squamous cell carcinomas can be more aggressive with more rapid local growth as well as frequency of metastasis.

Interstitial cells of Cajal in human gut and gastrointestinal disease

This paper reviews the distribution of interstitial cells of Cajal (ICC) in the human gastrointestinal (GI) tract, based on ultrastructural and immunohistochemical evidence. The distribution and morphology of ICC at each level of the normal GI tracts is addressed from the perspective of their functional significance. Alterations of ICC reported in achalasia of cardia, infantile hypertrophic pyloric stenosis, chronic intestinal pseudoobstruction, Hirschsprung's disease, inflammatory bowel diseases, slow transit constipation, and some other disorders of GI motility as well as in gastrointestinal stromal tumors are reviewed, with emphasis on the place of ICC in the pathophysiology of disease.

Interstitial cells of Cajal in human gut and gastrointestinal disease

This paper reviews the distribution of interstitial cells of Cajal (ICC) in the human gastrointestinal (GI) tract, based on ultrastructural and immunohistochemical evidence. The distribution and morphology of ICC at each level of the normal GI tracts is addressed from the perspective of their functional significance. Alterations of ICC reported in achalasia of cardia, infantile hypertrophic pyloric stenosis, chronic intestinal pseudoobstruction, Hirschsprung's disease, inflammatory bowel diseases, slow transit constipation, and some other disorders of GI motility as well as in gastrointestinal stromal tumors are reviewed, with emphasis on the place of ICC in the pathophysiology of disease.

Localization and activity of nitric oxide synthases in the gastrointestinal tract of Trypanosoma cruzi-infected mice

Chagas' disease, caused by the protozoan parasite, Trypanosoma cruzi, is associated with gastrointestinal abnormalities. Since nitric oxide (NO) has been shown to be a factor influencing intestinal function we evaluated the distributions and activities of the NO synthase (NOS) isoforms, in the gut of mice infected with T. cruzi. Ca2+-dependent (NOS1/NOS3) activity was decreased, whereas Ca2+-independent (NOS2) activity was increased in infected mice. NOS2-immunoreactivity was demonstrated in cells within the muscle layers and epithelium in infected mice and NOS1 immunoreactivity was seen in nerve structures. These data indicate that alterations in the NO-system may be important in the pathogenesis of the gastrointestinal manifestations in Chagas' disease.

Seroprevalence of Trypanosoma cruzi infection in students at the seven-fourteen age range, Londrina, PR, Brazil, in 1995

Seropositivity for Chagas disease was evaluated in 834 children aged between 7 and 14 from the Municipal Teaching System in the district of Londrina, State of Paraná. A seroprevalence rate of 0.1% was found through the use of an indirect immunofluorescent test and an enzyme-linked immunosorbent assay. This low rate of seroprevalence provides evidence that the vectorial transmission of Chagas disease has been eliminated in Londrina. The main reason for the elimination of vectorial transmission of Trypanosoma cruzi infection, as evaluated by serological tests, may be a remarkable change in the economic structure of the northern region of Paraná in the 1960's. At that time coffee production was almost completely replaced by soy beans, wheat and grazing in the rural areas. This change deeply affected the rural ecology and caused an exodus of the population from rural to urban areas as well as a decrease in the total number of the population of that region. The measures introduced for controlling the disease through the Program of Chagas Disease Control established by the Fundação Nacional de Saúde of the Brazilian Ministry of Health, certainly, had a positive impact on the reduction of American trypanosomiasis prevalence in the area under study. However, it does not seem that this was the most relevant factor responsible for the elimination of vectorial transmission of Chagas disease in Londrina.

Gastric myoelectrical and antroduodenal motor activity in patients with achalasia

Achalasia is a primary motor disorder of the oesophagus, in which the myenteric plexus is involved. However, abnormalities in other parts of the digestive tract have also been described in achalasia. Whether gastric myoelectrical and duodenal motor activity in these patients is also affected is unknown. Therefore, interdigestive and postprandial gastric myoelectrical and antroduodenal motor activity were studied in 11 patients with achalasia, using electrogastrography (EGG) and stationary antroduodenal manometry. Electrogastrographically, no differences were found in the gastric frequency, incidence of dysrhythmias and postprandial/fasting power ratio. In the interdigestive state a lower propagation velocity of phase III episodes was found in the achalasia patients, but other parameters were unaltered. Postprandially, no differences were found in the number of pressure waves, in the amplitude of pressure waves or in antroduodenal coordination. We conclude that gastric myoelectrical activity and antral motor activity in patients with achalasia is normal, suggesting an intact extrinsic and intrinsic neural innervation of the distal stomach. Although postprandial duodenal motility is normal, a lower propagation velocity of phase III suggests involvement of the small intestine in achalasia.