Antiparasitic Efficacy Research Articles

Exploring Amino Acid-Capped Nanoparticles for Selective Anti-Parasitic Action and Improved Host Biocompatibility.

Toxoplasma gondii causes toxoplasmosis, a common infection against which better drugs are needed. Recently, we showed that inorganic nanoparticles have anti-Toxoplasma activity. Here, we sought to enhance the anti-parasitic efficacy and host biocompatibility of these nanoparticles by modifying their surface with amino acids. The amino acids used were selected based on the nutritional requirements of Toxoplasma gondii. Amino acid-capped nanoparticles (amino-NPs) were synthesized, purified, and then screened for anti-Toxoplasma activity in in vitro infection models. The amino-NPs showed enhanced anti-parasitic selectivity as well as improved host biocompatibility. Oxidative stress, modulation of host HIF-1α, and activation of the kynurenine pathway contributed to the anti-parasitic action of the amino-NPs. Our findings provide additional support for the potential use of nanoparticles as innovative anti-parasitic agents. Findings glean additional perspective that highlight prospects of nanoparticles not only as innovative source of anti-parasitic agents but also provide evidence for probable biological mechanism.

Antiparasitic efficacy and safety assessment of magnolol against Ichthyophthirius multifiliis in goldfish

Ichthyophthirius multifiliis causes high mortality rate of freshwater fish. It is necessary to find the effective alternatives that may both be affordable and environmentally acceptable since malachite green is banned to use. In this work, magnolol exhibited great anti-parasitic activity against all stages of I. multifiliis. Magnolol at concentrations of 0.6mg/L or more resulted in 100% mortality of I. multifiliis theronts within 4h exposure; and terminated reproduction of I. multifiliis post 6h exposure of protomonts and encysted tomonts to 0.8 and 1.0mg/L, respectively. Moreover, some of tomonts presented morphological characteristic changes and a larger part of tomonts were unable to reproduce. Magnolol possibly had a directly effect on the cell membrane, and more importantly, it could permeate into an encysted tomont across the cyst wall and then impact on the tomont proliferation. In vivo trials showed that 5h exposure of infected fish to 1.5mg/L of magnolol significantly reduced the number of theronts released from tomonts. In addition to determination of anti-Ichthyophthirius activity, we also systematically evaluated the safety of magnolol against fish. First of all, the results of acute toxicity experiment showed that the 96h median lethal concentration (LC50) of magnolol to goldfish was 6.02mg/L. Furthermore, gene expression (cyp1a, hsp70, gst and sod) and enzyme activity (GSH, SOD and T-AOC) in liver, spleen and kidney could recover to the same level as the control group up to 48h, though magnolol induced goldfish stress response during 6–24h exposure. More than that, magnolol can be easily synthesized with low cost, and further embellished and modified for higher bioactivity and lower toxicity because of its simple and symmetry chemical structure. Therefore, magnolol has the potential to be a safe and effective therapeutant, and it also can be used as a probable leading compound for the development of commercial drug to control ichthyophthiriasis in aquaculture.

In Vitro Pharmacodynamics of Benzimidazole and Tetrahydropyrimidine Derivatives in European Bison Gastro-Intestinal Nematodes

The present study was aimed to evaluate the efficacy of anthelmintic agents against intestinal nematodes found in European bison. It was performed between October 2016 and May 2017, using Egg Hatch Assay (EHA) and Larval Development Assay (LDA). The parasites were obtained from faecal samples, harvested from bisons in Romania and Sweden. The efficacy of albendazole (ABZ), mebendazole (MBZ) thiabendazole (TBZ) and pyrantel (PYR) was tested. In EHA, the maximum efficacy was observed in MBZ (EC50 = - 0.227 μg/ml), and then TBZ (EC50 = - 0.2228). ABZ had a weaker result, EC50 being 0.326 μg/ml. All tested benzimidazoles registered hatching percentages below 50%, reflecting the lack of parasitic resistance. MIC obtained in the LDA tests were 0.2144 μg/ml for TBZ, 0.2792 μg/ml for PYR, 0.5429 μg/ml for MBZ, while ABZ came last (MIC = 0.8187 μg/ml). The in vitro tests proved the antiparasitic molecules efficacy against bisons nematode population and a limited risk of inducing resistance phenomena.

Efficacy of a series of alpha-pyrone derivatives against Leishmania (L.) infantum and Trypanosoma cruzi

The neglected tropical diseases Chagas disease and leishmaniasis affect together more than 20 million people living mainly in developing countries. The mainstay of treatment is chemotherapy, however the drugs of choice, which include benznidazole and miltefosine, are toxic and have numerous side effects. Safe and effective therapies are urgently needed. Marine alpha-pyrones have been previously identified as scaffolds with potential antiprotozoan activities. In this work, using a phenotypic screen, twenty-seven examples of 3-substituted 4-hydroxy-6-methyl alpha-pyrones were synthesized and their antiparasitic efficacy evaluated against Leishmania (L.) infantum and Trypanosoma cruzi in order to evaluate structure-activity relationships within the series. The mechanism of action and the in vivo efficacy of the most selective compound against T. cruzi were evaluated using different techniques. In vitro data indicated that compounds 8, 15, 25, 26 and 28 presented IC50 values in the range between 13 and 54 μM against L. infantum intracellular amastigotes. Among them, hexanoyl substituted pyrone 8 was the most selective and potent, with a Selectivity Index (SI) > 14. Fifteen of the alpha-pyrones were effective against T. cruzi trypomastigotes, with 3-undecanoyl (11) and 3-tetradecanoyl (12) substituted pyrones being the most potent against trypomastigotes, with IC50 values of 1 and 2 μM, respectively, and SI higher than 70. Using flow cytometry and fluorescent-based assays, pyrone 12 was found to induce hyperpolarization of the mitochondrial membrane potential of T. cruzi, without affecting plasma membrane permeability. An experimental acute phase-murine model, demonstrated that in vivo dosing of 12 (30 mg/kg/day; 5 days), had no efficacy at the first parasitemia onset of T. cruzi, but reduced the second onset by 55% (p < 0.05), suggesting a delayed action in BALB/c mice. Additionally, a histopathology study demonstrated no toxic effects to the treated mice. The finding that several 3-substituted alpha-pyrones have in vitro efficacy against both L. infantum and T. cruzi, and that one analogue exhibited moderate and non-toxic in vivo efficacy against T. cruzi is encouraging, and suggests that this compound class should be explored as long-term treatments in experimental Chagas disease.

Treatment of Schistosoma mansoni with miltefosine in vitro enhances serological recognition of defined worm surface antigens.

BackgroundMiltefosine, an anti-cancer drug that has been successfully repositioned for treatment of Leishmania infections, has recently also shown promising effects against Schistosoma spp targeting all life cycle stages of the parasite. The current study examined the effect of treating Schistosoma mansoni adult worms with miltefosine on exposure of worm surface antigens in vitro.Methodology/Principal findingsIn an indirect immunofluorescence assay, rabbit anti-S.mansoni adult worm homogenate and anti-S. mansoni infection antisera gave strong immunofluorescence of the S. mansoni adult worm surface after treatment with miltefosine, the latter antiserum having previously been shown to synergistically enhance the schistosomicidal activity of praziquantel. Rabbit antibodies that recognised surface antigens exposed on miltefosine-treated worms were recovered by elution off the worm surface in low pH buffer and were used in a western immunoblotting assay to identify antigenic targets in a homogenate extract of adult worms (SmWH). Four proteins reacting with the antibodies in immunoblots were purified and proteomic analysis (MS/MS) combined with specific immunoblotting indicated they were the S. mansoni proteins: fructose-1,6 bisphosphate aldolase (SmFBPA), Sm22.6, alkaline phosphatase and malate dehydrogenase. These antibodies were also found to bind to the surface of 3-hour schistosomula and induce immune agglutination of the parasites, suggesting they may have a role in immune protection.Conclusion/SignificanceThis study reveals a novel mode of action of miltefosine as an anti-schistosome agent. The immune-dependent hypothesis we investigated has previously been lent credence with praziquantel (PZQ), whereby treatment unmasks parasite surface antigens not normally exposed to the host during infection. Antigens involved in this molecular mechanism could have potential as intervention targets and antibodies against these antigens may act to increase the drug’s anti-parasite efficacy and be involved in the development of resistance to re-infection.

Characterization of the Activities of Dinuclear Thiolato-Bridged Arene Ruthenium Complexes against Toxoplasma gondii.

The in vitro effects of 18 dinuclear thiolato-bridged arene ruthenium complexes (1 monohiolato compound, 4 dithiolato compounds, and 13 trithiolato compounds), originally designed as anticancer agents, on the apicomplexan parasite Toxoplasma gondii grown in human foreskin fibroblast (HFF) host cells were studied. Some trithiolato compounds exhibited antiparasitic efficacy at concentrations of 250 nM and below. Among those, complex 1 and complex 2 inhibited T. gondii proliferation with 50% inhibitory concentrations (IC50s) of 34 and 62 nM, respectively, and they did not affect HFFs at dosages of 200 μM or above, resulting in selectivity indices of >23,000. The IC50s of complex 9 were 1.2 nM for T. gondii and above 5 μM for HFFs. Transmission electron microscopy detected ultrastructural alterations in the matrix of the parasite mitochondria at the early stages of treatment, followed by a more pronounced destruction of tachyzoites. However, none of the three compounds applied at 250 nM for 15 days was parasiticidal. By affinity chromatography using complex 9 coupled to epoxy-activated Sepharose followed by mass spectrometry, T. gondii translation elongation factor 1α and two ribosomal proteins, RPS18 and RPL27, were identified to be potential binding proteins. In conclusion, organometallic ruthenium complexes exhibit promising activities against Toxoplasma, and the potential mechanisms of action of these compounds as well as their prospective applications for the treatment of toxoplasmosis are discussed.

Antiparasitic efficacy of commercial curcumin against Ichthyophthirius multifiliis in grass carp (Ctenopharyngodon idellus)

Ichthyophthiriasis, caused by Ichthyophthirius multifiliis, is a prevalent parasitic disease in freshwater fish, it leads to a significant economic loss in fish farming industry. Following the ban of malachite green in usage of treating food fish, new antiparasitic agents for the treatment of ichthyophthiriasis is being studied. The aims of the present study were to investigate in vitro and in vivo antiparasitic efficacy of a commercial curcumin against I. multifiliis and evaluate its acute toxicity in grass carp. In vitro tests, curcumin killed all theronts at 1mg/L for 38.7min, caused 100.0% mortality of nonencysted tomonts at 8mg/L for 47.3min, and terminated the reproduction of encysted tomonts at 4mg/L for 16h, respectively. In vivo trials, curcumin at 4mg/L for 10days exposure eradicated all parasitic trophonts in situ, and protected both infected and naive fish from I. multifiliis infections. The results of in vitro and in vivo experiments proved curcumin to be effective against the parasite. The 96h median lethal concentration (LC50) of curcumin to grass carp (58.5mg/L) was about 146.3 times median effective concentration (EC50) of curcumin to theronts (0.4mg/L), and 18.9 times EC50 of curcumin to nonencysted tomonts (3.1mg/L). Therefore, the commercially available curcumin can be used as a potential lead compound for the development of commercial drugs against I. multifiliis.

Antiparasitic efficacy and blood effects of formalin on Arapaima gigas (Pisces: Arapaimidae)

This study evaluated the in vitro and in vivo antiparasitic efficacy of formalin against Dawestrema cycloancistrium, the effects on the physiological response of Arapaima gigas and the residual action on fish muscle after 96h of exposure. As regards the in vitro assay, 0, 22, 44, 66, 88, 110, 330, 660 and 880 mg L−1 formalin were tested. After 1h of exposure to 660 and 880 mg L−1 formalin, there was a 100% mortality of D. cycloancistrium as well as after 2h of exposure at 330 and 110 mg L−1 and 3h of exposure at 44, 66 and 88 mg L−1. Concerning the in vivo test, when fish were exposed to formalin at 0, 220, 330, 440 and 550 mg L−1, there was 100% survival at all concentrations and exposure times evaluated. Baths of 1h with 440 and 550 mg L−1 formalin showed 93.3% and 99.3% efficacy respectively. However, the baths of 12h with 55 and 66 mg L−1 formalin had the efficacy of 44.5% and 55.5% respectively. In 1h baths with 220, 330, 440 and 550 mg L−1 formalin, hematocrit, hemoglobin, number of total erythrocytes, mean corpuscular volume, mean corpuscular hemoglobin concentration, mean corpuscular hemoglobin, plasma glucose levels, cortisol, total proteins, chloride, calcium, sodium, potassium and magnesium of the fish presented no differences in relation to the control values. However, in baths of 12h with 33, 44, 55 and 66 mg L−1 formalin, there was a decrease in hematocrit, plasma levels of calcium and chloride, and increased levels of glucose and cortisol, depending on the concentration of formalin used. In the fish muscle, the formalin residue decreased after 96h in all concentrations and periods evaluated, returning to values close to the control ones. The results indicate that formalin had its efficacy successfully proved in the treatment against D. cycloancistrium at higher concentrations such as 440 and 550 mg L−1 formalin and shorter exposure time (1h) without compromising fish homeostasis and consumer food safety. Statement of relevanceThe manuscript represents original research on use of formalin in vitro and in vivo for treating infection by monogenoidean Dawestrema cycloancistrium in Arapaima gigas, the giant fish from Amazon. In the fish, muscle the residue levels of formalin after exposure was also investigated. Formalin have efficacy in the treatment against D. cycloancistrium at higher concentrations (440 and 550 mg.L−1) of formalin and shorter exposure time (1h) and without compromising A. gigas homeostasis and consumer food safety.

Antiparasitic efficacy of curcumin from Curcuma longa against Ichthyophthirius multifiliis in grass carp

Ichthyophthirius multifiliis is a ciliated parasite that elicits great economic losses in aquaculture. In the present study, a polyphenol compound, curcumin, was obtained from the rhizome of Curcuma longa by bioassay-guided isolation based on the efficacy of anti-I. multifiliis theronts. Anti-I. multifiliis efficacy of curcumin was evaluated in vitro and in vivo. Curcumin resulted in 100% mortality of I. multifiliis theronts at a concentration of 1mg/L within 21.7±1.2min and killed all tomonts at 8mg/L within 31.0±1.0min. Curcumin at 4mg/L for 16h exposure can completely terminate the reproduction of tomonts. The pretreatment with curcumin at concentrations of 0.5, 0.25, and 0.125mg/L for 2h significantly reduced the infectivity of I. multifiliis theronts. Curcumin at 4mg/L completely cured the infected grass carp and protected naive fish from I. multifiliis infection after 10days exposure. The 4h median effective concentration (EC50) of curcumin to I. multifiliis theronts and the 5h EC50 of curcumin to I. multifiliis tomonts were 0.303mg/L and 2.891mg/L, respectively. The 96h median lethal concentration (LC50) of curcumin to grass carp was 56.8mg/L, which was approximately 187.4 times EC50 of curcumin to theronts and 19.6 times EC50 of curcumin to tomonts. The results demonstrated that curcumin has the potential to be a safe and effective therapeutant for controlling ichthyophthiriasis in aquaculture.

Pharmacokinetics of new high-concentration and long-acting praziquantel oily suspensions after intramuscular administration in cattle.

The aim of the study was to develop praziquantel (PZQ) oily suspensions with 30% PZQ high concentration for intramuscular injection and investigate their pharmacokinetics in cattle. Two optimized formulations containing 30% PZQ were developed in this study, and their quality met the technical standards set by the Ministry of Agriculture of the People's Republic of China. After intramuscular administrations of the suspensions (30mg/kg), no significant differences were observed between the two oily suspensions. However, compared with the market available PZQ tablet after oral administration (150mg/kg), our injections revealed longer plasma elimination half-life (26.23, 22.16h vs 6.35h) and mean residence time (27.10, 25.88h vs 9.16h), indicating the antiparasitic efficacy of our suspensions may be prolonged, and further clinical efficacy investigation is needed. In addition, the relative bioavailability of our formulated suspensions was improved up to 441.32% and 425.60% compared with the oral reference product. Therefore, the injectable suspensions have the potential to become antiparasitic agents for the treatment of cattle schistosomiasis.

English

Plant products are a rich source of bioactive organic chemicals and offer an advantage over synthetic pesticides as these are less toxic, less prone to development of resistance and easily biodegradable. The present study aimed at screening the acaricidal potential of crude methanolic and aqueous extracts of Schinus molle (L.) leaves on the adult Bophilus decoloratus and Rhipicephalus pulchellus cattle ticks, using in vitro immersion method. Freshly collected adult ticks were exposed to three graded concentrations of the crude extracts; 1% (1g/100ml), 2% (1g/50ml), and 4% (1g/25ml) for 24 h and mortality rates were recorded post exposure for each concentration every 3 h. Diazinon (0.2%) and distilled water were used as positive and negative controls respectively. Acaricidal activities of each concentration were measured by mean number of ticks died and antiparasitic efficacy (%) relative to the negative control. Analysis result indicated that highest (4%) and middle (2%) concentrations of both extracts caused a statistically significant (P&lt;0.05) killing effect on R. pulchellus and B. decoloratus for most of the observation hours as compared to the extract unloaded in vitro groups.&nbsp; The relative antiparasitic efficacy (%) was highest for 4% concentration of both extracts (100%). The standard acaricide failed to completely eliminate the parasites after 24 h of exposure although it showed a slightly better effect against B. decoloratus (96.7%) compared to R. pulchellus (93.3%).&nbsp; Put together, this finding showed that the crude extracts of the plant have promising acaricidal properties and warrant further investigation. Key words: Acaricidal, crude extracts, Boophilus decoloratus, Rhipicephalus pulchellus, Schinus molle.

Evaluation of medicated feeds with antiparasitical and immune-enhanced Chinese herbal medicines against Ichthyophthirius multifiliis in grass carp (Ctenopharyngodon idellus).

Since malachite green was banned for using in food fish due to its carcinogenic and teratogenic effects on human, the search of alternative drug to treat Ichthyophthirius multifiliis becomes urgent. This study aimed to (1) evaluate the ethanol extracts of medicinal plants Cynanchum atratum, Zingiber officinale, Cynanchum paniculatum, immunostimulant (A), and immunostimulant (B) for their efficacy against I. multifiliis, and (2) determine effects of medicated feeds with C. atratum, Z. officinale, C. paniculatum, and immunostimulant (A) to treat I. multifiliis in grass carp. The results in this study showed that the minimum concentrations of C. atratum, Z. officinale, and C. paniculatum extracts for killing all theronts were 16, 8, and 16mg/L, respectively. In vivo experiments, fish fed with medicated feeds of C. atratum for 10days, or Z. officinale for 3days, or combination of three plants for 10days resulted in a significant reduction in the I. multifiliis infective intensity on grass carp after theronts exposure. Grass carp fed with medicated feeds of immunostimulant (A) for 21days showed no infection and 100% of survival 15days post theronts exposure. Therefore, immunostimulant (A) is a promising feed supplement to treated I. multifiliis with good antiparasitic efficacy.

Anti-parasitic effects of Leptomycin B isolated from Streptomyces sp. CJK17 on marine fish ciliate Cryptocaryon irritans

The present study was conducted aiming to evaluate the in vitro and in vivo anti-parasitic efficacy of an isolated compound against the ciliate Cryptocaryon irritans. The compound was previously isolated from fermentation products of Streptomyces sp. CJK17 and designated as SFrD. Toxicity of the compound SFrD against the fish hosts (Larimichthys crocea) was also tested and its chemical structure was elucidated. The obtained results showed that the compound has potent anti-parasitic efficacy with the 10min-, 1h-, 2h-, 3h- and 4h-LC50 (95% Confidence Intervals) of 6.8 (6.5–7.1), 3.9 (2.8–5.0), 3.3 (2.6–4.0), 2.7 (2.3–3.1) and 2.5 (2.2–2.8)mgL−1 against theronts of C. irritans and the 6h-LC50 (95% CI) of 3.0 (2.8–3.2)mgL−1 against the tomonts, respectively. Exposure of the compound SFrD remarkably reduced the mortality of fish infected with C. Irritans, from 100% in the control group to 61.7% and 38.3% in groups of 3.1mgL−1 and 6.3mgL−1, respectively. In the test of exposing fish to 40mgL−1 compound SFrD for 24h, no visible effects were observed affecting the normal behavior or any macroscopic changes. By spectrum analysis (EI-MS, 1H NMR and 13C NMR), the compound SFrD was identified as Leptomycin B. This study firstly demonstrated that Leptomycin B has potent anti-parasitic efficacy against ciliates in cultured marine fish.

English

Tick infestation is considered to be a major concern as ticks cause widespread distress, act as vectors of disease and affect the economic conditions of livestock-rearing. Although the use of chemicals is still the most effective method of tick control, uncontrolled applications may have accelerated the emergence of tick resistance to several active ingredients available. The present work estimated the efficacy of two commonly used acaricides (amitraz and diazinon) against Rhipicephalus pulchellus and Hyalomma dromedarii collected from Camelus dromedarius by using in vitro and in vivo field trial methods. The in vitro test employed a preliminary immersion technique and the field trial involved a manual application of the acaricides on camels predominantly infested with both tick species under field condition. Three groups of camels (I, II and III) containing six head of animals each with a mean number of &gt;20 tick counts received diazinon, amitraz and distilled water, respectively. The in vitro assay showed no statistically significant tickicidal difference (p&gt;0.05) between these compounds although amitraz proved a relatively better efficacy. For both acaricides, doubled concentration was more effective in tick killing. The field trial evidenced that both drugs caused a significant reduction (p&lt;0.05) in mean tick count when compared to the negative control. However, amitraz showed a significant superiority (p&lt;0.05) as compared to diazinon (85.2%) eliminating almost all ticks from the body of infested camels 72 h post treatment with 99.1% efficacy. Whereas, the maximum antiparasitic efficacy brought about by diazinon was 85.2% after 72 h of application. In conclusion, comparing the efficacy of the two acaricides from these preliminary tests, amitraz is the preferable one. Furthermore, right application and choice of acaricides needs to be pursued in order to avoid any resistance against ticks in camels. &nbsp; Key words: Amitraz, camel, diazinon, efficacy, Rhipicephalus pulchellus, Hyalomma dromedarii.

Efficacy of Albendazole-Chitosan Microsphere-based Treatment for Alveolar Echinococcosis in Mice.

This study aimed to investigate the pharmacology and anti-parasitic efficacy of albendazole–chitosan microspheres (ABZ-CS-MPs) for established intraperitoneal infections of Echinococcus multilocularis metacestodes in an experimental murine model. Male outbred Kunming mice infected with E. multilocularis Metacestodes were administered with three ABZ formulations, namely, ABZ-CS-MPs, Liposome–Albendazole (L-ABZ), and albendazole tablet (ABZ-T). Each of the ABZ formulations was given orally at three different doses of 37.5, 75, and 150mg/kg, three times a week for 12 weeks postinfection. After administering the drugs, we monitored the pharmacological performance and anti-parasitic efficacy of ABZ-CS-MPs compared with L-ABZ, and ABZ-T treated mice. ABZ-CS-MPs reduced the weight of tissues containing E. multilocularis metacestodes most effectively compared with the ABZ-T group and untreated controls. Metacestode grown was Highly suppressed during treatment with ABZ-CS-MPs. Significantly higher plasma levels of ABZ metabolites were measured in mice treated with ABZ-CS-MPs or L-ABZ compared with ABZ-T. In particular, enhanced ABZ-sulfoxide concentration profiles were observed in the mice given 150mg/kg of ABZ-CS-MPs, but not in the mice treated with L-ABZ. Histological examination showed that damages caused disorganization of both the germinal and laminated layers of liver hyatid cysts, demolishing their characteristic structures after treatment with ABZ-CS-MPs or L-ABZ. Over time, ABZ-CS-MPs treatment induced a shift from Th2-dominant to Th1-dominant immune response. CS-MPs As a new carrier exhibited improved absorption and increased bioavailability of ABZ in the treatment of E. multilocularis infections in mice.

A Two-Component DNA-Prime/Protein-Boost Vaccination Strategy for Eliciting Long-Term, Protective T Cell Immunity against Trypanosoma cruzi.

In this study, we evaluated the long-term efficacy of a two-component subunit vaccine against Trypanosoma cruzi infection. C57BL/6 mice were immunized with TcG2/TcG4 vaccine delivered by a DNA-prime/Protein-boost (D/P) approach and challenged with T. cruzi at 120 or 180 days post-vaccination (dpv). We examined whether vaccine-primed T cell immunity was capable of rapid expansion and intercepting the infecting T. cruzi. Our data showed that D/P vaccine elicited CD4+ (30-38%) and CD8+ (22-42%) T cells maintained an effector phenotype up to 180 dpv, and were capable of responding to antigenic stimulus or challenge infection by a rapid expansion (CD8>CD4) with type 1 cytokine (IFNγ+ and TFNα+) production and cytolytic T lymphocyte (CTL) activity. Subsequently, challenge infection at 120 or 180 dpv, resulted in 2-3-fold lower parasite burden in vaccinated mice than was noted in unvaccinated/infected mice. Co-delivery of IL-12- and GMCSF-encoding expression plasmids provided no significant benefits in enhancing the anti-parasite efficacy of the vaccine-induced T cell immunity. Booster immunization (bi) with recombinant TcG2/TcG4 proteins 3-months after primary vaccine enhanced the protective efficacy, evidenced by an enhanced expansion (1.2-2.8-fold increase) of parasite-specific, type 1 CD4+ and CD8+ T cells and a potent CTL response capable of providing significantly improved (3-4.5-fold) control of infecting T. cruzi. Further, CD8+T cells in vaccinated/bi mice were predominantly of central memory phenotype, and capable of responding to challenge infection 4-6-months post bi by a rapid expansion to a poly-functional effector phenotype, and providing a 1.5-2.3-fold reduction in tissue parasite replication. We conclude that the TcG2/TcG4 D/P vaccine provided long-term anti-T. cruzi T cell immunity, and bi would be an effective strategy to maintain or enhance the vaccine-induced protective immunity against T. cruzi infection and Chagas disease.

Evaluation of nystatin isolated from Streptomyces griseus SDX-4 against the ciliate, Ichthyophthirius multifiliis.

The present study was conducted to evaluate the in vitro and in vivo antiparasitic efficacy of active compounds from the bacterial extracellular products of Streptomyces griseus SDX-4 against Ichthyophthirius multifiliis. Bioassay-guided fractionation and isolation of compounds with antiparasitic activity were performed on n-butanol extract of S. griseus yielding a pure bioactive compound, nystatin (Nys), identified by comparing spectral data (EI-MS, (1)H NMR, and (13)C NMR) with literature values. Results from in vitro antiparasitic assays revealed that Nys could be 100% effective against I. multifiliis theronts and encysted tomonts at the concentration of 6.0 mg L(-1), with the median effective concentration (EC50) values of 3.1 and 2.8 mg L(-1) for theronts and encysted tomonts (4 h), respectively. Results of in vivo test demonstrated that the number of I. multifiliis trophonts on the gold fish treated with Nys was markedly lower than the control group at 10 days after exposed to theronts (p < 0.05). In the control group, 85.7% mortality was observed owing to heavy I. multifiliis infection at 10 days after the exposure. On the other hand, only 23.8% mortality owing to parasite infection was recorded in the groups treated with the Nys (4.0 and 6.0 mg L(-1)). In addition, our results showed that the survival and reproduction of I. multifiliis tomont exited from the fish were significantly reduced after treated with the 6.0 mg L(-1) Nys. The median lethal dose (LD50) of Nys for goldfish was 16.8 mg L(-1). This study firstly demonstrated that Nys has potent antiparasitic efficacy against I. multifiliis, and it can be a good candidate drug for chemotherapy and control of I. multifiliis infections.

Anti-Parasitic Efficacy of Some Essential Oils/Extracts Against Itch Mite, Sarcoptes scabiei

Anti-Parasitic Efficacy of Some Essential Oils/Extracts Against Itch Mite, Sarcoptes scabiei

Lead Identification to Clinical Candidate Selection: Drugs for Chagas Disease

Chagas disease affects 8 million people worldwide and remains a main cause of death due to heart failure in Latin America. The number of cases in the United States is now estimated to be 300,000, but there are currently no Food and Drug Administration (FDA)–approved drugs available for patients with Chagas disease. To fill this gap, we have established a public-private partnership between the University of California, San Francisco and the Genomics Institute of the Novartis Research Foundation (GNF) with the goal of delivering clinical candidates to treat Chagas disease. The discovery phase, based on the screening of more than 160,000 compounds from the GNF Academic Collaboration Library, led to the identification of new anti-Chagas scaffolds. Part of the screening campaign used and compared two screening methods, including a colorimetric-based assay using Trypanosoma cruzi expressing β-galactosidase and an image-based, high-content screening (HCS) assay using the CA-I/72 strain of T. cruzi. Comparing molecules tested in both assays, we found that ergosterol biosynthesis inhibitors had greater potency in the colorimetric assay than in the HCS assay. Both assays were used to inform structure-activity relationships for antiparasitic efficacy and pharmacokinetics. A new anti–T. cruzi scaffold derived from xanthine was identified, and we describe its development as lead series.

In Vitro and In Vivo Antiparasitic Efficacy of Praziquantel against Monogenean Ligictaluridus floridanus in Channel Catfish (Ictalurus punctatus)

In Vitro and In Vivo Antiparasitic Efficacy of Praziquantel against Monogenean Ligictaluridus floridanus in Channel Catfish (Ictalurus punctatus)