Protective immunisation of mice using cell surface glycoprotein from Trypanosoma cruzi

Abstract

The parasitic protozoan Trypanosoma cruzi is the causative agent of the chronic debilitating Chagas' disease in man. It is estimated that at least 12 million people in South and Central America are infected with T. cruzi, for which there is so far no suitable chemotherapy^1,2. The development of vaccines using killed or attenuated whole organisms is hindered by the presence of endotoxin-like material in the protozoa³, and the possible existence of antigens in T. cruzi which cross-react with, and thereby stimulate immunity against, mammalian heart and nervous tissue^4,5. Because autoimmunity induced in this way has been thought to cause the cardiac and neural lesions characteristic of the chronic stage of the disease^6,7, it has been assumed that immunisation based on a whole organism vaccine might carry the risk of itself inducing symptoms of the disease. Recently an integral membrane glycoprotein of molecular weight 90,000, was isolated from the cell surface of T. cruzi. It is the only major cell surface glycoprotein, it is present throughout the life cycle of the parasite⁸, and it does not undergo antigenic variation⁹. We have successfully protected mice against acute lethal T. cruzi infection by vaccinating them with glycoprotein in combination with adjuvants. Moreover this glycoprotein does not seem to be the one carrying the antigens causing autoimmune antibody formation.