Correlation of virulence and collagenolytic activity in Entamoeba histolytica

The levels of collagenolytic activity of strains HM-1:1 MSS (HM-1), (HM-1), 200-NIH, and HK-9 of Entamoeba histolytica were compared. Collagen degradation was evaluated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Conditioned media as well as extracts of the highly virulent strain HM-1 effectively degraded native type I collagen. Significantly lower activity was found in the analogous fractions of strains 200-NIH and HK-9, which are not as virulent. The collagenolytic activity of strain HM-1 was associated with the isolated plasma membrane fraction and could be eluted from the membranes by buffers of high ionic strength, indicating that it is not an integral membrane protein. Unlike the vertebrate and the clostridial collagenases, the collagenolytic activity of E. histolytica HM-1 was enhanced in presence of dithiothreitol and was inhibited by N-ethylmaleimide. The correlation between virulence of the individual strains and their collagenolytic activity suggests that collagenase might play a role in pathogenesis of amoebiasis. The localization of the enzyme on the plasma membrane and its presence in the extracellular medium favor this view.