Biomedical applications of monoclonal antibodies (McAb) against entamoeba histolytzca

Abstract

© 1991 by CRC Press, Inc. Amebiasis, a disease caused by Entamoeba histolytica, with or without clinical symptoms, occurs throughout the world, especially in tropical and subtropical climates and in places with poor sanitary conditions due to fecal contamination of water and food or direct fecal-oral contact. E. histolytica is the third leading parasitic cause of death in the world after malaria and schistosomiasis and infects about 10% of the world’s population, 10% again of whom (approximately 48 million cases) develop invasive colitis or liver abscess with at least 40,000 deaths per year, while the other 90% are asymptomatic. 1 The high percentage of asymptomatic cases suggests that differences in invasiveness and/or pathogenicity occur among two different isolates of amebae, pathogenic and nonpathogenic strains, as first mentioned by Brumpt in 1925. 2 In vitro and in vivo experimental studies have demonstrated that E. histolytica adherence and cytolytic mechanisms are absolutely required for the pathogenesis of amebiasis. 35 Intestinal amebiasis occurs after ingestion of contaminating mature cysts. Excystation occurs in the lower ileum followed by intestinal colonization via adherence of ameba trophozoites to gut epithelial cells throughout the colon. Encystation takes place in the lower colon and the cysts leave the host via feces. Pathogenic amebae invade the intestinal wall, causing lesions and the symptoms of amebic colitis, and if they spread via the blood stream they may reach and invade other organs of the body, especially the liver, lung, and brain, causing extraintestinal amebiasis. Amebic brain infection causes changes in the CSF that mimic meningitis. Therefore, development of vaccines effective in preventing invasive amebiasis and even intestinal colonization by amebae would be the most cost-effective approach for prevention. 4 To develop a vaccine against amebiasis or other parasitic infections using recombinant DNA or synthetic peptide approaches, it is important to identify protective antigens, which may be facilitated by the use of monoclonal antibodies (McAb). E. histolytica-specific McAb have been produced in many laboratories 6 - 8 and have been used in a McAb-based ELISA for detection of amebic antigen in clinical specimens, 9 for typing of pathogenic amebae, 10 for prevention of parasite-mediated cytotoxicity of target cells, 7 for characterization of proteins involved in adherence to target cells, 11 for amebic antigen purification, 8 and hopefully in the future for the development of vaccine against invasive amebiasis.