Genetic Diversity and Protective Efficacy of the RTS,S/AS01 Malaria Vaccine.

BACKGROUND: The RTS,S/AS01 vaccine targets the circumsporozoite protein of Plasmodium falciparum and has partial protective efficacy against clinical and severe malaria disease in infants and children. We investigated whether the vaccine efficacy was specific to certain parasite genotypes at the circumsporozoite protein locus. METHODS: We used polymerase chain reaction-based next-generation sequencing of DNA extracted from samples from 4985 participants to survey circumsporozoite protein polymorphisms. We evaluated the effect that polymorphic positions and haplotypic regions within the circumsporozoite protein had on vaccine efficacy against first episodes of clinical malaria within 1 year after vaccination. RESULTS: In the per-protocol group of 4577 RTS,S/AS01-vaccinated participants and 2335 control-vaccinated participants who were 5 to 17 months of age, the 1-year cumulative vaccine efficacy was 50.3% (95% confidence interval [CI], 34.6 to 62.3) against clinical malaria in which parasites matched the vaccine in the entire circumsporozoite protein C-terminal (139 infections), as compared with 33.4% (95% CI, 29.3 to 37.2) against mismatched malaria (1951 infections) (P=0.04 for differential vaccine efficacy). The vaccine efficacy based on the hazard ratio was 62.7% (95% CI, 51.6 to 71.3) against matched infections versus 54.2% (95% CI, 49.9 to 58.1) against mismatched infections (P=0.06). In the group of infants 6 to 12 weeks of age, there was no evidence of differential allele-specific vaccine efficacy. CONCLUSIONS: These results suggest that among children 5 to 17 months of age, the RTS,S vaccine has greater activity against malaria parasites with the matched circumsporozoite protein allele than against mismatched malaria. The overall vaccine efficacy in this age category will depend on the proportion of matched alleles in the local parasite population; in this trial, less than 10% of parasites had matched alleles. (Funded by the National Institutes of Health and others.).

The effects of aflatoxin exposure on Hepatitis B-vaccine induced immunity in Kenyan children.

BACKGROUND: Globally, approximately three million children die each year from vaccine preventable infectious diseases mainly in developing countries. Despite the success of the expanded immunization program, not all infants and children around the world develop the same protective immune response to the same vaccine. A vaccine must induce a response over the basal immune response that may be driven by population-specific, environmental or socio-economic factors. Mycotoxins like aflatoxins are immune suppressants that are confirmed to interfere with both cell-mediated and acquired immunity. The mechanism of aflatoxin toxicity is through the binding of the bio-activated AFB1-8, 9-epoxide to cellular macromolecules. METHODS: We studied Hepatitis B surface antibodies [anti-HBs] levels to explore the immune modulation effects of dietary exposure to aflatoxins in children aged between one and fourteen years in Kenya. Hepatitis B vaccine was introduced for routine administration for Kenyan infants in November 2001. To assess the effects of aflatoxin on immunogenicity of childhood vaccines Aflatoxin B1-lysine in blood serum samples were determined using High Performance Liquid Chromatography with Fluorescence detection while anti-HBs were measured using Bio-ELISA anti-HBs kit. RESULTS: The mean ± SD of AFB1-lysine adducts in our study population was 45.38 ± 87.03 pg/mg of albumin while the geometric mean was 20.40 pg/mg. The distribution of AFB1-lysine adducts was skewed to the right. Only 98/205 (47.8%) of the study population tested positive for Hepatitis B surface antibodies. From regression analysis, we noted that for every unit rise in serum aflatoxin level, anti-HBs dropped by 0.91 mIU/ml (-0.9110038; 95% C.I -1.604948, -0.21706). CONCLUSION: Despite high coverage of routine immunization, less than half of the study population had developed immunity to HepB. Exposure to aflatoxin was high and weakly associated with low anti-HBs antibodies. These findings highlight a potentially significant role for environmental factors that may contribute to vaccine effectiveness warranting further research.

Estimating terrestrial gross primary productivity in water limited ecosystems across Africa using the Southampton Carbon Flux (SCARF) model.

The amount of carbon uptake by vegetation is an important component to understand the functioning of ecosystem processes and their response/feedback to climate. Recently, a new diagnostic model called the Southampton Carbon Flux (SCARF) Model driven by remote sensing data was developed to predict terrestrial gross primary productivity (GPP) and successfully applied in temperate regions. The model is based on the concept of quantum yield of plants and improves on the previous diagnostic models by (i) using the fraction of photosynthetic active radiation absorbed by the photosynthetic pigment (FAPARps) and (ii) using direct quantum yield by classifying the vegetation into C3 or C4 classes. In this paper, we calibrated and applied the model to evaluate GPP across various ecosystems in Africa. The performance of the model was evaluated using data from seven eddy covariance flux tower sites. Overall, the modelled GPP values showed good correlation (R>0.59, p<0.0001) with estimated flux tower GPP at most sites (except at a tropical rainforest site, R=0.38, p=0.02) in terms of their seasonality and absolute values. Mean daily GPP across the investigated period varied significantly across sites depending on the vegetation types from a minimum of 0.44gCm-2day-1 at the semi-arid and sub-humid savanna grassland sites to a maximum of 9.86gCm-2day-1 at the woodland and tropical rain forest sites. Generally, strong correlation is observed in savanna woodlands and grasslands where vegetation follows a prescribed seasonal cycle as determined by changes in canopy chlorophyll content and leaf area index. Finally, the mean annual GPP value for Africa predicted by the model was 35.25PgCyr-1. The good performance of the SCARF model in water-limited ecosystems across Africa extends its potential for global application.

Building Capability for Clinical Pharmacology Research in Sub-Saharan Africa.

A strong scientific rationale exists for conducting clinical pharmacology studies in target populations because local factors such as genetics, environment, comorbidities, and diet can affect variability in drug responses. However, clinical pharmacology studies are not widely conducted in sub-Saharan Africa, in part due to limitations in technical expertise and infrastructure. Since 2012, a novel public-private partnership model involving research institutions and a pharmaceutical company has been applied to developing increased capability for clinical pharmacology research in multiple African countries.

Attention deficit hyperactivity disorder symptom self-report in adults in Kenya and its associated risk factors, an analysis from a household survey in a demographic surveillance site.

BACKGROUND: There have been no household surveys of adult attention deficit and hyperactivity disorder (ADHD) in Kenya, and only one in sub-Saharan Africa. METHODS: Data on ADHD was used from a household survey of mental disorders and their associated risk factors conducted in Maseno area (population 70 805), near Lake Victoria in Kenya, using a demographic surveillance site as the sample frame, as part of a wider survey of mental health, malaria and immunity A total of 1190 households were selected, and 1158 adult participants consented to the study while 32 refused to participate in the study interviews, giving a response rate of 97.3%. ADHD symptoms were assessed with the WHO Adult ADHD Self-Report Scale (ASRS) Screener. RESULTS: This survey found that the overall prevalence of ADHD using the ASRS was 13.1%. This suggests a high level of ADHD in the Kenyan population which needs to be further investigated for its impact on adult mental health. In the adjusted analysis, increased odds ratios (ORs) were found in those with higher assets (OR 1.7, p = 0.023), those with life events (OR 2.4, p = 0.001 for those with 2-3 life events and OR 2.6, p < 0.001 for those with 4 or more life events), and those with common mental disorders (OR 2.3, p = 0.001). CONCLUSION: The study demonstrates the magnitude of ADHD symptoms as a public health issue, relevant for health worker training, and the importance of further research into its prevalence in adults and associated risk factors.

Selective and sensitive liquid chromatographic assay of amodiaquine and desethylamodiaquine in whole blood spotted on filter paper.

We have developed a sensitive, selective and reproducible reversed-phase HPLC method with ultraviolet detection (340 nm) for the simultaneous quantification of amodiaquine (AQ) and its major metabolite, desethylamodiaquine (AQm) in a small volume (200 microl) of whole blood spotted on filter paper. The method involves liquid-liquid extraction with diethyl ether followed by elution from a reversed-phase phenyl column with an acidic (pH 2.8) mobile phase (25 mM KH2PO4-methanol; 80:20% (v/v) +1% (v/v) triethylamine). Calibration curves in spiked whole blood were linear from 100-2500 ng/ml (r2 > or = 0.99) for AQ and 200-2500 ng/ml (r2 > or = 0.99) for AQm. The limit of detection was 5 ng for AQ and 10 ng for AQm. The relative recovery at 150 ng/ml of AQ (n = 6) was 84.0% and at 300 ng/ml of AQm the relative recovery was 74.3%. The intra-assay coefficients of variation at 150, 600 and 2250 ng/ml of AQ and 300, 600 and 2250 ng/ml of AQm were 7.7, 8.9 and 6.2% (AQ) and 10.1, 5.4 and 3.9% (AQm), respectively. The inter-assay coefficient of variation at 150, 600 and 2250 ng/ml of AQ and 300, 600 and 2250 ng/ml of AQm were 5.2, 8.1 and 6.9% (AQ) and 3.3, 2.3 and 4.6% (AQm). There was no interference from other commonly used antimalarial and antipyretic drugs (chloroquine, quinine, sulfadoxine, pyrimethamine, artesunate, acetaminophen and salicylate). The method is particularly suitable for pharmacokinetic studies in settings where facilities for storing blood/plasma samples are not available.

Intention-to-treat analysis in the chronic suppurative otitis media trials.

OBJECTIVE: To determine the extent of application of the intention to treat principle in the chronic suppurative otitis media (CSOM) randomised controlled trials. DESIGN: Data were extracted from 28 CSOM randomised controlled trials. MAIN OUTCOME MEASURES: Conceptual and methodological approaches of dealing with protocol deviations with respect to withdrawal, missing response and non-compliance. RESULTS: Of the 28 CSOM trials included in this study, only one (4%) trial mentioned intention-to-treat (ITT) analysis. However, 10(36%) other trials which did not mention ITT, had no protocol deviations and thus carried out an ITT analysis by default. It is highly likely that a biased treatment effect existed in the trial that mentioned ITT since the authors undertook a complete case analysis disregarding the 22% protocol deviators. There were no attempts in any of the trials to impute for missing responses and carrying out a sensitivity analysis. For trials with a big percentage of protocol deviations, the validity of their results are brought to question. CONCLUSIONS: In practice, not all those entered into a randomised-controlled trial will complete the trial. Thus intention-to-treat analysis is an important aspect of randomised controlled trials of health care interventions which tries to bridge this gap. It is important for authors to explicitly state the protocol deviations, the methods used to handle them and the potential effect with reference to bias and study outcome.

Management of seizures in children with falciparum malaria.

Falciparum malaria is the most common cause of convulsions in children admitted to hospital in malaria endemic areas. Detection of convulsions requires close monitoring and one should be on the look out for signs of subtle convulsions. About a third of acute seizures in children with cerebral malaria, do not manifest as convulsions, but as changes in eye deviation, salivation and/or eye deviation. It is important to terminate convulsions lasting more than 5 min, since prolonged convulsions are associated with neurological deficits in survivors of children with severe malaria. Initial management should include putting the child into the left lateral position, checking the blood glucose and administering oxygen if hypoxic. The benzodiazepines, particularly diazepam, are used as the initial anticonvulsants. Phenobarbital and phenytoin are used as second-line treatments. Prompt and effective management of falciparum malaria associated convulsions may contribute to a better outcome in children with severe malaria.

The role of sequential administration of sulphadoxine/pyrimethamine following quinine in the treatment of severe falciparum malaria in children.

Sulphadoxine/pyrimethamine (SP) is often administered with quinine in the treatment of severe falciparum malaria to shorten the course of quinine. The efficacy of SP alone in the treatment of non-severe malaria has been declining rapidly in East Africa, raising concerns of the usefulness of a shortened course of quinine followed SP. We audited the efficacy of quinine/SP in the treatment of severe malaria in Kenyan children. Children with severe falciparum malaria were treated with parenteral quinine followed by a single oral dose of SP. A clinical evaluation was performed 3 weeks later in which a blood sample was obtained for full haemogram, blood slide and analysis of the parasite dihydrofolate reductase (DHFR) and dihydropteroate synthase (DHPS) codons, mutations of which are associated with resistance to SP. A total of 452 children were enrolled, of whom 374 completed the study. Fifty-two (13.9%) children were parasitaemic by 3 weeks of whom 17 (4.5%) had fever as well. The treatment failure group had a significantly higher parasitaemia (129 061 vs. 43 339; P<0.001) and haemoglobin on admission, but only admission parasitaemia independently predicted treatment failure. Those with treatment failure had a significantly lower rise in haemoglobin at 3 weeks compared with treatment successes (9.0 vs. 10.0 g/dl). Of the 76 parasite isolates collected before treatment, 40 (53%) were triple mutant DHFR-double DHPS (Tp-Db), the genotype most associated with SP resistance. Three weeks after SP treatment, the proportion of Tp-Db increased to 72% (31/43). The high treatment failure rate and proportion of parasites with Tp-Db negate the use of SP to shorten the course of quinine treatment in East Africa.

High-performance liquid chromatographic determination of diazepam in plasma of children with severe malaria.

A sensitive, selective and reproducible reversed-phase HPLC method with ultraviolet detection was developed for the quantification of diazepam in small plasma samples from children with severe malaria. The method involves plasma deproteinization with acetonitrile, followed by liquid-liquid extraction with ethyl acetate-n-hexane. Diazepam was eluted at ambient temperatures from a reversed-phase C18 column with an acidic (pH 3.5) aqueous mobile phase (10 mM KH2PO4-acetonitrile, 69:31, v/v). Calibration curves in spiked plasma were linear from 10 to 200 ng (r2 > or = 0.99). The limit of detection was 5.0 ng/ml, and relative recoveries at 25 and 180 ng were >87%. Intra- and inter-assay relative standard deviations were <15%. There was no interference from drugs commonly administered to children with severe malaria (phenobarbitone, phenytoin, chloroquine, quinine, sulfadoxine, pyrimethamine, halofantrine, cycloguanil, chlorcycloguanil, acetaminophen and salicylate). This method has been used for monitoring plasma diazepam concentrations in children with seizures associated with severe malaria.

Pharmacokinetics and anticonvulsant effects of diazepam in children with severe falciparum malaria and convulsions.

AIMS: Convulsions are a common complication of severe malaria in children and are associated with poor outcome. Diazepam is used to terminate convulsions but its pharmacokinetics and pharmacodynamics have not been studied in this group. Accordingly, we carried out a comparative study of the pharmacokinetics of intravenous (i.v.) and rectal (p.r.) diazepam. METHODS: Twenty-five children with severe malaria and a convulsion lasting >5 min were studied. Sixteen children received diazepam intravenously (i.v.; 0.3 mg kg(-1)) and nine rectally (p.r.; 0.5 mg kg(-1)). Plasma diazepam concentrations were measured by reversed phase high-performance liquid chromatography. The duration of convulsions, depth of coma, respiratory and cardiovascular parameters were monitored. RESULTS: Median maximum plasma diazepam concentrations of 634 (range 402-1507) ng ml(-1) and 423 (range 112-1953) ng ml(-1) were achieved at 5 and 25 min following i.v. and p.r. administration, respectively. All patients except three (one i.v. and two p.r.) achieved plasma diazepam concentration >200 ng ml(-1) within 5 min. Following p.r. administration, plasma diazepam concentrations were more variable than i.v. administration. A single dose of i.v. diazepam terminated convulsions in all children but in only 6/9 after p.r. administration. However, nine children treated with i.v. and all those treated with p.r. diazepam had a recurrence of convulsions occurring at median plasma diazepam concentrations of 157 (range: 67-169) and 172 (range: 74-393) ng ml(-1) , respectively. All the children in the i.v. and four in the PR diazepam group who had recurrence of convulsions required treatment. None of the children developed respiratory depression or hypotension. CONCLUSIONS: Administration of diazepam i.v. or p.r. resulted in achievement of therapeutic concentrations of diazepam rapidly, without significant cardio-respiratory adverse effects. However, following p.r. administration, diazepam did not terminate all convulsions and plasma drug concentrations were more variable.