INHIBITION OF EXPRESSION OF THE LYSINE-RICH 30 KDA SURFACE-ANTIGEN OFENTAMOEBA-DISPAR BY THE TRANSCRIPTION OF ITS ANTISENSE RNA

The gene coding for the 30 kDa lysine rich surface antigen (Ed-Ag) tha t is present on membrane surfaces of Entamoeba dispar trophozoites has been characterized. A specific monoclonal antibody MAb? 318-28 prepar ed against this antigen reacts with all E. dispar strains tested, but not with any of the antigens of E. histolytica. Ln order to understand the function of this antigen, we constructed two plasmids, pEdA-9 and pEdA-Rev, in which the antigen-coding sequence was introduced into th e pEkAct-Neo shuttle vector in the direct and opposite orientation, re spectively. When E. dispar trophozoites were transfected with pEdA-9, only a slight increase was observed in the expression of the antigen. However, when E. dispar trophozoites were transfected with pEdA-Rev, t he expression of the native 30 kDa antigen was significantly inhibited . This inhibition was proportional to the level of resistance of the E . dispar culture to the neomycin derivative G418. Cytopathic assays de tected only a slight difference between untransfected, pEdA-9 transfec ted and pEdA-Rev transfected trophozoites. (C) 1997 Elsevier Science B .V.