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At least 307 records · Page 17Linked to original sources
PubMed2005

Enhanced pro-inflammatory chemokine/cytokine response triggered by pathogenic Entamoeba histolytica : basis of invasive disease.

The virulence of Entamoeba histolytica is governed by adhesion/colonization in the gut which is mediated by a galactose specific lectin. Two morphologically identical but distinct species i.e. pathogenic E. histolytica and non-pathogenic E. dispar, can be differentiated by distinct epitopes in the lectin. Both species bind to colonic epithelial cells, but only E. histolytica infection induces an inflammatory response and subsequent pathogenesis. Thus, comparing the responses of the intestinal cells to pathogenic and non-pathogenic lectins is a point of interest. The pathogenic lectin causes cytolysis of epithelial and immune-competent cells. Our data (both qualitative and mRNA quantitation) indicate that the epithelial cells responded to E. histolytica lectin with an increased expression of pro-inflammatory IL-2, IL-6, IL-8, MIP-1alpha, MCP-1, RANTES, GROalpha and GMCSF as compared to E. dispar lectin. The pathogenic LCM induced a significant increase in intracellular calcium concentration, proliferative response and chemotaxis of lymphocytes from ALA patients as compared to non-pathogenic LCM. High RANTES and IL-6 were induced in patients' lymphocytes by pathogenic LCM, along with their receptors CCR5 and CD126 as compared to NP-LCM. The local release of such a complex network of cytokines/chemokines could explain the histopathology of E. histolytica infection. The comparative low levels of these chemokines/pro-inflammatory cytokines and high levels of anti-inflammatory IL-10 in response to non-pathogenic E. dispar could explain the absence of an acute inflammatory response and the disease process. The cytokines and chemokines may provide a mechanism for initiation, amplification or containment of inflammation during disease state.

Agglutination Tests↗
PubMed2000

Absence of lipophosphoglycan-like glycoconjugates in Entamoeba dispar.

Invasive amoebiasis is the result of infection of Entamoeba histolytica. The closely related Entamoeba dispar can colonize the human gut but does not cause invasive disease. In this study, E. dispar was analysed for the presence of the lipophosphoglycan-like (LPG) glycoconjugate known to be present on the cell surface of E. histolytica. E. dispar cells were radio-isotope labelled with [3H]galactose or [3H]inositol. The acidic glycoconjugates were extracted and analysed by hydrophobic chromatography over phenyl-Sepharose and by sodium dodecyl sulphate polyacrylamide gel electrophoresis. No LPG-like molecules could be identified in E. dispar in contrast to E. histolytica, suggesting that these molecules may be absent in the non-pathogenic species.

Animals↗
PubMed2004

Present characteristics of symptomatic Entamoeba histolytica infection in the big cities of Japan.

Medical records, for 2000 and 2001, of symptomatic amoebic patients who were treated at our hospitals in Tokyo, Yokohama and Osaka were studied retrospectively for the purpose of gathering epidemiological data on symptomatic Entamoeba histolytica infection. A total of 58 patients were treated. Fifty-five of them were male, and 96% of the male patients were Japanese. The mean age of patients was 44.9 years old, and 91% of patients contracted the disease in Japan. Fifty-six per cent of the male patients indicated that they were practising homosexuals, and 44% of the male patients denied these practices or left the question unanswered. The serum Treponema pallidum haemagglutination test was positive in 45% of the patients, and antibody to human immunodeficiency virus (HIV) was positive in 45%. Our study revealed that recent symptomatic E. histolytica infection almost exclusively afflicted middle-aged males in the big cities of Japan, that a majority of the patients were probably exposed to the causative organism during homosexual activity, and that an increasing number of patients will be co-infected with HIV.

AIDS Serodiagnosis↗
PubMed2005

[Amoebic infections of the lung and pleura].

INTRODUCTION: Pleuropulmonary involvement is the second most common extra-intestinal manifestation of entamoeba histolytica infection after liver abscess. CASE REPORT: We report 2 cases of pleuropulmonary disease occurring in two men aged 32 and 48 years following an episode of dysentery. Purulent pleural infection was noted in one case. In the other both lung and liver abscesses occurred. CONCLUSION: The diagnosis was confirmed by strongly positive serology in both cases. Treatment with metronidazole (1.5 g per day) for 15 days combined with pleural drainage led to a satisfactory outcome in both cases.

Adult↗
PubMed1980

Antiamebic amidines and sulfonamides of 5- and 6-amino-2,3-bis(4-alkyl-1-piperazinyl)quinoxalines.

A series of amidines and sulfonamides of 5- and 6-amino-2,3-bis(4-alkyl-1-piperazinyl)quinoxalines was synthesized and tested against cecal and hepatic forms of Entamoeba histolytica infections in rats and hamsters, respectively. Four compounds (5, 6, 8, and 9) were found to have acceptable activity against infections in both species but were too toxic to be considered for use in man.

Amebicides↗
PubMed1978

Bisamidines of 2,6-diaminoanthraquinone as antiamebic agents.

A series of bisamidines of 2,6-diaminoanthraquinone was synthesized and tested against cecal and hepatic forms of Entamoeba histolytica infections in rats and hamsters, respectively. A number of compounds were found to have good activity against infections in both species.

Amebiasis↗
PubMed2004

Effects of bisphosphonates on the growth of Entamoeba histolytica and Plasmodium species in vitro and in vivo.

The effects of a series of 102 bisphosphonates on the inhibition of growth of Entamoeba histolytica and Plasmodium falciparum in vitro have been determined, and selected compounds were further investigated for their in vivo activity. Forty-seven compounds tested were active (IC(50) < 200 microM) versus E. histolytica growth in vitro. The most active compounds (IC(50) approximately 4-9 microM) were nitrogen-containing bisphosphonates with relatively large aromatic side chains. Simple n-alkyl-1-hydroxy-1,1-bisphosphonates, known inhibitors of the enzyme farnesylpyrophosphate (FPP) synthase, were also active, with optimal activity being found with C9-C10 side chains. However, numerous other nitrogen-containing bisphosphonates known to be potent FPP synthase inhibitors, such as risedronate or pamidronate, had little or no activity. Several pyridine-derived bisphosphonates were quite active (IC(50) approximately 10-20 microM), and this activity was shown to correlate with the basicity of the aromatic group, with activity decreasing with increasing pK(a) values. The activities of all compounds were tested versus a human nasopharyngeal carcinoma (KB) cell line to enable an estimate of the therapeutic index (TI). Five bisphosphonates were selected and then screened for their ability to delay the development of amebic liver abscess formation in an E. histolytica infected hamster model. Two compounds were found to decrease liver abscess formation at 10 mg/kg ip with little or no effect on normal liver mass. With P. falciparum, 35 compounds had IC(50) values <200 microM in an in vitro assay. The most active compounds were also simple n-alkyl-1-hydroxy-1,1-bisphosphonates, having IC(50) values around 1 microM. Five compounds were again selected for in vivo investigation in a Plasmodium berghei ANKA BALB/c mouse suppressive test. The most active compound, a C9 n-alkyl side chain containing bisphosphonate, caused an 80% reduction in parasitemia with no overt toxicity. Taken together, these results show that bisphosphonates appear to be useful lead compounds for the development of novel antiamebic and antimalarial drugs.

Animals↗
PubMed1985

Interactions between trophozoites of Entamoeba histolytica and cells of the immune system.

The interaction between Entamoeba histolytica trophozoites and cells of the immune system was studied in vitro. Both immune as well as non-immune mononuclear cells (MNC) to some extent were capable of exerting a cytotoxic effect on E. histolytica trophozoites. Incorporation of immune serum directed against the trophozoites in the reaction mixture resulted in a marked increase in the killing capacity of MNC. Highest killing was observed (96.7 +/- 1.04%) with MNC obtained from animals immunized with fraction-I(F-I) of the crude amoebic extract in association with anti-F-I serum. This cytotoxic event was found to be independent of complement involvement and required very low antibody concentrations. This antibody-dependent cellular cytotoxicity against E. histolytica in vitro was found to correlate well with the results of experiments reported earlier by us and others where a high degree of protection has been shown after vaccination of animals with F-I followed by challenge with highly virulent strains of E. histolytica.

Animals↗
PubMed1987

Elicitation of protective immunity to Entamoeba histolytica--an experimental study.

Immunization of hamsters with plasma membrane (PM) antigens of virulent subline of axenic Entamoeba histolytica (NIH: 200 V) entrapped in multilamellar phosphatidyl choline liposomes conferred 100% protection to a subsequent intrahepatic amoebic challenge. In contrast, vaccination of hamsters with live amoebic trophozoites injected intradermally failed to protect any of the animals. The protected animals had significantly high levels of anti-PM anti-amoebic antibodies, cellular sensitization and macrophage-mediated antibody-dependent cytotoxicity against amoebic trophozoites. However, none of the intradermally immunized animals had anti-PM anti-amoebic antibodies at the time of challenge. Such animals also had significantly low macrophage-mediated antibody-dependent cellular cytotoxicity. The data indicate the potential prophylactic use of PM antigens against hepatic amoebic infection.

Amebiasis↗
PubMed2003

Short communication: Prevalence of Entamoeba histolytica and Entamoeba dispar in northern Ghana.

Since the redescription of the potentially invasive Entamoeba histolytica, separating it from the morphologically identical non-invasive Entamoeba dispar, there is a need for the reassessment of epidemiological data on amoebiasis. In this context we conducted a descriptive survey on the presence of E. histolytica and E. dispar in a rural area in northern Ghana. We found a high prevalence (39.8%) of the E. histolytica/E. dispar complex with microscopy, but E. histolytica and E. dispar-specific DNA amplification using real-time polymerase chain reaction identified only one E. histolytica case and revealed a considerably higher prevalence of E. dispar (82.8%).

Animals↗
PubMed1997

Sensitivity of Entamoeba histolytica and Entamoeba dispar patient isolates to human complement.

Twenty-one Entamoeba histolytica and 56 Entamoeba dispar patient isolates were investigated for their sensitivity to the classical and alternative pathway of human complement, E. histolytica and E. dispar patient isolates were differentiated by polymerase chain reaction and hexokinase isoenzyme typing. It was found that 90.3% (+/- 12.0%) of the trophozoites of E. histolytica were lysed after 30 min by the alternative pathway of complement in the presence of 50% human serum (19 isolates showed lysis rates higher than 80%), whereas E. dispar cells were less susceptible to the alternative pathway as 68.8% (+/- 28.2%) of lysis occurred. However, 23 of the E. dispar isolates were lysed between 100 and 80% (90.9% +/- 9.1%), demonstrating that about half of the tested E. dispar isolates were highly sensitive to complement lysis. Only 11 of the E. dispar isolates were proven to be ¿resistant' to the alternative pathway of complement and were lysed less than 40%. These results are in conflict to earlier publications, describing resistance of E. dispar to complement lysis (Hamelmann et al. 1992, 1993).

Animals↗