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Infection and Immunity, January 2004, p. 527-536, Vol. 72, No. 1
0019-9567/04/$08.00+0     DOI: 10.1128/IAI.72.1.527-536.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.

Isolation and Characterization of a Secretory Component of Echinococcus multilocularis Metacestodes Potentially Involved in Modulating the Host-Parasite Interface

Institute of Parasitology,¹ Department of Chemistry and Biochemistry, University of Berne, CH-3012 Berne, Switzerland,³ Immunology Department, School of Chemistry, School of Sciences, Montevideo, Uruguay²

Received 13 August 2003/ Returned for modification 29 September 2003/ Accepted 20 October 2003

Echinococcus multilocularis metacestodes are fluid-filled, vesicle-like organisms, which are characterized by continuous asexual proliferation via external budding of daughter vesicles, predominantly in the livers of infected individuals. Tumor-like growth eventually leads to the disease alveolar echinococcosis (AE). We employed the monoclonal antibody (MAb) E492/G1, previously shown to be directed against a carbohydrate-rich, immunomodulatory fraction of Echinococcus granulosus, to characterize potentially related components in E. multilocularis. Immunofluorescence studies demonstrated that MAb E492/G1-reactive epitopes were found predominantly on the laminated layer and in the periphery of developing brood capsules. The respective molecules were continuously released into the exterior medium and were also found in the parasite vesicle fluid. The MAb E492/G1-reactive fraction in E. multilocularis, named Em492 antigen, was isolated by immunoaffinity chromatography. Em492 antigen had a protein/carbohydrate ratio of 0.25, reacted with a series of lectins, and is related to the laminated layer-associated Em2(G11) antigen. The epitope recognized by MAb E492/G1 was sensitive to sodium periodate but was not affected by protease treatment. Anti-Em492 immunoglobulin G1 (IgG1) and IgG2 and, at lower levels, IgG3 were found in sera of mice suffering from experimentally induced secondary, but not primary, AE. However, with regard to cellular immunity, a suppressive effect on concanavalin A- or crude parasite extract-induced splenocyte proliferation in these mice was observed upon addition of Em492 antigen, but trypan blue exclusion tests and transmission electron microscopy failed to reveal any cytotoxic effect in Em492 antigen-treated spleen cells. This indicated that Em492 antigen could be modulating the periparasitic cellular environment during E. multilocularis infection through as yet unidentified mechanisms and could be one of the factors contributing to immunosuppressive events that occur at the host-parasite interface.

Editor: W. A. Petri, Jr.