Malarial pathocoenosis: beneficial and deleterious interactions between malaria and other human diseases

International audienceIn nature, organisms are commonly infected by an assemblage of different parasite species or by genetically distinct parasite strains that interact in complex ways. Linked to co-infections, pathocoenosis, a term proposed by M. Grmek in 1969, refers to a pathological state arising from the interactions of diseases within a population and to the temporal and spatial dynamics of all of the diseases. In the long run, malaria was certainly one of the most important component of past pathocoenoses. Today this disease, which affects hundreds of millions of individuals and results in approximately one million deaths each year, is always highly endemic in over 20% of the world and is thus co-endemic with many other diseases. Therefore, the incidences of co-infections and possible direct and indirect interactions with Plasmodium parasites are very high. Both positive and negative interactions between malaria and other diseases caused by parasites belonging to numerous taxa have been described and in some cases, malaria may modify the process of another disease without being affected itself. Interactions include those observed during voluntary malarial infections intended to cure neuro-syphilis or during the enhanced activations of bacterial gastro-intestinal diseases and HIV infections. Complex relationships with multiple effects should also be considered, such as those observed during helminth infections. Moreover, reports dating back over 2000 years suggested that co-and multiple infections have generally deleterious consequences and analyses of historical texts indicated that malaria might exacerbate both plague and cholera, among other diseases. Possible biases affecting the research of etiological agents caused by the protean manifestations of malaria are discussed. A better understanding of the manner by which pathogens, particularly Plasmodium, modulate immune responses is particularly important for the diagnosis, cure, and control of diseases in human populations

Could FIV zoonosis responsible of the breakdown of the pathocenosis which has reduced the European CCR5-Delta32 allele frequencies?

<p>Abstract</p> <p>Background</p> <p>In Europe, the north-south downhill cline frequency of the chemokine receptor CCR5 allele with a 32-bp deletion (<it>CCR5-Δ32</it>) raises interesting questions for evolutionary biologists. We had suggested first that, in the past, the European colonizers, principally Romans, might have been instrumental of a progressively decrease of the frequencies southwards. Indeed, statistical analyses suggested strong negative correlations between the allele frequency and historical parameters including the colonization dates by Mediterranean civilisations. The gene flows from colonizers to native populations were extremely low but colonizers are responsible of the spread of several diseases suggesting that the dissemination of parasites in naive populations could have induced a breakdown rupture of the fragile pathocenosis changing the balance among diseases. The new equilibrium state has been reached through a negative selection of the null allele.</p> <p>Results</p> <p>Most of the human diseases are zoonoses and cat might have been instrumental in the decrease of the allele frequency, because its diffusion through Europe was a gradual process, due principally to Romans; and that several cat zoonoses could be transmitted to man. The possible implication of a feline lentivirus (FIV) which does not use CCR5 as co-receptor is discussed. This virus can infect primate cells <it>in vitro </it>and induces clinical signs in macaque. Moreover, most of the historical regions with null or low frequency of <it>CCR5-Δ32 </it>allele coincide with historical range of the wild felid species which harbor species-specific FIVs.</p> <p>Conclusion</p> <p>We proposed the hypothesis that the actual European CCR5 allelic frequencies are the result of a negative selection due to a disease spreading. A cat zoonosis, could be the most plausible hypothesis. Future studies could provide if CCR5 can play an antimicrobial role in FIV pathogenesis. Moreover, studies of ancient DNA could provide more evidences regarding the implications of zoonoses in the actual <it>CCR5-Δ32 </it>distribution.</p

A new nonlocal thermodynamical equilibrium radiative transfer method for cool stars

Context: The solution of the nonlocal thermodynamical equilibrium (non-LTE) radiative transfer equation usually relies on stationary iterative methods, which may falsely converge in some cases. Furthermore, these methods are often unable to handle large-scale systems, such as molecular spectra emerging from, for example, cool stellar atmospheres. Aims: Our objective is to develop a new method, which aims to circumvent these problems, using nonstationary numerical techniques and taking advantage of parallel computers. Methods: The technique we develop may be seen as a generalization of the coupled escape probability method. It solves the statistical equilibrium equations in all layers of a discretized model simultaneously. The numerical scheme adopted is based on the generalized minimum residual method. Result:. The code has already been applied to the special case of the water spectrum in a red supergiant stellar atmosphere. This demonstrates the fast convergence of this method, and opens the way to a wide variety of astrophysical problems.Comment: 13 pages, 9 figure

The 15N-enrichment in dark clouds and Solar System objects

The line intensities of the fundamental rotational transitions of H13CN and HC15N were observed towards two prestellar cores, L183 and L1544, and lead to molecular isotopic ratios 140 6 14N/15N 6 250 and 140 6 14N/15N 6 360, respectively. The range of values reflect genuine spatial variations within the cores. A comprehensive analysis of the available measurements of the nitrogen isotopic ratio in prestellar cores show that molecules carrying the nitrile functional group appear to be systematically 15N-enriched com- pared to those carrying the amine functional group. A chemical origin for the differential 15N-enhance- ment between nitrile- and amine-bearing interstellar molecules is proposed. This sheds new light on several observations of Solar System objects: (i) the similar N isotopic fractionation in Jupiter's NH3 and solar wind N+; (ii) the 15N-enrichments in cometary HCN and CN (that might represent a direct inter- stellar inheritance); and (iii) 15N-enrichments observed in organics in primitive cosmomaterials. The large variations in the isotopic composition of N-bearing molecules in Solar System objects might then simply reflect the different interstellar N reservoirs from which they are originating

True Mitochondrial tRNA Punctuation and Initiation Using Overlapping Stop and Start Codons at Specific and Conserved Positions

In all the taxa and genomic systems, numerous trn genes (specifying tRNA) exhibit at specific conserved positions nucleotide triplets corresponding to stop codons (TAG/TAA). Similarly, relatively high frequencies of start codons (ATG/ATA) occur in fungi/metazoan mitochondrial-trn genes. The last nucleotide of these triplets is the first involved in the 5′-D- or 5′-T-stem, respectively. Their frequencies are tRNA species dependent. The products of these genes which bear one or two types of these codons are called ss-tRNAs (for stop/start). Metazoan mt-genomes are generally very compact, and many same strand overlapping sequences may simultaneously code for tRNAs and mRNAs. However, this study suggests that overlaps are not a direct mechanism to substantially reduce genome size. For protein-encoding genes, occulting possible overlaps, there are only alternative start codons and/or truncated stop codons, but the first putative in-frame standard initiation codon or complete stop codon is in the upstream or downstream overlapping ss-trn sequences, respectively. Even if, to date, experimental data are missing, stress signals might regulate producing extended or not proteins. Finally, possible implications of tRNA/mRNA hybrid molecules in the “RNA world” to “RNA/protein world” transition will be discussed

Monitoring of open areas in the Regional natural park of Luberon by using butterflies (Rhopalocera) like bioindicators

Dans le Parc naturel régional du Luberon la préservation de la biodiversité est notamment Liée au maintien des pelouses sèches situées sur les crêtes des massifs. L’intérêt scientifique de ces espaces ouverts réside dans l’originalité biologique de leur composition. L'évaluation écologique De ces habitats consiste à analyser la dynamique de la biodiversité à partir des réponses De la végétation et de certains éléments de la faune en fonction des principaux modes de gestion mis en oeuvre pour maintenir ces milieux ouverts dans le territoire de ce Parc. De nombreux Rhopalocères sont connus comme de bons bioindicateurs d’espaces ouverts. Dans ce travail préliminaire, un protocole de suivi et d’inventaire de ces derniers a été mis en place sur six espaces ouverts situés sur les crêtes du Luberon. Cette étude a permis de révéler une faible densité en espèce et individus. Diverses hypothèses permettant d’expliquer ces résultats sont développées.The biodiversity conservation in the Regional natural park of Luberon is related to the maintenance of the dry grasslands located on the massif tops. The scientific interest of these open areas lies in the biological originality of their composition. Ecological valuation of these habitats consists in analyzing the biodiversity dynamic starting from the answers of the vegetation and some elements of fauna according to the principal modes of management implemented to maintain these environments open in the territory of this Park. Many Rhopalocera being known like good bioindicators of open areas, in this preliminary work, a protocol of follow-up and inventory of the latter was set up on six open areas located on the Luberon tops. This study underlines a low density in species and individuals. Various hypotheses which could explain these results are developed