Antisense inhibition of expression of the light subunit (35 kDa) of the Gal/GalNac lectin complex inhibits Entamoeba histolytica virulence

One of the under-represented genes identified by cDNA representational diff erence analysis (RDA) between avirulent Entamoeba histolytica strain Rahman and virulent strain HM-1:IMSS was the amoebic right (35 kDa) subunit of th e Gal/GalNac lectin complex. This lectin complex, which mediates the adhesi on of the parasite to the target cell, also contains a heavy (170 kDa) subu nit, which has the carbohydrate-binding domain. Stable transfectants of the virulent strain in which the expression of the 35 kDa subunit was inhibite d by antisense RNA were not significantly affected in their adhesion activi ty to mammalian or bacterial cells but were strongly inhibited in their cyt opathic activity, cytotoxic activity and in their ability to induce the for mation of liver lesions in hamsters. These findings suggest that the 35 kDa subunit may have a specific function in the pathogenic pathway and provide s a new insight into the role of this component of the Gal/GalNac lectin co mplex in amoebic virulence.