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Infection and Immunity, December 2009, p. 5564-5571, Vol. 77, No. 12
0019-9567/09/$08.00+0     doi:10.1128/IAI.00653-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Molecular Characterization of EmABP, an Apolipoprotein A-I Binding Protein Secreted by the Echinococcus multilocularis Metacestode{triangledown}

Peter Bernthaler,1 Kerstin Epping,1 Gerd Schmitz,2 Peter Deplazes,3 and Klaus Brehm1*

Institute of Hygiene and Microbiology, University of Würzburg, D-97080 Würzburg, Germany,1 Institute of Clinical Chemistry and Laboratory Medicine, Regensburg University Medical Center, D-93042 Regensburg, Germany,2 Institute of Parasitology, University of Zürich, CH-8057 Zürich, Switzerland3

Received 9 June 2009/ Returned for modification 13 July 2009/ Accepted 18 September 2009

Cestodes are unable to synthesize de novo most of their own membrane lipids, including cholesterol, and have to take them up from the host during an infection. The underlying molecular mechanisms are so far unknown. Here we report the identification and characterization of a novel gene, Emabp, which is expressed by larval stages and adults of the fox tapeworm Echinococcus multilocularis. The encoded protein, EmABP, displays significant homologies to apolipoprotein A-I binding protein (AI-BP) of mammalian origin and to metazoan YjeF_N domain proteins. Like mammalian AI-BP, EmABP carries an export-directing signal sequence which is absent in predicted AI-BP orthologs from the related flatworms Schistosoma japonicum and Schmidtea mediterranea. Using a specific antibody and immunoprecipitation techniques, we demonstrate that EmABP is secreted into the extraparasitic environment and into the hydatid fluid of in vitro-cultivated metacestode vesicles. Furthermore, we show that apolipoprotein A-I (apoA-I), a major constituent of cholesterol-transporting high-density lipoproteins, is present in hydatid fluid. By pulldown experiments, we demonstrate that recombinantly expressed, purified EmABP interacts with purified human apoA-I and is able to precipitate apoA-I from human serum. On the basis of these features and the suggested function of AI-BP in cholesterol transport in higher eukaryotes, we propose a role for EmABP in cholesterol and lipid uptake mechanisms of larval E. multilocularis.

* Corresponding author. Mailing address: Institute of Hygiene and Microbiology, University of Würzburg, Josef-Schneider-Strasse 2, D-97080 Würzburg, Germany. Phone: 49 931 20146168. Fax: 49 931 20146445. E-mail: kbrehm{at}hygiene.uni-wuerzburg.de

{triangledown} Published ahead of print on 5 October 2009.

Editor: J. F. Urban, Jr.

Infection and Immunity, December 2009, p. 5564-5571, Vol. 77, No. 12
0019-9567/09/$08.00+0     doi:10.1128/IAI.00653-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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