Prevalence and Risk Factors of Lassa Seropositivity in Inhabitants of the Forest Region of Guinea: A Cross-Sectional Study

Background

Lassa fever is a viral hemorrhagic fever endemic in West Africa. The reservoir host of the virus is a multimammate rat, Mastomys natalensis. Prevalence estimates of Lassa virus antibodies in humans vary greatly between studies, and the main modes of transmission of the virus from rodents to humans remain unclear. We aimed to (i) estimate the prevalence of Lassa virus–specific IgG antibodies (LV IgG) in the human population of a rural area of Guinea, and (ii) identify risk factors for positive LV IgG.

Methods and Findings

A population-based cross-sectional study design was used. In April 2000, all individuals one year of age and older living in three prefectures located in the tropical secondary forest area of Guinea (Gueckedou, Lola and Yomou) were sampled using two-stage cluster sampling. For each individual identified by the sampling procedure and who agreed to participate, a standardized questionnaire was completed to collect data on personal exposure to potential risk factors for Lassa fever (mainly contact with rodents), and a blood sample was tested for LV IgG. A multiple logistic regression model was used to determine risk factors for positive LV IgG. A total of 1424 subjects were interviewed and 977 sera were tested. Prevalence of positive LV Ig was of 12.9% [10.8%–15.0%] and 10.0% [8.1%–11.9%] in rural and urban areas, respectively. Two risk factors of positive LV IgG were identified: to have, in the past twelve months, undergone an injection (odds ratio [OR] = 1.8 [1.1–3.1]), or lived with someone displaying a haemorrhage (OR = 1.7 [1.1–2.9]). No factors related to contacts with rats and/or mice remained statistically significant in the multivariate analysis.

Conclusions

Our study underlines the potential importance of person-to-person transmission of Lassa fever, via close contact in the same household or nosocomial exposure.     

The E3 Ubiquitin-Ligase Bmi1/Ring1A Controls the Proteasomal Degradation of Top2α Cleavage Complex – A Potentially New Drug Target

Background

The topoisomerases Top1, Top2α and Top2β are important molecular targets for antitumor drugs, which specifically poison Top1 or Top2 isomers. While it was previously demonstrated that poisoned Top1 and Top2β are subject to proteasomal degradation, this phenomena was not demonstrated for Top2α.

Methodology/Principal Findings

We show here that Top2α is subject to drug induced proteasomal degradation as well, although at a lower rate than Top2β. Using an siRNA screen we identified Bmi1 and Ring1A as subunits of an E3 ubiquitin ligase involved in this process. We show that silencing of Bmi1 inhibits drug-induced Top2α degradation, increases the persistence of Top2α-DNA cleavage complex, and increases Top2 drug efficacy. The Bmi1/Ring1A ligase ubiquitinates Top2α in-vitro and cellular overexpression of Bmi1 increases drug induced Top2α ubiquitination. A small-molecular weight compound, identified in a screen for inhibitors of Bmi1/Ring1A ubiquitination activity, also prevents Top2α ubiquitination and drug-induced Top2α degradation. This ubiquitination inhibitor increases the efficacy of topoisomerase 2 poisons in a synergistic manner.

Conclusions/Significance

The discovery that poisoned Top2α is undergoing proteasomal degradation combined with the involvement of Bmi1/Ring1A, allowed us to identify a small molecule that inhibits the degradation process. The Bmi1/Ring1A inhibitor sensitizes cells to Top2 drugs, suggesting that this type of drug combination will have a beneficial therapeutic outcome. As Bmi1 is also a known oncogene, elevated in numerous types of cancer, the identified Bmi1/Ring1A ubiquitin ligase inhibitors can also be potentially used to directly target the oncogenic properties of Bmi1.     

Effects of available surface on gaseous emissions from group-housed gestating sows kept on deep litter

In the European Union, the group-housed pregnant sows have to have a minimal legal available area of 2.25 m²/sow. However, it has been observed that an increased space allowance reduces agonistic behaviour and consecutive wounds and thus induces better welfare conditions. But, what about the environmental impacts of this greater available area? Therefore, the aim of this study was to quantify pollutant gases emissions (nitrous oxide, N₂O, methane, CH₄, carbon dioxide, CO₂ and ammonia, NH₃), according to the space allowance in the raising of gestating sows group-housed on a straw-based deep litter. Four successive batches of 10 gestating sows were each divided into two homogeneous groups and randomly allocated to a treatment: 2.5 v. 3.0 m²/sow. The groups were separately kept in two identical rooms. A restricted conventional cereals based diet was provided once a day in individual feeding stalls available only during the feeding time. Rooms were automatically ventilated. The gas emissions were measured by infra red photoacoustic detection during six consecutive days at the 6th, 9th and 12th weeks of gestation. Sows performance (body weight gain, backfat thickness, number and weight of piglets) was not significantly different according to the space allowance. In the room with 3.0 m²/sow and compared with the room with 2.5 m²/sow, gaseous emissions were significantly greater for NH₃ (6.29 v. 5.37 g NH₃-N/day per sow; P < 0.01) and significantly lower for N₂O (1.78 v. 2.48 g N₂O-N/day per sow; P < 0.01), CH₄ (10.15 v. 15.21 g/day per sow; P < 0.001), CO₂ equivalents (1.11 v. 1.55 kg/day per sow; P < 0.001), CO₂ (2.12 v. 2.41 kg/day per sow; P < 0.001) and H₂O (3.10 v. 3.68 kg/day per sow; P < 0.001). In conclusion, an increase of the available area for group-housed gestating sow kept on straw-based deep litter seems to be ambiguous on an environmental impacts point of view. Compared with a conventional and legal available area, it favoured NH₃ emissions, probably due to an increased emitting surface. However, about greenhouse gases, it decreased N₂O, CH₄ and CO₂ emissions, probably due to reduced anaerobic conditions required for their synthesis, and led to a reduction of CO₂ equivalents emissions.     

Evolution and population structure of Salmonella enterica serovar Newport

Salmonellosis caused by Salmonella enterica serovar Newport is a major global public health concern, particularly because S. Newport isolates that are resistant to multiple drugs (MDR), including third-generation cephalosporins (MDR-AmpC phenotype), have been commonly isolated from food animals. We analyzed 384 S. Newport isolates from various sources by a multilocus sequence typing (MLST) scheme to study the evolution and population structure of the serovar. These were compared to the population structure of S. enterica serovars Enteritidis, Kentucky, Paratyphi B, and Typhimurium. Our S. Newport collection fell into three lineages, Newport-I, Newport-II, and Newport-III, each of which contained multiple sequence types (STs). Newport-I has only a few STs, unlike Newport-II or Newport-III, and has possibly emerged recently. Newport-I is more prevalent among humans in Europe than in North America, whereas Newport-II is preferentially associated with animals. Two STs of Newport-II encompassed all MDR-AmpC isolates, suggesting recent global spread after the acquisition of the bla(CMY-2) gene. In contrast, most Newport-III isolates were from humans in North America and were pansusceptible to antibiotics. Newport was intermediate in population structure to the other serovars, which varied from a single monophyletic lineage in S. Enteritidis or S. Typhimurium to four discrete lineages within S. Paratyphi B. Both mutation and homologous recombination are responsible for diversification within each of these lineages, but the relative frequencies differed with the lineage. We conclude that serovars of S. enterica provide a variety of different population structures.     

Identifying common prognostic factors in genomic cancer studies: A novel index for censored outcomes

Background  

With the growing number of public repositories for high-throughput genomic data, it is of great interest to combine the results produced by independent research groups. Such a combination allows the identification of common genomic factors across multiple cancer types and provides new insights into the disease process. In the framework of the proportional hazards model, classical procedures, which consist of ranking genes according to the estimated hazard ratio or the p-value obtained from a test statistic of no association between survival and gene expression level, are not suitable for gene selection across multiple genomic datasets with different sample sizes. We propose a novel index for identifying genes with a common effect across heterogeneous genomic studies designed to remain stable whatever the sample size and which has a straightforward interpretation in terms of the percentage of separability between patients according to their survival times and gene expression measurements.     

Diversity of Monomers in Nonribosomal Peptides: towards the Prediction of Origin and Biological Activity

Nonribosomal peptides (NRPs) are molecules produced by microorganisms that have a broad spectrum of biological activities and pharmaceutical applications (e.g., antibiotic, immunomodulating, and antitumor activities). One particularity of the NRPs is the biodiversity of their monomers, extending far beyond the 20 proteogenic amino acid residues. Norine, a comprehensive database of NRPs, allowed us to review for the first time the main characteristics of the NRPs and especially their monomer biodiversity. Our analysis highlighted a significant similarity relationship between NRPs synthesized by bacteria and those isolated from metazoa, especially from sponges, supporting the hypothesis that some NRPs isolated from sponges are actually synthesized by symbiotic bacteria rather than by the sponges themselves. A comparison of peptide monomeric compositions as a function of biological activity showed that some monomers are specific to a class of activities. An analysis of the monomer compositions of peptide products predicted from genomic information (metagenomics and high-throughput genome sequencing) or of new peptides detected by mass spectrometry analysis applied to a culture supernatant can provide indications of the origin of a peptide and/or its biological activity.Nonribosomal peptides (NRPs) are molecules produced by microorganisms and synthesized by huge multienzymatic complexes (38, 41), called nonribosomal peptide synthetases (NRPSs). These megaenzymes are organized into modules, one for each amino acid to be built into the peptide product. This is accomplished by division of each catalytic step into specialized semiautonomous domains. The basic set of domains (adenylation, thiolation, and condensation) within a module can be extended by substrate-modifying domains, including domains for substrate epimerization, β hydroxylation, N methylation, and heterocyclic ring formation. The peptide release is catalyzed by a thioesterase domain which can also, in many cases, be involved in an intramolecular reaction leading to a cyclic or partially cyclic peptide or, in fewer cases, in the oligomerization of peptide units (iterative biosynthesis). NRPs show a broad spectrum of biological activities and pharmaceutical applications. They can harbor antimicrobial, immunomodulator, or antitumor activities. Cyclosporine (5), an immunosuppressant drug widely used in organ transplantation, daptomycin (60) (marketed in the United States under the trade name Cubicin), used in the treatment of certain infections caused by Gram-positive bacteria, aminoadipyl-cysteinyl-valine (ACV)-tripeptide, which is the precursor of cephalosporin and penicillin (29), the most famous antibiotic, and also bleomycin (57), used in the treatment of several cancers, are some common examples of NRPs of high therapeutic importance. Two main structural traits distinguish these peptides from ribosomally synthesized peptides: first, their primary structure is more frequently cyclic (partially or totally) branched or polycyclic rather than linear and, second, the biodiversity of monomers incorporated in NRPs goes far beyond the 20 proteogenic amino acids residues. NRP monomers include modified versions of the proteogenic amino acids (e.g., methylated, hydroxylated, and d-forms) but also other monomers, such as, for example, 2-aminoisobutyric acid (Aib), hydroxyphenylglycine (Hpg), and 2,3-dihydroxybenzoic acid (diOH-Bz). However, essential characteristics of this diversity and its relationship with biological functions and producing organisms have been poorly understood until now.The development of the Norine database, the first resource entirely dedicated to NRPs (8, 9), filled this gap. Based on Norine data, we performed the first large-scale analysis of about a thousand peptides which represent a total coverage of more than 10,000 monomer occurrences, revealing the presence of as many as 500 different monomer types. A data-mining analysis of the monomeric compositions of NRPs allowed us to reveal a strong relationship between certain monomeric characteristics of NRPs and their biological function and producing organism. In addition to providing a comprehensive overview of monomeric biodiversity in NRPs, this work demonstrated (i) a dissimilarity of structural properties between bacterial and fungal NRPs; (ii) a significant relationship between NRPs synthesized by bacteria and those isolated from metazoa, especially from sponges, supporting the hypothesis that the peptides isolated from sponges are in reality synthesized by symbiotic bacteria rather than by the sponges themselves; and (iii) a certain monomer specificity to a class of biological activities. Those observations are supported by successful statistical predictions of biological activities of NRPs based on their monomeric compositions.     

Molecular systematics and origin of sociality in mongooses (Herpestidae, Carnivora)

The Herpestidae are small terrestrial carnivores comprising 18 African and Asian genera, currently split into two subfamilies, the Herpestinae and the Galidiinae. The aim of this work was to resolve intra-familial relationships and to test the origin of sociality in the group. For this purpose we analysed sequences of the complete cytochrome b gene for 18 species of Herpestidae. The results showed that the mongooses were split into three clades: (1) the Malagasy taxa (Galidiinae and Cryptoprocta), (2) the true social mongooses and (3) the solitary mongooses, each group being also supported by morphological and chromosomal data. Our results suggested unexpected phylogenetic relationships: (1) the genus Cynictis is included in the solitary mongoose clade, (2) the genera Liberiictis and Mungos are sister-group, and (3) the genus Herpestes is polyphyletic. We examined the evolution of the sociality in mongooses by combining behavioural traits with the cytochrome b data. Some of the behavioural traits provided good synapomorphies for characterizing the social species clade, showing the potential benefit of using such characters in phylogeny. The mapping of ecological and behavioural features resulted in hypothesizing solitary behavior and life in forest as the conditions at the base of the mongoose clade.     

Cross-talk between the paired domain and the homeodomain of Pax3: DNA binding by each domain causes a structural change in the other domain, supporting interdependence for DNA Binding

The Pax3 protein has two DNA binding domains, a Paired domain (PD) and a paired-type Homeo domain (HD). Although the PD and HD can bind to cognate DNA sequences when expressed individually, genetic and biochemical data indicate that the two domains are functionally interdependent in intact Pax3. The mechanistic basis of this functional interdependence is unknown and was studied by protease sensitivity. Pax3 was modified by the creation of Factor Xa cleavage sites at discrete locations in the PD, the HD, and in the linker segment joining the PD and the HD (Xa172, Xa189, and Xa216) in individual Pax3 mutants. The effect of Factor Xa insertions on protein stability and on DNA binding by the PD and the HD was measured using specific target site sequences. Independent insertions at position 100 in the linker separating the first from the second helix-turn-helix motif of the PD and at position 216 immediately upstream of the HD were found to be readily accessible to Factor Xa cleavage. The effect of DNA binding by the PD or the HD on accessibility of Factor Xa sites inserted in the same or in the other domain was monitored and quantitated for multiple mutants bearing different numbers of Xa sites at each position. In general, DNA binding reduced accessibility of all sites, suggesting a more compact and less solvent-exposed structure of DNA-bound versus DNA-free Pax3. Results of dose response and time course experiments were consistent and showed that DNA binding by the PD not only caused a local structural change in the PD but also caused a conformational change in the HD (P3OPT binding to Xa216 mutants); similarly, DNA binding by the HD also caused a conformational change in the PD (P2 binding to Xa100 mutants). These results provide a structural basis for the functional interdependence of the two DNA binding domains of Pax3.     

Disentangling invasion processes in a dynamic shipping-boating network

The relative importance of multiple vectors to the initial establishment, spread and population dynamics of invasive species remains poorly understood. This study used molecular methods to clarify the roles of commercial shipping and recreational boating in the invasion by the cosmopolitan tunicate, Botryllus schlosseri. We evaluated (i) single vs. multiple introduction scenarios, (ii) the relative importance of shipping and boating to primary introductions, (iii) the interaction between these vectors for spread (i.e. the presence of a shipping-boating network) and (iv) the role of boating in determining population similarity. Tunicates were sampled from 26 populations along the Nova Scotia, Canada, coast that were exposed to either shipping (i.e. ports) or boating (i.e. marinas) activities. A total of 874 individuals (c. 30 per population) from five ports and 21 marinas was collected and analysed using both mitochondrial cytochrome c oxidase subunit I gene (COI) and 10 nuclear microsatellite markers. The geographical location of multiple hotspot populations indicates that multiple invasions have occurred in Nova Scotia. A loss of genetic diversity from port to marina populations suggests a stronger influence of ships than recreational boats on primary coastal introductions. Population genetic similarity analysis reveals a dependence of marina populations on those that had been previously established in ports. Empirical data on marina connectivity because of boating better explains patterns in population similarities than does natural spread. We conclude that frequent primary introductions arise by ships and that secondary spread occurs gradually thereafter around individual ports, facilitated by recreational boating.