Novel Cross-Border Approaches to Optimise Identification of Asymptomatic and Artemisinin-Resistant Plasmodium Infection in Mobile Populations Crossing Cambodian Borders

Background

Human population movement across country borders presents a real challenge for malaria control and elimination efforts in Cambodia and its neighbouring countries. To quantify Plasmodium infection among the border-crossing population, including asymptomatic and artemisinin resistant (AR) parasites, three official border crossing points, one from each of Cambodia''s borders with Thailand, Laos and Vietnam, were selected for sampling.

Methods and Findings

A total of 3206 participants (of 4110 approached) were recruited as they crossed the border, tested for malaria and interviewed. By real-time polymerase chain reaction (RT-PCR), 5.4% of all screened individuals were found to harbour Plasmodium parasites. The proportion was highest at the Laos border (11.5%). Overall there were 97 P. vivax (55.7%), 55 P. falciparum (31.6%), two P. malariae (1.1%) and 20 mixed infections (11.5%). Of identified infections, only 20% were febrile at the time of screening. Of the 24 P. falciparum samples where a further PCR was possible to assess AR, 15 (62.5%) had mutations in the K13 propeller domain gene, all from participants at the Laos border point. Malaria rapid diagnostic test (RDT) pLDH/HRP-2 identified a positivity rate of 3.2% overall and sensitivity compared to RT-PCR was very low (43.1%). Main individual risk factors for infection included sex, fever, being a forest-goer, poor knowledge of malaria prevention methods and previous malaria infection. Occupation, day of the week and time of crossing (morning vs. afternoon) also appeared to play an important role in predicting positive cases.

Conclusions

This study offers a novel approach to identify asymptomatic infections and monitor AR parasite flow among mobile and migrant populations crossing the borders. Similar screening activities are recommended to identify other hot borders and characterise potential hot spots of AR. Targeted “customised” interventions and surveillance activities should be implemented in these sites to accelerate elimination efforts in the region.     

Spectroscopic study of conformational changes accompanying self-assembly of HCV core protein

Electron microscopy and infrared and Raman spectroscopy have been used here to study the morphology, size distribution, secondary and tertiary structures of protein particles assembled from a truncated hepatitis C virus (HCV) core protein covering the first 120 aa. Particles of pure protein, having similar morphology and size distribution of those of nucleocapsids found in sera from HCV-infected patients, have been visualized for the first time. The secondary structure of these protein particles involve beta-sheet enrichment in relation to its protein monomer. Tertiary/quaternary structure has also been studied using the dynamics of H/D exchange. With this aim infrared spectra were measured as a function of H/D exchange time and subsequently analyzed by principal component analysis and two-dimensional correlation spectroscopy. Temporal dynamics of exchange for these protein particles were as follows: arginine residues exchanged first, followed by turn and unordered structures, followed by beta-sheets which may act as linkers of protein monomers.     

The METTL5-TRMT112 N6-methyladenosine methyltransferase complex regulates mRNA translation via 18S rRNA methylation

Ribosomal RNAs (rRNAs) have long been known to carry chemical modifications, including 2′O-methylation, pseudouridylation, N⁶-methyladenosine (m⁶A), and N^6,6-dimethyladenosine. While the functions of many of these modifications are unclear, some are highly conserved and occur in regions of the ribosome critical for mRNA decoding. Both 28S rRNA and 18S rRNA carry single m⁶A sites, and while the methyltransferase ZCCHC4 has been identified as the enzyme responsible for the 28S rRNA m⁶A modification, the methyltransferase responsible for the 18S rRNA m⁶A modification has remained unclear. Here, we show that the METTL5-TRMT112 methyltransferase complex installs the m⁶A modification at position 1832 of human 18S rRNA. Our work supports findings that TRMT112 is required for METTL5 stability and reveals that human METTL5 mutations associated with microcephaly and intellectual disability disrupt this interaction. We show that loss of METTL5 in human cancer cell lines and in mice regulates gene expression at the translational level; additionally, Mettl5 knockout mice display reduced body size and evidence of metabolic defects. While recent work has focused heavily on m⁶A modifications in mRNA and their roles in mRNA processing and translation, we demonstrate here that deorphanizing putative methyltransferase enzymes can reveal previously unappreciated regulatory roles for m⁶A in noncoding RNAs.     

Complete Genome Sequence of the Naphthalene-Degrading Bacterium Pseudomonas stutzeri AN10 (CCUG 29243)

Pseudomonas stutzeri AN10 (CCUG 29243) can be considered a model strain for aerobic naphthalene degradation. We report the complete genome sequence of this bacterium. Its 4.71-Mb chromosome provides insights into other biodegradative capabilities of strain AN10 (i.e., benzoate catabolism) and suggests a high number of horizontal gene transfer events.     

Influence of the g− conformation of Ser and Thr on the structure of transmembrane helices

In order to study the influence of Ser and Thr on the structure of transmembrane helices we have analyzed a database of helix stretches extracted from crystal structures of membrane proteins and an ensemble of model helices generated by molecular dynamics simulations. Both complementary analyses show that Ser and Thr in the g? conformation induce and/or stabilize a structural distortion in the helix backbone. Using quantum mechanical calculations, we have attributed this effect to the electrostatic repulsion between the side chain Oγ atom of Ser and Thr and the backbone carbonyl oxygen at position i ? 3. In order to minimize the repulsive force between these negatively charged oxygens, there is a modest increase of the helix bend angle as well as a local opening of the helix turn preceding Ser/Thr. This small distortion can be amplified through the helix, resulting in a significant displacement of the residues located at the other side of the helix. The crystal structures of aquaporin Z and the β₂-adrenergic receptor are used to illustrate these effects. Ser/Thr-induced structural distortions can be implicated in processes as diverse as ligand recognition, protein function and protein folding.     

Advances in the synthesis and recent therapeutic applications of 1,2,4-thiadiazole heterocycles

Chemical properties of 1,2,4-thiadiazole have been reviewed in the last few years. However, the usefulness of 1,2,4-thiadiazole as a privileged system in medicinal chemistry has prompted the advances on the therapeutic potential of this system. This review provides a brief summary of the medicinal chemistry of 1,2,4-thiadiazole system and highlights some examples of 1,2,4-thiadiazole-containing drug substances in the current literature. A survey of representative literature procedures for the preparation of 1,2,4-thiadiazole is presented in sections by generalized synthetic methods.     

Non-ATP competitive glycogen synthase kinase 3beta (GSK-3beta) inhibitors: study of structural requirements for thiadiazolidinone derivatives

The 2,4-disubstituted thiadiazolidinones (TDZD) were described as the first non-ATP competitive GSK-3beta inhibitors. New modifications in this heterocyclic ring are here reported to study the influence on the biological activity. The basic skeleton of 1,2,4-thiadiazole and also one of the carbonyl groups are kept, while different modifications are introduced in positions 3 and 5, respectively. The GSK-3beta activity of the new thiadiazole derivatives here synthesized showed IC(50) values for some of the compounds in the micromolar range. Additionally, ATP competition studies have been carried out, showing that as well as the first generation of TDZD, these new compounds act in a non-competitive manner. With this study, additional requirements for the biological activity of the TDZD family have been delineated.