Sarcocystis neurona is the most frequent cause of equine protozoal myeloencephalitis, a debilitating neurological disease of horses that can be difficult to treat. We identified SnCDPK1, the S. neurona homologue of calcium-dependent protein kinase 1 (CDPK1), a validated drug target in Toxoplasma gondii. SnCDPK1 shares the glycine “gatekeeper” residue of the well-characterized T. gondii enzyme, which allows the latter to be targeted by bumped kinase inhibitors. This study presents detailed molecular and phenotypic evidence that SnCDPK1 can be targeted for rational drug development. Recombinant SnCDPK1 was tested against four bumped kinase inhibitors shown to potently inhibit both T. gondii (Tg) CDPK1 and T. gondii tachyzoite growth. SnCDPK1 was inhibited by low nanomolar concentrations of these BKIs and S. neurona growth was inhibited at 40–120 nM concentrations. Thermal shift assays confirmed these bumped kinase inhibitors bind CDPK1 in S. neurona cell lysates. Treatment with bumped kinase inhibitors before or after invasion suggests that bumped kinase inhibitors interfere with S. neurona mammalian host cell invasion in the 0.5–2.5 μM range but interfere with intracellular division at 2.5 μM. In vivo proof-of-concept experiments were performed in a murine model of S. neurona infection. The experimental infected groups treated for 30 days with compound BKI-1553 (n = 10 mice) had no signs of disease, while the infected control group had severe signs and symptoms of infection. Elevated antibody responses were found in 100% of control infected animals, but only 20% of BKI-1553 treated infected animals. Parasites were found in brain tissues of 100% of the control infected animals, but only in 10% of the BKI-1553 treated animals. The bumped kinase inhibitors used in these assays have been chemically optimized for potency, selectivity and pharmacokinetic properties, and hence are good candidates for treatment of equine protozoal myeloencephalitis.
|Number of pages||10|
|Journal||International Journal for Parasitology|
|State||Published - Dec 1 2016|
Bibliographical noteFunding Information:
This research study was supported by the National Institute of Allergy and Infectious Diseases (USA) and National Institute of Child Health and Human Development of the National Institutes of Health (USA) under the award numbers R01AI089441, R01AI111341, R01GM086858 and R01HD080670. The work was also supported by awards # 2014-06183 and #2009-65109-05918 from the United States Department of Agriculture National Institute of Food and Agriculture, and funds from the Amerman Family Equine Research Fund (USA).
© 2016 Australian Society for Parasitology
- Bumped kinase inhibitors
- Calcium-dependent protein kinase 1
- Drug target
- Equine protozoal myeloencephalitis
- Gatekeeper residue
- Sarcocystis neurona
ASJC Scopus subject areas
- Infectious Diseases