Detail

Keywords

Allergens; Antigens, Surface; Entamoeba histolytica; Enzyme Assays; Galactose; Gene Knockdown Techniques; Parasitology; Peptidoglycan

Research group(s)

• Molecular Microbiology
  Head: David Leitsch
  Research Area: Molecular biology of anaerobic parasites, drug resistance, mode of action of and resistance to metronidazole and other nitro drugs
  Members:
  Anna Nagode
  David Leitsch
  Michael Duchene

Research interests

The intestinal protozoan parasite Entamoeba histolytica still claims more than 50,000 human lives every year. Our work aims to understand the antigenic structures of the parasite on the one hand to view them as vaccine candidates and on the other hand to understand their biosynthesis to identify new ways to interfere with the parasite. Another part of our work tries to understand how exactly the classical drug metronidazole works, which remains the gold standard drug to treat the parasite as well as other microaerophilic microorganisms (4). In a current project we collaborate with the lab of Iain Wilson at the BOKU Vienna. In this project funded by the FWF we returned to a very complex surface antigen, called lipopeptidophosphoglycan (LPPG), against which we had once raised a monoclonal antibody (1). One aim is to identify the suspected core protein component, the other aim is to unravel the bioythesis of LPPG and its precursors. Galactose is an important sugar in the glycan part of LPPG, and E. histolytica displays intesting pathways to make use of this sugar. 

A second major interest has always been a cooperation on allergy research with the lab of Rudolf Valenta.

Techniques, methods & infrastructure

The parasite Entamoeba histolytica is cultured routinely in our lab. Earlier, several monoclonal antibodies were raised against a surface antigen preparation of E. histolytica (1). One of these, Mab EH5, binds to a complex lipopeptidophosphoglycan (LPPG) molecule on the surface of the amoebae. Mimotope peptides were identified which bind to Mab EH5 (2). As it appeared that Mab EH5 recognizes a protein sequence epitope, the sequence was searched and a gene candidate was identified in the E. histolytica genome (3). One aim of the current project is to examine whether the product of the identified gene is really contained in the LPPG structure. The other part of the project aims at the biosynthesis of the structure and its precursors. This is done by conventional molecular cloning and expression methods as well as two-dimensional electrophoreses and identification os spots by mass spectrometry (e.g. 4). Enzyme products are examined by HPLC in the lab of our collaborator Iain Wilson.  In addition, specific knockdown of selected genes in E. histolytica is attempted. The effect of various drugs and drug candidates against E. histolytica has been studied (4, 5).

Selected publications

1. Marinets, A. et al., 1997. Protection against Invasive Amebiasis by a Single Monoclonal Antibody Directed against a Lipophosphoglycan Antigen Localized on the Surface of Entamoeba histolytica. Journal of Experimental Medicine, 186(9), pp.1557–1565. Available at: http://dx.doi.org/10.1084/jem.186.9.1557.
2. Melzer, H. et al., 2002. Antigenicity and immunogenicity of phage library-selected peptide mimics of the major surface proteophosphoglycan antigens of Entamoeba histolytica. Parasite Immunology, 24(6), pp.321–328. Available at: http://dx.doi.org/10.1046/j.1365-3024.2002.00463.x.
3. Loftus, B. et al., 2005. The genome of the protist parasite Entamoeba histolytica. Nature, 433(7028), pp.865–868. Available at: http://dx.doi.org/10.1038/nature03291.
4. Leitsch, D. et al., 2007. Nitroimidazole Action in Entamoeba histolytica: A Central Role for Thioredoxin Reductase G. E. Ward, ed. PLoS Biology, 5(8), p.e211. Available at: http://dx.doi.org/10.1371/journal.pbio.0050211.
5. Drinić, M. et al., 2019. Activity of methylgerambullin from Glycosmis species (Rutaceae) against Entamoeba histolytica and Giardia duodenalis in vitro. International Journal for Parasitology: Drugs and Drug Resistance, 10, pp.109–117. Available at: http://dx.doi.org/10.1016/j.ijpddr.2019.08.001.