Entamoeba histolytica proteins modulate the respiratory burst potential by murine macrophages

Reactive oxygen intermediates are important components of macrophage microbicidal mechanisms and pathogenesis of parasitic disease. The purpose of the present study was to investigate the effect of virulent Entamoeba histolytica (strain HM1-IMSS) on respiratory burst potential of macrophages. Pretreatment of elicited peritoneal macrophages (EPM) with crude soluble amoebic proteins from 1 to 6 hr was found to prime EPM for enhanced O2 and H2O2 release in response to phorbol myristate acetate (PMA) in a dose-dependent manner, whereas pretreatment with the same concentrations of the non-pathogenic E. histolytica-like Laredo strain was without priming effect. Low molecular weight (MW) amoebic proteins (27,000-67,000) purified by Sephacryl-200 column chromatography and subfractionated by diethylaminoethyl cellulose chromatography were 10-fold more potent than crude amoebic proteins in priming EPM for an enhanced respiratory burst potential. Both crude and purified amoebic proteins inhibited the priming effect of lipopolysaccharide (LPS) or interferon-gamma (IFN-gamma) and antagonized the stimulating effect of PMA. Amoebic proteins by themselves were incapable of stimulating EPM respiratory burst. These findings demonstrate that amoebic proteins are capable of modulating the respiratory burst response of macrophages, suggesting an important role for them in the immunoregulation and pathogenesis of amoebiasis.