Evaluation of putative anti-cryptosporidial drugs in an in vitro culture system.

Cryptosporidium species are major pathogens severely affecting the health of neonate animals, in particular calves, but also cause life-threatening infection of immunocompromised humans. Currently, only halofuginone is approved for prophylactic and metaphylactic treatment of calves but this drug suffers from its limited safety margins. For treatment of immunodeficient human patients, only nitazoxanide and paramomycin are used but data regarding their efficacy are controversial. Aim of the present study was to test a substituted benzimidazole (BAY-AF76184) and a heterocyclic substituted 1,2,4-triazin (BAY-AB24992), both drugs with known anti-protozoal activity, for their potential ability to interfere with Cryptosporidium parvum development in vitro. Development of C. parvum in HCT-8 cells treated with these compounds was compared to negative controls and parasites treated with paromomycin or halofuginone using real-time PCR targeting the 18S rDNAs of parasites and host cells as template. Potential cytotoxic and anti-proliferative effects of drugs were analysed using a lactate dehydrogenase and a WST-1 assay, respectively. BAY-AF76184 and paromomycin dose-dependently inhibited development of C. parvum with EC50 values of 2.37 µM and 69.5 µM, respectively. Although high concentrations of halofuginone and BAY-AB24992 also significantly inhibited parasite development, effects of lower concentrations were very heterogeneous preventing calculation of EC50 values. Halofuginone and BAY-AF76184 dose-dependently interfered with host cell proliferation (EC50 values of 0.35 µM and 9.07 µM, respectively) and the latter also had direct cytotoxic effects (EC50=48.78 µM). However, drug concentrations required for cytopathic were higher than those for effects against C. parvum. Therefore, both BAY-AB24992 and BAY-AF76184 should be considered for further evaluation, e.g. using in vivo models.

Evaluation of nifurtimox for potential use in control of histomoniasis in turkeys.

Nifurtimox (NFX), a compound with known antiprotozoal activity, was evaluated for potential use in the prevention or treatment of histomoniasis in turkeys. A test of NFX in vitro showed that the compound was progressively active at concentrations of 12.5-200 ppm. Lower concentrations appeared only to delay growth of histomonads, while a concentration of 200 ppm was completely inhibitory. A series of tests in turkey poults showed that NFX had significant (P < 0.05) efficacy at 300-400 ppm when given in the feed throughout a 14-day experimental infection period. The beneficial effect was most prominent in the reduction of mortality and the suppression of liver lesions. Cecal lesions appeared less affected. Treatment with 400 ppm for a 3-day period after inoculation of turkeys was partially effective. In all tests, liver lesions were suppressed more effectively than cecal lesions, indicating that the concentration of the compound in the liver during metabolic excretion was important in the observed efficacy of this compound. Lack of any effect on growth or feed consumption in uninfected turkeys during a medication period of 16 days indicated that this compound was well tolerated by turkeys at 400 ppm in the feed and might be of benefit in the prevention or treatment of histomoniasis in turkeys.

In silico analysis of the cyclophilin repertoire of apicomplexan parasites.

BACKGROUND: Cyclophilins (Cyps) are peptidyl cis/trans isomerases implicated in diverse processes such as protein folding, signal transduction, and RNA processing. They are also candidate drug targets, in particular for the immunosuppressant cyclosporine A. In addition, cyclosporine is known to exhibit anti-parasitic effects on a wide range of organisms including several apicomplexa. In order to obtain new non-immunosuppressive drugs targeting apicomplexan cyclophilins, a profound knowledge of the cyclophilin repertoire of this phylum would be necessary. RESULTS: BLAST and maximum likelihood analyses identified 16 different cyclophilin subfamilies within the genomes of Cryptosporidium hominis, Toxoplasma gondii, Plasmodium falciparum, Theileria annulata, Theileria parva, and Babesia bovis. In addition to good statistical support from the phylogenetic analysis, these subfamilies are also confirmed by comparison of cyclophilin domain architecture. Within an individual genome, the number of different Cyp genes that could be deduced varies between 7-9 for Cryptosporidia and 14 for T. gondii. Many of the putative apicomplexan cyclophilins are predicted to be nuclear proteins, most of them presumably involved in RNA processing. CONCLUSION: The genomes of apicomplexa harbor a cyclophilin repertoire that is at least as complex as that of most fungi. The identification of Cyp subfamilies that are specific for lower eukaryotes, apicomplexa, or even the genus Plasmodium is of particular interest since these subfamilies are not present in host cells and might therefore represent attractive drug targets.

Eimeria tenella: genomic organization and expression of an 89kDa cyclophilin.

Though parasite cyclophilins are promising new drug targets, Eimeria tenella cyclophilins have not been characterized yet. Here, we describe an 89kDa cyclophilin, designated EtCYP89. It is expressed throughout the developmental cycle of E. tenella, both in the intracellular stages in chicken and in extracellular sporulated oocysts and sporozoites. The EtCYP89 protein contains two Ser-rich domains in its NH2-terminus separated by a His-rich stretch. WD40 repeats are localized in the central part of the protein followed by a cyclophilin domain at the COOH-terminus. Both protein and genomic organization of EtCyp89 are conserved in comparison with its ortholog TgCyp81.6 in Toxoplasma gondii, except for the absence of a Ser- and His-rich NH2-terminus in TgCYP81.6. In particular, those 13 residues are conserved which are responsible for binding the anti-coccidial drug cyclosporine A.

Excystation of Eimeria tenella sporozoites impaired by antibody recognizing gametocyte/oocyst antigens GAM22 and GAM56.

Eimeria tenella is the causative agent of coccidiosis in poultry. Infection of the chicken intestine begins with ingestion of sporulated oocysts releasing sporocysts, which in turn release invasive sporozoites. The monoclonal antibody E2E5 recognizes wall-forming body type II (WFBII) in gametocytes and the WFBII-derived inner wall of oocysts. Here we describe that this antibody also binds to the stieda body of sporocysts and significantly impairs in vitro excystation of sporozoites. Using affinity chromatography and protein sequence analysis, E2E5 is shown to recognize EtGAM56, the E. tenella ortholog of the Eimeria maxima gametocyte-specific GAM56 protein. In addition, this antibody was used to screen a genomic phage display library presenting E. tenella antigens as fusion proteins with the gene VIII product on the surfaces of phagemid particles and identified the novel 22-kDa histidine- and proline-rich protein EtGAM22. The Etgam22 mRNA is expressed predominantly at the gametocyte stage, as detected by Northern blotting. Southern blot analysis in combination with data from the E. tenella genome project revealed that Etgam22 is an intronless multicopy gene, with approximately 12 to 22 copies in head-to-tail arrangement. Conspicuously, Etgam56 is also intronless and is localized adjacent to another gam56-like gene, Etgam59. Our data suggest that amplification is common for genes encoding oocyst wall proteins.

Humoral immune reaction of newborn calves congenitally infected with Neospora caninum and experimentally treated with toltrazuril.

Neospora caninum is widely recognized as one of the most important infectious organisms causing abortion and stillbirth in cattle. This parasite causes severe economical losses worldwide. Infection is mostly passed vertically from mother to calf during pregnancy. Under certain circumstances, an infection can lead to abortion, but in most cases it results in a chronically infected calf, which itself will represent the next endogenously infectious generation. So far, no reliable therapeutic or metaphylactic tool has been developed. One possibility to control the problem may consist of treating newborn calves that became vertically infected by a persistently infected mother. This may allow parasite-free offspring. The aim of the present study was to address the questions: (1) can serology be used to assess efficiency of treatment in toltrazuril-medicated animals? and (2) is a strategic prevention measure possible by means of producing N. caninum-free calves from positive cows? Calves from Neospora-seropositive cows and heifers were randomly split into two different medication groups: 36 calves were medicated with toltrazuril and 36 calves obtained a placebo. Medication (20 mg toltrazuril per kg bw) was administered three times, every second day, within the 7 days post natum. Three months after medication, there was no difference in antibody reactivity between the two groups. At later time points (4-6 months), however, significant differences were found, as explained by a strong humoral immunity after chemotherapeutical affection of parasites, while the placebo-treated animals only responded weakly to the persistent infection. In summary, we concluded that (1) serology was not an entirely appropriate tool to answer our initial question and (2) toltrazuril has the potential to eliminate N. caninum in newborn calves. As a consequence, we plan to follow up toltrazuril-medicated calves clinically and serologically over a longer period and investigate if they give birth to Neospora-free calves.

Treatment of mice with the anticoccidial drug Toltrazuril does not interfere with the development of a specific cellular intestinal immune response to Eimeria falciformis.

Immunity against Eimeria-infections is highly specific and it depends on cell-mediated effector mechanisms. Infections of BALB/c mice with 1,000 sporulated oocysts of Eimeria falciformis led to protection against challenge infections. Treatment with the anti-coccidium Toltrazuril, during primary infection, terminated the ongoing disease and did not interfere with the establishment of protective immunity against challenge infections. Mesenteric lymph node cells of infected, treated as well as non-treated and challenged BALB/c mice, showed a similar proliferation upon stimulation with parasite antigen. In contrast, neither cells of the Peyer's patches, intraepithelial lymphocytes, nor spleen cells responded to stimulation with parasite antigens. Cells from all compartments and of all investigated groups proliferated and released the cytokines IFN-gamma and IL-4 in response to the mitogen Concanavalin A. The number of cells releasing IFN-gamma or IL-4 was not dependent on the status of infection or previous treatment with Toltrazuril. The serum IgG response against total sporozoite antigens of individual mice showed that in addition, a systemic humoral response developed in infected mice, independent of a previous drug treatment, although the specific IgG antibody concentration was higher in non-treated mice. Thus, Toltrazuril does not impair the parasite specific intestinal cellular and systemic antibody response and does not prevent the development of protection against challenge infection.

Pochonins A-F, new antiviral and antiparasitic resorcylic acid lactones from Pochonia chlamydosporia var. catenulata.

Monorden (1) and the novel resorcylic acid lactones pochonins A (2), B (4), C (6), D (7), and E (8) as well as tetrahydromonorden (5) and pseurotin A (22) were isolated from cultures of the clavicipitaceous hyphomycete Pochonia chlamydosporia var. catenulata strain P 0297. Fermentation of P 0297 in bromide-containing culture media led to a shift in secondary metabolite production and yielded monocillins III (3) and II (9) as major metabolites besides monorden (1) as well as the novel compounds pochonin F (10) and a monocillin II glycoside (11) as minor metabolites. Most of these compounds showed moderate activities in a cellular replication assay against Herpes Simplex Virus 1 (HSV1) and against the parasitic protozoan Eimeria tenella. In contrast to the structurally related zearalenone derivatives none of the metabolites of strain P 0297 were found to be active in a fluorescence polarization assay for determination of modulatory activities on the human estrogenic receptor ERbeta. Beta-zearalenol (17), but not zearalenone (15) and alpha-zearalenol (16), showed antiherpetic effects. We report the production, isolation, and structure elucidation of compounds 1-11 and their biological characterization.

An explorative study to assess the efficacy of toltrazuril-sulfone (ponazuril) in calves experimentally infected with Neospora caninum.

BACKGROUND: Neospora caninum is an important cause of infectious abortion and stillbirth in cattle world-wide. Infection is common and may frequently be passed from mother to calf (vertical transmission) with no signs of disease. Based on our previous observation that N. caninum-infection can be efficiently controlled with toltrazuril-sulfone (ponazuril) in experimentally infected mice, we addressed the question if efficacy could also be obtained in experimentally infected calves. MATERIAL AND METHODS: The study included 19 calves and represents an initial explorative approach to document a basic effectiveness at first. Fifteen animals received each 2 x 10(8) N. caninum trophozoites, half of the dose being injected intravenously and the other half subcutaneously. Efficacy of treatment was assessed using molecular detection of parasite DNA with PCR and pathological alterations by immunohistochemistry in different organs of the animals. Assessment included also clinical, serological and pathophysiological parameters. RESULTS: In those calves medicated with ponazuril (one, or six consecutive days, respectively, starting one day after infection), a complete abrogation of the parasite detectability was obtained in the brain and other organs, while 50% of non-treated calves became PCR-positive in brain and muscles. Clinically, ponazuril chemotherapy of infected calves--in comparison to non-treated infected animals--reduced symptoms (fever), but no differences were observed between treated and non-treated animals with regard to serum enzymes and metabolites. Efficacy of a six-day treatment was also reflected by significantly lower anti-Neospora antibody concentrations developed after infection, when compared to non-treated animals. CONCLUSION: Based on our findings in this initially explorative approach that indicate a basic effectiveness of ponazuril against experimental N. caninum infection in calves, we plan to follow our chemotherapeutical intervention strategy to control bovine neosporosis with a subsequent more extensive field study with naturally infected calves.