Intravascular Parasite Research Articles

Abstract 17450: Sex Influences the Gut-Lung Microbiome Composition in Schistosomiasis-Associated Pulmonary Arterial Hypertension

Introduction: Pulmonary arterial hypertension (PAH) is an uncurable cardiopulmonary disease highly incident in women. Infection by the intravascular parasite Schistosoma mansoni recapitulates several aspects of widespread inflammation that leads to PAH (Sch-PAH). Our data indicate that after infection, the S. mansoni eggs translocate within the cardiopulmonary system, disturbing gut-lung microbiome and leading to severe PAH. Hypotheses: S. mansoni eggs disturb the lung microbiome, contributing to vascular inflammation and PAH in a sex-dependent manner. Methods: To test this hypothesis, we induced Sch-PAH in end-Scl.creERT2;Rosamt/mg mice by intraperitoneal sensibilization with 240 eggs/gram body weight (bw; 2 weeks) followed by intravenous injection of 175 eggs/gram bw. After 7 days, we analyzed the Right Ventricular Systolic Pressure and hypertrophy (RVSP; RVH). Lung sections were used for TUNEL stain and for microbiome analysis by shotgun metagenomics. Results: Metagenomic analysis revealed that S. mansoni egg infection disrupted the lung microbiome reducing α-diversity compared to controls. Infection also reduced the Phylum Ascomycota in the lungs, whereas the ratio Firmicutes:Bacteroidetes (F/B) remained similar between groups. No difference was observed in the Simpson and Chao index. In the guts, the infection did not alter the α-diversity or the relative abundance of Deferribacteres and Proteobacteria, but it significantly increased the ratio F/B, indicative of gut dysbiosis. In terms of sex, our preliminary data indicated female mice exhibit a lower lung α-diversity compared to male mice, characterized by a significant reduction in the Firmicutes Phylum (Mean reads: 0.013 and 0.119, respectively; reads normalized by Readcount with Children). Principal coordinate analysis identified a distance in the clustering pattern between sexes, which may account for microbiome differences in Sch-PAH. Finally, our data revealed increased RVH and presence of microvascular apoptosis in female compared to male group. Conclusion: Understanding whether the disrupted gut and lung microbiome composition contributes to the onset and progression of Sch-PAH in a sex-dependent manner opens a novel therapeutic direction.

A Comparative Cross-Sectional Study of Coagulation Profiles and Platelet Parameters of Schistosoma mansoni-Infected Adults at Haik Primary Hospital, Northeast Ethiopia.

Introduction Schistosoma mansoni is an intravascular parasite that interacts with all components of the host blood. Nearly, 10% of S. mansoni-infected patients progress to severe hepatosplenic Schistosomiasis is characterized by periportal fibrosis, obstruction of intrahepatic veins, presinusoidal portal hypertension, and splenomegaly. Thus, this study aimed to compare the basic coagulation profiles and platelet parameters of S. mansoni-infected adults and noninfected individuals as controls at Haik Primary Hospital, Northeast Ethiopia. Methods A comparative cross-sectional study was conducted at Haik Primary Hospital from April to June 2021. The diagnosis and intensity of S. mansoni infection was determined using the Kato–Katz technique. The coagulation profiles and platelet parameters were analyzed using coagulation and hematology analyzers. Data were analyzed using SPSS version 26.0. The Kolmogorov–Smirnov and Shapiro–Wilk tests were done to check the distribution of continuous variables. The Mann–Whitney U test was used to compare the coagulation profiles and platelet parameters. Spearman's rank-order correlation was done to assess the correlation between the intensity of infection and coagulation profiles and platelet parameters. In all comparison, a P value <0.05 was considered statistically significant. Result In this study, a total of 180 study participants (90 S. mansoni-infected adults and 90 controls) were included. Of the total S. mansoni-infected adults, 55.6%, 28.9%, 33, and 15.6% had light, moderate, and heavy intensity of infections, respectively. All S. mansoni-infected study participants had prolonged prothrombin time (PT) and international normalized ratio (INR). Moreover, about 80% of S. mansoni-infected adults had prolonged activated partial thromboplastin time (APTT). Thrombocytopenia was found in 26.7% of the S. mansoni-infected adults. The Mann–Whitney U test showed a statistically significant difference in coagulation profiles between S. mansoni-infected adults and healthy controls (P-value ≤0.001). The Kruskal–Wallis H-test showed a significant difference in PT, APTT, and INR between the intensity of infection and healthy controls (P-value <0.05). Conclusion This study showed a prolonged coagulation time in S. mansoni-infected individuals. Thus, screening of schistosomiasis patients for hemostatic abnormalities and treating the underlying disorder is crucial.

Vitamin B6 Acquisition and Metabolism in Schistosoma mansoni.

Schistosomes are parasitic platyhelminths that currently infect >200 million people globally. The adult worms can live within the vasculature of their hosts for many years where they acquire all nutrients necessary for their survival and growth. In this work we focus on how Schistosoma mansoni parasites acquire and metabolize vitamin B6, whose active form is pyridoxal phosphate (PLP). We show here that live intravascular stage parasites (schistosomula and adult males and females) can cleave exogenous PLP to liberate pyridoxal. Of the three characterized nucleotide-metabolizing ectoenzymes expressed at the schistosome surface (SmAP, SmNPP5, and SmATPDase1), only SmAP hydrolyzes PLP. Heat-inactivated recombinant SmAP can no longer cleave PLP. Further, parasites whose SmAP gene has been suppressed by RNAi are significantly impaired in their ability to cleave PLP compared to controls. When schistosomes are incubated in murine plasma, they alter its metabolomic profile—the levels of both pyridoxal and phosphate increase over time, a finding consistent with the action of host-exposed SmAP acting on PLP. We hypothesize that SmAP-mediated dephosphorylation of PLP generates a pool of pyridoxal around the worms that can be conveniently taken in by the parasites to participate in essential, vitamin B6-driven metabolism. In addition, since host PLP‐dependent enzymes play active roles in inflammatory processes, parasite-mediated cleavage of this metabolite may serve to limit parasite-damaging inflammation. In this work we also identified schistosome homologs of enzymes that are involved in intracellular vitamin B6 metabolism. These are pyridoxal kinase (SmPK) as well as pyridoxal phosphate phosphatase (SmPLP-Ph) and pyridox(am)ine 5’-phosphate oxidase (SmPNPO) and cDNAs encoding these three enzymes were cloned and sequenced. The three genes encoding these enzymes all display high relative expression in schistosomula and adult worms suggestive of robust vitamin B6 metabolism in the intravascular life stages.

A single-cell RNA-seq atlas of Schistosoma mansoni identifies a key regulator of blood feeding.

Schistosomiasis is a neglected tropical disease that infects 240 million people. With no vaccines and only one drug available, new therapeutic targets are needed. The causative agents, schistosomes, are intravascular flatworm parasites that feed on blood and lay eggs, resulting in pathology. The function of the parasite's various tissues in successful parasitism are poorly understood, hindering identification of therapeutic targets. Using single-cell RNA sequencing (RNA-seq), we characterize 43,642 cells from the adult schistosome and identify 68 distinct cell populations, including specialized stem cells that maintain the parasite's blood-digesting gut. These stem cells express the gene hnf4, which is required for gut maintenance, blood feeding, and pathology in vivo. Together, these data provide molecular insights into the organ systems of this important pathogen and identify potential therapeutic targets.

Changes in mammalian copper homeostasis during microbial infection.

Animals carefully control homeostasis of Cu, a metal that is both potentially toxic and an essential nutrient. During infection, various shifts in Cu homeostasis can ensue. In mice infected with Candida albicans, serum Cu progressively rises and at late stages of infection, liver Cu rises, while kidney Cu declines. The basis for these changes in Cu homeostasis was poorly understood. We report here that the progressive rise in serum Cu is attributable to liver production of the multicopper oxidase ceruloplasmin (Cp). Through studies using Cp-/- mice, we find this elevated Cp helps recover serum Fe levels at late stages of infection, consistent with a role for Cp in loading transferrin with Fe. Cp also accounts for the elevation in liver Cu seen during infection, but not for the fluctuations in kidney Cu. The Cu exporting ATPase ATP7B is one candidate for kidney Cu control, but we find no change in the pattern of kidney Cu loss during infection of Atp7b-/- mice, implying alternative mechanisms. To test whether fungal infiltration of kidney tissue was required for kidney Cu loss, we explored other paradigms of infection. Infection with the intravascular malaria parasite Plasmodium berghei caused a rise in serum Cu and decrease in kidney Cu similar to that seen with C. albicans. Thus, dynamics in kidney Cu homeostasis appear to be a common feature among vastly different infection paradigms. The implications for such Cu homeostasis control in immunity are discussed.

Progress on Immunopathogenesis of Hepatic Fibrosis by Schistosome Infections

Schistosomiasis is a widespread zoonosis. It seriously threats human health. Schistosomiasis is caused by schistosomes, which belong to <i>Schistosoma</i> genus, a kind of blood-dwelling fluke worms, mainly living in the venus portal-mesenteric system of human by digenetic intravascular parasite. People who infected by schistosomes may appear the symptoms with abdominal pain, diarrhea, anemia, and splenomegaly, progressing from egg-granulomas eventually to hepatic fibrosis. This review describes hepatic fibrosis caused by schistosomes, <i>Clonorchis sinensis</i> and <i>Toxoplasma gondii</i>, <i>Capillaria hepatica</i> and hydatid, mainly focused on the hepatic fibrosis caused by <i>S. mansoni</i> and <i>S. japonicum</i>. T helper (Th) cells (Th1, Th2, Th17 and Treg cells) play an important role in the process of anti-schistosomiasis infection and immune regulation. Especially, the balance of Th1/Th2, Th17/Treg is closely related to the development of hepatic fibrosis. Th2 and Th17 cells can promote the granuloma formation by the secretion of IL-4 and IL-17 respectively; while Th1 and Treg cells can suppress the granuloma formation. These CD4⁺ T cell subsets are in complicated cross-talk in schistosomiasis immunity. Hepatic fibrosis caused by these parasites are also the key and difficult points of prevention and treatment of parasitic diseases, with further study about their molecular mechanism will provide us more thinking about parasitic effective prevention and treatment.

Gurltia paralysans Infection in Domestic Cats in the State of Pernambuco, Brazil

Background: The Gurltia paralysans nematode was initially described in Chile and for many years it was believed that the disease caused by this parasite was restricted to this country. However, in Argentina, Uruguay and more recently in Brazil, among other countries, cases of Gurltiosis have been described in both domestic and wild cats. This disease is chronic and debilitating due to the progressive paralysis developed. This study aimed to describe the clinical, epidemiological and pathological aspects of G. paralysans infection in domestic cats of the Agreste region of the state of Pernambuco, Northeast Brazil.Case: Clinical, epidemiological and pathological aspects of Gurltia paralysans infection in domestic cats in the rural area of two Agreste municipalities in the state of Pernambuco, Brazil, are described. Seven farms were visited, in which 11 male and female affected felines were evaluated. Among these, euthanasia was performed in four cases, at the owners' request and due to the advanced stage of the disease. Clinical signs began with ataxia of the pelvic limbs and evolved to jumping difficulty, lateral falls, muscle atrophy, pelvic limb scarring, and paralysis at the most severe stage of the disease, which developed in a one-year period, approximately. According to the owners, the affected cats died between six months and one year after the initial clinical signs. At necropsy, there were segments of the spinal cord with extensive reddish areas in the dura, between T7 and S2, corresponding to varices. These were characterized by numerous congestive, dilated and tortuous blood vessels observed in the dorsal plane, but more pronounced in the ventral plane of the meninges. In the bladder, multifocal areas of hemorrhage were observed. Histologically, vascular lesions in veins and venules of the leptomeninges were characterized by venous varices with thrombosis, fibrosis and intravascular parasites associated with moderate, chronic non-suppurative meningoencephalomyelitis and Wallerian degeneration. Macroscopic and microscopic lesions were more pronounced in the lumbar region of the spinal cord. Discrete lesions similar to those found in the spinal cord were observed in the encephalon. Feline gurltiosis was confirmed by epidemiological, clinical and spinal cord lesions, associated with the presence of intravascular parasites in veins and venules of the leptomeninges. The identification of Gurltia paralysans was concluded due to the characteristic morphology of the parasite in the vessels.Discussion: The diagnosis of Gurltiosis can be performed by clinical-epidemiological findings and histopathological evaluation of the nervous system demonstrating the parasite inside the vessels. The parasite has affinity for the nervous tissue, especially the lumbar spinal cord, in which it can be found in the nervous parenchyma and not only in the veins as previously believed. The chronicity of the disease can be affirmed by clinical signs, secondary lesions, such as cystitis, and the evolution of the condition. The stasis of blood caused by the varicose veins favored the formation of thrombi and compression of the white matter by the parasites, which explains the clinical signs. The geographical distribution of the disease goes beyond the initially known sites. Although little is known about the pathogenesis of Gurltiosis, it is possible to affirm that domestic cats ingest the parasite from a paratenic host, which would justify the cases recorded in rural environments. It is concluded that the disease, popularly known as "derrengado" or "renga", refers to feline gurltiosis, characterized by venous varices and chronic progressive myelitis. These results demonstrate that the disease is distributed in other regions of Brazil. However, studies are necessary to describe the form of infection so that prevention measures can be investigated.Gabriel Barbosa de Melo Neto, Luis Raimundo da Silva, Rodrigo Cruz Alves, Robério Gomes Olinda, Antônio Flávio Medeiros Dantas &amp; Márcia Bersane Araújo de Medeiros Torres

Schistosomes can hydrolyze proinflammatory and prothrombotic polyphosphate (polyP) via tegumental alkaline phosphatase, SmAP

Schistosoma mansoni is a long-lived intravascular trematode parasite that can infect humans causing the chronic debilitating disease, schistosomiasis. We hypothesize that the action of host-interactive proteins found at the schistosome surface allows the worms to maintain a safe, anti-thrombotic and anti-inflammatory environment around them in the bloodstream. One such protein is the ˜60 kDa alkaline phosphatase SmAP which is known to be expressed in the outer tegument of all intravascular life stages. We demonstrate in this work that the parasites (schistosomula as well as adult males and females) can hydrolyze polyphosphate (polyP) - an anionic, linear polymer of inorganic phosphates that is produced and released by immune cells as well as by activated platelets and that induce proinflammatory and prothrombotic pathways. Purified recombinant SmAP can likewise cleave polyP and with a Km of 6.9 ± 1 mM. Finally, parasites whose SmAP gene has been suppressed by RNAi are significantly impaired in their ability to hydrolyze polyP. SmAP-mediated cleavage of polyP may contribute to the armamentarium of schistosomes that promotes their survival in the hostile intravascular habitat. This is the first report of any pathogen cleaving this bioactive metabolite.

Intravascular Schistosoma mansoni Cleave the Host Immune and Hemostatic Signaling Molecule Sphingosine-1-Phosphate via Tegumental Alkaline Phosphatase.

Schistosomes are parasitic flatworms that infect the vasculature of >200 million people around the world. These long-lived parasites do not appear to provoke blood clot formation or obvious inflammation around them in vivo. Proteins expressed at the host–parasite interface (such as Schistosoma mansoni alkaline phosphatase, SmAP) are likely key to these abilities. SmAP is a glycoprotein that hydrolyses the artificial substrate p-nitrophenyl phosphate in a reaction that requires Mg2+ and at an optimal pH of 9. SmAP additionally cleaves the nucleoside monophosphates AMP, CMP, GMP, and TMP, all with a similar Km (~600–650 μM). Living adult worms, incubated in murine plasma for 1 h, alter the plasma metabolome; a decrease in sphingosine-1-phosphate (S1P) is accompanied by an increase in the levels of its component parts—sphingosine and phosphate. To test the hypothesis that schistosomes can hydrolyze S1P (and not merely recruit or activate a host plasma enzyme with this function), living intravascular life-stage parasites were incubated with commercially obtained S1P and cleavage of S1P was detected. Parasites whose SmAP gene was suppressed using RNAi were impaired in their ability to cleave S1P compared to controls. In addition, recombinant SmAP hydrolyzed S1P. Since extracellular S1P plays key roles in controlling inflammation and platelet aggregation, we hypothesize that schistosome SmAP, by degrading S1P, can regulate the level of this bioactive lipid in the environment of the parasites to control these processes in the worm’s local environment. This is the first report of any parasite being able to cleave S1P.

The Essential Ectoenzyme SmNPP5 from the Human Intravascular Parasite Schistosoma mansoni is an ADPase and a Potent Inhibitor of Platelet Aggregation.

Schistosomes are intravascular parasitic platyhelminthes infecting > 200 million people globally and causing a debilitating disease, schistosomiasis. Despite the relatively large size of the adult worms and their disruption of blood flow, surprisingly, they do not appear to provoke thrombus formation around them in vivo. We hypothesize that proteins expressed at the host-parasite interface are key to this ability. Here, we functionally express an ectonucleotide pyrophosphatase/phosphodiesterase homologue, SmNPP5, that is expressed at the tegumental surface of intravascular Schistosoma mansoni. We report that SmNPP5, a known virulence factor for the worms, is a type one glycoprotein that cleaves the artificial substrate p-Nph-5'-TMP in a reaction that requires cations and at an optimal pH of 9. Using immunolocalization and enzyme activity measurements, we confirm that SmNPP5 is exclusively expressed at the host interactive surface of all intravascular life stages. SmNPP5 inhibits platelet aggregation in a dose-dependent manner, as measured by multiple electrode aggregometry (MEA) using whole blood. Inhibition is apparent when either collagen or adenosine diphosphate (ADP) is used as agonist but is lost following heat treatment of SmNPP5. Unlike its mammalian homologue, NPP5, the schistosome protein cleaves ADP and with a Km of 246 ± 34 µM. In sum, SmNPP5 is expressed in the intravascular environment where it can degrade ADP and act as an anticoagulant. In this manner, the protein likely helps limit blood clot formation around the worms in vivo to permit the parasites free movement within the vasculature.

The complement receptor CRIg dominates clearance of intravascular parasites during African trypanosome infection

Abstract Kupffer cells (KCs), the liver resident macrophages, play a prominent role in clearance of blood-borne pathogens. The mechanisms by which KCs engulf circulating parasites such as African trypanosomes have yet to be determined. Here we show that depletion of KCs resulted in uncontrolled parasitemia in mice infected with Trypanosoma congolense, indicating the essential role of KCs in clearance of intravascular parasites. By using intravital microscopy, we further investigated the dynamics of interactions of KCs with circulating T. congolense in real-time. The results demonstrate that KCs catch circulating parasites in the presence of specific IgM and IgG antibodies, but fail to do so in the absence of specific antibodies. Complement C3 is critically involved in the capture of the parasites mediated by both IgM and IgG. We further demonstrate that complement receptor CRIg, but not CR3, is crucial for KCs to catch the parasites. In support of the findings gained by in vivo imaging, mice deficient of C3 or CRIg, but not CR3, could not control the first wave of parasitemia, and had a dramatic reduced survival time compared to wild-type mice following infection with T. congolense (10 days vs over 100 days). Collectively, our data demonstrate that CRIg play a dominant role in the clearance of circulating parasites by KCs in an antibody dependent manner.

Increased expression of NTPDases 2 and 3 in mesenteric endothelial cells during schistosomiasis favors leukocyte adhesion through P2Y1 receptors

Schistosomiasis is caused by an intravascular parasite and linked to phenotypic changes in endothelial cells that favor inflammation. Endothelial cells express P2Y1 receptors (P2Y1R), and their activation by ADP favors leukocyte adhesion to the endothelial monolayer. We aimed to evaluate the influence of schistosomiasis upon endothelial purinergic signaling-mediated leukocyte adhesion. Mesenteric endothelial cells and mononuclear cells from control and Schistosoma mansoni-infected mice were used in co-culture. P2Y1R levels were similar in both groups. Basal leukocyte adhesion was higher in the infected than in the control group; leukocyte adhesion increased after treatment with the P2Y1R agonist 2-MeSATP in both groups, though it only marginally increased in the infected group. Pre-incubation with the selective P2Y1R antagonist MRS2179 (0.3μM) prevented the agonist effect. However, in the infected group it also reduced the basal leukocyte adhesion, suggesting endothelial cell pre-activation. The endothelial expressions of NTPDases 2 and 3 were significantly increased in the infected group, increasing extracellular ATP hydrolysis and ADP formation by endothelial cells. Therefore, mesenteric endothelial cells are primed by schistosomiasis to a pro-inflammatory phenotype characterized by an increased expression of NTPDases 2 and 3, favoring ADP accumulation and mononuclear cell adhesion, possibly contributing to mesenteric inflammation and schistosomiasis morbidity.

The impact of schistosomes and schistosomiasis on murine blood coagulation and fibrinolysis as determined by thromboelastography (TEG).

Schistosomes are parasitic platyhelminths that currently infect over 200 million people and cause the chronic debilitating disease schistosomiasis. While these large intravascular parasites can disturb blood flow, surprisingly they do not appear to provoke thrombus formation around them in vivo. In order to determine if the worms can alter their local environment to impede coagulation, we incubated adult worms (50 pairs) in murine blood (500 µl) for 1 h at 37 °C and, using thromboelastography (TEG), we compared the coagulation profile of the blood with control blood that never contained worms. Substantial differences were apparent between the two profiles. Blood that had been exposed to schistosomes clotted more slowly and yielded relatively poor, though stable, thrombi; all TEG measures of blood coagulation (R, K, α-angle, MA, G and TMA) differed significantly between conditions. No fibrinolysis (as determined by LY30 and LY60 values) was detected in either case. The observed TEG profile suggests that the worms are acting as local anti-coagulants. Blood recovered from schistosome-infected mice, however, does not behave in this way. At an early time point post infection (4-weeks), the TEG profile of infected murine blood is essentially the same as that of control blood. However at a later time point (7-weeks) infected murine blood clots significantly faster than control blood but these clots also break down faster. The R, K, α-angle, and TMA measures of coagulation are all significantly different between the control versus infected mice as are the LY30 and LY60 values. This profile is indicative of a hypercoagulable state with fibrinolysis and is akin to that seen in human patients with advanced schistosomiasis.

Potential role of Plasmodium falciparum-derived ammonia in the pathogenesis of cerebral malaria.

Cerebral malaria (CM) is the most severe complication associated with Plasmodium falciparum infection. The exact pathogenic mechanisms leading to the development of CM remains poorly understood while the mortality rates remain high. Several potential mechanisms including mechanical obstruction of brain microvasculature, inflammation, oxidative stress, cerebral energy defects, and hemostatic dysfunction have been suggested to play a role in CM pathogenesis. However, these proposed mechanisms, even when considered together, do not fully explain the pathogenesis and clinicopathological features of human CM. This necessitates consideration of alternative pathogenic mechanisms. P. falciparum generates substantial amounts of ammonia as a catabolic by-product, but lacks detoxification mechanisms. Whether this parasite-derived ammonia plays a pathogenic role in CM is presently unknown, despite its potential to cause localized brain ammonia elevation and subsequent neurotoxic effects. This article therefore, explores and proposes a potential role of parasite-derived ammonia in the pathogenesis and neuropathology of CM. A consideration of parasite-derived ammonia as a factor in CM pathogenesis provides plausible explanations of the various features observed in CM patients including how a largely intravascular parasite can cause neuronal dysfunction. It also provides a framework for rational development and testing of novel drugs targeting the parasite's ammonia handling.

Acute Kidney Injury in Children with Plasmodium falciparum Malaria: Determinants for Mortality.

♦ Acute kidney injury (AKI) in P. falciparum malaria infection is an important morbidity in children. The purpose of the present study was done to observe the renal involvement, associated morbidities and outcome. ♦ Out of 156 patients with severe P. falciparum malaria, diagnosed on the basis of compatible clinical presentations and positive malarial parasites in the peripheral blood smear and/or histidine rich protein 2 antigen, 31 had AKI at presentation and were analyzed. ♦ Of 31 (19.9%) patients with AKI, 4 were classified at risk, 11 injury, and 16 failure stage, as per pRIFLE criteria (pediatric version of RIFLE [R = risk, I = injury, F = failure, L = loss E = end-stage kidney disease]). Mean age of children with AKI was 7.7 ± 3.2 years. A significantly higher proportion of patients with AKI had hypoglycemia (41.9%), pulmonary edema (32.2%), and disseminated intravascular coagulation (DIC) (29.0%) compared to those without AKI (18.4%, 4.8%, and 3.2%, respectively). Twelve patients (38.7%) required peritoneal dialysis (PD), 8 (25.8%) died, and all were in failure stage. The non-survivors had significantly higher blood urea (p = 0.005) and serum creatinine levels (p = 0.042), lower glomerular filtration rate (p < 0.001), longer duration of illness (p = 0.003), and oliguria/anuria (p = 0.001) than survivors at admission. On logistic regression analysis, the disseminated intravascular coagulation (DIC), jaundice and parasite density (≥ 3+) were found to be significant factors contributing to mortality in children with AKI. ♦ Acute kidney injury in falciparum malaria is one of the severe systemic complications. Duration of illness and presence of comorbidities adversely affected the outcome.

Cellular cytokine and chemokine responses to parasite antigens and fungus and mite allergens in children co-infected with helminthes and protozoa parasites.

BackgroundIn sub-Saharan Africa poly-parasite infections are frequently observed in children, and with poly-parasitism modulating immune mechanisms, mediated by cytokines and chemokines, are required to prevent overwhelming inflammation and host tissue damage. We analyzed in children co-infected with helminthes and protozoan parasites their cellular production of regulatory and pro-inflammatory cytokines and chemokines in response to parasite antigens and allergens.MethodsIntestinal and intravascular parasite infections were detected in stool and urines samples. The in vitro cellular cytokine and chemokine responses of peripheral blood mononuclear cells (PBMC) to parasite antigens and allergens were analysed in children (n = 87) with single and poly-parasite infection, and skin prick test reactivity to fungus and mite allergens was determined in singly and poly-parasitized children (n = 509).ResultsIn children Entamoeba histolytica/dispar (62%), Necator americanus (31%), Schistosoma haematobium (28%), S. mansoni (21%), Hymenolepis nana (2%) and Strongyloides stercoralis (1%) were diagnosed. Singly infected were 37%, 47% were positive for 2 or more parasite species and 16% were infection-free. When PBMC were stimulated in vitro with parasite antigens and allergens, regulatory-type cytokine IL-27 and alarmin-type IL-33 enhanced with poly-parasite infections whilst IL-10 and pro-inflammatory MIP3-α/CCL20 and MIG/CXCL9 were produced in similar amounts in singly or poly-parasitized children. The co-stimulation in vitro of PBMC with mite allergens and Ascaris lumbricoides antigens depressed the allergen-induced pro-inflammatory IL-27, IL-33 and MIP3-α/CCL20 responses while regulatory IL-10 remained unaffected. Post albendazole and/or praziquantel treatment, the cellular release of IL-10, IL-33, MIP3-α/CCL20 and MIG/CXCL9 lessened significantly in all children infection groups. Skin prick test (SPT) reactivity to fungus Aspergillus fumigatus and mite Dermatophagoides pteronyssinus allergens was investigated in 509 children, and positive SPT responses were found in 23% of the infection-free, and in 47%, 53% and 56% of the singly, doubly and poly-parasite infected, respectively.ConclusionsIn children co-infected with helminthes and protozoan parasites a mixed cellular response profile of both inflammatory and regulatory chemokines and cytokines was stimulated by individual antigens and allergens, pro-inflammatory cytokines and chemokines enhanced with an increasing number of parasite infections, and in poly-parasitized children skin prick test reactivity to allergens extracts was highest.

Fatal cerebral malaria: a venous efflux problem.

Most Plasmodium falciparum-infected children with cerebral malaria (CM) die from respiratory arrest, but the underlying pathology is unclear. Here we present a model in which the ultimate cause of death from CM is severe intracranial hypertension. Dynamic imaging of mice infected with P. berghei ANKA, an accepted model for experimental CM, revealed that leukocyte adhesion impairs the venous blood flow by reducing the functional lumen of postcapillary venules (PCV). The resulting increase in intracranial pressure (ICP) exacerbates cerebral edema formation, a hallmark of both murine and pediatric CM. We propose that two entirely different pathogenetic mechanisms—cytoadherence of P. falciparum-infected erythrocytes in pediatric CM and leukocyte arrest in murine CM—result in the same pathological outcome: a severe increase in ICP leading to brainstem herniation and death from respiratory arrest. The intracranial hypertension (IH) model unifies previous hypotheses, applies to human and experimental CM alike, eliminates the need to explain any selective recognition mechanism Plasmodium might use to target multiple sensitive sites in the brain, and explains how an intravascular parasite can cause so much neuronal dysfunction.

Diminazene Aceturate (Berenil) Modulates the Host Cellular and Inflammatory Responses to Trypanosoma congolense Infection

Background Trypanosoma congolense are extracellular and intravascular blood parasites that cause debilitating acute or chronic disease in cattle and other domestic animals. Diminazene aceturate (Berenil) has been widely used as a chemotherapeutic agent for trypanosomiasis in livestock since 1955. As in livestock, treatment of infected highly susceptible BALB/c mice with Berenil leads to rapid control of parasitemia and survival from an otherwise lethal infection. The molecular and biochemical mechanisms of action of Berenil are still not very well defined and its effect on the host immune system has remained relatively unstudied. Here, we investigated whether Berenil has, in addition to its trypanolytic effect, a modulatory effect on the host immune response to Trypanosoma congolense.Methodology/Principal FindingsBALB/c and C57BL/6 mice were infected intraperitoneally with T. congolense, treated with Berenil and the expression of CD25 and FoxP3 on splenic cells was assessed directly ex vivo. In addition, serum levels and spontaneous and LPS-induced production of pro-inflammatory cytokines by splenic and hepatic CD11b+ cells were determined by ELISA. Berenil treatment significantly reduced the percentages of CD25+ cells, a concomitant reduction in the percentage of regulatory (CD4+Foxp3+) T cells and a striking reduction in serum levels of disease exacerbating pro-inflammatory cytokines including IL-6, IL-12, TNF and IFN-γ. Furthermore, Berenil treatment significantly suppressed spontaneous and LPS-induced production of inflammatory cytokines by splenic and liver macrophages and significantly ameliorated LPS-induced septic shock and the associated cytokine storm.Conclusions/SignificanceCollectively, these results provide evidence that in addition to its direct trypanolytic effect, Berenil also modulates the host immune response to the parasite in a manner that dampen excessive immune activation and production of pathology-promoting pro-inflammatory cytokines, suggesting that this drug may also be beneficial for treatment of disease conditions caused by excessive production of inflammatory cytokines.

Manipulation of vascular function by blood flukes?

Schistosomes (blood flukes) are long lived, intravascular parasites that afflict ~ 200 million people worldwide. Here we review the potential ability of these parasites to exert control on local vascular physiology. We examine schistosome kallikrein-like proteins that drive vasodilation. We review biogenic amine metabolism in the parasites that involve the vasodilator histamine and its receptors and the vasoconstrictor serotonin and its receptor. Schistosomes can trigger the release of histamine from host cells and can import serotonin. We consider the ability of schistosomes to generate and release the eicosanoid vasodilators PGD 2 and PGE 2 and the vasoconstrictors LTB 4 and LTC 4. The literature on nitric oxide metabolism in these blood flukes is assessed. Finally the potential impact of other schistosome metabolic processes (e.g. exogenous adenosine generation and acetylcholine degradation) on vascular function is appraised. An increased understanding of these processes could lead to novel anti-parasitics as well as new therapies to treat vascular dysfunction.

Characterization of schistosome tegumental alkaline phosphatase (SmAP).

Schistosomes are parasitic platyhelminths that currently infect over 200 million people globally. The parasites can live for years in a putatively hostile environment - the blood of vertebrates. We have hypothesized that the unusual schistosome tegument (outer-covering) plays a role in protecting parasites in the blood; by impeding host immunological signaling pathways we suggest that tegumental molecules help create an immunologically privileged environment for schistosomes. In this work, we clone and characterize a schistosome alkaline phosphatase (SmAP), a predicted ∼60 kDa glycoprotein that has high sequence conservation with members of the alkaline phosphatase protein family. The SmAP gene is most highly expressed in intravascular parasite life stages. Using immunofluorescence and immuno-electron microscopy, we confirm that SmAP is expressed at the host/parasite interface and in internal tissues. The ability of living parasites to cleave exogenous adenosine monophosphate (AMP) and generate adenosine is very largely abolished when SmAP gene expression is suppressed following RNAi treatment targeting the gene. These results lend support to the hypothesis that schistosome surface enzymes such as SmAP could dampen host immune responses against the parasites by generating immunosuppressants such as adenosine to promote their survival. This notion does not rule out other potential functions for the adenosine generated e.g. in parasite nutrition.