Use of Plasmodium falciparum culture-adapted field isolates for in vitro exflagellation-blocking assay

International audienceA major requirement for malaria elimination is the development of transmission-blocking interventions. In vitro transmission-blocking bioassays currently mostly rely on the use of very few Plasmodium falciparum reference laboratory strains isolated decades ago. To fill a piece of the gap between laboratory experimental models and natural systems, the purpose of this work was to determine if culture-adapted field isolates of P. falciparum are suitable for in vitro transmission-blocking bioassays targeting functional maturity of male gametocytes: exflagellation. Plasmodium falciparum isolates were adapted to in vitro culture before being used for in vitro gametocyte production. Maturation was assessed by microscopic observation of gametocyte morphology over time of culture and the functional viability of male gametocytes was assessed by microscopic counting of exflagellating gametocytes. Suitability for in vitro exflagellation-blocking bioassays was determined using dihydroartemisinin and methylene blue. In vitro gametocyte production was achieved using two isolates from French Guiana and two isolates from Cambodia. Functional maturity of male gametocytes was assessed by exflagellation observations and all four isolates could be used in exflagellation-blocking bioassays with adequate response to methylene blue and dihydroartemisinin. This work shows that in vitro culture-adapted P. falciparum field isolates of different genetic background, from South America and Southeast Asia, can successfully be used for bioassays targeting the male gametocyte to gamete transition, exflagellation

Building Better Bit-Blasting for Floating-Point Problems

An effective approach to handling the theory of floating-point is to reduce it to the theory of bit-vectors. Implementing the required encodings is complex, error prone and requires a deep understanding of floating-point hardware. This paper presents SymFPU, a library of encodings that can be included in solvers. It also includes a verification argument for its correctness, and experimental results showing that its use in CVC4 out-performs all previous tools. As well as a significantly improved performance and correctness, it is hoped this will give a simple route to add support for the theory of floating-point

Globally prevalent PfMDR1 mutations modulate Plasmodium falciparum susceptibility to artemisinin-based combination therapies

Antimalarial chemotherapy, globally reliant on artemisinin-based combination therapies (ACTs), is threatened by the spread of drug resistance in Plasmodium falciparum parasites. Here we use zinc-finger nucleases to genetically modify the multidrug resistance-1 transporter PfMDR1 at amino acids 86 and 184, and demonstrate that the widely prevalent N86Y mutation augments resistance to the ACT partner drug amodiaquine and the former first-line agent chloroquine. In contrast, N86Y increases parasite susceptibility to the partner drugs lumefantrine and mefloquine, and the active artemisinin metabolite dihydroartemisinin. The PfMDR1 N86 plus Y184F isoform moderately reduces piperaquine potency in strains expressing an Asian/African variant of the chloroquine resistance transporter PfCRT. Mutations in both digestive vacuole-resident transporters are thought to differentially regulate ACT drug interactions with host haem, a product of parasite-mediated haemoglobin degradation. Global mapping of these mutations illustrates where the different ACTs could be selectively deployed to optimize treatment based on regional differences in PfMDR1 haplotypes.This work was funded in part by the National Institutes of Health (R01 AI50234, AI124678 and AI109023) and a Burroughs Wellcome Fund Investigator in Pathogenesis of Infectious Diseases award to D.A.F. This research also received funding from the Portuguese Fundacao para a Ciencia e Tecnologia (FCT), cofunded by Programa Operacional Regional do Norte (ON.2-O Novo Norte); from the Quadro de Referencia Estrategico Nacional (QREN) through the Fundo Europeu de Desenvolvimento Regional (FEDER) and from the Projeto Estrategico - LA 26 - 2013-2014 (PEst-C/SAU/LA0026/2013). M.I.V. is the recipient of a postdoctoral fellowship from FCT/Ministerio da Ciencia e Ensino Superior, Portugal-MCES (SFRH/BPD/76614/2011). A.M.L. was supported by an Australian National Health and Medical Research Council (NHMRC) Overseas Biomedical Fellowship (585519). R.E.M. was supported by an NHMRC RD Wright Biomedical Fellowship (1053082). A.C.U. was supported by an Irving scholarship from Columbia University. We thank Dr Andrea Ecker for her help with plasmid design and Pedro Ferreira for his expert help with Fig. 6.info:eu-repo/semantics/publishedVersio

Drug Resistance in Eukaryotic Microorganisms

Eukaryotic microbial pathogens are major contributors to illness and death globally. Although much of their impact can be controlled by drug therapy as with prokaryotic microorganisms, the emergence of drug resistance has threatened these treatment efforts. Here, we discuss the challenges posed by eukaryotic microbial pathogens and how these are similar to, or differ from, the challenges of prokaryotic antibiotic resistance. The therapies used for several major eukaryotic microorganisms are then detailed, and the mechanisms that they have evolved to overcome these therapies are described. The rapid emergence of resistance and the restricted pipeline of new drug therapies pose considerable risks to global health and are particularly acute in the developing world. Nonetheless, we detail how the integration of new technology, biological understanding, epidemiology and evolutionary analysis can help sustain existing therapies, anticipate the emergence of resistance or optimize the deployment of new therapies

Incrementally Closing Octagons

The octagon abstract domain is a widely used numeric abstract domain expressing relational information between variables whilst being both computationally efficient and simple to implement. Each element of the domain is a system of constraints where each constraint takes the restricted form ±xi±xj≤c. A key family of operations for the octagon domain are closure algorithms, which check satisfiability and provide a normal form for octagonal constraint systems. We present new quadratic incremental algorithms for closure, strong closure and integer closure and proofs of their correctness. We highlight the benefits and measure the performance of these new algorithms

La memoria de los j\uf3venes y las luchas por la emancipati\uf3n

la questione della memoria sociale e della sua trasmissione intergenerazionale nel caso italiano; alcuni esempi di aspetti occultati; una questione di rappresentazione politic