Studies on the cytopathogenicity of Entamoeba histolytica

We have explored the interaction of virulent and avirulent E. histolytica (HM1 and 303 respectively) with human polymorphonuclear leukocytes (PMNs) and Chinese hamster ovary (CHO) cells. PMNs exhibit chemotaxis to both HMl and 303. On contact with HMl, PMNs degranulate and die (trypan blue uptake); incubation at a ratio of 100 PMNs per ameba for 40 minutes revealed 70 per cent PMN death with 84 per cent HMl viability. 303s are often ingested by PMNs on contact; after incubation as above, only 1 per cent of 303 were intact with PMN mortality equaling that of control. HMl leukotoxicity occurred under anaerobic conditions, in immune serum, and was not mediated by complement. CHO cells are disrupted by HMls, less than 50 per cent of CHO monolayer remains after < 3 hours with 10(4) HMl/ml. Sonicated HMls (.5 x 10(5)/ml) washed in phosphate buffered saline caused cell release without cell death versus control (by trypan blue uptake). When 5 microgram/ml of Cytochalasin B was added to PMNs and CHO cells, cytopathogenicity by HMls decreased 62 per cent (p < .01) and nearly to control values (p < .01) respectively. Colchicine 0.25 mM had no significant effect on PMN cytopathogenicity. Washed HMl and 303 (1 x 10(5)/ml) were agglutinated by 10 microgram/ml and 100 microgram/ml of the lectin concanavalin A. Cytopathogenicity was associated with intact microfilament function and ameba motility. Surface membrane receptors may be important mediators of virulence. Further studies of potential membrane receptors and inhibitors are underway.