Publications
381 results found
Angrisano F, Riglar DT, Sturm A, et al., 2012, Spatial Localisation of Actin Filaments across Developmental Stages of the Malaria Parasite, PLOS One23/1/12, Vol: 7, ISSN: 1932-6203
Delves M, Plouffe D, Scheurer C, et al., 2012, The Activities of Current Antimalarial Drugs on the Life Cycle Stages of Plasmodium: A Comparative Study with Human and Rodent Parasites, PLOS Medicine, Vol: 9, ISSN: 1549-1277
Background: Malaria remains a disease of devastating global impact, killing more than 800,000 people every year—the vastmajority being children under the age of 5. While effective therapies are available, if malaria is to be eradicated a broaderrange of small molecule therapeutics that are able to target the liver and the transmissible sexual stages are required. Thesenew medicines are needed both to meet the challenge of malaria eradication and to circumvent resistance.Methods and Findings: Little is known about the wider stage-specific activities of current antimalarials that were primarilydesigned to alleviate symptoms of malaria in the blood stage. To overcome this critical gap, we developed assays tomeasure activity of antimalarials against all life stages of malaria parasites, using a diverse set of human and nonhumanparasite species, including male gamete production (exflagellation) in Plasmodium falciparum, ookinete development in P.berghei, oocyst development in P. berghei and P. falciparum, and the liver stage of P. yoelii. We then compared 50 currentand experimental antimalarials in these assays. We show that endoperoxides such as OZ439, a stable synthetic moleculecurrently in clinical phase IIa trials, are strong inhibitors of gametocyte maturation/gamete formation and impactsporogony; lumefantrine impairs development in the vector; and NPC-1161B, a new 8-aminoquinoline, inhibits sporogony.Conclusions: These data enable objective comparisons of the strengths and weaknesses of each chemical class at targetingeach stage of the lifecycle. Noting that the activities of many compounds lie within achievable blood concentrations, theseresults offer an invaluable guide to decisions regarding which drugs to combine in the next-generation of antimalarialdrugs. This study might reveal the potential of life-cycle–wide analyses of drugs for other pathogens with complex lifecycles.
Sinden RE, Blagborough AM, Churcher T, et al., 2012, The design and interpretation of laboratory assays measuring mosquito transmission of Plasmodium., Trends in Parasitology
Since 2010 two global reviews of malaria research have recognized that local elimination and eradication of Plasmodium parasites are key drivers for further experimentation. To achieve these ambitious objectives it is universally recognized we must reduce malaria transmission through the mosquito vectors. A plethora of new laboratory assays are being developed to interrogate malaria transmission from the gametocyte to the sporozoite stage: assays that augment well-established field protocols to determine the entomological inoculation rate. However, the diverse readouts of these assays are not directly comparable. Here we attempt to identify the utility of each assay and provide rational frameworks by which to compare the impacts recorded by the diverse methodologies.
Guttery DS, Poulin B, Ferguson DJP, et al., 2012, A Unique Protein Phosphatase with Kelch-Like Domains (PPKL) in Plasmodium Modulates Ookinete Differentiation, Motility and Invasion, PloS Pathogens
Protein phosphorylation and dephosphorylation (catalysed by kinases and phosphatases, respectively) are post-translational modifications that play key roles in many eukaryotic signalling pathways, and are often deregulated in a number of pathological conditions in humans. In the malaria parasite Plasmodium, functional insights into its kinome have only recently been achieved, with over half being essential for blood stage development and another 14 kinases being essential for sexual development and mosquito transmission. However, functions for any of the plasmodial protein phosphatases are unknown. Here, we use reverse genetics in the rodent malaria model, Plasmodium berghei, to examine the role of a unique protein phosphatase containing kelch-like domains (termed PPKL) from a family related to Arabidopsis BSU1. Phylogenetic analysis confirmed that the family of BSU1-like proteins including PPKL is encoded in the genomes of land plants, green algae and alveolates, but not in other eukaryotic lineages. Furthermore, PPKL was observed in a distinct family, separate to the most closely-related phosphatase family, PP1. In our genetic approach, C-terminal GFP fusion with PPKL showed an active protein phosphatase preferentially expressed in female gametocytes and ookinetes. Deletion of the endogenous ppkl gene caused abnormal ookinete development and differentiation, and dissociated apical microtubules from the inner-membrane complex, generating an immotile phenotype and failure to invade the mosquito mid-gut epithelium. These observations were substantiated by changes in localisation of cytoskeletal tubulin and actin, and the micronemal protein CTRP in the knockout mutant as assessed by indirect immunofluorescence. Finally, increased mRNA expression of dozi, a RNA helicase vital to zygote development was observed in ppkl− mutants, with global phosphorylation studies of ookinete differentiation from 1.5–24 h post-fertilisation indicating major changes in the fi
Delves MJ, Ramakrishnan C, Blagborough AM, et al., 2012, A high-throughput assay for the identification of malarial transmission-blocking drugs and vaccines, Int J Parasitol
Following the cessation of the global malaria eradication initiative in the 1970s, the prime objective of malarial intervention has been to reduce morbidity and mortality. This motivated the development of high throughput assays to determine the impact of interventions on asexual bloodstage parasites. In response to the new eradication agenda, interrupting parasite transmission from the human to the mosquito has been recognised as an important and additional target for intervention. Current assays for Plasmodium mosquito stage development are very low throughput and resource intensive, and are therefore inappropriate for high throughput screening. Using an ookinete-specific GFP reporter strain of the rodent parasite Plasmodium berghei, it has been possible to develop and validate a high biological complexity, high throughput bioassay that can rapidly, reproducibly and accurately evaluate the effect of transmission-blocking drugs or vaccines on the ability of host-derived gametocytes to undergo the essential onward steps of gamete formation, fertilization and ookinete maturation. This assay may greatly accelerate the development of malaria transmission-blocking interventions.
Churcher TS, Blagborough AM, Delves M, et al., 2012, Measuring the blockade of malaria transmission - an analysis of the standard membrane feeding assay, Int J Parasitol, Vol: 42, Pages: 1037-1044
The Standard Membrane Feeding Assay (SMFA) is currently considered to be the 'gold standard' for assessing the effectiveness of malaria transmission blocking interventions (TBIs) in vivo. The operation and analysis of SMFAs has varied between laboratories: field scientists often measure TBI efficacy as a reduction in the prevalence of infected mosquitoes whilst laboratory scientists are more likely to quote efficacy as a change in the number of oocysts within the mosquito. These metrics give outputs that differ widely, resulting in a need for greater understanding of how the SMFA informs TBI assessment. Using data from 536 different assays (conducted on Plasmodium falciparum and Plasmodiumberghei, in either Anopheles gambiae or Anopheles stephensi) it is shown that the relationship between these metrics is complex, yet predictable. Results demonstrate that the distribution of oocysts between mosquitoes is highly aggregated, making efficacy estimates based on reductions in intensity highly uncertain. Analysis of 30 SMFAs carried out on the same TBI confirms that the observed reduction in prevalence depends upon the parasite exposure (as measured by oocyst intensity in the control group), with assays which have lower exposure appearing more effective. By contrast, if efficacy is estimated as a reduction in oocyst intensity, then this candidate demonstrated constant efficacy, irrespective of the exposure level. To report transmission-blockade efficacy accurately, the results of SMFAs should give both the prevalence and intensity of oocysts in both the control and intervention group. Candidates should be assessed against a range of parasite exposures to allow laboratory results to be extrapolated to different field situations. Currently, many studies assessing TBIs are underpowered and uncertainties in efficacy estimates rarely reported. Statistical techniques that account for oocyst over-dispersion can reduce the number of mosquitoes that need to be dissected and allow
Goodman AL, Blagborough AM, Biswas S, et al., 2011, A viral vectored prime-boost immunization regime targeting the malaria pfs25 antigen induces transmission-blocking activity, PLOS One, Vol: 6, ISSN: 1932-6203
The ookinete surface protein Pfs25 is a macrogamete-to-ookinete/ookinete stage antigen of Plasmodium falciparum,capable of exerting high-level anti-malarial transmission-blocking activity following immunization with recombinantprotein-in-adjuvant formulations. Here, this antigen was expressed in recombinant chimpanzee adenovirus 63 (ChAd63),human adenovirus serotype 5 (AdHu5) and modified vaccinia virus Ankara (MVA) viral vectored vaccines. Twoimmunizations were administered to mice in a heterologous prime-boost regime. Immunization of mice with AdHu5Pfs25 at week 0 and MVA Pfs25 at week 10 (Ad-MVA Pfs25) resulted in high anti-Pfs25 IgG titers, consisting of predominantlyisotypes IgG1 and IgG2a. A single priming immunization with ChAd63 Pfs25 was as effective as AdHu5 Pfs25 with respect toELISA titers at 8 weeks post-immunization. Sera from Ad-MVA Pfs25 immunized mice inhibited the transmission of P.falciparum to the mosquito both ex vivo and in vivo. In a standard membrane-feeding assay using NF54 strain P. falciparum,oocyst intensity in Anopheles stephensi mosquitoes was significantly reduced in an IgG concentration-dependent mannerwhen compared to control feeds (96% reduction of intensity, 78% reduction in prevalence at a 1 in 5 dilution of sera). Inaddition, an in vivo transmission-blocking effect was also demonstrated by direct feeding of immunized mice infected withPfs25DR3, a chimeric P. berghei line expressing Pfs25 in place of endogenous Pbs25. In this assay the density of Pfs25DR3oocysts was significantly reduced when mosquitoes were fed on vaccinated as compared to control mice (67% reduction ofintensity, 28% reduction in prevalence) and specific IgG titer correlated with efficacy. These data confirm the utility of theadenovirus-MVA vaccine platform for the induction of antibodies with transmission-blocking activity, and support thecontinued development of this alternative approach to transmission-blocking malaria subunit vaccines.
Sheehy S, Duncan C, Anagnostou N, et al., 2011, CLINICAL EVALUATION OF NEW VIRAL VECTORED VACCINES TARGETING THE PLASMODIUM FALCIPARUM BLOOD-STAGE ANTIGENS; MSP1 AND AMA1, JOURNAL OF INFECTION, Vol: 63, Pages: 492-493, ISSN: 0163-4453
Siden-Kiamos I, Ganter M, Kunze A, et al., 2011, Stage-specific depletion of myosin A supports an essential role in motility of malarial ookinetes, CELLULAR MICROBIOLOGY, Vol: 13, Pages: 1996-2006, ISSN: 1462-5814
- Author Web Link
- Cite
- Citations: 36
Angrisano F, Delves MJ, Sturm A, et al., 2011, A GFP-Actin reporter line to explore microfilament dynamics across the malaria parasite lifecycle, MOLECULAR AND BIOCHEMICAL PARASITOLOGY, Vol: 182, Pages: 93-96, ISSN: 0166-6851
- Author Web Link
- Cite
- Citations: 13
Porter DW, Thompson FM, Berthoud TK, et al., 2011, A human Phase I/IIa malaria challenge trial of a polyprotein malaria vaccine, VACCINE, Vol: 29, Pages: 7514-7522, ISSN: 0264-410X
- Author Web Link
- Cite
- Citations: 39
Talman AM, Lacroix C, Marques SR, et al., 2011, PbGEST mediates malaria transmission to both mosquito and vertebrate host, MOLECULAR MICROBIOLOGY, Vol: 82, Pages: 462-474, ISSN: 0950-382X
- Author Web Link
- Cite
- Citations: 69
Ramakrishnan C, Dessens JT, Armson R, et al., 2011, Vital functions of the malarial ookinete protein, CTRP, reside in the A domains, INTERNATIONAL JOURNAL FOR PARASITOLOGY, Vol: 41, Pages: 1029-1039, ISSN: 0020-7519
- Author Web Link
- Cite
- Citations: 24
Slavic K, Delves MJ, Prudencio M, et al., 2011, Use of a Selective Inhibitor To Define the Chemotherapeutic Potential of the Plasmodial Hexose Transporter in Different Stages of the Parasite's Life Cycle, ANTIMICROBIAL AGENTS AND CHEMOTHERAPY, Vol: 55, Pages: 2824-2830, ISSN: 0066-4804
- Author Web Link
- Cite
- Citations: 31
Farrance CE, Chichester JA, Musiychuk K, et al., 2011, Antibodies to plant-produced <i>Plasmodium falciparum</i> sexual stage protein Pfs25 exhibit transmission blocking activity, 7th World Congress on Vaccines, Immunisation and Immunotherapy (WCVII), Publisher: LANDES BIOSCIENCE, Pages: 191-198, ISSN: 1554-8600
- Author Web Link
- Cite
- Citations: 52
Baum J, Billker O, Bousema T, et al., 2011, A Research Agenda for Malaria Eradication: Basic Science and Enabling Technologies, PLOS MEDICINE, Vol: 8, ISSN: 1549-1676
- Author Web Link
- Cite
- Citations: 37
Alonso PL, Eubank S, Ghani A, et al., 2011, A Research Agenda for Malaria Eradication: Modeling, PLOS MEDICINE, Vol: 8, ISSN: 1549-1277
- Author Web Link
- Cite
- Citations: 22
Alonso PL, Brown G, Arevalo-Herrera M, et al., 2011, A Research Agenda to Underpin Malaria Eradication, PLOS MEDICINE, Vol: 8, ISSN: 1549-1277
- Author Web Link
- Cite
- Citations: 484
Churcher TS, Dawes EJ, Sinden RE, et al., 2010, Population biology of malaria within the mosquito: density-dependent processes and potential implications for transmission-blocking interventions, MALARIA JOURNAL, Vol: 9, ISSN: 1475-2875
- Author Web Link
- Open Access Link
- Cite
- Citations: 27
Sheehy SH, Duncan CJ, Elias S, et al., 2010, HETEROLOGOUS PRIME-BOOST VACCINATION WITH ADCH63 AND MVA EXPRESSING MSP1 CAN INDUCE PROTECTIVE EFFICACY AGAINST SPOROZOITE CHALLENGE IN VOLUNTEERS, 59th Annual Meeting of the American-Society-of-Tropical-Medicine-and-Hygiene (ASTMH), Publisher: AMER SOC TROP MED & HYGIENE, Pages: 48-49, ISSN: 0002-9637
Kambris Z, Blagborough AM, Pinto SB, et al., 2010, Wolbachia stimulates immune gene expression and inhibits Plasmodium development in Anopheles gambiae, Plos Pathogens, Vol: 6, ISSN: 1553-7374
The over-replicating wMelPop strain of the endosymbiont Wolbachia pipientis has recently been shown to be capable ofinducing immune upregulation and inhibition of pathogen transmission in Aedes aegypti mosquitoes. In order to examinewhether comparable effects would be seen in the malaria vector Anopheles gambiae, transient somatic infections ofwMelPop were created by intrathoracic inoculation. Upregulation of six selected immune genes was observed compared tocontrols, at least two of which (LRIM1 and TEP1) influence the development of malaria parasites. A stably infected An.gambiae cell line also showed increased expression of malaria-related immune genes. Highly significant reductions inPlasmodium infection intensity were observed in the wMelPop-infected cohort, and using gene knockdown, evidence forthe role of TEP1 in this phenotype was obtained. Comparing the levels of upregulation in somatic and stably inheritedwMelPop infections in Ae. aegypti revealed that levels of upregulation were lower in the somatic infections than in the stablytransinfected line; inhibition of development of Brugia filarial nematodes was nevertheless observed in the somaticwMelPop infected females. Thus we consider that the effects observed in An. gambiae are also likely to be more pronouncedif stably inherited wMelPop transinfections can be created, and that somatic infections of Wolbachia provide a useful modelfor examining effects on pathogen development or dissemination. The data are discussed with respect to the comparativeeffects on malaria vectorial capacity of life shortening and direct inhibition of Plasmodium development that can beproduced by Wolbachia.
Straschil U, Talman AM, Ferguson DJP, et al., 2010, The Armadillo Repeat Protein PF16 Is Essential for Flagellar Structure and Function in <i>Plasmodium</i> Male Gametes, PLOS ONE, Vol: 5, ISSN: 1932-6203
- Author Web Link
- Cite
- Citations: 41
Blagborough AM, Yoshida S, Sattabongkot J, et al., 2010, Intranasal and intramuscular immunization with Baculovirus Dual Expression System-based Pvs25 vaccine substantially blocks <i>Plasmodium</i> <i>vivax</i> transmission, VACCINE, Vol: 28, Pages: 6014-6020, ISSN: 0264-410X
- Author Web Link
- Cite
- Citations: 42
Sinden RE, Talman A, Marques SR, et al., 2010, The flagellum in malarial parasites, CURRENT OPINION IN MICROBIOLOGY, Vol: 13, Pages: 491-500, ISSN: 1369-5274
- Author Web Link
- Cite
- Citations: 55
Talman AM, Blagborough AM, Sinden RE, 2010, A Plasmodium falciparum strain expressing GFP throughout the parasite’s life-cycle, PLOS One, Vol: 5, ISSN: 1932-6203
The human malaria parasite Plasmodium falciparum is responsible for the majority of malaria-related deaths. Tools allowingthe study of the basic biology of P. falciparum throughout the life cycle are critical to the development of new strategies totarget the parasite within both human and mosquito hosts. We here present 3D7HT-GFP, a strain of P. falciparumconstitutively expressing the Green Fluorescent Protein (GFP) throughout the life cycle, which has retained its capacity tocomplete sporogonic development. The GFP expressing cassette was inserted in the Pf47 locus. Using this transgenic strain,parasite tracking and population dynamics studies in mosquito stages and exo-erythrocytic schizogony is greatly facilitated.The development of 3D7HT-GFP will permit a deeper understanding of the biology of parasite-host vector interactions, andfacilitate the development of high-throughput malaria transmission assays and thus aid development of new interventionstrategies against both parasite and mosquito.
Delves MJ, Sinden RE, 2010, A semi-automated method for counting fluorescent malaria oocysts increases the throughput of transmission blocking studies, Malaria Journal, Vol: 9, ISSN: 1475-2875
Sinden RE, 2010, A biologist's perspective on malaria vaccine development, HUMAN VACCINES, Vol: 6, Pages: 3-11, ISSN: 1554-8600
- Author Web Link
- Cite
- Citations: 50
Dawes EJ, Zhuang S, Sinden RE, et al., 2009, The temporal dynamics of <i>Plasmodium</i> density through the sporogonic cycle within <i>Anopheles</i> mosquitoes, TRANSACTIONS OF THE ROYAL SOCIETY OF TROPICAL MEDICINE AND HYGIENE, Vol: 103, Pages: 1197-1198, ISSN: 0035-9203
- Author Web Link
- Cite
- Citations: 14
Dawes EJ, Churcher TS, Zhuang S, et al., 2009, Anopheles mortality is both age- and <i>Plasmodium</i>-density dependent: implications for malaria transmission, MALARIA JOURNAL, Vol: 8
- Author Web Link
- Open Access Link
- Cite
- Citations: 80
Lal K, Bromley E, Oakes R, et al., 2009, Proteomic comparison of four <i>Eimeria tenella</i> life-cycle stages: Unsporulated oocyst, sporulated oocyst, sporozoite and second-generation merozoite, PROTEOMICS, Vol: 9, Pages: 4566-4576, ISSN: 1615-9853
- Author Web Link
- Cite
- Citations: 81
This data is extracted from the Web of Science and reproduced under a licence from Thomson Reuters. You may not copy or re-distribute this data in whole or in part without the written consent of the Science business of Thomson Reuters.