Malnutrition et politiques agro-alimentaires en Bolivie

Sutout connue en Europe pour son instabilité politique, ses coups d'Etat incessants et, aujourd'hui, pour sa culture de la coca, la Bolivie est aussi, on le sait moins, le pays le plus pauvre d'Amérique du Sud comme en témoignent tous les indicateurs socio-économiques disponibles. Mais la malnutrition qui sévit dans ce pays et qui semble bien en voie d'aggravation, n'est nullement le produit d'une nature particulièrement ingrate, car Altiplano, Vallées et Oriente pourraient heureusement combiner leurs ressources agricoles pour satisfaire la demande alimentaire nationale. Elle est bien davantage le résultat de politiques agricoles, passées et présentes, conduites en fonction d'intérêts qui furent rarement ceux de l'ensemble de la population. (Résumé d'auteur

Protein crystals in adenovirus type 5-infected cells: requirements for intranuclear crystallogenesis, structural and functional analysis

Intranuclear crystalline inclusions have been observed in the nucleus of epithelial cells infected with Adenovirus serotype 5 (Ad5) at late steps of the virus life cycle. Using immuno-electron microscopy and confocal microscopy of cells infected with various Ad5 recombinants modified in their penton base or fiber domains, we found that these inclusions represented crystals of penton capsomers, the heteromeric capsid protein formed of penton base and fiber subunits. The occurrence of protein crystals within the nucleus of infected cells required the integrity of the fiber knob and part of the shaft domain. In the knob domain, the region overlapping residues 489–492 in the FG loop was found to be essential for crystal formation. In the shaft, a large deletion of repeats 4 to 16 had no detrimental effect on crystal inclusions, whereas deletion of repeats 8 to 21 abolished crystal formation without altering the level of fiber protein expression. This suggested a crucial role of the five penultimate repeats in the crystallisation process. Chimeric pentons made of Ad5 penton base and fiber domains from different serotypes were analyzed with respect to crystal formation. No crystal was found when fiber consisted of shaft (S) from Ad5 and knob (K) from Ad3 (heterotypic S5-K3 fiber), but occurred with homotypic S3K3 fiber. However, less regular crystals were observed with homotypic S35-K35 fiber. TB5, a monoclonal antibody directed against the Ad5 fiber knob was found by immunofluorescence microscopy to react with high efficiency with the intranuclear protein crystals in situ. Data obtained with Ad fiber mutants indicated that the absence of crystalline inclusions correlated with a lower infectivity and/or lower yields of virus progeny, suggesting that the protein crystals might be involved in virion assembly. Thus, we propose that TB5 staining of Ad-infected 293 cells can be used as a prognostic assay for the viability and productivity of fiber-modified Ad5 vectors

Mécanismes moléculaires de l assemblage intracellulaire des virions d Adénovirus humain (applications thérapeutiques)

Dans le cadre des applications médicales en Biothérapie des Adénovirus (Ad), nous avons analysé le pouvoir infectieux et la viabilité de vecteurs dérivés de l Ad 5 modifiés dans leurs capsomères d apex afin de changer leur tropisme et leur antigénicité et échapper ainsi à la surveillance immunitaire de l hôte receveur. Tout d abord, nous avons caractérisé les voies d entrée cellulaire de vecteurs portant, sur leurs fibres, des ligands cellulaires d attachement ou d endocytose. Nous avons étudié les réactions immunes observées chez des patients porteurs d hépatocarcinome recevant un vecteur Ad oncolytique. Nous avons également caractérisé certains des mécanismes de cytotoxicité induite par l Ad dans le poumon néonatal en développement et identifié un vecteur non cytotoxique susceptible de servir de plateforme à des constructions futures. Enfin, nous avons plus particulièrement analysé la viabilité de vecteurs modifiés dans leurs protéines de capside et identifié les domaines critiques pour la morphogénèse adénovirale. Nous avons ainsi montré (1) que la protéine virale 100K joue le rôle de chaperon indispensable au repliement de l hexon trimérique et à son import nucléaire, (2) que le domaine globulaire C-terminal de la fibre (ou knob ) joue un rôle crucial dans l encapsidation de la fibre et la formation de virions infectieux. Les resultats de nos analyses in situ dans les cellules infectées par l Ad5, suggèrent une corrélation entre l efficacité d assemblage des virus (ou vecteurs) infectieux et la présence de cristaux intranucléaires de capsomères penton (base + fibre) qui constitueraient une plate-forme d assemblage des virions d Ad5For making Adenovirus (Ad) vectors suitable for gene therapy, genetic modifications of the apical capsomers, fibre and penton base, have been designed to redirect the vectors to desired cell targets, and to evade the immune surveillance of the host. We have first characterized the cell entry pathway of vectors carrying novel attachment or endocytic ligands. We have studied the anti-Ad immune reactions induced in patients with hepatocarcinoma receiving oncolytic Ad vector. We have also characterized some of the mechanisms of Ad-induced cytotoxicity in developmental lung in neonates, and identified a non-toxic Ad5 vector which is a potential leader for future constructs. In the last phase of our project, we have analysed the viability of vectors genetically modified in their capsid proteins, and identified the critical domains for Ad morphogenesis. We have shown that the adenoviral 100K protein acts as a chaperon for proper folding of hexon trimer and its nuclear import. We also showed that the C-terminal globular domain of the fibre, called the knob , plays a crucial role in fibre encapsidation and assembly of mature, infectious virions. The results of our in situ analysis of Ad5-infected cells indicate that the intranuclear crystalline inclusions observed at late steps of the virus life cycle consist of crystals of penton capsomers. Data obtained with fibre-modified Ad vectors suggest that the absence of crystalline inclusions correlate with a lower fibre content and a lower infectivity of the virus progeny. Thus, we hypothesize that nuclear protein inclusions represent a privileged assembly platform for Ad5 virionsLYON1-BU.Sciences (692662101) / SudocSudocFranceF

Effect of environmental ARG expression under selective pressure on ARG transfer to bacteria

International audienceThe continuous increase of antibiotic-resistant bacteria (ARBs) in medical clinics is a major global health concern. Although the use of antibiotics for human and animal treatment seems to be related to the spread of ARBs, antibiotic resistance dispersion is a natural environmental process. Furthermore, several studies have documented the influence of anthropogenic activity on the environmental “resistome”. Novel antibiotic resistance genes (ARGs) may emerge in the non-clinical environment and spread to the human microbiome, from where the probability of their transfer to human pathogens increases. Thus, we are interested in the environmental factors that influence the rate and probability of ARGs transfer from non-human microbiome bacteria to human microbiome bacteria in non-clinical environments. Here we report on the influence of in situ transcription rates on the transfer of genes in soil. In order to determine whether the transcription of ARGs under different selective pressures increases their transfer rate to human microbiome bacteria, natural soils and soils incubated with antibiotics were inoculated with a labelled strain of E. coli. At different time points, these E. coli were isolated from soil microcosms by flow cytometry and a combination of metatranscriptomics and qPCR was used to evaluate the transfer of environmental ARG to E. coli as a function of their transcription rate in the donor bacteria. This approach provided a model for the study of environmental ARG transfer to human microbiome bacteria directly in soil and highlights the importance of gene expression monitoring in risk assessment studies

A new platform for culture and electroporation of 3d cell constructs based on a porous scaffold

International audienc

Environmental resistome transcriptional response to gentamicin pollution at sub-inhibitory concentrations

National audienc

Linking environmental prokaryotic viruses and their host through CRISPRs

International audienceThe ecological pressure that viruses place on microbial communities is not only based on predation, but also on gene transfer. In order to determine the potential impact of viruses and transduction, we need a better understanding of the dynamics of interactions between viruses and their hosts in the environment. Data on environmental viruses are scarce, and methods for tracking their interactions with prokaryotes are needed. Clustered regularly interspaced short palindromic repeats (CRISPRs), which contain viral sequences in bacterial genomes, might help document the history of virus-host interactions in the environment. In this study, a bioinformatics network linking viruses and their hosts using CRISPR sequences obtained from metagenomic data was developed and applied to metagenomes from Arctic glacial ice and soil. The application of our network approach showed that putative interactions were more commonly detected in the ice samples than the soil which would be consistent with the ice viral-bacterial interactions being more dynamic than those in soil. Further analysis of the viral sequences in the CRISPRs indicated that Ralstonia phages might be agents of transduction in the Arctic glacial ice

Microbial soil community analyses for forensic science: Application to a blind test

International audienceSoil complexity, heterogeneity and transferability make it valuable in forensic investigations to help obtain clues as to the origin of an unknown sample, or to compare samples from a suspect or object with samples collected at a crime scene. In a few countries, soil analysis is used in matters from site verification to estimates of time after death. However, up to date the application or use of soil information in criminal investigations has been limited. In particular, comparing bacterial communities in soil samples could be a useful tool for forensic science. To evaluate the relevance of this approach, a blind test was performed to determine the origin of two questioned samples (one from the mock crime scene and the other from a 50:50 mixture of the crime scene and the alibi site) compared to three control samples (soil samples from the crime scene, from a context site 25 m away from the crime scene and from the alibi site which was the suspect’s home). Two biological methods were used, Ribosomal Intergenic Spacer Analysis (RISA), and 16S rRNA gene sequencing with Illumina Miseq, to evaluate the discriminating power of soil bacterial communities. Both techniques discriminated well between soils from a single source, but a combination of both techniques was necessary to show that the origin was a mixture of soils. This study illustrates the potential of applying microbial ecology methodologies in soil as an evaluative forensic tool