Toxoplasma gondii Tissue Cyst: Cyst Wall Incorporation Activity and Matrix Cytoskeleton Proteins Paving the Way to Nutrient Acquisition

Toxoplasma gondii is an intracellular parasite that causes chronic infection by the development of bradyzoites housed in tissue cysts, preferably in the muscles and central nervous system. The composition and the function of the cyst wall are still not fully understood. Are T. gondii cysts able to incorporate nutrients through its wall? If so, how would these nutrients be traversed to cross the cyst matrix to reach the bradyzoite forms? Herein, we tested the uptake capacity of the Toxoplasma tissue cyst wall by employing some fluid-phase endocytosis tracers as peroxidase (HRP) and bovine serum albumin (BSA). Fluorescence images revealed these molecules on the cyst wall as well as in the cyst matrix. The subcellular localization of the tracer was confirmed by ultrastructural analysis showing numerous labeled vesicles and tubules distributed within the cyst matrix in close association with intracystic bradyzoite membrane, suggesting the cyst wall as a route of nutrient uptake. Furthermore, we confirmed the presence of cytoskeleton proteins, such as tubulin, actin, and myosin, in the tissue cyst matrix that may explain the nutrient input mechanism through the cyst wall. A better understanding of the nutrient acquisition process by the cyst might potentially contribute to the development of new therapeutic targets against chronic toxoplasmosis

Toxoplasma gondii down modulates cadherin expression in skeletal muscle cells inhibiting myogenesis

<p>Abstract</p> <p>Background</p> <p><it>Toxoplasma gondii </it>belongs to a large and diverse group of obligate intracellular parasitic protozoa. Primary culture of mice skeletal muscle cells (SkMC) was employed as a model for experimental toxoplasmosis studies. The myogenesis of SkMC was reproduced <it>in vitro </it>and the ability of <it>T. gondii </it>tachyzoite forms to infect myoblasts and myotubes and its influence on SkMC myogenesis were analyzed.</p> <p>Results</p> <p>In this study we show that, after 24 h of interaction, myoblasts (61%) were more infected with <it>T. gondii </it>than myotubes (38%) and inhibition of myogenesis was about 75%. The role of adhesion molecules such as cadherin in this event was investigated. First, we demonstrate that cadherin localization was restricted to the contact areas between myocytes/myocytes and myocytes/myotubes during the myogenesis process. Immunofluorescence and immunoblotting analysis of parasite-host cell interaction showed a 54% reduction in cadherin expression at 24 h of infection. Concomitantly, a reduction in M-cadherin mRNA levels was observed after 3 and 24 h of <it>T. gondii-</it>host cell interaction.</p> <p>Conclusions</p> <p>These data suggest that <it>T. gondii </it>is able to down regulate M-cadherin expression, leading to molecular modifications in the host cell surface that interfere with membrane fusion and consequently affect the myogenesis process.</p

FIRST RECORD OF A NUCLEAR-FOLLOWER ASSOCIATION BETWEEN CORYDORAS VITTATUS (NIJSSEN, 1971), CORYDORAS CF. JULII (CALLICHTHYIDAE) AND KNODUS VICTORIAE (STEINDACHNER, 1907) (CHARACIDAE)

Nuclear-follower interactions are a particular type of interspecific foraging association which involves a nuclear species, which revolves or scans through the substrate, and follower species that access the food items made available by the nuclear species’ activity. This type of association was observed in a headwater stream at the Itapecuru basin, in the Maranhão cerrado, involving the catfishes Corydoras vittatus, Corydoras cf. julii as nuclear species and Knodus victoriae as its follower. Individuals of C. vittatus, Corydoras cf. julii revolved the substrate during their foraging, promoting sediment suspension. Their followers, in turn, moved through the “cloud” of particles in suspension, capturing food items. Food particles in suspension do not seem to be used by the catfishes but become available for K. victoriae. The follower behavior represents a feeding tactic for these species, reinforcing the general idea of behavioral plasticity between follower species

Morphological and Transcriptional Changes in Human Bone Marrow During Natural Plasmodium vivax Malaria Infections.

--- - Label: BACKGROUND NlmCategory: BACKGROUND content: The presence of Plasmodium vivax malaria parasites in the human bone marrow (BM) is still controversial. However, recent data from a clinical case and experimental infections in splenectomized nonhuman primates unequivocally demonstrated the presence of parasites in this tissue. - Label: METHODS NlmCategory: METHODS content: In the current study, we analyzed BM aspirates of 7 patients during the acute attack and 42 days after drug treatment. RNA extracted from CD71+ cell suspensions was used for sequencing and transcriptomic analysis. - Label: RESULTS NlmCategory: RESULTS content: We demonstrated the presence of parasites in all patients during acute infections. To provide further insights, we purified CD71+ BM cells and demonstrated dyserythropoiesis and inefficient erythropoiesis in all patients. In addition, RNA sequencing from 3 patients showed that genes related to erythroid maturation were down-regulated during acute infections, whereas immune response genes were up-regulated. - Label: CONCLUSIONS NlmCategory: CONCLUSIONS content: This study thus shows that during P. vivax infections, parasites are always present in the BM and that such infections induced dyserythropoiesis and ineffective erythropoiesis. Moreover, infections induce transcriptional changes associated with such altered erythropoietic response, thus highlighting the importance of this hidden niche during natural infections

Mortality from gastrointestinal congenital anomalies at 264 hospitals in 74 low-income, middle-income, and high-income countries: a multicentre, international, prospective cohort study

Summary Background Congenital anomalies are the fifth leading cause of mortality in children younger than 5 years globally. Many gastrointestinal congenital anomalies are fatal without timely access to neonatal surgical care, but few studies have been done on these conditions in low-income and middle-income countries (LMICs). We compared outcomes of the seven most common gastrointestinal congenital anomalies in low-income, middle-income, and high-income countries globally, and identified factors associated with mortality. Methods We did a multicentre, international prospective cohort study of patients younger than 16 years, presenting to hospital for the first time with oesophageal atresia, congenital diaphragmatic hernia, intestinal atresia, gastroschisis, exomphalos, anorectal malformation, and Hirschsprung’s disease. Recruitment was of consecutive patients for a minimum of 1 month between October, 2018, and April, 2019. We collected data on patient demographics, clinical status, interventions, and outcomes using the REDCap platform. Patients were followed up for 30 days after primary intervention, or 30 days after admission if they did not receive an intervention. The primary outcome was all-cause, in-hospital mortality for all conditions combined and each condition individually, stratified by country income status. We did a complete case analysis. Findings We included 3849 patients with 3975 study conditions (560 with oesophageal atresia, 448 with congenital diaphragmatic hernia, 681 with intestinal atresia, 453 with gastroschisis, 325 with exomphalos, 991 with anorectal malformation, and 517 with Hirschsprung’s disease) from 264 hospitals (89 in high-income countries, 166 in middleincome countries, and nine in low-income countries) in 74 countries. Of the 3849 patients, 2231 (58·0%) were male. Median gestational age at birth was 38 weeks (IQR 36–39) and median bodyweight at presentation was 2·8 kg (2·3–3·3). Mortality among all patients was 37 (39·8%) of 93 in low-income countries, 583 (20·4%) of 2860 in middle-income countries, and 50 (5·6%) of 896 in high-income countries (p<0·0001 between all country income groups). Gastroschisis had the greatest difference in mortality between country income strata (nine [90·0%] of ten in lowincome countries, 97 [31·9%] of 304 in middle-income countries, and two [1·4%] of 139 in high-income countries; p≤0·0001 between all country income groups). Factors significantly associated with higher mortality for all patients combined included country income status (low-income vs high-income countries, risk ratio 2·78 [95% CI 1·88–4·11], p<0·0001; middle-income vs high-income countries, 2·11 [1·59–2·79], p<0·0001), sepsis at presentation (1·20 [1·04–1·40], p=0·016), higher American Society of Anesthesiologists (ASA) score at primary intervention (ASA 4–5 vs ASA 1–2, 1·82 [1·40–2·35], p<0·0001; ASA 3 vs ASA 1–2, 1·58, [1·30–1·92], p<0·0001]), surgical safety checklist not used (1·39 [1·02–1·90], p=0·035), and ventilation or parenteral nutrition unavailable when needed (ventilation 1·96, [1·41–2·71], p=0·0001; parenteral nutrition 1·35, [1·05–1·74], p=0·018). Administration of parenteral nutrition (0·61, [0·47–0·79], p=0·0002) and use of a peripherally inserted central catheter (0·65 [0·50–0·86], p=0·0024) or percutaneous central line (0·69 [0·48–1·00], p=0·049) were associated with lower mortality. Interpretation Unacceptable differences in mortality exist for gastrointestinal congenital anomalies between lowincome, middle-income, and high-income countries. Improving access to quality neonatal surgical care in LMICs will be vital to achieve Sustainable Development Goal 3.2 of ending preventable deaths in neonates and children younger than 5 years by 2030

Detection of fibronectin and laminin in Toxoplasma gondii tissue cysts: Immunocytochemical assays

AIMS: To analyze the existence and distribution of some matrix proteins in tissue cysts of Toxoplasma gondii. METHODS: Laminin and fibronectin in tissue cysts of Toxoplasma gondii were detected by confocal microscopy and transmission electron microscopy. RESULTS: Ultrastructural immunocytochemistry showed both glycoproteins in the granular region of tissue cysts, cystic matrix, micronemes, rhoptries, dense granules and rarely at the membrane of bradyzoites of Toxoplasma gondii. CONCLUSIONS: The presence of both laminin and fibronectin in secretory organelles and in the apical region of bradyzoites suggests that exocytosis of these glycoproteins can contribute to their interaction with host cells, besides composing the cyst matrix of Toxoplasma gondii

Efficient uptake of mannosylated proteins by a human Schwann cell line

Complex carbohydrate structures are essential molecules of infectious microbes and host cells, and are involved in cell signaling associated with inflammatory and immune responses. The uptake of mannose-tailed glycans is usually carried out by macrophages, dendritic cells (DCs), and other professional phagocytes to trigger MHC class I- and MHC class II-restricted antigen presentation, and to promote T cell effector responses. Since Schwann cells (SCs) have been proposed as immunocompetent cells, we investigated whether a human cell line (ST88-14 cells) could bind mannosylated ligands in a specific manner. The saturation of uptake of mannosylated molecules by ST88-14 cells and the internalization and distribution pathway of these ligands were tested by cytometry and confocal plus electron microscopy, respectively. This uptake showed a dose-dependent increase, the saturation point being reached at high concentrations of mannosyl residues/240mM mannose. Merging of man/BSA-FITC and S100 labeling showed their partial, but, significant colocalization. Ultrastructural analysis of ST88-14 cells after incubation with HRP-colloidal gold, without or with subsequent chasing at 37°C, showed an initial location on the cell surface and temperature- and time-dependent internalization of the probe. Our findings suggest an efficient mannosylated ligand uptake system through putative lectin(s) that may be operational in inflammatory and immune responses