Host–Parasite interactions in Entamoeba histolytica and Entamoeba dispar: what have we learned from their genomes?

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Abstract

Invasive amoebiasis caused by Entamoeba histolytica is a major global health problem. Virulence is a rare outcome of infection, occurring in fewer than 1 in 10 infections. Not all strains of the parasite are equally virulent, and understanding the mechanisms and causes of virulence is an important goal of Entamoeba research. The sequencing of the genome of E. histolytica and the related avirulent species Entamoeba dispar has allowed whole-genome-scale analyses of genetic divergence and differential gene expression to be undertaken. These studies have helped elucidate mechanisms of virulence and identified genes differentially expressed in virulent and avirulent parasites. Here, we review the current status of the E. histolytica and E. dispar genomes and the findings of a number of genome-scale studies comparing parasites of different virulence.

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Amoebiasis.

Samuel L. Stanley (2003)

Amoebiasis is the second leading cause of death from parasitic disease worldwide. The causative protozoan parasite, Entamoeba histolytica, is a potent pathogen. Secreting proteinases that dissolve host tissues, killing host cells on contact, and engulfing red blood cells, E histolytica trophozoites invade the intestinal mucosa, causing amoebic colitis. In some cases amoebas breach the mucosal barrier and travel through the portal circulation to the liver, where they cause abscesses consisting of a few E histolytica trophozoites surrounding dead and dying hepatocytes and liquefied cellular debris. Amoebic liver abscesses grow inexorably and, at one time, were almost always fatal, but now even large abscesses can be cured by one dose of antibiotic. Evidence that what we thought was a single species based on morphology is, in fact, two genetically distinct species--now termed Entamoeba histolytica (the pathogen) and Entamoeba dispar (a commensal)--has turned conventional wisdom about the epidemiology and diagnosis of amoebiasis upside down. New models of disease have linked E histolytica induction of intestinal inflammation and hepatocyte programmed cell death to the pathogenesis of amoebic colitis and amoebic liver abscess.

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The genome of the protist parasite Entamoeba histolytica.

Brendan Loftus, Iain Anderson, Rob Davies … (2005)

Entamoeba histolytica is an intestinal parasite and the causative agent of amoebiasis, which is a significant source of morbidity and mortality in developing countries. Here we present the genome of E. histolytica, which reveals a variety of metabolic adaptations shared with two other amitochondrial protist pathogens: Giardia lamblia and Trichomonas vaginalis. These adaptations include reduction or elimination of most mitochondrial metabolic pathways and the use of oxidative stress enzymes generally associated with anaerobic prokaryotes. Phylogenomic analysis identifies evidence for lateral gene transfer of bacterial genes into the E. histolytica genome, the effects of which centre on expanding aspects of E. histolytica's metabolic repertoire. The presence of these genes and the potential for novel metabolic pathways in E. histolytica may allow for the development of new chemotherapeutic agents. The genome encodes a large number of novel receptor kinases and contains expansions of a variety of gene families, including those associated with virulence. Additional genome features include an abundance of tandemly repeated transfer-RNA-containing arrays, which may have a structural function in the genome. Analysis of the genome provides new insights into the workings and genome evolution of a major human pathogen.

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Entamoeba histolytica cysteine proteases cleave the MUC2 mucin in its C-terminal domain and dissolve the protective colonic mucus gel.

Kris Chadee, Gunnar Hansson, Martin E. Lidell … (2006)

In order for the protozoan parasite Entamoeba histolytica (E.h.) to cause invasive intestinal and extraintestinal infection, which leads to significant morbidity and mortality, it must disrupt the protective mucus layer by a previously unknown mechanism. We hypothesized that cysteine proteases secreted from the amoeba disrupt the mucin polymeric network, thereby overcoming the protective mucus barrier. The MUC2 mucin is the major structural component of the colonic mucus gel. Heavily O-glycosylated and protease-resistant mucin domains characterize gel-forming mucins. Their N- and C-terminal cysteine-rich domains are involved in mucin polymerization, and these domains are likely to be targeted by proteases because they are less glycosylated, thereby exposing their peptide chains. By treating recombinant cysteine-rich domains of MUC2 with proteases from E.h. trophozoites, we showed that the C-terminal domain was specifically targeted at two sites by cysteine proteases, whereas the N-terminal domain was resistant to proteolysis. The major cleavage site is predicted to depolymerize the MUC2 polymers, thereby disrupting the protective mucus gel. The ability of the cysteine proteases to dissolve mucus gels was confirmed by treating mucins from a MUC2-producing cell line with amoeba proteases. These findings suggest a major role for E.h. cysteine proteases in overcoming the protective mucus barrier in the pathogenesis of invasive amoebiasis. In this report, we identify a specific cleavage mechanism used by an enteric pathogen to disrupt the polymeric nature of the mucin gel.

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Author and article information

Journal

Journal ID (nlm-ta): Parasite Immunol

Journal ID (iso-abbrev): Parasite Immunol

Journal ID (publisher-id): pim

Title: Parasite Immunology

Publisher: Blackwell Publishing Ltd (Oxford, UK )

ISSN (Print): 0141-9838

ISSN (Electronic): 1365-3024

Publication date (Print): February 2012

Volume: 34

Issue: 2-3

Pages: 90-99

Affiliations

simpleInstitute of Integrative Biology, University of Liverpool Crown Street, Liverpool, UK

Author notes

Gareth D. Weedall, Institute of Integrative Biology, University of Liverpool, Crown Street, Liverpool L69 7ZB, UK (e-mail: gweedall@ 123456liv.ac.uk ).

Re-use of this article is permitted in accordance with the Terms and Conditions set out at http://wileyonlinelibrary.com/onlineopen#OnlineOpen_Terms.

Article

DOI: 10.1111/j.1365-3024.2011.01325.x

PMC ID: 3378717

PubMed ID: 21810102

SO-VID: 65b0fb7d-7c22-4226-9f78-3a303ab60def

License:

Re-use of this article is permitted in accordance with the Creative Commons Deed, Attribution 2.5, which does not permit commercial exploitation.

Host–Parasite interactions in Entamoeba histolytica and Entamoeba dispar: what have we learned from their genomes?

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Abstract

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Gamma Delta T cells

Most cited references 100

Amoebiasis.

The genome of the protist parasite Entamoeba histolytica.

Entamoeba histolytica cysteine proteases cleave the MUC2 mucin in its C-terminal domain and dissolve the protective colonic mucus gel.

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