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A surface amebic cysteine proteinase inactivates interleukin-18
Xuchu Que1, Soo-Hyun Kim, Mohammed Sajid
1Department of Pathology, University of California, San Diego, California 92103, USA.
Infection and Immunity
|February 22, 2003
Summary
Entamoeba histolytica proteinases inactivate interleukin-18 (IL-18), a key immune signaling molecule. This parasite mechanism may block host inflammatory responses, contributing to amebiasis severity.
Area of Science:
- Immunology
- Parasitology
- Molecular Biology
Background:
- Amebiasis, caused by Entamoeba histolytica, leads to significant global morbidity and mortality.
- E. histolytica virulence factors, including cysteine proteinases, interact with host defenses, cleaving immunoglobulins and complement components.
- Host inflammatory cytokines like IL-1beta and IL-18 are crucial in combating parasitic infections.
Purpose of the Study:
- To investigate the effect of E. histolytica proteinases on the cytokine IL-18.
- To determine if amebic proteinases can modulate the host immune response by targeting IL-18.
Main Methods:
- Expression and purification of the E. histolytica surface proteinase EhCP5.
- Incubation of recombinant proIL-18 and mature IL-18 with amebic proteinases.
- Analysis of proteinase activity on IL-18 using biochemical assays.
Main Results:
- A complex of E. histolytica proteinases cleaved recombinant proIL-18 into fragments.
- Purified EhCP5 cleaved both proIL-18 and mature IL-18 into biologically inactive fragments.
- Unlike amebic lysates activating proIL-1beta, E. histolytica proteinases inactivate IL-18.
Conclusions:
- E. histolytica employs a novel mechanism to evade host immunity by inactivating IL-18.
- This inactivation of IL-18 by parasite proteinases likely contributes to the pathogenesis of amebiasis.
- Understanding this interaction offers potential targets for therapeutic intervention.