Pathogenesis of infection byEntamoeba histolytica |
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Authors: | Devinder Sehgal Alok Bhattacharya Sudha Bhattacharya |
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Institution: | (1) School of Life Sciences, Jawaharlal Nehru University, 110067 New Delhi, India;(2) School of Environmental Sciences, Jawaharlal Nehru University, 110067 New Delhi, India |
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Abstract: | Entamoeba histolytica, a protozoan parasite, is the etiologic agent of amoebiasis in humans. It exists in two forms—the trophozoite which is the
active, dividing form, and the cyst which is dormant and can survive for prolonged periods outside the host. In most infected
individuals the trophozoites exist as commensals. In a small percentage of infections, the trophozoites become invasive and
penetrate the intestinal mucosa, causing ulcers. The trophozoites may reach other parts of the body—mainly liver, where they
cause tissue necrosis, leading to lifethreatening abscesses. It is thought that pathogenesis of infection byEntamoeba histolytica is governed at several levels, chief among them are (i) adherence of trophozoite to the target cell, (ii) lysis of target
cell, and (iii) phagocytosis of target cell. Several molecules which may be involved in these processes have been identified.
A lectin inhibitable by galactose and N-acetyl-D-galactosamine is present on the trophozoite surface. This is implicated in
adherence of trophozoite to the target cell. Various amoebic poreforming proteins are known, of which 5kDa protein (amoebapore)
has been extensively studied. These can insert into the lipid bilayers of target cells, forming ion-channels. The phagocytic
potential of trophozoites is directly linked to virulence as measured in animal models. Factors like association of bacteria
with trophozoites also influence virulence. Thus, pathogenesis is determined by multiple factors and a unifying picture taking
into account the relative contributions of each factor is sought. Recent technical advances, which includes the development
of a transfection system to introduce genes into trophozoites, should help to understand the mechanism of pathogenesis in
amoebiasis. |
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Keywords: | Entamoeba histolytica pathogenesis amoebiasis |
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