The Effect of Dosing Regimens on the Antimalarial Efficacy of Dihydroartemisinin-Piperaquine: A Pooled Analysis of Individual Patient Data

Background

Dihydroartemisinin-piperaquine (DP) is increasingly recommended for antimalarial treatment in many endemic countries; however, concerns have been raised over its potential under dosing in young children. We investigated the influence of different dosing schedules on DP''s clinical efficacy.

Methods and Findings

A systematic search of the literature was conducted to identify all studies published between 1960 and February 2013, in which patients were enrolled and treated with DP. Principal investigators were approached and invited to share individual patient data with the WorldWide Antimalarial Resistance Network (WWARN). Data were pooled using a standardised methodology. Univariable and multivariable risk factors for parasite recrudescence were identified using a Cox''s regression model with shared frailty across the study sites. Twenty-four published and two unpublished studies (n = 7,072 patients) were included in the analysis. After correcting for reinfection by parasite genotyping, Kaplan–Meier survival estimates were 97.7% (95% CI 97.3%–98.1%) at day 42 and 97.2% (95% CI 96.7%–97.7%) at day 63. Overall 28.6% (979/3,429) of children aged 1 to 5 years received a total dose of piperaquine below 48 mg/kg (the lower limit recommended by WHO); this risk was 2.3–2.9-fold greater compared to that in the other age groups and was associated with reduced efficacy at day 63 (94.4% [95% CI 92.6%–96.2%], p<0.001). After adjusting for confounding factors, the mg/kg dose of piperaquine was found to be a significant predictor for recrudescence, the risk increasing by 13% (95% CI 5.0%–21%) for every 5 mg/kg decrease in dose; p = 0.002. In a multivariable model increasing the target minimum total dose of piperaquine in children aged 1 to 5 years old from 48 mg/kg to 59 mg/kg would halve the risk of treatment failure and cure at least 95% of patients; such an increment was not associated with gastrointestinal toxicity in the ten studies in which this could be assessed.

Conclusions

DP demonstrates excellent efficacy in a wide range of transmission settings; however, treatment failure is associated with a lower dose of piperaquine, particularly in young children, suggesting potential for further dose optimisation. Please see later in the article for the Editors'' Summary     

Individual variation evades the Prisoner's Dilemma

Background  

The Prisoner's Dilemma (PD) is a widely used paradigm to study cooperation in evolutionary biology, as well as in fields as diverse as moral philosophy, sociology, economics and politics. Players are typically assumed to have fixed payoffs for adopting certain strategies, which depend only on the strategy played by the opponent. However, fixed payoffs are not realistic in nature. Utility functions and the associated payoffs from pursuing certain strategies vary among members of a population with numerous factors. In biology such factors include size, age, social status and expected life span; in economics they include socio-economic status, personal preference and past experience; and in politics they include ideology, political interests and public support. Thus, no outcome is identical for any two different players.     

Intragenic duplication and divergence in the spectrin superfamily of proteins

Many structural, signaling, and adhesion molecules contain tandemly repeated amino acid motifs. The alpha-actinin/spectrin/dystrophin superfamily of F-actin-crosslinking proteins contains an array of triple alpha-helical motifs (spectrin repeats). We present here the complete sequence of the novel beta-spectrin isoform beta(Heavy)- spectrin (beta H). The sequence of beta H supports the origin of alpha- and beta-spectrins from a common ancestor, and we present a novel model for the origin of the spectrins from a homodimeric actin-crosslinking precursor. The pattern of similarity between the spectrin repeat units indicates that they have evolved by a series of nested, nonuniform duplications. Furthermore, the spectrins and dystrophins clearly have common ancestry, yet the repeat unit is of a different length in each family. Together, these observations suggest a dynamic period of increase in repeat number accompanied by homogenization within each array by concerted evolution. However, today, there is greater similarity of homologous repeats between species than there is across repeats within species, suggesting that concerted evolution ceased some time before the arthropod/vertebrate split. We propose a two-phase model for the evolution of the spectrin repeat arrays in which an initial phase of concerted evolution is subsequently retarded as each new protein becomes constrained to a specific length and the repeats diverge at the DNA level. This evolutionary model has general applicability to the origins of the many other proteins that have tandemly repeated motifs.      

Analysing overexpression of l-valine biosynthesis genes in pyruvate-dehydrogenase-deficient Corynebacterium glutamicum

l-Valine biosynthesis was analysed by comparing different plasmids in pyruvate-dehydrogenase-deficient Corynebacterium glutamicum strains in order to achieve an optimal production strain. The plasmids contained different combinations of the genes ilvBNCDE encoding for the l-valine forming pathway. It was shown that overexpression of the ilvBN genes encoding acetolactate synthase is obligatory for efficient pyruvate conversion and to prevent l-alanine as a by-product. In contrast to earlier studies, overexpression of ilvE encoding transaminase B is favourable in pyruvate-dehydrogenase-negative strains. Its amplification enhanced l-valine formation and avoided extra- and intracellular accumulation of ketoisovalerate.     

Studies on substrate utilisation in l-valine-producing Corynebacterium glutamicum strains deficient in pyruvate dehydrogenase complex

The pyruvate dehydrogenase complex was deleted to increase precursor availability in Corynebacterium glutamicum strains overproducing l-valine. The resulting auxotrophy is treated by adding acetate in addition glucose for growth, resulting in the puzzling fact of gluconeogenic growth with strongly reduced glucose uptake in the presence of acetate in the medium. This result was proven by intracellular metabolite analysis and labelling experiments. To increase productivity, the SugR protein involved in negative regulation of the phosphotransferase system, was inactivated, resulting in enhanced consumption of glucose. However, the surplus in substrate uptake was not converted to l-valine; instead, the formation of up to 289 μM xylulose was observed for the first time in C. glutamicum. As an alternative to the genetic engineering solution, a straightforward process engineering approach is proposed. Acetate limitation resulted in a more efficient use of acetate as cosubstrate, shown by an increased biomass yield Y _X/Ac and improved l-valine formation.     

Structure of a novel thermostable GH51 α-L-arabinofuranosidase from Thermotoga petrophila RKU-1

α‐L ‐arabinofuranosidases (EC 3.2.1.55) participate in the degradation of a variety of L ‐arabinose‐containing polysaccharides and interact synergistically with other hemicellulases in the production of oligosaccharides and bioconversion of lignocellulosic biomass into biofuels. In this work, the structure of a novel thermostable family 51 (GH51) α‐L ‐arabinofuranosidase from Thermotoga petrophila RKU‐1 (TpAraF) was determined at 3.1 Å resolution. The TpAraF tertiary structure consists of an (α/β)‐barrel catalytic core associated with a C‐terminal β‐sandwich domain, which is stabilized by hydrophobic contacts. In contrast to other structurally characterized GH51 AraFs, the accessory domain of TpAraF is intimately linked to the active site by a long β‐hairpin motif, which modifies the catalytic cavity in shape and volume. Sequence and structural analyses indicate that this motif is unique to Thermotoga AraFs. Small angle X‐ray scattering investigation showed that TpAraF assembles as a hexamer in solution and is preserved at the optimum catalytic temperature, 65°C, suggesting functional significance. Crystal packing analysis shows that the biological hexamer encompasses a dimer of trimers and the multiple oligomeric interfaces are predominantly fashioned by polar and electrostatic contacts.     

Stimulation of the autonomic nervous system in colorectal surgery: a study protocol for a randomized controlled trial

In this study we describe the sociodemographic characteristics of people participating in a clinical trial on the safety and immunogenicity of a H5N1 influenza vaccine and we identify the main motivations for joining it.     

Application of immobilized bovine enterokinase in repetitive fusion protein cleavage for the production of mucin 1

Bovine enterokinase is a serine protease that catalyzes the hydrolysis of peptide bonds and plays a key role in mammalian metabolism. Because of its high specificity towards the amino acid sequence (Asp)₄-Lys, enterokinase is a potential tool for the cleavage of fusion proteins, which are gaining more importance in biopharmaceutical production. A candidate for adaptive cancer immunotherapy is mucin 1, which is produced recombinantly as a fusion protein in CHO cells. Here, we present the first repetitive application of immobilized enterokinase for the cleavage of the mucin fusion protein. The immobilization enables a facile biocatalytic process due to simplified separation of the biocatalyst and the target protein. Immobilized enterokinase was applied in a maximum of 18 repetitive reactions. The enzyme utilization (total turnover number) was increased significantly 419-fold compared to unbound enzyme by both immobilization and optimization of process conditions. Slight enzyme inactivation throughout the reaction cycles was observed, but was compensated by adjusting the process time accordingly. Thus, complete fusion protein cleavage was achieved. Furthermore, we obtained isolated mucin 1 with a purity of more than 90% by applying a simple and efficient purification process. The presented results demonstrate enterokinase to be an attractive tool for fusion protein cleavage.