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BioMed Research International
Volume 2017 (2017), Article ID 6746437, 15 pages
Research Article

First Characterization of the Neospora caninum Dense Granule Protein GRA9

1Institute of Medical Microbiology and Hospital Hygiene, Heinrich-Heine-University, Düsseldorf, Germany
2Federal Research Institute for Animal Health, Institute of Epidemiology, Friedrich-Loeffler-Institute, Greifswald-Insel Riems, Germany
3Institute of Parasitology, Vetsuisse Faculty, University of Berne, Berne, Switzerland

Correspondence should be addressed to Walter Däubener

Received 22 May 2017; Accepted 28 June 2017; Published 12 November 2017

Academic Editor: Heide Schatten

Copyright © 2017 Margret Leineweber et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


The obligate intracellular apicomplexan parasite Neospora caninum (N. caninum) is closely related to Toxoplasma gondii (T. gondii). The dense granules, which are present in all apicomplexan parasites, are important secretory organelles. Dense granule (GRA) proteins are released into the parasitophorous vacuole (PV) following host cell invasion and are known to play important roles in the maintenance of the host-parasite relationship and in the acquisition of nutrients. Here, we provide a detailed characterization of the N. caninum dense granule protein NcGRA9. The in silico genomic organization and key protein characteristics are described. Immunofluorescence-based localization studies revealed that NcGRA9 is located in the dense granules and is released into the interior of the PV following host cell invasion. Immunogold-electron microscopy confirmed the dense granule localization and showed that NcGRA9 is associated with the intravacuolar network. In addition, NcGRA9 is found in the “excreted secreted antigen” (ESA) fraction of N. caninum. Furthermore, by analysing the distribution of truncated versions of NcGRA9, we provide evidence that the C-terminal region of this protein is essential for the targeting of NcGRA9 into the dense granules of N. caninum, and the truncated proteins show reduced secretion.