SPONTANEOUS RELEASE OF CYSTEINE PROTEINASES BUT NOT OF PORE-FORMING PEPTIDES BY VIABLE ENTAMOEBA-HISTOLYTICA

Invasive properties of pathogenic Entnmoeba histolytica have been post ulated to depend on the secretion or release of cysteine proteinases a nd pore-forming peptides (amoebapores) by trophozoites. To establish w hether such toxic molecules are released by viable trophozoites or upo n cellular disintegration, amoebae were maintained in various culture media, and activities in supernatants were monitored over time in corr elation to cellular integrity. By measuring the release of the cytopla smic marker enzyme NADP(+)-alcohol dehydrogenase, it became apparent t hat release of amoebapore in as accompanied by cellular disintegration . In contrast, considerable quantities of cysteine proteinases were fo und to be present in culture supernatants also when amoebae remained i ntact. Treatment of amoebae with concanavalin A, bacterial lipopolysac charides or the calcium ionophore A23187 did not result in amoebapore secretion suggesting that here target cell contact is required as an e ssential stimulus.