An outbreak of febrile illness occurred in Gabon in 2007, with 20,000 suspected cases. Chikungunya or dengue-2 virus infections were identified in 321 patients; 8 patients had documented co-infections. Aedes albopictus was identified as... more
An outbreak of febrile illness occurred in Gabon in 2007, with 20,000 suspected cases. Chikungunya or dengue-2 virus infections were identified in 321 patients; 8 patients had documented co-infections. Aedes albopictus was identified as the principal vector for the transmission of both viruses.
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Chikungunya (CHIKV) and Dengue (DENV) viruses, both arboviruses, have caused multiple outbreaks worldwide. Their clinical features are poorly described in Africa and there is no comparative study, although Chikungunya is considered as a... more
Chikungunya (CHIKV) and Dengue (DENV) viruses, both arboviruses, have caused multiple outbreaks worldwide. Their clinical features are poorly described in Africa and there is no comparative study, although Chikungunya is considered as a dengue-like disease. We conducted a comparative study of clinical and biological data from CHIKV and DENV positive patients during the 2010 Gabonese outbreak. Patients consulting with general symptoms and having laboratory confirmation for CHIKV or DENV were included. Clinical and biological data were recorded. Statistical analyses were performed using Epi Info. A P value < 0.05 was considered significant. In all, 270 CHIKV+, 53 DENV+ and 20 co-infected patients were included in the study. Headaches, hemorrhage, leukopenia and lymphopenia were significantly (P respectively 0.01, 0.001, 0.02 and 0.001) more frequent in DENV+ patients than in CHIKV+. There was no additive effect of the two viruses.These clinical and hematological disorders are non s...
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Chikungunya and dengue viruses emerged in Gabon in 2007, with large outbreaks primarily affecting the capital Libreville and several northern towns. Both viruses subsequently spread to the south-east of the country, with new outbreaks... more
Chikungunya and dengue viruses emerged in Gabon in 2007, with large outbreaks primarily affecting the capital Libreville and several northern towns. Both viruses subsequently spread to the south-east of the country, with new outbreaks occurring in 2010. The mosquito species Aedes albopictus, that was known as a secondary vector for both viruses, recently invaded the country and was the primary vector involved in the Gabonese outbreaks. We conducted a retrospective study of human sera and mosquitoes collected in Gabon from 2007 to 2010, in order to identify other circulating arboviruses. Sample collections, including 4312 sera from patients presenting with painful febrile disease, and 4665 mosquitoes belonging to 9 species, split into 247 pools (including 137 pools of Aedes albopictus), were screened with molecular biology methods. Five human sera and two Aedes albopictus pools, all sampled in an urban setting during the 2007 outbreak, were positive for the flavivirus Zika (ZIKV). Th...
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Sickle Cell Disease (SCD) is an important cause of death in young children in Africa, which the World Health Organization has declared a public health priority. Although SCD has been studied at the continental scale and at the local... more
Sickle Cell Disease (SCD) is an important cause of death in young children in Africa, which the World Health Organization has declared a public health priority. Although SCD has been studied at the continental scale and at the local scale, a picture of its distribution at the scale of an African country has never been given. The aim of this study is to provide such a picture for the Republic of Gabon, a country where precisely the epidemiology of SCD has been poorly investigated. To this effect, 4250 blood samples from persons older than 15 were collected between June 2005 and September 2008 in 210 randomly selected villages from the nine administrative provinces of Gabon. Two methods were used to screen Sickle Cell Trait (SCT) carriers: isoelectric focusing (IEF) and high-performance liquid chromatography (HPLC). SCT prevalence in Gabon was 21.1% (895/4249). SCT prevalence was significantly larger for the Bantu population (21.7%, n=860/3959) than for the Pygmy population (12.1%, n=...
Research Interests: Genetics, Malaria, Adolescent, Plasmodium, Humans, and 9 moreGabon, Female, Male, Young Adult, Aged, Middle Aged, Adult, Age Factors, and Sickle Cell Trait
Dengue fever is the most important arthropod-borne viral disease worldwide, affecting 50-100 million individuals annually. The clinical picture associated with acute dengue virus (DENV) infections ranges from classical febrile illness to... more
Dengue fever is the most important arthropod-borne viral disease worldwide, affecting 50-100 million individuals annually. The clinical picture associated with acute dengue virus (DENV) infections ranges from classical febrile illness to life-threatening disease. The innate immunity is the first line of defense in the control of viral replication. This review will examine the particular role of natural killer (NK) cells in DENV infection. Over recent years, our understanding of the interplay between NK cells and viral pathogenesis has improved significantly. NK cells express an array of inhibitory and activating receptors that enable them to detect infected targets while sparing normal cells, and to recruit adaptive immune cells. To date, the exact mechanism by which NK cells may contribute to the control of DENV infection remains elusive. Importantly, DENV has acquired mechanisms to evade NK cell responses, further underlining the relevance of these cells in pathophysiology. Hence,...
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Ebola virus (EBOV) is a highly virulent human pathogen. Recovery of infected patients is associated with efficient EBOV-specific immunoglobulin G (IgG) responses, whereas fatal outcome is associated with defective humoral immunity. As... more
Ebola virus (EBOV) is a highly virulent human pathogen. Recovery of infected patients is associated with efficient EBOV-specific immunoglobulin G (IgG) responses, whereas fatal outcome is associated with defective humoral immunity. As B-cell epitopes on EBOV are poorly defined, we sought to identify specific epitopes in four EBOV proteins (Glycoprotein (GP), Nucleoprotein (NP), and matrix Viral Protein (VP)40 and VP35). For the first time, we tested EBOV IgG+ sera from asymptomatic individuals and symptomatic Gabonese survivors, collected during the early humoral response (seven days after the end of symptoms) and the late memory phase (7-12 years post-infection). We also tested sera from EBOV-seropositive patients who had never had clinical signs of hemorrhagic fever or who lived in non-epidemic areas (asymptomatic subjects). We found that serum from asymptomatic individuals was more strongly reactive to VP40 peptides than to GP, NP or VP35. Interestingly, anti-EBOV IgG from asympt...
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The rising incidence of emerging infectious diseases (EID) is mostly linked to biodiversity loss, changes in habitat use and increasing habitat fragmentation. Bats are linked to a growing number of EID but few studies have explored the... more
The rising incidence of emerging infectious diseases (EID) is mostly linked to biodiversity loss, changes in habitat use and increasing habitat fragmentation. Bats are linked to a growing number of EID but few studies have explored the factors of viral richness in bats. These may have implications for role of bats as potential reservoirs. We investigated the determinants of viral richness in 15 species of African bats (8 Pteropodidae and 7 microchiroptera) in Central and West Africa for which we provide new information on virus infection and bat phylogeny. We performed the first comparative analysis testing the correlation of the fragmented geographical distribution (defined as the perimeter to area ratio) with viral richness in bats. Because of their potential effect, sampling effort, host body weight, ecological and behavioural traits such as roosting behaviour, migration and geographical range, were included into the analysis as variables. The results showed that the geographical...
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In 2010, a large outbreak of poliomyelitis with unusual 47% lethality occurred in Pointe Noire, Republic of Congo. Vaccine-mediated immunity against the outbreak virus was never investigated. A wild poliovirus 1 (WPV1) isolated from a... more
In 2010, a large outbreak of poliomyelitis with unusual 47% lethality occurred in Pointe Noire, Republic of Congo. Vaccine-mediated immunity against the outbreak virus was never investigated. A wild poliovirus 1 (WPV1) isolated from a fatal case (termed PV1-RC2010) showed a previously unknown combination of amino acid exchanges in critical antigenic site 2 (AgS2, VP1 capsid protein positions 221SAAL → 221PADL). These exchanges were also detected in an additional 11 WPV1 strains from fatal cases. PV1-RC2010 escaped neutralization by three different mAbs relevant for AgS2. Virus neutralization was tested in sera from fatal cases, who died before supplementary immunization (n = 24), Gabonese recipients of recent oral polio vaccination (n = 12), routinely vaccinated German medical students (n = 34), and German outpatients tested for antipoliovirus immunity (n = 17) on Vero, human rhabdomyosarcoma, and human epidermoid carcinoma 2 cells. Fatal poliomyelitis cases gave laboratory evidence...
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Chikungunya virus (CHIKV) is an alphavirus of the Togaviridae family that causes chronic and incapacitating arthralgia in human populations. Since its discovery in 1952, CHIKV was responsible for sporadic and infrequent outbreaks.... more
Chikungunya virus (CHIKV) is an alphavirus of the Togaviridae family that causes chronic and incapacitating arthralgia in human populations. Since its discovery in 1952, CHIKV was responsible for sporadic and infrequent outbreaks. However, since 2005, global Chikungunya outbreaks have occurred, inducing some fatalities and associated with severe and chronic morbidity. Chikungunya is thus considered as an important re-emerging public health problem in both tropical and temperate countries, where the distribution of the Aedes mosquito vectors continues to expand. This review highlights the most recent advances in our knowledge and understanding of the epidemiology, biology, treatment and vaccination strategies of CHIKV.
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Bats are known to harbor multiple paramyxoviruses. Despite the creation of two new genera, Aquaparamyxovirus and Ferlavirus, to accommodate this increasing diversity, several recently isolated or characterized viruses remain unclassified... more
Bats are known to harbor multiple paramyxoviruses. Despite the creation of two new genera, Aquaparamyxovirus and Ferlavirus, to accommodate this increasing diversity, several recently isolated or characterized viruses remain unclassified beyond the subfamily level. In the present study, among 985 bats belonging to 6 species sampled in the Belinga caves of Gabon, RNA of an unclassified paramyxovirus (Belinga bat virus, BelPV) was discovered in 14 African sheath-tailed bats (Coleura afra), one of which exhibited several hemorrhagic lesions at necropsy, and viral sequence was obtained in two animals. Phylogenetically, BelPV is related to J virus and Beilong virus (BeiPV), two other unclassified paramyxoviruses isolated from rodents. In the diseased BelPV-infected C. afra individual, high viral load was detected in the heart, and the lesions were consistent with those reported in wild rodents and mice experimentally infected by J virus. BelPV was not detected in other tested bat species...
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ABSTRACT The vulcanization bonding process is used in a growing number of industrial applications where rubber-to-metal bonded assemblies are needed. The complexity of this process lies in the fact that the vulcanization of the rubber and... more
ABSTRACT The vulcanization bonding process is used in a growing number of industrial applications where rubber-to-metal bonded assemblies are needed. The complexity of this process lies in the fact that the vulcanization of the rubber and curing of an adhesive previously coated on the metallic surface have to take place simultaneously during a single molding step. In the present work, we present an instrumented molding device allowing the production of adhesion peeling test samples under well controlled curing temperature cycles. Tests performed on a model natural rubber compound with a commercial adhesive system show that, for high cure temperatures, the quality of the rubber-to-metal bonding obtained is significantly reduced. The decrease of the peeling energy appears to be inversely proportional to the reversion undergone by the rubber during cure. Such a result points out the necessity of taking into account this phenomenon for optimization of the vulcanization bonding process.
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The overall size and composition of the pool of naive and memory T cells are tightly regulated by homeostatic mechanisms. Recent work has shown that homeostasis of naive T cells is con- trolled by two factors, self-major... more
The overall size and composition of the pool of naive and memory T cells are tightly regulated by homeostatic mechanisms. Recent work has shown that homeostasis of naive T cells is con- trolled by two factors, self-major histocompatibility complex (MHC)/peptide ligands and a cy- tokine, interleukin (IL)-7. In particular, contact with these two factors is required for naive CD4 �
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Unbiased next-generation sequencing (NGS) approaches enable comprehensive pathogen detection in the clinical microbiology laboratory and have numerous applications for public health surveillance, outbreak investigation, and the diagnosis... more
Unbiased next-generation sequencing (NGS) approaches enable comprehensive pathogen detection in the clinical microbiology laboratory and have numerous applications for public health surveillance, outbreak investigation, and the diagnosis of infectious diseases. However, practical deployment of the technology is hindered by the bioinformatics challenge of analyzing results accurately and in a clinically relevant timeframe. Here we describe SURPI ("sequence-based ultrarapid pathogen identification"), a computational pipeline for pathogen identification from complex metagenomic NGS data generated from clinical samples, and demonstrate use of the pipeline in the analysis of 237 clinical samples comprising more than 1.1 billion sequences. Deployable on both cloud-based and standalone servers, SURPI leverages two state-of-the-art aligners for accelerated analyses, SNAP and RAPSearch, which are as accurate as existing bioinformatics tools but orders of magnitude faster in perform...
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Natural killer (NK) cells provide defense in the early stages of the immune response against viral infections. Killer cell immunoglobulin-like receptors (KIR) expressed on the surface of NK cells play an important role in regulating NK... more
Natural killer (NK) cells provide defense in the early stages of the immune response against viral infections. Killer cell immunoglobulin-like receptors (KIR) expressed on the surface of NK cells play an important role in regulating NK cell response through recognition of human leukocyte antigen (HLA) class I molecules on target cells. Previous studies have shown that specific KIR/ligand combinations are associated with the outcome of several viral infectious diseases. We investigated the impact of inhibitory and activating KIR and their HLA-class I ligand genotype on the susceptibility to Chikungunya virus (CHIKV) and Dengue virus (DENV2) infections. From April to July 2010 in Gabon, a large outbreak of CHIKV and DENV2 concomitantly occurred in two provinces of Gabon (Ogooué-Lolo and Haut-Ogooué). We performed the genotypic analysis of KIR in the combination with their cognate HLA-class I ligands in 73 CHIKV and 55 DENV2 adult cases, compared with 54 healthy individuals. We found i...
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Magnetotactic bacteria (MTB) are known to produce single-domain magnetite or greigite crystals within intracellular membrane organelles and to navigate along the Earth's magnetic field lines. MTB have been suggested as being one of... more
Magnetotactic bacteria (MTB) are known to produce single-domain magnetite or greigite crystals within intracellular membrane organelles and to navigate along the Earth's magnetic field lines. MTB have been suggested as being one of the most ancient biomineralizing metabolisms on the Earth and they represent a fundamental model of intracellular biomineralization. Moreover, the determination of their specific crystallographic signature (e.g. structure and morphology) is essential for palaeoenvironmental and ancient-life studies. Yet, the mechanisms of MTB biomineralization remain poorly understood, although this process has been extensively studied in several cultured MTB strains in the Proteobacteria phylum. Here, we show a comprehensive transmission electron microscopy (TEM) study of magnetic and structural properties down to atomic scales on bullet-shaped magnetites produced by the uncultured strain MYR-1 belonging to the Nitrospirae phylum, a deeply branching phylogenetic MTB ...
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BACKGROUND: Malaria may be perennial or epidemic in sub-Saharan Africa, and its transmission may be stable or unstable, depending on the region. The prevalence of asymptomatic Plasmodium falciparum carriage is poorly documented in Gabon.... more
BACKGROUND: Malaria may be perennial or epidemic in sub-Saharan Africa, and its transmission may be stable or unstable, depending on the region. The prevalence of asymptomatic Plasmodium falciparum carriage is poorly documented in Gabon. A large survey of P. falciparum infection was conducted in asymptomatic individuals living in rural Gabon. METHODS: Two hundred and twenty-two villages were randomly selected in
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The first recorded human outbreak of Ebola virus was in 1976, but the wild reservoir of this virus is still unknown. Here we test for Ebola in more than a thousand small vertebrates that were collected during Ebola outbreaks in humans and... more
The first recorded human outbreak of Ebola virus was in 1976, but the wild reservoir of this virus is still unknown. Here we test for Ebola in more than a thousand small vertebrates that were collected during Ebola outbreaks in humans and great apes between 2001 and 2003 in Gabon and the Republic of the Congo. We find evidence of
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The complex thermorheological behaviour observed in miscible polymer blends is modelled by combining two existing theoretical approaches: The Thermal Concentration Fluctuation model (A. Zetsche, E.W. Fischer, Acta Polymer.1994, 45, 168)... more
The complex thermorheological behaviour observed in miscible polymer blends is modelled by combining two existing theoretical approaches: The Thermal Concentration Fluctuation model (A. Zetsche, E.W. Fischer, Acta Polymer.1994, 45, 168) and the Effective Concentration model (T.P. Lodge, T.C.B. McLeish, Macromolecules2000, 33, 5278), giving rise to a simple model with only one adjustable parameter. This model is then tested in the case of two model blends allowing to show its abilities and limitations to describe how the respective segmental dynamics of lowest or highest Tg component are affected by blending.
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The tribe Myonycterini comprises five fruit bat species of the family Pteropodidae, which are endemic to tropical Africa. Previous studies have produced conflicting results about their interspecific relationships. Here, we performed a... more
The tribe Myonycterini comprises five fruit bat species of the family Pteropodidae, which are endemic to tropical Africa. Previous studies have produced conflicting results about their interspecific relationships. Here, we performed a comparative phylogeographic analysis based on 148 complete cytochrome b gene sequences from the three species distributed in West Africa and Central Africa (Myonycteris torquata, Lissonycteris angolensis and Megaloglossus woermanni). In addition, we investigated phylogenetic relationships within ...