14 research outputs found
Evasion of immune responses by Trypanosoma cruzi, the etiological agent of Chagas disease
No full textInfection with the protozoan parasite Trypanosoma cruzi leads to Chagas disease, which affects millions of people in Latin America. Infection with T. cruzi cannot be eliminated by the immune system. A better understanding of immune evasion mechanisms is required in order to develop more effective vaccines. During the acute phase, parasites replicate extensively and release immunomodulatory molecules that delay parasite-specific responses mediated by T cells. This immune evasion allows the parasite to spread in the host. In the chronic phase, parasite evasion relies on its replication strategy of hijacking the TGF-β signaling pathway involved in inflammation and tissue regeneration. In this article, the mechanisms of immune evasion described for T. cruzi are reviewed
Apoptosis in parasites and parasite-induced apoptosis in the host immune system: a new approach to parasitic diseases
No full textApoptosis, a form of programmed cell death (PCD), has been described as essential for normal organogenesis and tissue development, as well as for the proper function of cell-renewal systems in adult organisms. Apoptosis is also pivotal in the pathogenesis of several different diseases. In this paper we discuss, from two different points of view, the role of apoptosis in parasitic diseases. The description of apoptotic death in three different species of heteroxenic trypanosomatids is reviewed, and considerations on the phylogenesis of apoptosis and on the eventual role of PCD on their mechanism of pathogenesis are made. From a different perspective, an increasing body of evidence is making clear that regulation of host cell apoptosis is an important factor on the definition of a host-pathogen interaction. As an example, the molecular mechanisms by which Trypanosoma cruzi is able to induce apoptosis in immunocompetent cells, in a murine model of Chagas' disease, and the consequences of this phenomenon on the outcome of the experimental disease are discussed
Ecotin-like serine peptidase inhibitor ISP1 of Leishmania major plays a role in flagellar pocket dynamics and promastigote differentiation
Get PDFLeishmania ISPs are ecotin-like natural peptide inhibitors of trypsin-family serine peptidases, enzymes that are absent from the Leishmania genome. This led to the proposal that ISPs inhibit host serine peptidases and we have recently shown that ISP2 inhibits neutrophil elastase, thereby enhancing parasite survival in murine macrophages. In this study we show that ISP1 has less serine peptidase inhibitory activity than ISP2, and in promastigotes both are generally located in the cytosol and along the flagellum. However, in haptomonad promastigotes there is a prominent accumulation of ISP1 and ISP2 in the hemidesmosome and for ISP2 on the cell surface. An L. major mutant deficient in all three ISP genes (Δisp1/2/3) was generated and compared with Δisp2/3 mutants to elucidate the physiological role of ISP1. In in vitro cultures, the Δisp1/2/3 mutant contained more haptomonad, nectomonad and leptomonad promastigotes with elongated flagella and reduced motility compared with Δisp2/3 populations, moreover it was characterized by very high levels of release of exosome-like vesicles from the flagellar pocket. These data suggest that ISP1 has a primary role in flagellar homeostasis, disruption of which affects differentiation and flagellar pocket dynamics
Measurements of the Lambda_b0 -> J/psi Lambda decay amplitudes and the Lambda_b0 polarisation in pp collisions at sqrt(s) = 7 TeV
Get PDFAn angular analysis of View the Λb0→J/ψΛ decays is performed using a data sample corresponding to 1.0 fb−11.0 fb−1 collected in pp collisions at s=7 TeV with the LHCb detector at the LHC. A parity violating asymmetry parameter characterising the View the Λb0→J/ψΛ decay of 0.05±0.17±0.070.05±0.17±0.07 and a View the Λb0 transverse production polarisation of 0.06±0.07±0.020.06±0.07±0.02 are measured, where the first uncertainty is statistical and the second systematic
Attention deficit hyperactivity disorder (ADHD) within a South Indian (Keralian) mainstream school context
No full textAttention Deficit Hyperactivity Disorder (ADHD) is a widely discussed special educational issue in Western contexts and developed countries. By contrast, limited information is available about ADHD in Eastern contexts and developing countries. In India in particular, the only available information is about the medical perspective of ADHD; little or no attention is given to social or educational perspectives. DSM IV criteria are the most commonly used standard assessment procedures. However, limited research is reported to discuss the potential cultural influences of this North American model. The present study examines the incidence and interpretation of ADHD within the context of five mainstream schools in Trivandrum, South India. It also explored cultural influences impact upon the cultural validity and reliability of DSM IV criteria when introduced into a South Indian context. In order to identify children with ADHD characteristics, culturally valid assessment tools such as behaviour checklist and behaviour rating scales, were developed from DSM IV (TR) symptoms criteria. Qualitative data was gathered from the five sample schools during the academic year of 2006-07 using a variety of methods including in-depth interviews (with 21 teachers), classroom observations (of 26 children), rating scale and document scrutiny. The case study method was adopted to gain in-depth information about the identified children. Informal interviews with parents (24) were also utilised to triangulate the information gathered from the school contexts. Qualitative data analysis techniques such as open coding and case analysis were used to assess children's behavioural characteristics and difficulties. The findings indicate that three percent of children (21) had ADHD characteristics within the sample schools. Some of the findings are consistent with the studies reported in Western contexts. There are also some contrasting results: a) most of the identified children had inattention rather than hyperactivity characteristics, b) a higher number of children with ADHD characteristics were from lower socio-economic backgrounds, c) teachers used coercive methods of physical punishments and sanctions as they interpreted the children's ADHD characteristics as a result of their lack of interest in learning. Most importantly, though DSM IV (TR) criteria are useful in identifying ADHD, two items of the 'symptoms' criteria were not identifiable within the present context of the sample schools. The findings suggest that socio-cultural factors do influence the validity and reliability of DSM IV criteria. The study has implications not only for further research but also for planning and policy making in the field of education for all. The conclusions suggest that an educational provision should be considered with regards to the varied and complex needs of children with special educational needs such as ADHD. Teacher education programmes should be enhanced with positive intervention strategies
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Immunity to Leishmania mexicana parasite
No full textBackground: Cutaneous Leishmaniasis caused by the Leishmania mexicana complex is associated with unpleasant or disfiguring lesions, for which there only limited treatment options. The life cycle of L. mexicana consists of two stages which involve different immune evasion mechanisms: promastigote and amastigote. Understanding parasitic interactions with host cells and developing a protective vaccine could improve the management and treatment of the disease
Phenolics with Leishmanicidal and Immunomodulatory Properties
Get PDFLa leishmanioisis permanece actualmente como un problema de salud pública que ha cobrado gran relevancia, sobre todo en países en vía de desarrollo, en cuya mayoría, la enfermedad es endémica. El incremento de reportes de fallo terapéutico por la aparición de cepas resistentes así como la severidad de los efectos adversos conocidos para los tratamientos actuales, han hecho imperativa la búsqueda de nuevos agentes antileishmaniales. En ésta búsqueda se ha establecido que, adicional al efecto parasitocida, un potencial inmunomodulador podría contribuir significativamente en la terapéutica contra leishmaniosis. Una observación importante, a través de los resultados relacionados con compuestos que poseen efecto inmunomodulador, es la actividad parasitocida selectiva contra la forma amastigote internalizada en macrófagos, ya que la acción contra promastigotes es prácticamente nula. No obstante, en la literatura se encuentran muy pocos ejemplos de este tipo de acciones aunque son muy interesantes. Por lo tanto, el presente trabajo muestra una revisión acerca de compuestos fenólicos con potencial antileishmanial, cuyo mecanismo sugerido es la inmunomodulación
Phenolics with Leishmanicidal and Immunomodulatory Properties
No full textLa leishmanioisis permanece actualmente como un problema de salud pública que ha cobrado gran relevancia, sobre todo en países en vía de desarrollo, en cuya mayoría, la enfermedad es endémica. El incremento de reportes de fallo terapéutico por la aparición de cepas resistentes así como la severidad de los efectos adversos conocidos para los tratamientos actuales, han hecho imperativa la búsqueda de nuevos agentes antileishmaniales. En ésta búsqueda se ha establecido que, adicional al efecto parasitocida, un potencial inmunomodulador podría contribuir significativamente en la terapéutica contra leishmaniosis. Una observación importante, a través de los resultados relacionados con compuestos que poseen efecto inmunomodulador, es la actividad parasitocida selectiva contra la forma amastigote internalizada en macrófagos, ya que la acción contra promastigotes es prácticamente nula. No obstante, en la literatura se encuentran muy pocos ejemplos de este tipo de acciones aunque son muy interesantes. Por lo tanto, el presente trabajo muestra una revisión acerca de compuestos fenólicos con potencial antileishmanial, cuyo mecanismo sugerido es la inmunomodulación
