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Molecular characterization of Neospora caninum MAG1, a dense granule protein secreted into the parasitophorous vacuole, and associated with the cyst wall and the cyst matrix

Published online by Cambridge University Press:  06 May 2010

Institute of Veterinary Pharmacology and Toxicology, Vetsuisse Faculty, University of Berne, Länggass-Strasse 124, CH-3012Berne, Switzerland
Institute of Parasitology, Vetsuisse Faculty, University of Berne, Länggass-Strasse 122, CH-3012Berne, Switzerland
Institute of Veterinary Pharmacology and Toxicology, Vetsuisse Faculty, University of Berne, Länggass-Strasse 124, CH-3012Berne, Switzerland
Institute of Veterinary Pharmacology and Toxicology, Vetsuisse Faculty, University of Berne, Länggass-Strasse 124, CH-3012Berne, Switzerland
*Corresponding author: Institute of Veterinary Pharmacology and Toxicology, Vetsuisse Faculty, University of Berne, Länggass-Strasse 124, CH-3012Berne, Switzerland. Tel: +41 31 631 22 41. Fax: +41 31 631 26 30. E-mail:


In Neospora caninum and Toxoplasma gondii, the parasitophorous vacuole (PV) is synthesized at the time of infection. During tachyzoite-to-bradyzoite stage conversion, the PV is later transformed into a tissue cyst that allows parasites to survive in their host for extended periods of time. We report on the characterization of NcMAG1, the N. caninum orthologue of T. gondii MAG1 (matrix antigen 1; TgMAG1). The 456 amino acid predicted NcMAG1 protein is 54% identical to TgMAG1. By immunoblotting, a rabbit antiserum raised against recombinant NcMAG1 detected a major product of ~67 kDa in extracts of N. caninum tachyzoite-infected Vero cells, which was stained more prominently in extracts of infected Vero cells treated to induce in vitro bradyzoite conversion. Immunofluorescence and TEM localized the protein mainly within the cyst wall and the cyst matrix. In both tachyzoites and bradyzoites, NcMAG1 was associated with the parasite dense granules. Comparison between NcMAG1 and TgMAG1 amino acid sequences revealed that the C-terminal conserved regions exhibit 66% identity, while the N-terminal variable regions exhibit only 32% identity. Antibodies against NcMAG1-conserved region cross-reacted with the orthologuous protein in T. gondii but those against the variable region did not. This indicates that the variable region possesses unique antigenic characteristics.

Research Article
Copyright © Cambridge University Press 2010

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