Immunopathology of Entamoeba histolytica infections

Toxicological Evaluation of Kaempferol and Linearolactone as Treatments for Amoebic Liver Abscess Development in Mesocricetus auratus

Several studies with kaempferol (KP) and linearolactone (LL) have demonstrated their antiparasitic activity. However, the toxicity of these treatments is unknown. Therefore, this study aimed to evaluate the possible toxicological effects of intraperitoneal (i.p.) administration of KP or LL on the amoebic liver abscess model (ALA) in Mesocricetus auratus. An ALA was induced in male hamsters with 1.5 × 105Entamoeba histolytica (E. histolytica) trophozoites inoculated in the left hepatic lobe. The lesion evolved for 4 days, and then KP (5 mg/kg body weight/day) or LL (10 mg/kg body weight/day) was administered for 4 consecutive days. Then, magnetic resonance imaging (MRI), paraclinical analyses, and necropsy for histopathological evaluation were performed. There was similar ALA inhibition by KP (19.42%), LL (28.16%), and metronidazole, the antiamoebic control (20.87%) (p ≤ 0.05, analysis of variance [ANOVA]). There were hepatic and renal biochemical alterations in all treatment groups, mainly for KP (aspartate aminotransferase: 347.5 ± 37.5 U/L; blood urea nitrogen: 19.4 ± 1.9 g/dL; p ≤ 0.05, ANOVA). Lesions found in the organs were directly linked to the pathology. In conclusion, KP and LL decreased ALA development and exerted fewer toxicological effects compared with metronidazole. Therefore, both compounds exhibit therapeutic potential as an alternative treatment of amoebiasis caused by E. histolytica. However, additional clinical studies in different contexts are required to reaffirm this assertion.

Intestinal parasitism in pediatric oncology children receiving chemotherapy: unexpected low prevalence

Background

Children with underlying malignancies and those on chemotherapy are at risk for having intestinal parasitic infections, which can lead to a severe course and death. This cross-sectional study was done to assess the copro-parasitological and copro-molecular prevalence of entero-parasites in children with malignancies and those on chemotherapy.

Procedure

Stool samples were collected from 137 Egyptian hospitalized cancerous children with different malignancies in the National Cancer Institute, and receiving chemotherapy.

Faecal samples were examined microscopically. Genomic copro-DNA was extracted from fecal samples and amplified by 3 separate nPCR assays targeting Cryptosporidium, G. intestinalis and Entamoeba histolytica complex.

Result

The overall prevalence of enteroparasites was 6.6 % (9 cases). Only Giardia copro-DNA was encountered in 2 (1.4%) faecal samples of patients. Coproscopy detected parasites in 7 cases: Blastocystis spp. in 5 cases (3.6%), Hymenolepis nana in 1 case (0.7%) and Ascaris lumbericoides in 1 case (0.7%).

Conclusion

Low prevalence may be due to patient's use of prophylactic anti-parasitic and anti-fungal drugs, a standard protocol, basic hygienic practices and good nursing all of which are preventive against enteroparasites transmission. Among studied variables only diarrhoeic individuals who had a solid tumor, and soft/liquid stool with mucus and blood were predictors of intestinal parasitism.

Parasites

Parasites are an important cause of human disease worldwide. The clinical severity and outcome of parasitic disease is often dependent on the immune status of the host. Specific parasitic diseases discussed in this chapter are amebiasis, giardiasis, cryptosporidiosis, cyclosporiasis, cystoisosporiasis, microsporidosis, granulomatous amebic encephalitis, toxoplasmosis, leishmaniasis, Chagas disease, malaria, babesiosis, strongyloidiasis, and scabies.

Ethnomedicinal Evaluation of Medicinal Plants Used against Gastrointestinal Complaints

Aim of the present study was to document ethnomedicinal plants used against gastrointestinal complaints in five selected remote regions of Pakistan and to select potential medicinal plants for further in vitro and in vivo investigation. Data on ethnomedicinal plants and ethnographic profile of respondents was documented using semistructured questionnaires. The present study revealed utilization of 52 medicinal plants for the treatment of different gastrointestinal infections in studied regions. Apiaceae was the most dominant family reported to be used for the treatment of these infections (4 plants). Among all the plant parts fruit (24%), whole plants and leaves (23% each) were the most preferred plant parts used by the healers. Dosage of recipe was found to be related with the age of the patient. Highest degree of informant consensus was reported for vomiting, nausea (0.92 each), abdominal pain (0.9), and diarrhea (0.89). Withania coagulans scored highest FL value (86%) followed by Mentha longifolia and Melia azadirachta ranked second with FL value (75% each). Young generation was found to possess little traditional knowledge about utilizing plant recipes against these infections. Plants with high Fic and FL values should be subjected for further phytochemical and pharmacological investigation for scientific validation.

The immunology of parasite infections in immunocompromised hosts

Immune compromise can modify the severity and manifestation of some parasitic infections. More widespread use of newer immnosuppressive therapies, the growing population of individuals with immunocompromised states as well as the prolonged survival of these patients have altered the pattern of parasitic infection. This review article discusses the burden and immunology of parasitic infections in patients who are immunocompromised secondary to congenital immunodeficiency, malnutrition, malignancy, and immunosuppressive medications. This review does not address the literature on parasitic infections in the setting of HIV-1 infection.

Effect of Zinc-Treated Entamoeba histolytica on the Human Polymorphonuclear Respiratory Burst

One of the mechanisms that Entamoeba histolytica uses to evade host immune response is inhibition of the polymorphonuclear (PMN) leukocyte respiratory burst. In studies previously conducted in a model used in our laboratory, we observed that when treating trophozoites with different zinc concentrations certain amebic functions are inhibited while significantly limiting development of hepatic abscess in golden hamsters (Mesocricetus aureatus). We carried out an in vitro study using a chemoluminescent method to assess the effect zinc-treated amebic trophozoites exercise on respiratory burst in human PMNs. We measured response of PMNs incubated with E. histolytica trophozoites from cultures with TYI-S33 medium alone and with zinc. Zinc concentrations between 0.1 and 1.0 mM did not affect amebic trophozoite viability, and PMNs in contact with these in a zinc-free medium had an oxidative response similar to that obtained with zymosan and significantly greater (p <0.05) than that generated by cells co-incubated with amebas cultured in TYI-S33 medium alone. These results suggest that zinc alters the amebic mechanism that inhibits the oxidative function of human polymorphonuclear leukocyte.

Amebic liver abscess

Amebic liver abscess is the most common extraintestinal manifestation of infection with Entamoeba histolytica, and it is associated with significant morbidity and mortality. In this article the most recent available information is reviewed relating to epidemiology, pathogenesis, presentation, diagnosis, and treatment. We reviewed thousands of cases of amebic liver abscess in the medical literature and present that information as it pertains to mortality, gender, anatomic location of abscesses, and clinical signs and symptoms.

The tumor necrosis factor alpha-stimulating region of galactose-inhibitable lectin of Entamoeba histolytica activates gamma interferon-primed macrophages for amebicidal activity mediated by nitric oxide

Entamoeba histolytica adheres via galactose-lectin (Gal-lectin) to human colonic mucins and intestinal epithelial cells as a prerequisite to amebic invasion. Native Gal-lectin is a protective antigen in the gerbil model of amebiasis. Amino acids 596 to 1082 of Gal-lectin mediate E. histolytica adherence to target cells and stimulate tumor necrosis factor alpha (TNF-alpha) production by naive murine bone marrow macrophages (BMM). Resistance to amebiasis requires an effective cell-mediated immune response against E. histolytica trophozoites mediated by nitric oxide (NO) released from activated macrophages. Herein, we determine whether the TNF-alpha-stimulating region of Gal-lectin can activate gamma interferon (IFN-gamma)-primed BMM for NO production and amebicidal activity. Native Gal-lectin (100 to 500 ng/ml) stimulated TNF-alpha and inducible nitric oxide synthase (iNOS) mRNA expression in IFN-gamma-primed BMM as did lipopolysaccharide (100 ng/ml). Primed BMM produced TNF-alpha and NO in response to Gal-lectin in a dose-dependent manner. Antilectin monoclonal antibody IG7, which recognizes a domain (amino acids 596 to 818) of the TNF-alpha mRNA-stimulating region of Gal-lectin, specifically inhibited TNF-alpha and iNOS mRNA induction and TNF-alpha and NO production by primed BMM in response to Gal-lectin (100 ng/ml). Simultaneous treatment of BMM with IFN-gamma and Gal-lectin (100 ng/ml) activated the cells to kill E. histolytica trophozoites, whereas IFN-gamma treatment alone had no effect. In the presence of monoclonal antibody 1G7 or aminoguanidine (an iNOS inhibitor), NO production and amebicidal activity were inhibited >80%. These results suggest that the TNF-alpha-stimulating region of native Gal-lectin is a potent stimulus of IFN-gamma-primed BMM for NO production, which is essential for host defense against amebiasis.

Identification of the galactose-adherence lectin epitopes of Entamoeba histolytica that stimulate tumor necrosis factor-alpha production by macrophages

The 170-kDa subunit of the galactose-adherence lectin (Gal-lectin) of Entamoeba histolytica mediates adherence to human colonic mucins and intestinal epithelium as a prerequisite to amebic invasion. The Gal-lectin is an immunodominant molecule and a protective antigen in the gerbil model of amebiasis. Tumor necrosis factor alpha (TNF-alpha) produced by activated macrophages enhances nitric oxide-dependent cytotoxicity in host defense against E. histolytica. The purpose of this study was to identify the Gal-lectin epitopes which stimulate TNF-alpha production by macrophages. Murine bone marrow-derived macrophages (BMMs) exposed to Gal-lectin (100-500 ng/ml) stimulated stable expression of TNF-alpha mRNA (8-fold increase) and TNF-alpha production similar to that of lipopolysaccharide-stimulated cells (100 ng/ml). Polyclonal anti-lectin serum specifically inhibited TNF-alpha mRNA induction in response to the Gal-lectin but not to lipopolysaccharide. Anti-lectin monoclonal antibodies 8C12, H85 and 1G7, which recognize nonoverlapping epitopes of the cysteine-rich region of the 170-kDa heavy subunit, inhibited both amebic adherence to mammalian cells and Gal-lectin-stimulated TNF-alpha mRNA expression by BMMs,but monoclonal antibody 7F4 did neither. As these inhibitory antibodies map to amino acids 596-1082 of the 170-kDa Gal-lectin, our results have identified the functional region that mediates amebic adherence and TNF-alpha mRNA induction in BMMMs; thus, this region of the Gal-lectin is a subunit vaccine candidate.

Tumor necrosis factor alpha augments nitric oxide-dependent macrophage cytotoxicity against Entamoeba histolytica by enhanced expression of the nitric oxide synthase gene

Nitric oxide (NO measured as nitrite, NO2-) is the major effector molecule produced by activated macrophages for in vitro cytotoxicity against Entamoeba histolytica trophozoites. In this study, we determine whether tumor necrosis factor alpha (TNF-alpha) produced by activated bone marrow-derived macrophages (BMM) is involved in the induction of the inducible NO synthase gene (mac-NOS) for NO-dependent amebicidal activity. TNF-alpha alone did not directly induce macrophage NO2- production to kill amebae; however, in combination with increasing concentrations of TNF-alpha and gamma interferon (IFN-gamma), BMM amebicidal activity and NO2- production progressively increased and showed a significant linear correlation. Antiserum to TNF-alpha and the NO synthase inhibitor NG-monomethyl L-arginine (L-NMMA) inhibited the synergistic effects of TNF-alpha and IFN-gamma. BMM activated with increasing concentrations of lipopolysaccharide (LPS) and IFN-gamma showed a significant linear correlation between TNF-alpha release and NO2- production. Antiserum to TNF-alpha suppressed TNF-alpha release, NO2- production, and amebicidal activity by 93, 53, and 86%, respectively. L-NMMA diminished NO2- production by 74% and macrophage amebicidal activity by 83% but had no effect on TNF-alpha release. Quantification by Northern (RNA) blot analyses demonstrated that IFN-gamma in combination with TNF-alpha or LPS increased markedly the accumulation of mac-NOS and TNF-alpha mRNAs in a time-dependent manner with a concomitant increase in NO and TNF-alpha production. Peak induction of mac-NOS occurred after 24 h, whereas TNF-alpha mRNA was rapidly expressed after 4 h and remained stable for 48 h. Taken together, these data argue that TNF-alpha augments NO-dependent macrophage cytotoxicity against E. histolytica via elevated levels of mac-NOS mRNA expression which may be associated with the accumulation of TNF-alpha mRNA.

Amebiasis

Entamoeba histolytica, the causative agent of amebiasis, was first described in 1875. Although a large number of people throughout the world are infected with this organism, only a small percentage will develop clinical symptoms. Morbidity and mortality due to E. histolytica vary from area to area and person to person. Recent findings have suggested that there are pathogenic and nonpathogenic strains of E. histolytica that can be differentiated by isoenzyme (zymodeme) analysis, monoclonal antibodies, and DNA probes. Whether pathogenicity is a genotypic trait or can be changed by environmental influences has not been resolved. Exchange of genetic material between strains of amebae can influence zymodeme patterns. Currently, detection of E. histolytica infections depends on examinations for ova and parasites and on serologic tests; however, the development of monoclonal antibodies and DNA probes specific for pathogenic zymodemes may be beneficial for clinical laboratory testing and therapeutic decisions when approved tests become available. A better understanding of the mechanisms of pathogenicity at the molecular level is evolving and should promote the development of vaccines and better target selection for therapeutic agents.

Missing infections in AIDS

In north America and Europe, the opportunistic infections from which patients with acquired immune deficiency syndrome (AIDS) frequently suffer are Pneumocystis carinii pneumonia and Mycobacterium avium-intracellulare: in central Africa these infections are uncommon or non-existent. Serious infections with Entamoeba histolytica and Strongyloides stercoralis would be expected to occur in AIDS patients: they do not. Falciparum malaria might be expected to interact with HIV infection: it does not. The epidemiology and pathophysiology of these infections are discussed with respect to HIV co-infection.