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NcGRA2 as a molecular target to assess the parasiticidal activity of toltrazuril against Neospora caninum

Published online by Cambridge University Press:  13 June 2008

M. STROHBUSCH ,
N. MÜLLER ,
A. HEMPHILL ,
G. GREIF  and
B. GOTTSTEIN
M. STROHBUSCH
Affiliation:
Institute of Parasitology, University of Berne, Laenggass-Strasse 122, CH-3012 Berne, Switzerland
N. MÜLLER
Affiliation:
Institute of Parasitology, University of Berne, Laenggass-Strasse 122, CH-3012 Berne, Switzerland
A. HEMPHILL
Affiliation:
Institute of Parasitology, University of Berne, Laenggass-Strasse 122, CH-3012 Berne, Switzerland
G. GREIF
Affiliation:
Bayer HealthCare AG, Leverkusen, Germany
B. GOTTSTEIN*
Affiliation:
Institute of Parasitology, University of Berne, Laenggass-Strasse 122, CH-3012 Berne, Switzerland
*
*Corresponding author: Institute of Parasitology, Vetsuisse Faculty, University of Bern, Laenggass-Strasse 122, CH-3001 Bern, Switzerland. Tel: +41 31 631 24 18. E-mail: [email protected]
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Summary

The treatment of Neospora caninum infection in the bovine host is still at an experimental stage. In contrast to the in vivo situation, a wide range of compounds have been intensively investigated in cell-culture-based assays. Tools to demonstrate efficacy of treatment have remained conventional including morphological and cell biological criteria. In this work, we present a molecular assay that allows the distinction between live and dead parasites. Live parasites can be detected by measuring the mRNA level of specific genes, making use of the specific mRNA available in live cells. The NcGra2 gene of N. caninum, which is known to be expressed in both tachyzoites and bradyzoites, was used to establish a quantitative real-time RT-PCR, for monitoring parasite viability. Validation of the system in vitro was achieved using Neospora-infected cells that had been treated for 2–20 days with 30 μg/ml toltrazuril. NcGRA2-RT-real time PCR demonstrated that a 10-day toltrazuril-treatment exerted parasitostatic activity, as assessed by the presence of NcGRA2-transcripts, whereas after a 14-day treatment period no NcGRA2-transcripts were detected, showing that the parasites were no longer viable. Concurrently, extended culture for a period of 4 weeks in the absence of the drug following the 14-day toltrazuril treatment did not lead to further parasite proliferation, confirming the parasiticidal effect of the treatment. This assay has the potential to be widely used in the development of novel drugs against N. caninum, with a view to distinguishing between parasiticidal and parasitostatic efficacy of given compounds.

Keywords

Neospora caninumRT-PCRcell-culture assaytoltrazuril
Type
Original Articles
Information
Parasitology , Volume 135 , Issue 9 , August 2008 , pp. 1065 - 1073
Copyright
Copyright © 2008 Cambridge University Press

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