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PubMed2006

Proteomic analysis of the eukaryotic parasite Encephalitozoon cuniculi (microsporidia): a reference map for proteins expressed in late sporogonial stages.

The microsporidian Encephalitozoon cuniculi is a unicellular obligate intracellular parasite considered as an emerging opportunistic human pathogen. The differentiation phase of its life cycle leads to the formation of stress-resistant spores. The E. cuniculi genome (2.9 Mbp) having been sequenced, we undertook a descriptive proteomic study of a spore-rich cell population isolated from culture supernatants. A combination of 2-DE and 2-DE-free techniques was applied to whole-cell protein extracts. Protein identification was performed using an automated MALDI-TOF-MS platform and a nanoLC-MS/MS instrument. A reference 2-DE map of about 350 major spots with multiple isoforms was obtained, and for the first time in microsporidia, a large set of unique proteins (177) including proteins with unknown function in a proportion of 25.6% was identified. The data are mainly discussed with reference to secretion and spore structural features, energy and carbohydrate metabolism, cell cycle control and parasite survival in the environment.

Amino Acids↗
PubMed1997

Ascariasis and hookworm.

Ascariasis and hookworm (ancylostomiasis) remain the most common intestinal nematodes in the world with significant economic, social, and medical impact. An understanding of the transmission and pathogenesis of ascariasis and hookworm are necessary to recognize their clinical manifestations and to manage the pulmonary sequelae of infection. Transmission occurs predominantly in the tropics and rural areas where there is suboptimal sanitation, personal hygiene, and education regarding these parasites. Ascariasis generally occurs through hand-to-mouth ingestion of agricultural products or food contaminated with parasite eggs. Hookworm is transmitted through larval penetration of the skin. Larval pulmonary migration generally is asymptomatic. However, symptomatic pulmonary disease may occur with fever, cough, chest pain, hemoptysis, dyspnea, and wheezing due to (1) Loffler's syndrome, (2) the effects of larval tissue migration, (3) airway reactivity or bronchospasm, (4) infectious bacterial complications from parasitic migration and associated aspiration, and rarely (5) chronic eosinophilic pneumonia, transdiaphragmatic penetration, or symptoms of upper airway obstruction. Clinical evaluation shows pulmonary opacities on chest radiograph, peripheral blood eosinophilia, and larvae in respiratory or gastric secretions. Symptomatic treatment may be necessary with bronchodilators and systemic steroids or antibiotics for bacterial complications. The drug of choice is mebendazole (Vermox) 100 mg twice a day for 3 days. Alternatives include a single dose of pyrantel pamoate (Antiminth) 11 mg/kg (maximum dose, 1 g) or albendazole (Zentel) 400 mg orally once. Invermectin (Mectizan) is available through the World Health Organization, and, in the United States, through the manufacturer on a compassionate-use basis. Ivermectin is as effective as currently available drugs against Ascaris but shows only partial efficacy against hookworms, which infest humans. Preventive measures, improvement of sanitary facilities, education, and school screening may be important in the endemic areas to control these parasitic infections.

Animals↗
PubMed2002

Transcriptional cosuppression of yeast Ty1 retrotransposons.

Cosuppression, the silencing of dispersed homologous genes triggered by high copy number, may have evolved in eukaryotic organisms to control molecular parasites such as viruses and transposons. Ty1 retrotransposons are dispersed gene repeats in Saccharomyces cerevisiae, where no cosuppression has been previously observed. Ty1 elements are seemingly expressed undeterred to a level as high as 10% of total mRNA. Using Ty1-URA3 reporters and negative selection with 5-fluoroorotic acid, it is shown that Ty1 genes can undergo transcriptional cosuppression that is independent of DNA methylation and polycomb-mediated repression. Expression of Ty1-related genes was shown to be in one of two states, the coexpressed state with all Ty1-related genes transcribed or the cosuppressed state with all Ty1-related genes shut off, without uncoordinated or mosaic expression in any individual cell. Rapid switches between the two states were observed. A high copy number of Ty1 elements was shown to be required for the initiation of Ty1 homology-dependent gene silencing, implying that Ty1 gene expression is under negative feedback control. Ty1 transcriptional repressors facilitated the onset of Ty1 cosuppression, and the native Ty1 promoters were required for Ty1 cosuppression, indicating that Ty1 cosuppression occurs at the transcriptional level.

Base Sequence↗
PubMed2003

Arbuscular mycorrhizal fungi-parasite-host interaction for the control of Striga hermonthica (Del.) Benth. in sorghum [Sorghum bicolor (L.) Moench].

Five Glomus species (G. intraradices, G. albidum, G. mosseae, G. fasciculatum, and G. etunicatum) were compared against a check [without arbuscular mycorrhizal (AM) fungi, plus Striga] and control (without AM fungi or Striga) treatments for the control of Striga in a tolerant sorghum variety (War-wara bashi) in an experiment carried out in 12-cm-diameter clay pots. The experiment was carried out in a controlled growth chamber. G. mosseae significantly reduced the number of Striga emerging per plant, increased plant growth, shoot and total dry matter yield of sorghum, did not affect the root dry matter compared with the other AM fungi species, but had a comparable effect to the control treatment. All the AM fungi except G. mosseae, and also the Striga-infested treatment, increased the root:shoot ratio compared to the control treatment. The percent reduction (62%) of Striga emergence after G. mosseae inoculation resulted in about a 30% increase in total dry matter yield of sorghum over the control, while the total loss in dry matter yield of sorghum due to Striga infestation was 36%. Root colonization of sorghum by AM fungi was highest for G. mosseae (44%) followed by G. intraradices (24%) and G. albidum (23%) then G. fasciculatum (18%), with the lowest recorded for G. etunicatum (14%). No colonization of Striga roots was observed. The potential of AM fungi to reduce or to compensate for Striga infestation could be important for soil management, especially in the tropics, and for the reduction of Striga-resistant varieties of sorghum which are mycorrhiza-responsive.

Fungi↗
PubMed2004

Intracellular growth of Trypanosoma cruzi in cardiac myocytes is inhibited by cytokine-induced nitric oxide release.

The effect of interleukin-1beta (IL-1beta), tumor necrosis factor alpha (TNF-alpha), and gamma interferon (IFN-gamma) on Trypanosoma cruzi multiplication and nitric oxide (NO) production in cardiac myocytes was investigated. Cardiac myocyte cultures were obtained from neonatal Wistar rat hearts, infected with T. cruzi, and treated with IL-1beta, TNF-alpha, IFN-gamma, or N-monomethyl-L-arginine (L-NAME) for 72 h. Parasite growth was calculated from the number of infected cells in Giemsa-stained smears. Nitric oxide production was determined with the Griess reagent. Inducible nitric oxide synthase (iNOS) expression by cardiac myocytes was detected by Western blot. The results showed that the percentages of cardiac myocytes containing T. cruzi amastigotes in cytokine-treated cultures were significantly lower than in nontreated cultures. The addition of L-NAME reversed the inhibitory effect on parasite growth of IL-1beta and TNF-alpha but not of IFN-gamma. Nitrite levels released by T. cruzi-infected and noninfected cardiac myocyte cultures after 72 h of stimulation with IL-1beta were significantly higher than those produced upon treatment with TNF-alpha, IFN-gamma, or medium alone, regardless of the infection status. Nitrite levels in TNF-alpha-stimulated infected cultures were significantly higher than in untreated infected cultures and TNF-alpha-treated noninfected cultures. L-NAME inhibited IL-1beta- but not TNF-alpha-induced NO production, indicating the presence of iNOS-dependent and iNOS-independent mechanisms for NO formation in this experimental system. iNOS expression was detected in infected and noninfected cardiac myocytes stimulated with IL-1 beta and TNF-alpha but not with IFN-gamma. These results suggest an important role for cardiac myocytes and locally secreted cytokines in the control of parasite multiplication in T. cruzi-induced myocarditis.

Animals↗
PubMed2003

Infection pattern and immune response in the spleen and liver of BALB/c mice intracardially infected with Leishmania donovani amastigotes.

Intracardial inoculation of BALB/c mice with Leishmania donovani amastigotes induced progressive visceral leishmaniasis (VL) with increasing splenic parasite load when followed upto 4-month postinfection period. In contrast, the liver parasite load reached maximum around 2-month postinfection period following which it started declining. The infection pattern differed somewhat from the earlier reports on mouse model of VL induced by intravenous inoculation of parasites with respect to the duration as well as magnitude of parasite burden in the organs (liver and spleen) and associated hepatosplenomegaly. Immunosuppression in mice with progressive VL was manifested in the form of impairment of proliferative response of the splenic mononuclear cells (SPMC) to in vitro stimulation with leishmanial antigen or the mitogen concanavalin A (ConA), although ConA stimulated cells were found to be capable of IL-2 and IFN-gamma synthesis. Differential expression of activating (IL-2, IFN-gamma and TNF-alpha) as well as deactivating (IL-4 and TGF-beta) cytokines was demonstrable in the spleen and liver of animals during the course of infection. Further, the synthesis of inducible nitric oxide synthase (iNOS) enzyme increased considerably in the liver as well as in the spleen of 4-month infected animal with parallel increase in the transcripts of the iNOS activating cytokines IFN-gamma and TNF-alpha. The temporal variation in the organ specific immune response could be related to the differential control of parasite burden in the liver and spleen of the infected host.

Animals↗
PubMed1993

Analysis of the human antibody response to thrombospondin-related anonymous protein of Plasmodium falciparum.

Thrombospondin-related anonymous protein (TRAP) of the malaria parasite Plasmodium falciparum shares two sequence motifs with other proteins which possess adhesive properties. Recently, findings indicate that TRAP is an antigen which contributes to antisporozoite immunity. We have cloned and expressed the TRAP coding sequences in Escherichia coli to investigate the human humoral immune response against this protein in a region of malaria endemicity of West Africa characterized by a seasonal transmission. Our results show that antibodies against TRAP are present in infected individuals. The anti-TRAP antibodies were analyzed in both a longitudinal and a prospective study. The longitudinal analysis shows seasonal fluctuations of the levels of specific antibodies as well as age-dependent quantitative differences. The immune response is long-lived in most of the adults and some of the older children but short-lived in young children. More importantly, the prospective analysis suggests that the presence of anti-TRAP antibodies in older children before the beginning of malaria transmission correlates with the subsequent control of parasite densities.

Adolescent↗