Separation of praziquantel enantiomers using simulated moving bed chromatographic unit with performance designed for semipreparative applications

Praziquantel (PZQ) composes a regular medicine available in a tablet form to fight schistosomiasis and just half of its mass is composed by the active principle (L‐PZQ), the other half, D‐PZQ, is frequently associated to a strong bitter taste. Moreover, optically pure L‐PZQ derivatives could be used in studies about adult and juvenile worms' resistance. Nowadays, these studies use racemic PZQ (rac‐PZQ) as starting point. The D‐PZQ, which would be discarded, could be racemized, coming back as feed concentration in the process. The present work aims to get L‐PZQ and D‐PZQ with high optical purities (more than 97%) and productivity (more than 253 g kg_ads^?1 day^?1) towards semipreparative scale for researches involving L‐PZQ, L‐PZQ derivatives, and D‐PZQ racemization. In order to achieve this goal, a built‐in‐house simulated moving bed chromatographic unit with the cellulose tris (3‐chloro‐4‐methylphenylcarbamate) (Chiralcel OZ) as chiral stationary phase (CSP) was used to investigate different scenarios of separation according to a well‐known design method called triangle theory. In all scenarios investigated, at least one of the outlet streams presented high optically purity for one of the enantiomers. Comparison with literature showed superior performance of our unit even at racemic mixture concentrations that were 10 times lower than the racemic concentrations found in literature.     

NMR studies of chiral discrimination relevant to the enantioseparation of N-acylarylalkylamines by an (R)-phenylglycinol-derived chiral selector

Recently, it was reported that the chiral recognition ability of (R)-N-3,5-dinitrobenzoyl phenylglycinol derivative was examined as a new HPLC chiral stationary phase (CSP 1) for the resolution of racemic N-acylnaphthylalkylamines. However, the mechanism of chiral discrimination on the CSP remained elusive until now. In this study, a spectroscopic investigation of the chiral discrimination mechanism of CSP 1 was undertaken using mixtures of (R)-N-3,5-dinitrobenzoyl phenylglycinol-derived chiral selector (2) and each of the enantiomers of N-acylnaphthylalkylamines (3) by NMR study. First, the differences in free energy changes (DeltaDeltaG) upon diastereomeric complexation in solution between the complex of each isomer with chiral selector 2 by NMR titration were calculated. The values were then compared with those estimated by chiral HPLC. The chemical shift changes of each proton on the chiral selector and analytes were also checked and it was found that the chemical shift changes decreased continuously as the acyl group on analytes increased in length. This observation was consistent with the HPLC data. From these experimental results, the interaction mechanism of chiral discrimination between the chiral selector and the analytes is more precisely explained.     

Validation of sensitivity to praziquantel using Schistosoma mansoni worm muscle tension and Ca2+-uptake as possible in vitro correlates to in vivo ED50 determination

Schistosome worm muscle tension and [45Ca2+]-uptake were tested as possible correlates of susceptibility to praziquantel (PZQ) assessed by estimating the drug ED50. Schistosoma mansoni cercariae of PZQ sensitive (S-CD, S-MOC and S-GP) and insensitive S. mansoni isolates (I-EE2, I-BANL and I-Senegal 47) were used to infect batches of CD-1 Swiss albino mice. Seven weeks after infection, animals of each batch were divided into six groups. Five of them received PZQ in doses of 12.5, 25, 50, 100 or 200 mg/kg PZQ, respectively, for five consecutive days, while the sixth was left as untreated controls. Two weeks after treatment mice were sacrificed, perfused and PZQ ED50's were estimated. Male worms recovered from infected untreated controls were examined for their muscle tension increase in response to PZQ using a physiological recorder coupled to a photooptic transducer. [45Ca2+]-uptake of male worms in the presence and absence of PZQ was determined using a liquid scintillation beta counter. Data revealed that PZQ insensitive isolates had significantly higher drug ED50 (>130 mg/kg) than PZQ sensitive isolates with ED50's <100 mg/kg. Moreover, in response to PZQ they were found to possess significant reductions in their worm muscle tension and their [45Ca2+]-uptake were <100%. Both parameters showed a significant negative correlation to PZQ ED50 in vivo and a significant positive correlation to each other.     

Pharmacodynamics of mefloquine and praziquantel combination therapy in mice harbouring juvenile and adult Schistosoma mansoni

Praziquantel (PZQ) is currently the only drug widely used for the treatment of schistosomiasis, but the antimalarial drug mefloquine (Mef) possesses interesting antischistosomal properties. Combination therapy with these two drugs has been suggested as a strategy for transmission control, as PZQ is active against adult worms and Mef is active against schistosomula. To examine the efficacy of combination therapy, Schistosoma mansoni-reinfected mice were separated into seven groups: untreated (I), treated with PZQ in doses of 200 mg/kg (II) or 1,000 mg/kg (III), treated with Mef in doses of 200 mg/kg (IV) or 400 mg/kg (V); each dose was divided equally and given on two consecutive days. Group VI was treated with doses of PZQ + Mef as in groups II and IV, respectively, while group VII was treated with PZQ + Mef as in groups III and V, respectively. PZQ + Mef at the reduced doses of 200 mg/kg each enhanced the therapeutic efficacy over the reduced PZQ dose alone as shown by a very high reduction in the total numbers of mature worms (95% vs. 49%), immature worms (96% vs. 29%) and the complete eradication of immature females, mature females and immature eggs. The reduction in worm burden was associated with the healing of hepatic granulomatous lesions and the normalisation of all liver enzymes. Therefore, the use of Mef with PZQ is more effective than PZQ alone and should be considered for clinical trials in humans as a potential treatment regimen to prevent treatment failures in areas with high rates of schistosomiasis.     

Direct screening of chiral discrimination abilities of chiral hosts using mass spectrometry

A simultaneous estimation of the chiral discrimination abilities of several chiral hosts was demonstrated on the basis of one mass spectrum. The chiral host mixture, including H(1), H(2), H(3) ..., and H(m) (m: number of hosts) was prepared by etherification of several chiral alcohols with bistosylate of diethylene glycol. An equimolar mixture of a deuterium-labeled (S)- and unlabeled (R)-enantiomer of an amino acid isopropyl ester hydrochloride (G(S-dn) (+)Cl(-) and G(R) (+)Cl(-), n: number of deuterium atoms) was added to the chiral host mixture, and the FAB mass spectrum was measured to evaluate the chiral discrimination ability of each host in the mixture without isolation. The chiral discrimination ability of each host toward the guest is represented by the relative peak intensity of the diastereomeric complex ion pair, I(H(m) + G(R)((+)/I(H(m) + G(S-dn))(+) (=I(R)/I(S-dn) value). Several new hosts showed good chiral discrimination toward the guest.     

Inhibition or Knockdown of ABC Transporters Enhances Susceptibility of Adult and Juvenile Schistosomes to Praziquantel

Parasitic flatworms of the genus Schistosoma cause schistosomiasis, a neglected tropical disease that affects hundreds of millions. Treatment of schistosomiasis depends almost entirely on the drug praziquantel (PZQ). Though essential to treating and controlling schistosomiasis, a major limitation of PZQ is that it is not active against immature mammalian-stage schistosomes. Furthermore, there are reports of field isolates with heritable reductions in PZQ susceptibility, and researchers have selected for PZQ-resistant schistosomes in the laboratory. P-glycoprotein (Pgp; ABCB1) and other ATP binding cassette (ABC) transporters remove a wide variety of toxins and xenobiotics from cells, and have been implicated in multidrug resistance (MDR). Changes in ABC transporter structure or expression levels are also associated with reduced drug susceptibility in parasitic helminths, including schistosomes. Here, we show that the activity of PZQ against schistosome adults and juveniles ex vivo is potentiated by co-administration of either the highly potent Pgp inhibitor tariquidar or combinations of inhibitors targeting multiple ABC multidrug transporters. Adult worms exposed to sublethal PZQ concentrations remain active, but co-administration of ABC transporter inhibitors results in complete loss of motility and disruption of the tegument. Notably, juvenile schistosomes (3–4 weeks post infection), normally refractory to 2 µM PZQ, become paralyzed when transporter inhibitors are added in combination with the PZQ. Experiments using the fluorescent PZQ derivative (R)-PZQ-BODIPY are consistent with the transporter inhibitors increasing effective intraworm concentrations of PZQ. Adult worms in which expression of ABC transporters has been suppressed by RNA interference show increased responsiveness to PZQ and increased retention of (R)-PZQ-BODIPY consistent with an important role for these proteins in setting levels of PZQ susceptibility. These results indicate that parasite ABC multidrug transporters might serve as important targets for enhancing the action of PZQ. They also suggest a potentially novel and readily-available strategy for overcoming reduced PZQ susceptibility of schistosomes.     

Pathological and immunological evaluation of different regimens of praziquantel treatment in a mouse model of Schistosoma mansoni infection

BackgroundOne of the considerable challenges of schistosomiasis chemotherapy is the inefficacy of praziquantel (PZQ) at the initial phase of the infection. Immature schistosomes are not susceptible to PZQ at the curative dose. Here, we investigated the efficacy of different PZQ regimens administered during the initial stage of Schistosoma mansoni infection in mice.Methodology/Principal findingsTwo months-old mice were individually infected with 80 S. mansoni cercariae and divided into one infected-untreated control group (IC) and four PZQ-treated groups: PZQ at 100 mg/kg/day for five consecutive days (group PZQ1), PZQ at 100 mg/kg/day for 28 days (group PZQ2), PZQ at 18 mg/kg/day for 28 days (group PZQ3) and a single dose of PZQ at 500 mg/kg (group PZQ4). The treatment started on day one post-infection (p.i), and each group of mice was divided into two subgroups euthanized on day 36 or 56 p.i, respectively. We determined the mortality rate, the parasitological burden, the hepatic and intestinal granulomas, the serum levels of Th-1, Th-2, and Th-17 cytokines, and gene expression. The treatment led to a significant (p < 0.001) reduction of worm burden and egg counts in the intestine and liver in groups PZQ2 and PZQ3. On 56^th day p.i, there was a significant reduction (p < 0.001) of the number and volume of the hepatic granulomas in groups PZQ2 and PZQ3 compared to group PZQ1 or PZQ4. Moreover, in group PZQ3, the serum levels of IFN-γ, TNF-α, IL-13, and IL-17 and their liver mRNA expressions were significantly reduced while IL-10 and TGF-β gene expression significantly increased. The highest mortality rate (81.25%) was recorded in group PZQ2.Conclusion/SignificanceThis study revealed that the administration of PZQ at 18 mg/kg/day for 28 consecutive days was the optimal effective posology for treating S. mansoni infection at the initial stage in a murine model.     

Drug-metabolizing enzymes and praziquantel bioavailability in mice harboring Schistosoma mansoni isolates of different drug susceptibilities

The level of drug-metabolizing enzymes (cytochrome P450 [CYP450] and cytochrome b5 [cyt b5]) and the bioavailability of praziquantel (PZQ) were investigated in batches of mice infected with Schistosoma mansoni displaying either a decreased susceptibility to PZQ ("EE2" and "BANL"-isolates), or a normal susceptibility to the drug ("CD" isolate). Each batch was divided into 2 groups. The first group was further subdivided into 5 subgroups. Subgroups 1 to 4 were treated 7 wk postinfection (PI) with oral PZQ at 25, 50, 100, and 200 mg/kg for 5 consecutive days, whereas the fifth subgroup was administered the vehicle only as control. Animals were perfused 9 wk PI, and worms were counted to estimate PZQ ED50. CYP450 and cyt b5 were examined in hepatic microsomes of infected untreated mice and of infected mice treated with 25 and 200 mg/ kg PZQ. The second group was given PZQ 7 wk PI and was further subdivided into 11 subgroups, killed at 2, 5, 15, 30, 60, 90, 120, 150, 180, 240, and 360 min postdosing to study pharmacokinetic parameters of PZQ. Mice harboring S. mansoni isolates having higher PZQ ED50 (170.3 mg/kg for EE2 and 249.9 mg/kg for BANL vs. 82.96 mg/kg for CD) had higher levels of CYP450 and cyt b5, a PZQ Cmax decreased by 19-30% and area under the serum concentration-time curve0-6 hr decreased by 57-74%. Data suggest that S. mansoni isolates that are less sensitive to PZQ induce a lower inhibition of hepatic drug-metabolizing enzymes, with a consequently higher metabolic transformation of PZQ.     

Efficacy of orally administered praziquantel against Zeuxapta seriolae and Benedenia seriolae (Monogenea) in yellowtail kingfish Seriola lalandi

We investigated the efficacy of praziquantel (PZQ) administered orally to yellowtail kingfish (Seriola lalandi in sea-cage aquaculture in South Australia) against the monogeneans Zeuxapta seriolae and Benedenia seriolae infesting gills and skin, respectively. PZQ was administered to fish by surface-coating feed pellets (Trial 1) or by direct intubation of the stomach (Trial 2). In both trials 4 daily doses were administered: 50 and 75 mg kg(-1) body weight (BW) d(-1) for 6 d, and 100 and 150 mg kg(-1) BW d(-1) for 3 d. Mean parasite intensity was compared between medicated fish and unmedicated control fish. In Trial 1, fish fed lower daily doses of PZQ for 6 d (50 and 75 mg kg(-1) BW d(-1)) had fewer Z. seriolae and B. seriolae than fish fed higher daily doses for 3 d (100 and 150 mg kg(-1) BW d(-1)). Fish rejected feed pellets surface-coated with PZQ, suggesting PZQ affected palatability of feed, and may explain differences in efficacy between treatments. In Trial 2, where PZQ was administered by intubation, there were fewer Z. seriolae and B. seriolae in medicated fish than control fish. Intubated PZQ was also effective against newly recruited Z. seriolae and B. seriolae. PZQ could be developed as a useful treatment for Z. seriolae and B. seriolae parasitising S. lalandi in sea-cage aquaculture if suspected palatability problems are resolved.     

Distribution of [3H]cholesterol-labelled liposomes with or without praziquantel in mice infected with Mesocestoides corti (Cestoda) tetrathyridia

The anthelmintic drug praziquantel (PZQ) has a short half-life in the circulation, necessitating repeated daily administration of PZQ for the therapy of larval stages of cestodes. The effect of incorporation of PZQ into multilamellar liposomes on their biodistribution in Mesocestoides corti (syn. M. vogae) infected mice has been examined using [3H]cholesterol as a liposomal marker. Incorporation of PZQ significantly increased the average size of liposomes with 70.3% of [3H]lip.PZQ particles up to 1.9 microm, whereas higher portion of [3H]liposomes (66.3% of total) were of smaller (up to 1.3 microm). Both liposome preparations were given intraperitoneally to avoid rapid sequestration in the liver. There were significant differences between [3H]liposomes and [3H]lip.PZQ-associated radioactivity in peritoneal adherent cells, liver- and peritoneal larvae, liver, spleen and lymph nodes within 16 days of examination. The highest uptake (about 2-fold more [3H]lip.PZQ than [3H]liposomes from the total dose) was found in peritoneal cells on day 1 post therapy (p.t.) followed by a rapid decline. The kinetic of decline in these cells recovered on day 1 p.t. was studied also in vitro. Disappearance of the marker due to the breakdown of liposomes and efflux of lipids and PZQ from cells was slower for [3H]lip.PZQ in comparison with drug-free liposomes and was not completed after 4 days-incubation. Significantly increased levels of radioactivity, more in [3H]liposomes treated groups, were recorded in the liver- and peritoneal larvae between days 8-16 p.t. indicating re-utilization of cholesterol by the larvae. The data suggest that incorporation of PZQ into liposomes contributes to the enlargement of liposome average size and slows down their degradation in phagocytosing cells. In this respect, these cells could serve as the secondary circulating depots for PZQ releasing it slowly to the circulation.     

Effect of bilirubin on toxicity induced by trifluoperazine, dibucaine and praziquantel to erythrocytes

Unconjugated bilirubin (UCB), like trifluoperazine (TFP), dibucaine (DBC) and praziquantel (PZQ), induces erythrocyte morphological changes, lysis and lipid exfoliation. In the present study we determined whether TFP, DBC and PZQ toxicity to erythrocytes was potentiated or reverted by UCB. Human erythrocytes were either treated or non-treated with 34.2 micromol/L UCB for 10 min prior to the incubation with toxic concentrations of TFP (0.12 mmol/L), DBC (1.5 mmol/L) or PZQ (3.0 mmol/L), for 1 h (37 degrees C). Studies of toxic effects included morphological analysis of erythrocytes, evaluation of hemoglobin release and loss of membrane lipids. Although UCB has an echinocytogenic effect, its co-incubation with TFP or PZQ did not alter the stomatocytogenic effect of the drug but enhanced DBC-induced stomatocytosis. Cell fusion was a common feature in experiments with DBC. Injurious effect of DBC to erythrocytes was potentiated by UCB as manifested by a marked increase in hemolysis (171%, p<0.05), and in elution of membrane cholesterol (73%, p<0.01) and phospholipids (123%, p<0.01). In opposite, toxic events produced by TFP and PZQ to erythrocytes were not aggravated by UCB. Interestingly, UCB prevented the loss of membrane cholesterol by PZQ (-36%, p<0.01), as well as that of phospholipids by TFP (-28%, p<0.05). These findings indicate that UCB potentiates DBC injury to erythrocytes, while protects membrane lipid elution by PZQ and TFP. Therefore, the relation of the benefits and risks of the administration of DBC to jaundiced patients should be carefully considered.     

Evaluation of chiral discrimination of highly negatively charged enantiomers by quaternary ammonium beta-cyclodextrin using 1H NMR

The positively charged quaternary ammonium cyclodextrin, QA-beta-CD, was previously used as a chiral selector to achieve baseline resolution of two of the dianionic enantiomers of disodium 3-(p-isothiocyanatophenoxy)-3-(p-isothiocyanatophenyl)propane-1,2-disulfate by capillary electrophoresis. The basis of the chiral discrimination between QA-beta-CD and the enantiomers was investigated by (1)H NMR spectroscopy. COSY and NOESY spectra were used to infer the role that molecular interactions and the stereocenters have upon association of QA-beta-CD with the enantiomers. A parallel two-step complexation model is used to rationalize the NMR and the chiral discrimination observed during separation of the enantiomers.     

Membrane effects of trifluoperazine, dibucaine and praziquantel on human erythrocytes

Trifluoperazine (TFP) is a potent antipsychotic agent, dibucaine (DBC) is a local anaesthetic and praziquantel (PZQ) is a highly effective agent against schistosomiasis. The present work was conducted to (i) investigate the cytotoxic effects of TFP, DBC and PZQ on human erythrocyte membranes; and (ii) compare the alterations induced by the cationic drugs (TFP and DBC) with those induced by the uncharged compound (PZQ), in an attempt to have a better insight on the pathways of each drug-membrane interaction. The erythrocyte morphological alterations induced by sublytic concentrations of TFP, DBC and PZQ were evaluated by scanning electron microscopy and expressed quantitatively by the morphological index. Haemolysis and release of membrane lipids (phospholipids and cholesterol) produced by selected concentrations of TFP, DBC and PZQ, were compared with those resulting from the corresponding triple concentrations of each drug. Our results showed that the uncharged molecule of PZQ induces the same morphological alterations (stomatocytosis) as the cationic drugs TFP and DBC. Haemolysis was shown to vary with the drug used and to be concentration-dependent, with values approximately 10-fold more elevated for TFP and DBC than for PZQ, which revealed a maximum of 6% haemolysis for the highest concentration tested. Different concentration-response curves were obtained for lipid elution, although the profiles of cholesterol and phospholipids released were similar for all drugs. Nevertheless, at a fixed rate of 50% haemolysis, TFP induced a approximately 2-fold increment in the elution of cholesterol when compared with that produced by DBC (P<0. 05). The different effects induced by TFP, DBC and PZQ on erythrocyte morphology, haemolysis and lipid exfoliation are related to the physical and chemical characteristics of each compound. These results suggest that distinct cell membrane interaction pathways lead to drug-specific mechanisms of cytotoxicity.     

Effect of Cyclodextrin Complexation on the Aqueous Solubility and Solubility/Dose Ratio of Praziquantel

Praziquantel (PZQ), the primary drug of choice in the treatment of schistosomiasis, is a highly lipophilic drug that possesses high permeability and low aqueous solubility and is, therefore, classified as a Class II drug according to the Biopharmaceutics Classification System (BCS). In this work, β-cyclodextrin (β-CD) and hydroxypropyl-β-cyclodextrin (HP-β-CD) were used in order to determine whether increasing the aqueous solubility of a drug by complexation with CDs, a BCS-Class II compound like PZQ could behave as BCS-Class I (highly soluble/highly permeable) drug. Phase solubility and the kneading and lyophilization techniques were used for inclusion complex preparation; solubility was determined by UV spectroscopy. The ability of the water soluble polymer polyvinylpyrolidone (PVP) to increase the complexation and solubilization efficiency of β-CD and HP-β-CD for PZQ was examined. Results showed significant improvement of PZQ solubility in the presence of both cyclodextrins but no additional effect in the presence of PVP. The solubility/dose ratios values of PZQ-cyclodextrin complexes calculated considering the low (150 mg) and the high dose (600 mg) of PZQ, used in practice, indicate that PZQ complexation with CDs may result in drug dosage forms that would behave as a BCS-Class I depending on the administered dose.     

Chiral separation and discrimination of catechin by sinorhizobial octasaccharides in capillary electrophoresis and C NMR spectroscopy

Succinoglycan, a sinorhizobial exopolysaccharide produced by Sinorhizobium meliloti, is composed of an octasaccharide subunit. S. meliloti produces both high-molecular-weight and low-molecular-weight (M_r < 10,000) succinoglycans which consist of monomers, dimers, or trimers. Succinoglycan monomers were isolated and further purified in the monomer series (M1, M2, and M3) by the degree of succinylation. We used sinorhizobial octasaccharides (M1, M2, and M3) as chiral additives in capillary electrophoresis (CE) for chiral separation of catechin and also as chiral shift reagents with ¹³C NMR spectroscopy for chiral discrimination of catechin. Chiral separation of catechin took place when sinorhizobial octasaccharides (M2 and M3) were added to the background electrolyte (BGE) in CE. NMR signal splittings were also observed in the interactions of sinorhizobial octasaccharides with the enantiomers of catechin. Both chiral separation and discrimination of catechin depend on the presence of succinate substituents of the linear monomeric octasaccharide in CE and NMR spectroscopy, suggesting that succinylation of sinorhizobial octasaccharide is decisive for the effective chiral separation and discrimination of catechin.     

Time-resolved fluorescent chirality sensing and imaging of malate in aqueous solution

Chiral discrimination of malates in aqueous solutions at near-neutral pH is achieved through fluorescence measurement and imaging using the europium-tetracycline complex (EuTc) as a fluorescent probe. The method is based on the significantly different fluorescence properties of the ternary complexes (Eu-Tc-malate) formed between EuTc and the enantiomeric malates. The enantiomeric excess (ee) of chiral malates can be quantified by both steady-state and time-resolved fluorescence, using either a conventional fluorescence microplate reader or fluorescence imaging. It offers a facile and sensitive method for high-throughput chiral discrimination.     

Praziquantel-encapsulated niosomes against Schistosoma mansoni with reduced sensitivity to praziquantel

Introduction: Praziquantel (PZQ) is the only commercially available drug for schistosomiasis. The current shortage of alternative effective drugs and the lack of successful preventive measures enhance its value. The increase in the prevalence of PZQ resistance under sustained drug pressure is, therefore, an upcoming issue.Objective: To overcome the tolerance to PZQ using nanotechnology after laboratory induction of a Schistosoma mansoni isolate with reduced sensitivity to the drug during the intramolluscan phase.Materials and methods: Shedding snails were treated with PZQ doses of 200 mg/kg twice/ week followed by an interval of one week and then repeated twice in the same manner. The success of inducing reduced sensitivity was confirmed in vitro via the reduction of cercarial response to PZQ regarding their swimming activity and death percentage at different examination times.Results: Oral treatment with a single PZQ dose of 500 mg/kg in mice infected with cercariae with reduced sensitivity to PZQ revealed a non-significant reduction (35.1%) of total worm burden compared to non-treated control mice. Orally inoculated PZQ- encapsulated niosomes against S. mansoni with reduced sensitivity to PZQ successfully regained the pathogen’s sensitivity to PZQ as evidenced by measuring different parameters in comparison to the non-treated infected animals with parasites with reduced sensitivity to PZQ. The mean total worm load was 1.33 ± 0.52 with a statistically significant reduction of 94.09% and complete eradication of male worms. We obtained a remarkable increase in the percentage reduction of tissue egg counts in the liver and intestine (97.68% and 98.56%, respectively) associated with a massive increase in dead eggs and the complete absence of immature stages.Conclusion: PZQ-encapsulated niosomes restored the drug sensitivity against laboratory- induced S. mansoni adult worms with reduced sensitivity to PZQ.     

Activity of praziquantel on in vitro transformed Schistosoma mansoni sporocysts

Praziquantel (PZQ) is effective against all the evolutive phases of Schistosoma mansoni. Infected Biomphalaria glabrata snails have their cercarial shedding interrupted when exposed to PZQ. Using primary in vitro transformed sporocysts, labeled with the probe Hoechst 33258 (indicator of membrane integrity), and lectin of Glycine max (specific for carbohydrate of N-acetylgalactosamine membrane), we evaluated the presence of lysosomes at this evolutive phase of S. mansoni, as well as the influence of PZQ on these acidic organelles and on the tegument of the sporocyst. Although the sporocyst remained alive, it was observed that there was a marked contraction of its musculature, and there occurred a change in the parasite's structure. Also, the acidic vesicles found in the sporocysts showed a larger delimited area after contact of the parasites with PZQ. Damages to the tegument was also observed, as show a well-marked labeling either with Hoechst 33258 or with lectin of Glycine max after contact of sporocysts with the drug. These results could partially explain the interruption/reduction mechanism of cercarial shedding in snails exposed to PZQ.     

Chiral recognition by fluorescent chemosensors based on N-dansyl-amino acid-modified cyclodextrins

Four kinds of N-dansyl-amino acid-modified beta-cyclodextrins (beta-CDs) were prepared as fluorescent chemosensors for chiral discrimination. The use of an amino acid as a spacer improved binding affinities and chiral discrimination abilities of the chemosensors. N-dansyl-l-Phe-modified beta-CD showed high d-selectivity for norbornane derivatives and N-dansyl-d-Phe-modified beta-CD showed high l-selectivity for menthol. Microcalorimetric titration results indicate that the chemosensors selectively accommodate the enantiomer that induces the least unfavorable entropy change on making an inclusion complex.     

Schistosoma haematobium treatment in 1-5 year old children: safety and efficacy of the antihelminthic drug praziquantel

Background

Morbidity due to schistosomiasis is currently controlled by treatment of schistosome infected people with the antihelminthic drug praziquantel (PZQ). Children aged up to 5 years are currently excluded from schistosome control programmes largely due to the lack of PZQ safety data in this age group. This study investigated the safety and efficacy of PZQ treatment in such children.

Methods

Zimbabwean children aged 1–5 years (n = 104) were treated with PZQ tablets and side effects were assessed by questionnaire administered to their caregivers within 24 hours of taking PZQ. Treatment efficacy was determined 6 weeks after PZQ administration through schistosome egg counts in urine. The change in infection levels in the children 1–5 years old (n = 100) was compared to that in 6–10 year old children (n = 435).

Principal Findings

Pre-treatment S. haematobium infection intensity in 1–5 year olds was 14.6 eggs/10 ml urine and prevalence was 21%. Of the 104 children, 3.8% reported side effects within 24 hours of taking PZQ treatment. These were stomach ache, loss of appetite, lethargy and inflammation of the face and body. PZQ treatment significantly reduced schistosome infection levels in 1–5 year olds with an egg reduction rate (ERR) of 99% and cure rate (CR) of 92%. This was comparable to the efficacy of praziquantel in 6–10 year olds where ERR was 96% and CR was 67%.

Interpretation/Significance

PZQ treatment is as safe and efficacious in children aged 1–5 years as it is in older children aged 6–10 years in whom PZQ is the drug of choice for control of schistosome infections.