Institute Research Program I:
 
Pathogenicity Factors of Entamoeba histolytica
 
 
 
 
 
 
 
Models of the tertiary structures generated for amoebapores and NK-lysin using the genetic algorithm. The predicted folds of amoebapore A, amoebapore C, and NK-lysin I are shown as ribbon illustrations of the Ca-backbones. Disulphide bonds are marked in white. The graphics were  
drawn using the RASMOL program (for more information see abstract Dandekar and Leippe).
Coordinator’s Summary 
 

The „amoebiasis program“ was initated in 1988. It deals with a variety of aspects concerning the biology and pathogenicity of Entamoeba histolytica. 

During 1996 work was continued to elucidate functions of the amoebae instrumental for pathogenic tissue invasion. One of these functions is the extraordinary capacity of E. histolytica to lyse human cells. Therefore, the underlying mechanism was further characterized, indicating that target cell death induced by E. histolytica is calcium-independent and occurs by necrosis of the cells rather than by apoptosis. In addition, the structure and function of amoebapore, the molecule considered most important for target cell lysis, was further characterized as extensively described within the investigators’ reports. 

Further activities dealt with the mechanism of acquired complement resistance of E. histolytica trophozoites. Under standard culture conditions trophozoites are sensitive to human complement but acquire complement resistance upon exposure to human serum. By analysing subtractive cDNA libraries enriched for transcripts of complement resistant amoebae, a gene was identified encoding a putative ATPase. This enzyme was found to be substantially higher expressed in cells grown in the presence of human serum compared to those cultured under standard conditions. 

In addition to complement resistance amoebae have to be protected against elevated levels of hydrogen peroxide (H2O2) after tissue invasion. However, this organism does not possess any catalase or peroxidase. Our recent work on the mechanism(s) that enable E. histolytica trophozoites to inactivate H2O2 resulted in the identification of an unusual amoeba protein, which is capable to remove H2O2 in the presence of a second amoeba molecule. Obviously, the latter is required as a hydrogen donor. 

An important step towards functional genetics in E. histolytica was the adaptation of a tetracyclin inducible vector system that allows precisely controlled expression of genes introduced into the amoebae. 

Progress was also made in the development of an amoebiasis vaccine. An epitope on the 170-kDa amoeba lectin was identified comprising just 25 amino acid residues able to confer antibody mediated resistance against invasive amoebiasis. 
 

Egbert Tannich
 
 

 
Staff 

Privatdozent Dr. Egbert Tannich, Molecular Biology (Coordinator) 
Dr. Iris Bruchhaus, Molecular Biology 
Dr. Frank Ebert, Parasitology 
Dr. Lutz Hamann, Molecular Biology 
Prof. Dr. Rolf D. Horstmann, Molecular Biology 
Privatdozent Dr. Matthias Leippe, Molecular Biology 
Dr. Hannelore Lotter, Molecular Biology 
Dr. Thomas Marti, Molecular Biology 
 

Doctoral Students 

Jörg Andrä 
Otto Berninghausen 
Simone Hick 
Thomas Jacobs 
Symi Richter 
Britta Urban 
 

Support Staff 

Claudia Benkert 
Heidrun Buß 
Martin Denart 
Birgit Förster 
Kerstin Jackisch 
Rosa Nickel 
Frauke Ruhe 
Jürgen Sievertsen 
Monika Söder 
Wenke Stoltenberg 
Thorsten Thye 
Britta Weseloh