Discovery of Infection Associated Metabolic Markers in Human African Trypanosomiasis

Peer reviewedPublisher PD

Aryl Phosphoramidates of 5-Phospho Erythronohydroxamic Acid, A New Class of Potent Trypanocidal Compounds

RNAi and enzymatic studies have shown the importance of 6-phosphogluconate dehydrogenase (6-PGDH) in Trypanosoma brucei for the parasite survival and make it an attractive drug target for the development of new treatments against human African trypanosomiasis. 2,3-O-Isopropylidene-4-erythrono hydroxamate is a potent inhibitor of parasite Trypanosoma brucei 6-phosphogluconate dehydrogenase (6-PGDH), the third enzyme of the pentose phosphate pathway. However, this compound does not have trypanocidal activity due to its poor membrane permeability. Consequently, we have previously reported a prodrug approach to improve the antiparasitic activity of this inhibitor by converting the phosphate group into a less charged phosphate prodrug. The activity of prodrugs appeared to be dependent on their stability in phosphate buffer. Here we have successfully further extended the development of the aryl phosphoramidate prodrugs of 2,3-O-isopropylidene-4-erythrono hydroxamate by synthesizing a small library of phosphoramidates and evaluating their biological activity and stability in a variety of assays. Some of the compounds showed high trypanocidal activity and good correlation of activity with their stability in fresh mouse blood

Window screening, ceilings and closed eaves as sustainable ways to control malaria in Dar es Salaam, Tanzania.

BACKGROUND\ud \ud Malaria transmission in Africa occurs predominantly inside houses where the primary vectors prefer to feed. Human preference and investment in blocking of specific entry points for mosquitoes into houses was evaluated and compared with known entry point preferences of the mosquitoes themselves.\ud \ud METHODS\ud \ud Cross-sectional household surveys were conducted in urban Dar es Salaam, Tanzania to estimate usage levels of available options for house proofing against mosquito entry, namely window screens, ceilings and blocking of eaves. These surveys also enabled evaluation of household expenditure on screens and ceilings and the motivation behind their installation.\ud \ud RESULTS\ud \ud Over three quarters (82.8%) of the 579 houses surveyed in Dar es Salaam had window screens, while almost half (48.9%) had ceilings. Prevention of mosquito entry was cited as a reason for installation of window screens and ceilings by 91.4% (394/431) and 55.7% (127/228) of respondents, respectively, but prevention of malaria was rarely cited (4.3%, 22/508). The median cost of window screens was between US $21-30 while that of ceilings was between US$301-400. The market value of insecticide-treated nets, window screening and ceilings currently in use in the city was estimated as 2, 5 and 42 million US$. More than three quarters of the respondents that lacked them said it was too expensive to install ceilings (82.2%) or window screens (75.5%).\ud \ud CONCLUSION\ud \ud High coverage and spending on screens and ceilings implies that these techniques are highly acceptable and excellent uptake can be achieved in urban settings like Dar es Salaam. Effective models for promotion and subsidization should be developed and evaluated, particularly for installation of ceilings that prevent entry via the eaves, which are the most important entry point for mosquitoes that cause malaria, a variety of neglected tropical diseases and the nuisance which motivates uptake

Anti-Paraflagellar Rodc Antibodies Inhibit the In-Vitro Growth of Trypanosoma Brucei Brucei

Paraflagellar rod (PFR), a conserved structure expressed in all lifecycle stages of the order kinetoplasida except in the amastigotes is vital for the parasites survival. In T.b.brucei, the PFR protein has two major components, PFRc and PFRa with molecular mass 73kDa and 68kDa respectively. Experimental evidences implicate the PFR protein as a highly immunogenic and protective antigen. However, its immunogenic properties underlying its suitability as vaccine candidate has not been adequately investigated in-vitro. This study aimed to demonstrate the growth inhibitory potential of PFR protein against T.b.brucei parasites in–vitro. Antibodies against a recombinant form of the PFRc protein were produced and used to generate immune response. A deoxyribonucleotide (DNA) segment of approximate 672bp encoding the PFRc protein component was amplified using polymerase chain reaction (PCR), cloned and expressed in E.coli (BL21) cells. A 200 µg portion of the purified PFRc protein mixed with 100µl Freund's complete adjuvant (FCA) was used to immunize rabbits. An antibody titre of 2.5 x 104 reciprocal dilutions was obtained following three immunisation boosts, spaced two weeks apart. Western blot analysis showed that rabbit anti-PFRc antibodies recognised specifically a 25kDa protein corresponding to the estimated size of the expressed PFRc protein. 25% of purified anti-rabbit IgG antibodies were able to inhibit ~70% T.b.brucei parasite in vitro. This confirmed that the PFRc protein is immunogenic in rabbits and can elicit specific growth inhibitory antibodies. However, we recommend invivo studies in humans and domestic animals infected by trypanosomes to ascertain the vaccine potential of this candidate protein for trypanosomiasis

Metabolic Profiling of Central Nervous System Disease in Trypanosoma brucei rhodesiense infection

Acknowledgments. We thank Isabel Garcia-Perez and Maria Lopez-Gonzales, for performing additional mass spectrometry analyses at Imperial College London. Financial support. This work was supported by the Medical Research Council MRC; (to S. D. L.), and Imperial College (MRC doctoral training award G1000390 to S. D. L.), and the Wellcome Trust (grant 082786 to J. M. S. and V. P. A.).Peer reviewedPublisher PD

A Predator from East Africa that Chooses Malaria Vectors as Preferred Prey

BACKGROUND: All vectors of human malaria, a disease responsible for more than one million deaths per year, are female mosquitoes from the genus Anopheles. Evarcha culicivora is an East African jumping spider (Salticidae) that feeds indirectly on vertebrate blood by selecting blood-carrying female mosquitoes as preferred prey. METHODOLOGY/PRINCIPAL FINDINGS: By testing with motionless lures made from mounting dead insects in lifelike posture on cork discs, we show that E. culicivora selects Anopheles mosquitoes in preference to other mosquitoes and that this predator can identify Anopheles by static appearance alone. Tests using active (grooming) virtual mosquitoes rendered in 3-D animation show that Anopheles' characteristic resting posture is an important prey-choice cue for E. culicivora. Expression of the spider's preference for Anopheles varies with the spider's size, varies with its prior feeding condition and is independent of the spider gaining a blood meal. CONCLUSIONS/SIGNIFICANCE: This is the first experimental study to show that a predator of any type actively chooses Anopheles as preferred prey, suggesting that specialized predators having a role in the biological control of disease vectors is a realistic possibility

ENTH and ANTH domain proteins participate in AP2-independent clathrin-mediated endocytosis

Clathrin-mediated endocytosis (CME) is a major route of entry into eukaryotic cells. A core of evolutionarily ancient genes encodes many components of this system but much of our mechanistic understanding of CME is derived from a phylogenetically narrow sampling of a few model organisms. In the parasite Trypanosoma brucei, which is distantly related to the better characterised animals and fungi, exceptionally fast endocytic turnover aids its evasion of the host immune system. Although clathrin is absolutely essential for this process, the adaptor protein complex 2 (AP2) has been secondarily lost, suggesting mechanistic divergence. Here, we characterise two phosphoinositide-binding monomeric clathrin adaptors, T. brucei (Tb)EpsinR and TbCALM, which in trypanosomes are represented by single genes, unlike the expansions present in animals and fungi. Depletion of these gene products reveals essential, but partially redundant, activities in CME. Ultrastructural analysis of TbCALM and TbEpsinR double-knockdown cells demonstrated severe defects to clathrin-coated pit formation and morphology associated with a dramatic inhibition of endocytosis. Depletion of TbCALM alone, however, produced a distinct lysosomal segregation phenotype, indicating an additional non-redundant role for this protein. Therefore, TbEpsinR and TbCALM represent ancient phosphoinositide-binding proteins with distinct and vital roles in AP2-independent endocytosis

Community engagement strategies for genomic studies in Africa: a review of the literature

Background: Community engagement has been recognised as an important aspect of the ethical conduct of biomedical research, especially when research is focused on ethnically or culturally distinct populations. While this is a generally accepted tenet of biomedical research, it is unclear what components are necessary for effective community engagement, particularly in the context of genomic research in Africa. Methods: We conducted a review of the published literature to identify the community engagement strategies that can support the successful implementation of genomic studies in Africa. Our search strategy involved using online databases, Pubmed (National Library of Medicine), Medline and Google scholar. Search terms included a combination of the following: community engagement, community advisory boards, community consultation, community participation, effectiveness, genetic and genomic research, Africa, developing countries. Results: A total of 44 articles and 1 thesis were retrieved of which 38 met the selection criteria. Of these, 21 were primary studies on community engagement, while the rest were secondary reports on community engagement efforts in biomedical research studies. 34 related to biomedical research generally, while 4 were specific to genetic and genomic research in Africa. Conclusion: We concluded that there were several community engagement strategies that could support genomic studies in Africa. While many of the strategies could support the early stages of a research project such as the recruitment of research participants, further research is needed to identify effective strategies to engage research participants and their communities beyond the participant recruitment stage. Research is also needed to address how the views of local communities should be incorporated into future uses of human biological samples. Finally, studies evaluating the impact of CE on genetic research are lacking. Systematic evaluation of CE strategies is essential to determine the most effective models of CE for genetic and genomic research conducted in African settings

Population genetic structure of the bean leaf beetle Ootheca mutabilis (Coleoptera: Chrysomelidae) in Uganda

Bean leaf beetle (BLB) (Ootheca mutabilis) has emerged as an important bean pest in Uganda, leading to devastating crop losses. There is limited information on the population genetic structure of BLB despite its importance. In this study, novel microsatellite DNA markers and the partial mitochondrial cytochrome oxidase subunit I (mtCOI) gene sequences were used to analyze the spatial population genetic structure, genetic differentiation and haplotype diversity of 86 O. mutabilis samples from 16 (districts) populations. We identified 19,356 simple sequence repeats (SSRs) (mono, di-, tri-, tetra-, penta-, and hexa-nucleotides) of which 81 di, tri and tetra-nucleotides were selected for primer synthesis. Five highly polymorphic SSR markers (4–21 alleles, heterozygosity 0.59–0.84, polymorphic information content (PIC) 50.13–83.14%) were used for this study. Analyses of the 16 O. mutabilis populations with these five novel SSRs found nearly all the genetic variation occurring within populations and there was no evidence of genetic differentiation detected for both types of markers. Also, there was no evidence of isolation by distance between geographical and genetic distances for SSR data and mtCOI data except in one agro-ecological zone for mtCOI data. Bayesian clustering identified a signature of admixture that suggests genetic contributions from two hypothetical ancestral genetic lineages for both types of markers, and the minimum-spanning haplotype network showed low differentiation in minor haplotypes from the most common haplotype with the most common haplotype occurring in all the 16 districts. A lack of genetic differentiation indicates unrestricted migrations between populations. This information will contribute to the design of BLB control strategie