Mecanismos efectores del interferón gamma contra la infección por Toxoplasma gondii

Toxoplasma gondii is an intracellular obligate protozoan parasite, Human infection is generally subclinical, but hosts with deffective cellular immunity are at risk of severe disease. In many countries, congenital toxoplasmosis and toxoplasmic encephalitis in HIV-infected individuals are significant causes of morbidity and mortality. We review here the effector mechanisms of gamma interferon, the major cytokine involved in the protection against T gondii The addition of IFN y to cultured infected THPl cells protected against Tgondii infection by an early mechanism involving a reduction in the number of parasitized cells.The reduction in the percentage of parasitized cells obtained by treatment with IFN y is linked to a decrease in parasite and cellular PLA, activity.This is a new effector mechanism of IFN y against T gondii infection. A second effect is by inducing indoleamine-oxigenase (IDO), an enzyme that reduces tryptophan stores.Tryptophan is essential for intracellular growth of T gondii. lnduction of IDO leads to a parasitostatic effect. In human monocytes induction of nitric oxide is not a part of the antitoxoplasmicidal effect induced by IFN y.Toxoplasma gondiies un protozoario parásito de desarrollo intracelular. La enfermedad humana producida por T: gondii es una causa importante de morbilidad y mortalidad neonatal y en pacientes inmunodeprimidos. En esta reseña, se revisan los conocimientos actuales sobre los mecanismos efectores del interferón gamma (IFN y), la principal citocina protectora contra Igondii, incluyendo los resultados que hemos obtenido en un modelo de infección in vifro de células humanas monocitarias (THPI). El IFN y protege las células humanas contra T gondii por mecanismos diferentes a aquéllos con los que protege las células de ratón. En el modelo de infección de célulasTHP1, el IFN y protege por dos mecanismos independientes. Un primer efecto es la reducción del porcentaje de células parasitadas, el cual está ligado a una disminución de la actividad PLA, parasitaria y celular. Se trata de un nuevo mecanismo efector del IFN y contra la infección toxoplásmica, diferente a los mecanismos parasiticidas y parasitostáticos previamente descritos. Un segundo efecto ocurre por interrupción del crecimiento parasitario intracelular a través de la activación de la enzima indoleamina-oxigenasa que degrada el triptófano, lo que constituye un efecto parasitostático. Contrariamente a lo que ocurre en el modelo de infección de células monocitarias de ratón, la producción de óxido nítrico (NO) no juega un papel determinante en los monocitos humanos

La bioindustrie aux Etats-Unis

Pinon Jean-Claude, Bernon Michel. La bioindustrie aux Etats-Unis. In: Revue d'économie industrielle, vol. 18, 4e trimestre 1981. Genèse et développement de la BIOINDUSTRIE. pp. 349-355

FTIR spectroscopy as a potential tool to analyse structural modifications during morphogenesis of Candida albicans

International audienc

FTIR spectroscopy in medical mycology: applications to the differentiation and typing of Candida

International audienc

Parallel EELS elemental mapping in scanning transmission electron microscopy: use of the difference methods

The feasibility to obtain semi-quantitative elemental maps with a STEM microscope from first or second difference recorded PEELS spectra is demonstrated. These methods called "FD or SD methods" have been already used for the local quantitative analysis of trace elements. It has been shown that it can be a powerful technique to overcome the problems related to the background subtraction and inhomogeneous responses of adjacent diodes in PEELS spectra and also to greatly improve the detectability of the elements. We extended this technique to create semi-quantitative multi-element maps on biological material. The experiments are done with a 300 kV STEM (C.M. 30 Philips) coupled with a GATAN PEELS and an EDAX computer. A software developed on a host computer allows the control of the STEM probe position and the acquisition of energy shifted EELS spectra for each pixel. By comparing elemental maps obtained, with the conventional method (power law background generation and subtraction above the edge), and with the difference methods we demonstrate both the validity and the advantages offered by FD and SD methods to create multi-elements semi-quantitative maps.Nous montrons la possibilité d'obtenir des cartes élémentaires semi-quantitatives en microscopie électronique à balayage transmission, à partir de spectres de pertes d'énergie acquis par des méthodes de différence. Ces méthodes notées "méthode FD ou SD" selon que les spectres sont acquis en première ou en seconde différence ont déjà été utilisées pour faire des microanalyses locales d'éléments en très faible concentration. Il avait été montré que cette technique pouvait résoudre les problèmes relatifs à la soustraction du fond continu ainsi que ceux liés à l'inhomogénéité de réponse des diodes dans le cas de la détection parallèle. De plus, cette méthode améliore considérablement la sensibilité de détection des éléments. Nous avons étendu cette technique d'analyse locale pour créer des cartes élémentaires semi-quantitatives. Les études ont été appliquées au matériel biologique cellulaire. Les expériences ont été faites avec un microscope 300 kV STEM (C.M. 30 Philips) couplé à un spectromètre à détection parallèle GATAN et un ordinateur EDAX. Sur un ordinateur hôte interfaçé dans cet ensemble, nous avons développé un logiciel qui assure le contrôle de la sonde STEM sur l'échantillon ainsi que l'acquisition de spectres décalés en énergie et le traitement des données. En comparant des cartes élémentaires obtenues par la méthode conventionnelle (soustraction du fond continu sous le seuil) et la méthode de différence, nous démontrons la validité et les avantages qu'offrent la méthode de différence pour générer des cartes élémentaires multi-éléments semi-quantitatives

Le GIS peuplier, 4 ans après sa création

National audienc

Detection and localization of a Ca2+-ATPase activity in Toxoplasma gondii.

Toxoplasma gondii, the agent causing toxoplasmosis, is an obligate intracellular protozoan parasite. A calcium signal appears to be essential for intracellular transduction during the active process of host cell invasion. We have looked for a Ca2+-transport ATPase in tachyzoites and found Ca2+-ATPase activity (11-22 nmol Pi liberated/mg protein/min) in the tachyzoite membrane fraction. This ATP-dependent activity was stimulated by Ca2+ and Mg2+ ions and by calmodulin, and was inhibited by pump inhibitors (sodium orthovanadate or thapsigargin). We used cytochemistry and X-ray microanalysis of cerium phosphate precipitates and immunolabelling to find the Ca2+, Mg2+-ATPase. It was located mainly in the membrane complex, the conoid, nucleus, secretory organelles (rhoptries, dense granules) and in vesicles with a high calcium concentration. Thus, Toxoplasma gondii possesses Ca2+-pump ATPase (Ca2+, Mg2+-ATPase) as do eukaryotic cells

Evaluation of a Strategy for Toxoplasma gondii Oocyst Detection in Water

Several recent outbreaks of toxoplasmosis were related to drinking water. We propose a strategy for Toxoplasma oocyst detection as part of an approach to detecting multiple waterborne parasites, including Giardia and Cryptosporidium spp., by the U.S. Environmental Protection Agency method with the same sample. Water samples are filtered to recover Toxoplasma oocysts and purified on a sucrose density gradient. Detection is based on PCR and mouse inoculation (bioassay) to determine the presence and infectivity of recovered oocysts. In an experimental seeding assay with 100 liters of deionized water, a parasite density of 1 oocyst/liter was successfully detected by PCR in 60% of cases and a density of 10 oocysts/liter was detected in 100% of cases. The sensitivity of the PCR assay varied from less than 10 to more than 1000 oocysts/liter, depending on the sample source. PCR was always more sensitive than mouse inoculation. This detection strategy was then applied to 139 environmental water samples collected over a 20-month period. Fifty-three samples contained PCR inhibitors, which were overcome in 39 cases by bovine serum albumin addition. Among 125 interpretable samples, we detected Toxoplasma DNA in 10 cases (8%). None of the samples were positive by mouse inoculation. This strategy efficiently detects Toxoplasma oocysts in water and may be suitable as a public health sentinel method

Prenatal diagnosis of congenital toxoplasmosis: A multicenter evaluation of different diagnostic parameters

OBJECTIVE: Our purpose was to evaluate different methods of diagnosing congenital toxoplasmosis prenatally by amniocentesis and cordocentesis. STUDY DESIGN: In a retrospective multicenter study, we investigated consecutive women who had seroconversion for Toxoplasma gondii during pregnancy and who underwent either amniocentesis or cordocentesis or both to obtain a prenatal diagnosis of fetal toxoplasmosis. Data were obtained from 122 patients recruited in 6 different European Toxoplasma reference centers. Infants born to these mothers were followed up until 1 year of age to confirm or exclude congenital toxoplasmosis. Sensitivity, specificity, positive predictive value, and negative predictive value were measured for the following parameters: (1) detection of the parasite in amniotic fluid by mouse inoculation, (2) detection of the parasite in amniotic fluid by in vitro cell culture, (3) detection of Toxoplasma deoxyribonucleic acid in amniotic fluid by a polymerase chain reaction assay, (4) detection of the parasite in fetal blood by mouse inoculation, (5) detection of specific immunoglobulin M antibodies in fetal blood, and (6) detection of specific immunoglobulin A antibodies in fetal blood. RESULTS: The polymerase chain reaction test performed on amniotic fluid had the highest level of sensitivity (81%) and also a high level of specificity (96%). The combination of the polymerase chain reaction test and mouse inoculation of amniotic fluid increased sensitivity to 91%. The sensitivity of immunoglobulins M and A in fetal blood was 47% and 38%, respectively. In congenitally infected fetuses a negative correlation was observed between positive serologic parameters and gestational age at the time of maternal infection and at prenatal diagnosis. CONCLUSION: Congenital toxoplasmosis is best predicted by prenatal examination with the combination of T gondii polymerase chain reaction and mouse inoculation of amniotic fluid. The role of cordocentesis in the diagnosis of congenital toxoplasmosis is limited.SCOPUS: cp.jinfo:eu-repo/semantics/publishe

Frequency of specific anti-toxoplasma gondii lgM, lgA and IgE in Colombian patients with acute and chronic ocular toxoplasmosis

We studied the frequency of specific anti-Toxoplasma IgM, IgA and IgE antibodies in serum of 28 immunocompetent Colombian patients, selected by ophthalmologists and with lesions that were compatible with ocular toxoplasmosis. Patients were classified in three groups: (i) group 1 consisted of ten patients with a first episode; (ii) group 2 with seven patients with a recurrence and (iii) group 3, consisted of eleven patients with chronic chorioretinal lesion without uveitis. We found that 10/28 (35%) of Colombian patients with ocular toxoplasmosis possessed at least one serological marker for Toxoplasma infection different from IgG. In group 1 (first episode), we found simultaneous presence of specific IgM plus IgA plus IgE in 1/10 (10%). In group 2 (recurrences) in 1/7(14%) we found IgM and IgA test positives and in 1/7(14%) we found IgM and IgE tests positives. In group 3 (toxoplasmic chorioretinal scar) the IgA serological test was positive in 2/11(18%). These results show that serum IgM or IgA or IgE can be present during recurrences