Laboratory capacity assessments in 25 African countries at high risk of yellow fever, August-December 2018.

INTRODUCTION: accurate and timely laboratory diagnosis of yellow fever (YF) is critical to the Eliminate Yellow Fever Epidemics (EYE) strategy. Gavi, the Vaccine Alliance recognized the need to support and build capacity in the national and regional laboratories in the Global YF Laboratory Network (GYFLN) as part of this strategy. METHODS: to better understand current capacity, gaps and needs of the GYFLN laboratories in Africa, assessments were carried out in national and regional reference laboratories in the 25 African countries at high risk for YF outbreaks that were eligible for new financial support from Gavi. RESULTS: the assessments found that the GYFLN in Africa has high capacity but 21% of specimens were not tested due to lack of testing kits or reagents and approximately 50% of presumptive YF cases were not confirmed at the regional reference laboratory due to problems with shipping. CONCLUSION: the laboratory assessments helped to document the baseline capacities of these laboratories prior to Gavi funding to support strengthening YF laboratories.

Inclusion Complex of O-phthalaldehyde-Buprofezin with Dimethyl-ß-Cyclodextrin Using Thermochemically-Induced Fluorescence Derivatization (TIFD) Method and its Analytical Application in Waters.

Improvement of the TIFD method to determine buprofezin (BUP) founded on the O-phthalaldehyde (OPA)-thermoproduct complex of buprofezin (OPA-BUP) with dimethyl-ß-cyclodextrin (DMßCD) was investigated at 25 °C. The TIFD method developed in DMßCD medium, was optimized with respect to the reaction time, DMßCD concentration and pH. Based on the inclusion reaction, the OPA-BUP: DMßCD inclusion complex was developed in two aqueous media pH 7 and pH 13. A 1:1 stoichiometric ratio of OPA-BUP: DMßCD complex was obtained. The binding constants (K) and Gibbs energy (ΔG°) values increasing and decreasing with pH, respectively, show the spontaneous and thermodynamically favorable at 25 °C of the inclusion complexes formation. Normalized TIFD spectra were measured at 425 nm for emission and at 345 nm for excitation. Limits of detection (LOD) and quantification (LOQ) obtained, according to the pH, were in the ranges 0.05-0.1 ng mL ̶ 1 and 0.2-0.4 ng mL ̶ 1, respectively. Relative standard deviation (RSD) values, less than 1.3% corroborated TIFD method repeatability in DMßCD medium. Solid phase extraction (SPE) procedure which was used for quantitative analysis of natural water samples collected from Niayes area, led to satisfactory recovery rates values 99.5-117.3%.

New method for the determination of metolachlor and buprofezin in natural water using orthophthalaldehyde by thermochemically-induced fluorescence derivatization (TIFD).

Herbicide metolachlor (MET) and insecticide buprofezin (BUP) were determined in natural waters by means of a newly-developed, simple and sensitive thermochemically-induced fluorescence derivatization (TIFD) method. The TIFD approach is based on the thermolysis transformation of naturally non-fluorescent pesticides into fluorescent complex O-phthalaldehyde-thermoproduct(s) in water at 70°C for MET and at 80°C for BUP. The TIFD method was optimized with respect to the temperature, pH, complex formation kinetic and pesticides concentrations. The limit of detection (LOD=0.8ngmL(-1) for MET and 3.0ngmL(-1) for BUP) and quantification (LOQ=2.6ngmL(-1) for MET and 9.5 ngmL(-1) for BUP) values were low, and the relative standard deviation (RSD) values were small (between 1.2% and 1.8%), which indicates a good analytical sensitivity and a great repeatability of TIFD method. Recovery studies were performed on spiked well, sea and draining waters samples collected in the Niayes area by using the solid phase extraction (SPE) procedure. Satisfactory recovery results (84-118%) were obtained for the determination of MET and BUP in these natural waters.

Detecting Foci of Malaria Transmission with School Surveys: A Pilot Study in the Gambia.

BACKGROUND: In areas of declining malaria transmission such as in The Gambia, the identification of malaria infected individuals becomes increasingly harder. School surveys may be used to identify foci of malaria transmission in the community. METHODS: The survey was carried out in May-June 2011, before the beginning of the malaria transmission season. Thirty two schools in the Upper River Region of The Gambia were selected with probability proportional to size; in each school approximately 100 children were randomly chosen for inclusion in the study. Each child had a finger prick blood sample collected for the determination of antimalarial antibodies by ELISA, malaria infection by microscopy and PCR, and for haemoglobin measurement. In addition, a simple questionnaire on socio-demographic variables and the use of insecticide-treated bed nets was completed. The cut-off for positivity for antimalarial antibodies was obtained using finite mixture models. The clustered nature of the data was taken into account in the analyses. RESULTS: A total of 3,277 children were included in the survey. The mean age was 10 years (SD = 2.7) [range 4-21], with males and females evenly distributed. The prevalence of malaria infection as determined by PCR was 13.6% (426/3124) [95% CI = 12.2-16.3] with marked variation between schools (range 3-25%, p<0.001), while the seroprevalence was 7.8% (234/2994) [95%CI = 6.4-9.8] for MSP119, 11.6% (364/2997) [95%CI = 9.4-14.5] for MSP2, and 20.0% (593/2973) [95% CI = 16.5-23.2) for AMA1. The prevalence of all the three antimalarial antibodies positive was 2.7% (79/2920). CONCLUSIONS: This survey shows that malaria prevalence and seroprevalence before the transmission season were highly heterogeneous.

The role of retinoid X receptor alpha in regulating alcohol metabolism.

There is substantial overlap in retinol and alcohol metabolism. Mice that lack retinoic acid (RA) receptor retinoid X receptor alpha (RXRalpha) expression in the liver are more susceptible to alcoholic liver disease. To investigate the interaction between RXRalpha and alcoholic liver disease, ethanol metabolism was studied in hepatocyte RXRalpha-deficient [RXRalpha knockout (KO)] mice. Hepatocyte RXRalpha deficiency resulted in a significant increase in hepatic alcohol dehydrogenase (ADH) activity, ADH1 protein, but not Adh1 mRNA. Polysomal distribution analysis indicated that more polysome-associated Adh1 mRNA was present in the mutant mouse livers, suggesting increased ADH1 protein synthesis in RXRalpha KO mice compared with wild-type mice. However, ADH2 and ADH3 enzyme activities were not affected by RXRalpha deficiency. Although ethanol clearance was increased, acetaldehyde elimination was reduced when RXRalpha was not expressed in the liver. Both mitochondrial aldehyde dehydrogenase (ALDH) 2 and cytosolic ALDH activities were reduced in the mutant mice compared with the wild type. Western blot analysis revealed that the levels of ALDH1A1 and ALDH1A2 were decreased in the mutant mice. Semiquantitative reverse transcriptase-polymerase chain reaction indicated that liver Aldh1a1 mRNA level was also reduced due to the lack of RXRalpha expression. Thus, RXRalpha differentially affects ADH and ALDH activity, leading to an increase in alcohol clearance, but a reduction in acetaldehyde elimination. In addition, CYP2E1 as well as mitochondrial and cytosolic glutathione S-transferase activities were significantly lower in RXRalpha KO mice than in wild-type mice. Our results reveal the central role of RXRalpha in ethanol metabolism.

Retinoids activate the RXR/SXR-mediated pathway and induce the endogenous CYP3A4 activity in Huh7 human hepatoma cells.

Steroid and xenobiotic receptor (SXR) or human pregnane X receptor (hPXR) dimerizes with retinoid X receptor (RXR) and regulates the transcription of genes encoding xenobiotic-metabolizing enzymes such as CYP3A4. Rifampin, the classical activator of CYP3A4, binds to SXR directly. It is unclear whether various natural and synthetic retinoids can regulate the expression of CYP3A4. To evaluate the effects of retinoids on the RXR/SXR-mediated pathway, transient transfection assays were performed on both CV-1 and human hepatoma Huh7 cells using a reporter construct containing multiple RXR/SXR consensus binding elements (an everted repeat with a 6-nucleotide spacer, ER-6). The results revealed that eight out of 13 retinoids screened significantly induced the RXR/SXR-mediated pathway in Huh7 cells. At an equal molar concentration, the acid forms (9-cis-RA, 13-cis-RA, and all-trans-RA) or aldehyde, the direct precursor of acid (9-cis-retinal and 13-cis-retinal), exhibited a greater or similar potency than rifampin. Depending on the ligands, RXR may serve as a silent or an active partner of SXR. Additionally, retinoids can increase CYP3A4 enzyme activity in Huh7 cells. To further evaluate the potential drug-drug interactions, which may be caused by retinoids, Huh7 cells were pretreated with 9-cis-RA and followed by acetaminophen. We showed that 9-cis-RA enhanced the covalent binding of N-acetyl-p-quinoneimine, a toxic intermediate of acetaminophen produced by phase I enzymes oxidation. This result suggested that drug-drug interaction might occur between 9-cis-RA and acetaminophen in human liver cells. Taken together, retinoids activate the RXR/SXR-mediated pathway and regulate the expression of CYP3A4. Thus, retinoids potentially can cause drug-drug interactions when they are administered with other CYP3A4 substrates.

Retinoid X receptor alpha Regulates the expression of glutathione s-transferase genes and modulates acetaminophen-glutathione conjugation in mouse liver.

Nuclear receptors, including constitutive androstane receptor, pregnane X receptor, and retinoid X receptor (RXR), modulate acetaminophen (APAP)-induced hepatotoxicity by regulating the expression of phase I cytochrome P450 (P450) genes. It has not been fully resolved, however, whether they regulate APAP detoxification at the phase II level. The aim of the current study was to evaluate the role of RXRalpha in phase II enzyme-mediated detoxification of APAP. Wild-type and hepatocyte-specific RXRalpha knockout mice were treated with a toxic dose of APAP (500 mg/kg i.p.). Mutant mice were protected from APAP-induced hepatotoxicity, even though basal liver glutathione (GSH) levels were significantly lower in mutant mice compared with those of wild-type mice. High-performance liquid chromatography analysis of APAP metabolites revealed significantly greater levels of APAP-GSH conjugates in livers and bile of mutant mice compared with those of wild-type mice. Furthermore, hepatocyte RXRalpha deficiency altered the gene expression profile of the glutathione S-transferase (Gst) family. Basal expression of 13 of 15 Gst genes studied was altered in hepatocyte-specific RXRalpha-deficient mice. This probably led to enhanced APAP-GSH conjugation and reduced accumulation of N-acetyl-p-benzoquinone imine, a toxic electrophile that is produced by biotransformation of APAP by phase I P450 enzymes. In conclusion, the data presented in this study define an RXRalpha-Gst regulatory network that controls APAP-GSH conjugation. This report reveals a potential novel strategy to enhance the detoxification of APAP or other xenobiotics by manipulating Gst activity through RXRalpha-mediated pathways.