Human cytosolic thymidine kinase (hTK1) has proven to be a suitable target for noninvasive imaging of cancer cell proliferation using radiolabeled substrates such as [ (18)F]fluorothymidine ([ (18)F]FLT). However, a thymidine tracer useful for single photon emission tomography (SPECT) based on the inexpensive radionuclide technetium-99m would be of significant interest. In this work, a series of thymidine derivatives labeled with the organometallic [M(CO) 3] (+) core (M = (99m)Tc, Re) were synthesized. Neutral, cationic, and anionic complexes were readily formed in aqueous media, and all were substrates of recombinant hTK1 when incubated with ATP. The neutral complexes were phosphorylated to a greater extent than the charged complexes. The extent of phosphorylation was further improved by increasing the spacer length separating thymidine and the organometallic core. A molecular dynamics simulation study performed with a modified hTK1 structure supported the experimental findings. In vitro cell internalization experiments performed in a human neuroblastoma cell line (SKNMC) showed low uptake of the charged complexes but significant uptake for the neutral, lipophilic complexes with a log P value >1.

Recently, the availability of protocols supporting genetic complementation of Eimeria has raised the prospect of generating transgenic parasite lines which can function as vaccine vectors, expressing and delivering heterologous proteins. Complementation with sequences encoding immunoprotective antigens from other Eimeria spp. offers an opportunity to reduce the complexity of species/strains in anticoccidial vaccines. Herein, we characterise and evaluate EtAMA1 and EtAMA2, two members of the apical membrane antigen (AMA) family of parasite surface proteins from Eimeria tenella. Both proteins are stage-regulated, and the sporozoite-specific EtAMA1 is effective at inducing partial protection against homologous challenge with E. tenella when used as a recombinant protein vaccine, whereas the merozoite-specific EtAMA2 is not. In order to test the ability of transgenic parasites to confer heterologous protection, E. tenella parasites were complemented with EmAMA1, the sporozoite-specific orthologue of EtAMA1 from E. maxima, coupled with different delivery signals to modify its trafficking and improve antigen exposure to the host immune system. Vaccination of chickens using these transgenic parasites conferred partial protection against E. maxima challenge, with levels of efficacy comparable to those obtained using recombinant protein or DNA vaccines. In the present work we provide evidence for the first known time of the ability of transgenic Eimeria to induce cross protection against different Eimeria spp. Genetically complemented Eimeria provide a powerful tool to streamline the complex multi-valent anticoccidial vaccine formulations that are currently available in the market by generating parasite lines expressing vaccine targets from multiple eimerian species.

bUpon the screening of 16 antiproliferative compounds against Toxoplasma gondii and Neospora caninum, two hydrolytically stable ruthenium complexes (compounds 16 and 18) exhibited 50% inhibitory concentrations of 18.7 and 41.1 nM (T. gondii) and 6.7 and 11.3 nM (N. caninum). To achieve parasiticidal activity with compound 16, long-term treatment (22 to 27 days at 80 to 160 nM) was required. Transmission electron microscopy demonstrated the rapid impact on and ultrastructural alterations in both parasites. These preliminary findings suggest that the potential of ruthenium-based compounds should thus be further exploited.T oxoplasma gondii and Neospora caninum are cyst-forming apicomplexan parasites that infect a wide range of hosts. In an immunocompetent host, infection with either parasite does not cause disease (1-3). N. caninum has emerged as one of the most important infectious causes of bovine abortion (4-6). In contrast, T. gondii causes toxoplasmosis in humans and many animal species, either in chronically infected individuals during a decrease in immunoreactivity or if a seronegative mother acquires a primary infection during pregnancy, leading to abortion or serious fetal abnormalities (7-9). Toxoplasmosis treatment is based on only a few chemotherapeutics with considerable adverse effects (10, 11). In Neospora-seropositive cattle, pregnancy and the associated immunomodulation are already sufficient to cause recrudescence, fetal damage, and abortion (2-6). Chemotherapy has been considered a promising option if effective drugs can be identified (12, 13). Several compounds were investigated in vitro (14-16), but only a few were evaluated in small-animal models (14,(17)(18)(19)(20)(21)(22)(23)(24).We have evaluated compounds originally synthesized as anticancer drugs. Currently used metal complexes (25-31) exhibit considerable toxicity. This has stimulated the interest in other compounds with more acceptable toxicity, such as ruthenium complexes (32-36). Effects of ruthenium compounds on some bacteria and parasites have been studied (37-46). "Classical ruthenium complexes" contain heteroatom ligands (e.g., azole derivatives), and NAMI-A and KP-1019 have been evaluated in phase I clinical trials for cancer treatment (47-49). Organometallic complexes are defined by at least one metal-carbon bond. The 6 -arene ruthenium(II) phosphite complexes 5, 6, 12, and 15 to 18 were characterized earlier (50), while [Ru( 6 -p-cymene)(bipyridine)Cl][Cl] 11 was synthesized as shown previously (51). Based on our experiences in the design of selective inhibitors of CYP11B2 (53) and CYP11B1 (54), the pyridine-based compounds 4, 7 to 10, and 14 were from a small in-house library of CYP enzyme inhibitors. 2,2=-Bipyridine 3 was obtained from Joachim W. Heinicke, Ernst Moritz Arndt University of Greifswald, Greifswald, Germany. The cytotoxic lipophilic imidazolium salt 1,3-bis(2,4,6-trimethylphenyl)imidazolium chloride 3 was synthesized as described previously (54-56). The arylimidamide DB745 2 (23) was kindly provided by David Bo...