Les vanilles de la Guyane, entre or vert et or noir, un patrimoine révélé

Présentation botanique de la vanille, qui est une orchidée poussant dans les sous-bois tel une liane grimpante. On en recense 11 espèces sur le territoire Guyanais, ainsi en 1819, un capitaine de navire transporte des plants de vanille guyanais à la réunion. Associé à la découverte de la pollinisation artificielle à cause de l\u27inexistence de pollinisateur naturel réunionnais, la production de vanille s\u27accroit. Récemment, il y a une tentative de se réapproprier une ressource guyanaise, de la voloriser, de créer une microfilière et un label. En effet, les vanilles guyanaises ont une biodiversité génétique recherchée par les cultivateurs en raison de l\u27autofécondation

Efficient reamplification of differential display products by transient ligation and thermal asymmetric PCR

International audienceA new method for specific reamplification of DDRT-PCR products is presented. After transient ligation of the primary DDRT-PCR fragments into a T-vector, the cDNAs of interest were reamplified by hemi-nested PCR and thermally asymmetric cycles. In contrast to the originally described protocol, this method of reamplification is specific, sensitive, reproducibly gives a high yield of DNA and allows direct sequencing of the reamplified product without purification or cloning

Transcripts of the malaria vector Anopheles gambiae that are differentially regulated in the midgut upon exposure to invasive stages of Plasmodium falciparum

International audienceUnderstanding the interactions between the most deadly malaria parasite, Plasmodium falciparum, and its main vector, Anopheles gambiae, would be of great help in developing new malaria control strategies. The malaria parasite undergoes several developmental transitions in the mosquito midgut and suffers population losses to which mosquito factors presumably contribute. To identify such factors, we analysed An. gambiae midgut transcripts whose expression is regulated upon ingestion of invasive or non-invasive forms of P. falciparum using a differential display approach. Sixteen cDNA were studied in detail; 12 represent novel genes of An. gambiae including a gene encoding profilin. Four transcripts were specifically regulated by P. falciparum gametocytes (invasive forms), whereas the others were regulated by either non-invasive or both non-invasive and invasive forms of the parasite. This differential regulation of some genes may reflect the adaptation of P. falciparum to its natural vector. These genes may be involved in the development of P. falciparum in An. gambiae or in the defence reaction of the mosquito midgut towards the parasite

Transcripts of the malaria vector Anopheles gambiae that are differentially regulated in the midgut upon exposure to invasive stages of Plasmodium falciparum

International audienceUnderstanding the interactions between the most deadly malaria parasite, Plasmodium falciparum, and its main vector, Anopheles gambiae, would be of great help in developing new malaria control strategies. The malaria parasite undergoes several developmental transitions in the mosquito midgut and suffers population losses to which mosquito factors presumably contribute. To identify such factors, we analysed An. gambiae midgut transcripts whose expression is regulated upon ingestion of invasive or non-invasive forms of P. falciparum using a differential display approach. Sixteen cDNA were studied in detail; 12 represent novel genes of An. gambiae including a gene encoding profilin. Four transcripts were specifically regulated by P. falciparum gametocytes (invasive forms), whereas the others were regulated by either non-invasive or both non-invasive and invasive forms of the parasite. This differential regulation of some genes may reflect the adaptation of P. falciparum to its natural vector. These genes may be involved in the development of P. falciparum in An. gambiae or in the defence reaction of the mosquito midgut towards the parasite

Frequency and distribution of mixed Plasmodium falciparum-vivax infections in French Guiana between 2000 and 2008.

International audienceThe two main plasmodial species in French Guiana are Plasmodium vivax and Plasmodium falciparum whose respective prevalence influences the frequency of mixed plasmodial infections. The accuracy of their diagnosis is influenced by the sensitivity of the method used, whereas neither microscopy nor rapid diagnostic tests allow a satisfactory evaluation of mixed plasmodial infections. In the present study, the frequency of mixed infections in different part of French Guiana was determined using real time PCR, a sensitive and specific technique. From 400 cases of malaria initially diagnosed by microscopy, real time PCR showed that 10.75 % of the cases were mixed infections. Their prevalence varied considerably between geographical areas. The presence, in equivalent proportions, of the two plasmodial species in eastern French Guiana was associated with a much higher prevalence of mixed plasmodial infections than in western French Guiana, where the majority of the population was Duffy negative and thus resistant to vivax malaria. Clinicians must be more vigilant regarding mixed infections in co-endemic P. falciparum/P. vivax areas, in order to deliver optimal care for patients suffering from malaria. This may involve the use of rapid diagnostic tests capable of detecting mixed infections or low density single infections. This is important as French Guiana moves towards malaria elimination

Unraveling the genetic diversity and phylogeny of Leishmania RNA virus 1 strains of infected Leishmania isolates circulating in French Guiana

International audienceIntroductionLeishmania RNA virus type 1 (LRV1) is an endosymbiont of some Leishmania (Vianna) species in South America. Presence of LRV1 in parasites exacerbates disease severity in animal models and humans, related to a disproportioned innate immune response, and is correlated with drug treatment failures in humans. Although the virus was identified decades ago, its genomic diversity has been overlooked until now.Methodology/Principles findingsWe subjected LRV1 strains from 19 L. (V.) guyanensis and one L. (V.) braziliensis isolates obtained from cutaneous leishmaniasis samples identified throughout French Guiana with next-generation sequencing and de novo sequence assembly. We generated and analyzed 24 unique LRV1 sequences over their full-length coding regions. Multiple alignment of these new sequences revealed variability (0.5%±23.5%) across the entire sequence except for highly conserved motifs within the 5' untranslated region. Phylogenetic analyses showed that viral genomes of L. (V.) guyanensis grouped into five distinct clusters. They further showed a species-dependent clustering between viral genomes of L. (V.) guyanensis and L. (V.) braziliensis, confirming a long-term co-evolutionary history. Noteworthy, we identified cases of multiple LRV1 infections in three of the 20 Leishmania isolates.Conclusions/SignificanceHere, we present the first-ever estimate of LRV1 genomic diversity that exists in Leishmania (V.) guyanensis parasites. Genetic characterization and phylogenetic analyses of these viruses has shed light on their evolutionary relationships. To our knowledge, this study is also the first to report cases of multiple LRV1 infections in some parasites. Finally, this work has made it possible to develop molecular tools for adequate identification and genotyping of LRV1 strains for diagnostic purposes. Given the suspected worsening role of LRV1 infection in the pathogenesis of human leishmaniasis, these data have a major impact from a clinical viewpoint and for the management of Leishmania-infected patients

Increased Production of Interferon-gamma by Leishmania Homologue of the Mammalian Receptor for Activated C Kinase-Reactive CD4+ T cells among Human Blood Mononuclear Cells: An Early Marker of Exposure to Leishmania?

International audienceA prospective study was undertaken to define early predictive immunological marker(s) of exposure to Leishmania in naïve subjects who have never been exposed to any Leishmania and who were also free of any cutaneous leishmaniasis lesions. These naïve subjects could have been exposed to Leishmania in a rain forest where Leishmania guyanensis and their natural vectors and mammalian host are cocirculating. The production of interferon (IFN)‐γ in response to the Leishmania homologue of the mammalian receptor for activated c kinase (LACK), a candidate for vaccine against leishmaniasis was analysed. At the end of their stay in the rain forest, LACK‐specific CD8+ T cells were detected in subjects whose peripheral blood mononuclear cell (PBMC) produced IFN‐γ in response to soluble Leishmania antigens (SLA) and in those whose PBMC remained unresponsive to SLA. However, LACK‐specific CD4+ T cells were detected only in PBMCs from individuals who became IFN‐γ responders to SLA. In subjects whose PBMC became positive to SLA, LACK‐reactive CD4+ T cells producing high level of IFN‐γ were detectable before the SLA‐reactive IFN‐γ producing CD4+ T cells, suggesting that the former readout assay could be used as an early predictive immunological marker of exposure to Leishmania in subjects who remained disease free

Treating leishmaniasis in Amazonia, part 2: Multi-target evaluation of widely used plants to understand medicinal practices

International audienceEthnopharmacological relevanceLeishmaniasis are widely distributed among tropical and subtropical countries, and remains a crucial health issue in Amazonia. Indigenous groups across Amazonia have developed abundant knowledge about medicinal plants related to this pathology.Aim of the studyWe intent to explore the weight of different pharmacological activities driving taxa selection for medicinal use in Amazonian communities. Our hypothesis is that specific activity against Leishmania parasites is only one factor along other (anti-inflammatory, wound healing, immunomodulating, antimicrobial) activities.Materials and methodsThe twelve most widespread plant species used against leishmaniasis in Amazonia, according to their cultural and biogeographical importance determined through a wide bibliographical survey (475 use reports), were selected for this study. Plant extracts were prepared to mimic their traditional preparations. Antiparasitic activity was evaluated against promastigotes of reference and clinical New-World strains of Leishmania (L. guyanensis, L. braziliensis and L. amazonensis) and L. amazonensis intracellular amastigotes. We concurrently assessed the extracts immunomodulatory properties on PHA-stimulated human PBMCs and RAW264.7 cells, and on L. guyanensis antigens-stimulated PBMCs obtained from Leishmania-infected patients, as well as antifungal activity and wound healing properties (human keratinocyte migration assay) of the selected extracts. The cytotoxicity of the extracts against various cell lines (HFF1, THP-1, HepG2, PBMCs, RAW264.7 and HaCaT cells) was also considered. The biological activity pattern of the extracts was represented through PCA analysis, and a correlation matrix was calculated.ResultsSpondias mombin L. bark and Anacardium occidentale L. stem and leaves extracts displayed high anti-promatigotes activity, with IC50 ≤ 32 μg/mL against L. guyanensis promastigotes for S. mombin and IC50 of 67 and 47 μg/mL against L. braziliensis and L. guyanensis promastigotes, respectively, for A. occidentale. In addition to the antiparasitic effect, antifungal activity measured against C. albicans and T. rubrum (MIC in the 16–64 μg/mL range) was observed. However, in the case of Leishmania amastigotes, the most active species were Bixa orellana L. (seeds), Chelonantus alatus (Aubl.) Pulle (leaves), Jacaranda copaia (Aubl.) D. Don. (leaves) and Plantago major L. (leaves) with IC50 < 20 μg/mL and infection rates of 14–25% compared to the control. Concerning immunomodulatory activity, P. major and B. orellana were highlighted as the most potent species for the wider range of cytokines in all tested conditions despite overall contrasting results depending on the model. Most of the species led to moderate to low cytotoxic extracts except for C. alatus, which exhibited strong cytotoxic activity in almost all models. None of the tested extracts displayed wound healing properties.ConclusionsWe highlighted pharmacologically active extracts either on the parasite or on associated pathophysiological aspects, thus supporting the hypothesis that antiparasitic activities are not the only biological factor useful for antileishmanial evaluation. This result should however be supplemented by in vivo studies, and attracts once again the attention on the importance of the choice of biological models for an ethnophamacologically consistent study. Moreover, plant cultural importance, ecological status and availability were discussed in relation with biological results, thus contributing to link ethnobotany, medical anthropology and biology

Outbreak of Cutaneous Leishmaniasis among military personnel in French Guiana, 2020: Clinical, phylogenetic, individual and environmental aspects

International audienceBackground: Cutaneous Leishmaniasis (CL) is endemic in French Guiana but cases are usually sporadic. An outbreak signal was issued on May 15th 2020 with 15 suspected cases after a military training course in the rainforest. An outbreak investigation was carried out.Methodology/principal findings: Thirty cases were confirmed. Leishmania guyanensis was the most frequent species (90%). The most frequent presentation was ulcerative (90%). Lesions on the face and hands were frequent (40% each). Eight cases (26%) presented a poor outcome after treatment with pentamidine and required a second line with amphotericin B. Three of them required further treatments with meglumine antimoniate or miltefosine. Two spots within the training area were deemed as likely sites of contamination, due to illegal logging. The isolated Leishmania strains did not form a separate cluster. Participation in Week 13 of year 2020 was associated with infection (OR = 4.59 [1.10-19.83]; p = 0.016) while undergoing only the "Fighting" exercise was protective (OR = 0.1 [0-0.74]; p = 0.021). There was no association between infection and other risk factors at the individual level. The attack rate of Regiment B (14/105 = 13.3%) was significantly higher (OR = 4.22 [1.84-9.53], p = 0.0001) compared to Regiment A (16/507 = 3.2%). The attack rate during this training course (30/858 = 3.5%) was significantly higher (OR 2.29 [1.28-4.13]; p = 0.002) than for other missions in French Guiana during the same period (22/1427 = 1.5%).Conclusions: This outbreak could be explained by a combination of factors: climatic conditions around week 13, at-risk activities including night trainings, absence of impregnation, a lesser experience of rainforest duties in Regiment B and illegal logging attracting sandflies on military training grounds