Drug development for the treatment of onchocerciasis: Population pharmacokinetic and adverse events modeling of emodepside

BackgroundTo accelerate the progress towards onchocerciasis elimination, a macrofilaricidal drug that kills the adult parasite is urgently needed. Emodepside has shown macrofilaricidal activity against a variety of nematodes and is currently under clinical development for the treatment of onchocerciasis. The aims of this study were i) to characterize the population pharmacokinetic properties of emodepside, ii) to link its exposure to adverse events in healthy volunteers, and iii) to propose an optimized dosing regimen for a planned phase II study in onchocerciasis patients.Methodology / Principal findingsPlasma concentration-time profiles and adverse event data were obtained from 142 subjects enrolled in three phase I studies, including a single-dose, and a multiple-dose, dose-escalation study as well as a relative bioavailability study. Nonlinear mixed-effects modeling was used to evaluate the population pharmacokinetic properties of emodepside. Logistic regression modeling was used to link exposure to drug-related treatment-emergent adverse events (TEAEs). Emodepside pharmacokinetics were well described by a transit-absorption model, followed by a 3-compartment disposition model. Body weight was included as an allometric function and both food and formulation had a significant impact on absorption rate and relative bioavailability. All drug-related TEAEs were transient, and mild or moderate in severity. An increase in peak plasma concentration was associated with an increase in the odds of experiencing a drug-related TEAE of interest.Conclusions/SignificancePharmacokinetic modeling and simulation was used to derive an optimized, body weight-based dosing regimen, which allows for achievement of extended emodepside exposures above target concentrations while maintaining acceptable tolerability margins.     

Prevalence rate and risk factors of human cystic echinococcosis: A cross-sectional,community-based,abdominal ultrasound study in rural and urban north-central Chile

BackgroundCystic echinococcosis (CE) caused by Echinococcus granulosus sensu lato (s.l.) is a neglected and underdiagnosed parasitic zoonosis that has a significant socioeconomic impact on rural communities relying on livestock farming. CE is endemic across Latin America, including Chile, where the Coquimbo region exhibits a relatively high record of hospital-based human cases and infected animals. However, the incidence of hospitalized CE cases may underestimate the real burden of infection in a population, since the majority of cases never reach medical attention or official disease records.Methodology/Principal findingsIn 2019, a cross-sectional, community-based study was conducted with the objectives of estimating for the first time the prevalence of human abdominal CE using abdominal ultrasound (US) screening in volunteers residing in urban and rural localities of the Monte Patria municipality located in Limarí province, Coquimbo region, Chile, and identifying the risk factors associated with human infection. Pre-screening activities included a 16-h lecture/hands-on training aimed at rural physicians that focused on the diagnosis of CE by US, based on current WHO recommendations. A total of 2,439 (~8% of municipality inhabitants) people from thirteen target localities were screened by abdominal US in June-July 2019. We found an overall CE prevalence of 1.6% (95% CI 1.1–2.2) with a significantly higher likelihood of infection in rural localities, older age classes and people drinking non-potable water; 84.6% of infected volunteers were newly diagnosed with CE. Cysts were either in active or inactive stages in equal proportions; active cysts were detected in all age classes, while 95.7% of inactive cysts occurred in >40 years-old subjects.Conclusions/SignificanceThis is the first US survey aimed at detecting human infection caused by Echinococcus granulosus s.l. in Chile. Our findings indicate a high CE prevalence in the area, and contribute to define the demographic and behavioral risk factors promoting the transmission of the parasitic infection within target communities. Our results support the implementation of cost-effective strategies for the diagnosis, treatment and control of CE, and the need to improve the epidemiological surveillance system in Chile.     

Remodeling of the actin cytoskeleton during mammalian sperm capacitation and acrosome reaction

The sperm acrosome reaction and penetration of the egg follow zona pellucida binding only if the sperm has previously undergone the poorly understood maturation process known as capacitation. We demonstrate here that in vitro capacitation of bull, ram, mouse, and human sperm was accompanied by a time-dependent increase in actin polymerization. Induction of the acrosome reaction in capacitated cells initiated fast F-actin breakdown. Incubation of sperm in media lacking BSA or methyl-beta-cyclodextrin, Ca(2+), or NaHCO(3), components that are all required for capacitation, prevented actin polymerization as well as capacitation, as assessed by the ability of the cells to undergo the acrosome reaction. Inhibition of F-actin formation by cytochalasin D blocked sperm capacitation and reduced the in vitro fertilization rate of metaphase II-arrested mouse eggs. It has been suggested that protein tyrosine phosphorylation may represent an important regulatory pathway that is associated with sperm capacitation. We show here that factors known to stimulate sperm protein tyrosine phosphorylation (i.e., NaHCO(3), cAMP, epidermal growth factor, H(2)O(2), and sodium vanadate) were able to enhance actin polymerization, whereas inhibition of tyrosine kinases prevented F-actin formation. These data suggest that actin polymerization may represent an important regulatory pathway in with sperm capacitation, whereas F-actin breakdown occurs before the acrosome reaction.     

Facile construction of mutations in Haemophilus ducreyi using lacZ as a counter-selectable marker

Haemophilus ducreyi is a Gram-negative bacterium which is the causative agent of chancroid, an ulcerative sexually transmitted disease. In order to understand the pathogenesis of H. ducreyi disease, studies designed to identify potential virulence determinants and construct mutants deficient in the elaboration of these determinants have been undertaken in several laboratories. At the present time, construction of isogenic mutants is accomplished by electroporation of linearized DNA containing insertionally inactivated H. ducreyi genes followed by selection for the resistance marker encoded on the inactivated gene. In our experience, certain mutants are difficult to construct using this procedure. In the construction of strains containing lacZ as a reporter gene, we observed that the growth of lacZ expressing H. ducreyi was inhibited in the presence of X-gal. We have exploited this observation to develop a new strategy for the construction of isogenic H. ducreyi mutants.     

Aerobic salivary bacteria in wild and captive Komodo dragons

During the months of November 1996, August 1997, and March 1998, saliva and plasma samples were collected for isolation of aerobic bacteria from 26 wild and 13 captive Komodo dragons (Varanus komodoensis). Twenty-eight Gram-negative and 29 Gram-positive species of bacteria were isolated from the saliva of the 39 Komodo dragons. A greater number of wild than captive dragons were positive for both Gram-negative and Gram-positive bacteria. The average number of bacterial species within the saliva of wild dragons was 46% greater than for captive dragons. While Escherichia coli was the most common bacterium isolated from the saliva of wild dragons, this species was not present in captive dragons. The most common bacteria isolated from the saliva of captive dragons were Staphylococcus capitis and Staphylococcus capitis and Staphylococcus caseolyticus, neither of which were found in wild dragons. High mortality was seen among mice injected with saliva from wild dragons and the only bacterium isolated from the blood of dying mice was Pasteurella multocida. A competitive inhibition enzyme-linked immunosorbent assay revealed the presence of anti-Pasteurella antibody in the plasma of Komodo dragons. Four species of bacteria isolated from dragon saliva showed resistance to one or more of 16 antimicrobics tested. The wide variety of bacteria demonstrated in the saliva of the Komodo dragon in this study, at least one species of which was highly lethal in mice and 54 species of which are known pathogens, support the observation that wounds inflicted by this animal are often associated with sepsis and subsequent bacteremia in prey animals.     

Synthesis and antiviral activity of novel HCV NS3 protease inhibitors with P4 capping groups

We have synthesized and evaluated a series of novel HCV NS3 protease inhibitors with various P4 capping groups, which include urea, carbamate, methoxy-carboxamide, cyclic carbamate and amide, pyruvic amide, oxamate, oxalamide and cyanoguanidine. Most of these compounds are remarkably potent, exhibiting single-digit to sub-nanomolar activity in the enzyme assay and cell-based replicon assay. Selected compounds were also evaluated in the protease-inhibitor-resistant mutant transient replicon assay, and they were found to show quite different potency profiles against a panel of HCV protease-inhibitor-resistant mutants.     

Changes in jasmonate and gibberellin levels during development of potato plants (Solanum tuberosum)

Among the multiple environmental signals and hormonal factors regulatingpotato plant morphogenesis and controlling tuber induction, jasmonates (JAs)andgibberellins (GAs) are important components of the signalling pathways in theseprocesses. In the present study, with Solanum tuberosum L.cv. Spunta, we followed the endogenous changes of JAs and GAs during thedevelopmental stages of soil-grown potato plants. Foliage at initial growthshowed the highest jasmonic acid (JA) concentration, while in roots the highestcontent was observed in the stage of tuber set. In stolons at the developmentalstage of tuber set an important increase of JA was found; however, in tubersthere was no change in this compound during tuber set and subsequent growth.Methyl jasmonate (Me-JA) in foliage did not show the same pattern as JA; Me-JAdecreased during the developmental stages in which it was monitored, meanwhileJA increased during those stages. The highest total amount of JAs expressed asJA+Me-JA was found at tuber set. A very important peak ofJA in roots was coincident with that observed in stolons at tuber set. Also, aprogressive increase of this compound in roots was shown during the transitionof stolons to tubers. Of the two GAs monitored, gibberellic acid(GA₃) was the most abundant in all the organs. While GA₁and GA₃ were also found in stolons at the time of tuber set, noothermeasurements of GAs were obtained for stolons at previous stages of plantdevelopment. Our results indicate that high levels of JA and GAs are found indifferent tissues, especially during stolon growth and tuber set.     

Phosphorylation of LHI β During Membrane Synthesis in the Photosynthetic Bacterium Rhodovulum sulfidophilum

Cells of Rhv. sulfidophilum were grown under different conditions in the presence of ³²P-phosphate and the corresponding H and L membrane fractions obtained and fractionated by SDS-PAGE. Both membranes showed almost identical polypeptide composition. The bacteriochlorophyll (Bchl) specific content in H was always lower that in L. As described before, oxygen did not regulate gene expression. Under high light, an almost two- to threefold decrease of the cellular specific Bchl content was observed. Pulse and chase experiments showed that transitions from aerobiosis to light-anaerobiosis did not quantitatively affect the Bchl content of the membranes, although a turnover of the ³²P-phosphate and ³⁵S-methionine was observed. LHI β was the only polypeptidic subunit of the Bchl-binding polypeptides that was phosphorylated in vivo, and phosphotyrosine was the only phosphorylated amino acid detectable. The phosphorylated LHI β was determined to be insoluble in the organic solvent mixture of (vol/vol) 1:1 chloroform-methanol containing ammonium acetate (0.1 m final concentration). Treatment with a chaotropic agent such as Na₂CO₃ solubilized the phosphorylated LHI β, indicating that part of this posttranslationally modified polypeptide was not inserted in a transmembrane position. These results were used to speculate about the regulatory properties of this posttranslational modification of LHI β on membrane differentiation. Received: 30 August 2000 / Accepted: 2 October 2000     

Potentiation of dimethylnitrosamine genotoxicity in rat hepatocytes isolated following ethanol treatment in vivo

Unscheduled DNA synthesis (UDS), following exposure to dimethylnitrosamine (DMN), was potentiated in cultured hepatocytes isolated following treatment of rats for 14 or 28 days with 20% ethanol/5% sucrose solution. Ethanol treatment was associated with increased UDS, a concomitant increase in hepatic microsomal protein concentration and DMN N-demethylase activity. Increased aniline hydroxylase activity of hepatic microsomes from ethanol-treated rats preceded the measured increase in microsomal protein content or DMN metabolism. The increase in metabolism of DMN in vitro and potentiation of DMN-induced UDS associated with ethanol treatment may contribute to a synergistic effect of ethanol on DMN hepatotoxicity and carcinogenicity. In contrast, ethanol pretreatment did not increase the cytotoxicity of DMN as characterized by enzyme release.