Publications by authors named "Cheikh Tidiane Diagne"

23 Publications

  • Page 1 of 1

infection induces cross-reactive antibodies to carbohydrate epitopes on the SARS-CoV-2 Spike protein.

medRxiv 2021 May 12. Epub 2021 May 12.

Individuals with acute malaria infection generated high levels of antibodies that cross-react with the SARS-CoV-2 Spike protein. Cross-reactive antibodies specifically recognized the sialic acid moiety on N-linked glycans of the Spike protein and do not neutralize SARS-CoV-2. Sero-surveillance is critical for monitoring and projecting disease burden and risk during the pandemic; however, routine use of Spike protein-based assays may overestimate SARS-CoV-2 exposure and population-level immunity in malaria-endemic countries.
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http://dx.doi.org/10.1101/2021.05.10.21256855DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8132281PMC
May 2021

Insecticide resistance status and mechanisms in Aedes aegypti populations from Senegal.

PLoS Negl Trop Dis 2021 May 10;15(5):e0009393. Epub 2021 May 10.

Medical Zoology Pole, Institut Pasteur de Dakar, Dakar, Sénégal.

Aedes aegypti is the main epidemic vector of arboviruses in Africa. In Senegal, control activities are mainly limited to mitigation of epidemics, with limited information available for Ae. aegypti populations. A better understanding of the current Ae. aegypti susceptibility status to various insecticides and relevant resistance mechanisms involved is needed for the implementation of effective vector control strategies. The present study focuses on the detection of insecticide resistance and reveals the related mechanisms in Ae. aegypti populations from Senegal. Bioassays were performed on Ae. aegypti adults from nine Senegalese localities (Matam, Louga, Barkedji, Ziguinchor, Mbour, Fatick, Dakar, Kédougou and Touba). Mosquitoes were exposed to four classes of insecticides using the standard WHO protocols. Resistance mechanisms were investigated by genotyping for pyrethroid target site resistance mutations (V1016G, V1016I, F1534C and S989P) and measuring gene expression levels of key detoxification genes (CYP6BB2, CYP9J26, CYP9J28, CYP9J32, CYP9M6, CCEae3a and GSTD4). All collected populations were resistant to DDT and carbamates except for the ones in Matam (Northern region). Resistance to permethrin was uniformly detected in mosquitoes from all areas. Except for Barkédji and Touba, all populations were characterized by a susceptibility to 0.75% Permethrin. Susceptibility to type II pyrethroids was detected only in the Southern regions (Kédougou and Ziguinchor). All mosquito populations were susceptible to 5% Malathion, but only Kédougou and Matam mosquitoes were susceptible to 0.8% Malathion. All populations were resistant to 0.05% Pirimiphos-methyl, whereas those from Louga, Mbour and Barkédji, also exhibited resistance to 1% Fenitrothion. None of the known target site pyrethroid resistance mutations was present in the mosquito samples included in the genotyping analysis (performed in > 1500 samples). In contrast, a remarkably high (20-70-fold) overexpression of major detoxification genes was observed, suggesting that insecticide resistance is mostly mediated through metabolic mechanisms. These data provide important evidence to support dengue vector control in Senegal.
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http://dx.doi.org/10.1371/journal.pntd.0009393DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8136859PMC
May 2021

Mayaro Virus Infects Human Brain Cells and Induces a Potent Antiviral Response in Human Astrocytes.

Viruses 2021 03 11;13(3). Epub 2021 Mar 11.

MIVEGEC, Université de Montpellier, IRD, CNRS, 34394 Montpellier, France.

Mayaro virus (MAYV) and chikungunya virus (CHIKV) are known for their arthrotropism, but accumulating evidence shows that CHIKV infections are occasionally associated with serious neurological complications. However, little is known about the capacity of MAYV to invade the central nervous system (CNS). We show that human neural progenitors (hNPCs), pericytes and astrocytes are susceptible to MAYV infection, resulting in the production of infectious viral particles. In primary astrocytes, MAYV, and to a lesser extent CHIKV, elicited a strong antiviral response, as demonstrated by an increased expression of several interferon-stimulated genes, including , and . Infection with either virus led to an enhanced expression of inflammatory chemokines, such as CCL5, CXCL10 and CXCL11, whereas MAYV induced higher levels of IL-6, IL-12 and IL-15 in these cells. Moreover, MAYV was more susceptible than CHIKV to the antiviral effects of both type I and type II interferons. Taken together, this study shows that although MAYV and CHIKV are phylogenetically related, they induce different types of antiviral responses in astrocytes. This work is the first to evaluate the potential neurotropism of MAYV and shows that brain cells and particularly astrocytes and hNPCs are permissive to MAYV, which, consequently, could lead to MAYV-induced neuropathology.
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http://dx.doi.org/10.3390/v13030465DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8001792PMC
March 2021

Multiple insecticide resistance target sites in adult field strains of An. gambiae (s.l.) from southeastern Senegal.

Parasit Vectors 2020 Nov 11;13(1):567. Epub 2020 Nov 11.

Laboratoire d'Écologie Vectorielle et Parasitaire, Université Cheikh Anta Diop de Dakar, Dakar, Senegal.

Background: High coverage of long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) are the cornerstones of vector control strategy in Senegal where insecticide resistance by the target vectors species is a great of concern. This study explores insecticide susceptibility profile and target-site mutations mechanisms within the Anopheles gambiae complex in southeastern Senegal.

Methods: Larvae of Anopheles spp. were collected in two sites from southeastern Senegal Kedougou and Wassadou/Badi in October and November 2014, and reared until adult emergence. Wild F adult mosquitoes were morphologically identified to species. Susceptibility of 3-5-day-old An. gambiae (s.l.) samples to 11 insecticides belonging to the four insecticide classes was assessed using the WHO insecticide susceptibility bioassays. Tested samples were identified using molecular techniques and insecticide resistance target-site mutations (kdr, ace-1 and rdl) were determined.

Results: A total of 3742 An. gambiae (s.l.) were exposed to insecticides (2439 from Kedougou and 1303 from Wassadou-Badi). Tests with pyrethroid insecticides and DDT showed high level of resistance in both Kedougou and Wassadou/Badi. Resistance to pirimiphos-methyl and malathion was not detected while resistance to bendoicarb and fenitrothion was confirmed in Kedougou. Of the 745 specimens of An. gambiae (s.l.) genotyped, An. gambiae (s.s.) (71.6%) was the predominant species, followed by An. arabiensis (21.7%), An. coluzzii (6.3%) and hybrids (An. gambiae (s.s.)/An. coluzzii; 0.4%). All target site mutations investigated (Vgsc-1014F, Vgsc-1014S, Ace-1 and Rdl) were found at different frequencies in the species of the Anopheles gambiae complex. Vgsc-1014F mutation was more frequent in An. gambiae (s.s.) and An. coluzzii than An. arabiensis. Vgsc-1014S was present in An. gambiae (s.l.) populations in Wassadou but not in Kedougou. Ace-1 and rdl mutations were more frequent in An. gambiae (s.s.) in comparison to An. arabiensis and An. coluzzii.

Conclusions: Resistance to all the four insecticide classes tested was detected in southeastern Senegal as well as all target site mutations investigated were found. Data will be used by the national Malaria Control Programme.
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http://dx.doi.org/10.1186/s13071-020-04437-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7661151PMC
November 2020

Mayaro Virus Pathogenesis and Transmission Mechanisms.

Pathogens 2020 Sep 8;9(9). Epub 2020 Sep 8.

MIVEGEC, IRD, Univ. Montpellier, CNRS, 34394 Montpellier, France.

Mayaro virus (MAYV), isolated for the first time in Trinidad and Tobago, has captured the attention of public health authorities worldwide following recent outbreaks in the Americas. It has a propensity to be exported outside its original geographical range, because of the vast distribution of its vectors. Moreover, most of the world population is immunologically naïve with respect to infection with MAYV which makes this virus a true threat. The recent invasion of several countries by underscores the risk of potential urban transmission of MAYV in both tropical and temperate regions. In humans, the clinical manifestations of MAYV disease range from mild fever, rash, and joint pain to arthralgia. In the absence of a licensed vaccine and clinically proven therapeutics against Mayaro fever, prevention focuses mainly on household mosquito control. However, as demonstrated for other arboviruses, mosquito control is rather inefficient for outbreak management and alternative approaches to contain the spread of MAYV are therefore necessary. Despite its strong epidemic potential, little is currently known about MAYV. This review addresses various aspects of MAYV, including its epidemiology, vector biology, mode of transmission, and clinical complications, as well as the latest developments in MAYV diagnosis.
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http://dx.doi.org/10.3390/pathogens9090738DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7558846PMC
September 2020

DNA Origami for Silicon Patterning.

ACS Appl Mater Interfaces 2020 Aug 4;12(32):36799-36809. Epub 2020 Aug 4.

CEA, LETI, MINATEC Campus, F-38054 Grenoble, France.

Desoxyribonucleic acid (DNA) origami architectures are a promising tool for ultimate lithography because of their ability to generate nanostructures with a minimum feature size down to 2 nm. In this paper, we developed a method for silicon (Si) nanopatterning to face up current limitations for high-resolution patterning with standard microelectronic processes. For the first time, a 2 nm-thick 2D DNA origami mask, with specific design composed of three different square holes (with a size of 10 and 20 nm), is used for positive pattern transfer into a Si substrate using a 15 nm-thick silicon dioxide (SiO) layer as an intermediate hard mask. First, the origami mask is transferred onto the SiO underlayer, by an HF vapor-etching process. Then, the Si underlayer is etched using an HBr/O plasma. Each hole is transferred in the SiO layer and the 20 nm-sized holes are transferred into the final stack (Si). The resulting patterns exhibited a lateral resolution in the range of 20 nm and a depth of 40 nm. Patterns are fully characterized by atomic force microscopy, scanning electron microscopy, focused ion beam-transmission electron microscopy, and ellipsometry measurements.
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http://dx.doi.org/10.1021/acsami.0c10211DOI Listing
August 2020

Concurrent amplification of Zika, chikungunya, and yellow fever virus in a sylvatic focus of arboviruses in Southeastern Senegal, 2015.

BMC Microbiol 2020 06 26;20(1):181. Epub 2020 Jun 26.

Pôle de Zoologie Médicale, Institut Pasteur de Dakar, 36 Avenue Pasteur, BP 220, Dakar, Senegal.

Background: Chikungunya (CHIKV), yellow fever (YFV) and Zika (ZIKV) viruses circulate in sylvatic transmission cycles in southeastern Senegal, where they share common hosts and vectors. All three viruses undergo periodic amplifications, during which they are detected in mosquitoes and sometimes in hosts. However, little is known about their spatio-temporal patterns in years in which they undergo concurrent amplification. The aim of this study was to describe the co-amplification of ZIKV, CHIKV, and YFV, and the daily dynamics of these arboviruses and theirs vectors within villages in southeastern Senegal.

Results: Mosquitoes were collected monthly from July to December 2015. Each evening, from 6 to 9 PM, landing collections were performed by teams of 3 persons working simultaneously in 70 sites situated in forest (canopy and ground), savannah, agriculture, barren, and village (indoor and outdoor) land covers. Collections within villages were continued until 6 AM. Mosquitoes were tested for virus infection by virus isolation and RT-PCR. Seventy-five mosquito pools comprising 10 mosquito species contained at least one virus. Ae. furcifer and Ae. luteocephalus were infected by all three viruses, Ae. taylori by YFV and ZIKV, and remaining seven species by only, only YFV or only ZIKV. No single mosquito pool contained more than one virus. CHIKV was the only virus detected in all land cover classes and was found in the greatest number of sampling sites (32.9%, n = 70). The proportion of sites in which more than one virus was detected was less than 6%. Ae. aegypti formosus, Ae. furcifer, Ae. luteocephalus, Ae. minutus, Ae. vittatus, and An. gambiae were found within villages. These vectors were mainly active around dusk but Ae. furcifer was collected until dawn. All viruses save ZIKV were detected indoors and outdoors, mainly around dusk. Virus positive pools were detected over 2, 3 and 4 months for YFV, CHIKV and ZIKV, respectively.

Conclusion: Our data indicate that the distribution of different vector species and different arboviruses vary substantially between sites, suggesting that CHIKV, YFV, and ZIKV may have different transmission cycles in Southeastern Senegal.
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http://dx.doi.org/10.1186/s12866-020-01866-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7318437PMC
June 2020

Mobile Laboratory Reveals the Circulation of Dengue Virus Serotype I of Asian Origin in Medina Gounass (Guediawaye), Senegal.

Diagnostics (Basel) 2020 Jun 16;10(6). Epub 2020 Jun 16.

Arboviruses and Hemorrhagic Fever Viruses Unit, Virology Department, Institut Pasteur de Dakar, BP220 Dakar, Senegal.

With the growing success of controlling malaria in Sub-Saharan Africa, the incidence of fever due to malaria is in decline, whereas the proportion of patients with non-malaria febrile illness (NMFI) is increasing. Clinical diagnosis of NMFI is hampered by unspecific symptoms, but early diagnosis is a key factor for both better patient care and disease control. The aim of this study was to determine the arboviral aetiologies of NMFI in low resource settings, using a mobile laboratory based on recombinase polymerase amplification (RPA) assays. The panel of tests for this study was expanded to five arboviruses: dengue virus (DENV), zika virus (ZIKV), yellow fever virus (YFV), chikungunya virus (CHIKV), and rift valley fever virus (RVFV). One hundred and four children aged between one month and 115 months were enrolled and screened. Three of the 104 blood samples of children <10 years presented at an outpatient clinic tested positive for DENV. The results were confirmed by RT-PCR, partial sequencing, and non-structural protein 1 (NS1) antigen capture by ELISA (Biorad, France). Phylogenetic analysis of the derived DENV-1 sequences clustered them with sequences of DENV-1 isolated from Guangzhou, China, in 2014. In conclusion, this mobile setup proved reliable for the rapid identification of the causative agent of NMFI, with results consistent with those obtained in the reference laboratory's settings.
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http://dx.doi.org/10.3390/diagnostics10060408DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7345902PMC
June 2020

Zika virus in southeastern Senegal: survival of the vectors and the virus during the dry season.

BMC Infect Dis 2020 May 24;20(1):371. Epub 2020 May 24.

Pôle de Zoologie Médicale, Institut Pasteur de Dakar, 36 Avenue Pasteur, BP 220, Dakar, Senegal.

Background: Zika virus (ZIKV, genus Flavivirus, family Flaviviridae) is transmitted mainly by Aedes mosquitoes. This virus has become an emerging concern of global public health with recent epidemics associated to neurological complications in the pacific and America. ZIKV is the most frequently amplified arbovirus in southeastern Senegal. However, this virus and its adult vectors are undetectable during the dry season. The aim of this study was to investigate how ZIKV and its vectors are maintained locally during the dry season.

Methods: Soil, sand, and detritus contained in 1339 potential breeding sites (tree holes, rock holes, fruit husks, discarded containers, used tires) were collected in forest, savannah, barren and village land covers and flooded for eggs hatching. The emerging larvae were reared to adult, identified, and blood fed for F1 production. The F0 and F1 adults were identified and tested for ZIKV by Reverse Transcriptase-Real time Polymerase Chain Reaction.

Results: A total of 1016 specimens, including 13 Aedes species, emerged in samples collected in the land covers and breeding sites investigated. Ae. aegypti was the dominant species representing 56.6% of this fauna with a high plasticity. Ae. furcifer and Ae. luteocephalus were found in forest tree holes, Ae. taylori in forest and village tree holes, Ae. vittatus in rock holes. ZIKV was detected from 4 out of the 82 mosquito pools tested. Positive pools included Ae. bromeliae (2 pools), Ae. unilineatus (1 pool), and Ae. vittatus (1 pool), indicating that the virus is maintained in these Aedes eggs during the dry season.

Conclusion: Our investigation identified breeding sites types and land cover classes where several ZIKV vectors are maintained, and their maintenance rates during the dry season in southeastern Senegal. The maintenance of the virus in these vectors in nature could explain its early amplification at the start of the rainy season in this area.
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http://dx.doi.org/10.1186/s12879-020-05093-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7247193PMC
May 2020

Comparative Analysis of Zika Virus Detection by RT-qPCR, RT-LAMP, and RT-RPA.

Methods Mol Biol 2020 ;2142:165-179

Arbovirus and Viral Haemorrhagic Fever Unit, Institut Pasteur de Dakar, Dakar, Senegal.

Molecular detection of Zika virus (ZIKV) is a key element of outbreak management. Multiple PCR and isothermal ZIKV assays targeting different ZIKV sequences have been published. In this study, we compared a qRT-PCR, 2 RT-LAMP assays (based on different primer design approaches), and an RT-RPA for the detection of African and Asian/American lineages of ZIKV isolates from human, mosquito, and monkey. Results showed that RT-LAMP detected 100% of samples with a time threshold (Tt) of 18.01 ± 11.71 min while qRT-PCR detected 88.88% of samples with a Tt of 58.30 ± 16.58 min and RT-RPA 50% of samples with a Tt of 3.70 ± 0.44 min.
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http://dx.doi.org/10.1007/978-1-0716-0581-3_14DOI Listing
March 2021

Development and Validation of Real-Time RT-LAMP Assays for the Specific Detection of Zika Virus.

Methods Mol Biol 2020 ;2142:147-164

Institute of Aquaculture, University of Stirling, Scotland, UK.

Two one-step real-time reverse transcription loop-mediated isothermal amplification (RT-LAMP) assays for the detection of Zika virus (ZIKV) were developed, based on two different primer design approaches: (1) open source, based on a combination of sequence diversity clustering (phylogeny and principal component analysis) and LAVA algorithm, using 45 whole genome ZIKV sequences retrieved from the National Center for Biotechnology Information (NCBI) database; (2) standard software for LAMP primer design (Primer Explorer V4), using 59 sequences of the ZIKV 3' UTR. The assays were firstly evaluated with External Quality Assessment panels from INSTAND e.V. (Germany) and EVD-LabNet (The Netherlands) including 4 and 12 unknown samples, respectively, and secondly, with 9 human, mosquito, and monkey ZIKV isolates from Africa (Senegal, Ivory Coast, and Uganda) and America (Brazil). The limit of detection as determined by probit analysis was 181 molecules for both RT-LAMP assays, and 100% reproducibility in the assays was obtained for 10 molecules (4/8 repetitions were positive for 10 molecules). Both assays were specific, amplifying only ZIKV RNA and not cross-detecting other arboviruses included in this study.
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http://dx.doi.org/10.1007/978-1-0716-0581-3_13DOI Listing
March 2021

Possible influence of Plasmodium/Trypanosoma co-infections on the vectorial capacity of Anopheles mosquitoes.

BMC Res Notes 2020 Mar 4;13(1):127. Epub 2020 Mar 4.

Pôle de Zoologie Médicale, Institut Pasteur de Dakar, 36 Avenue Pasteur, BP 220, Dakar, Sénégal.

Objective: In tropical Africa, trypanosomiasis is present in endemic areas with many other diseases including malaria. Because malaria vectors become more anthropo-zoophilic under the current insecticide pressure, they may be exposed to trypanosome parasites. By collecting mosquitoes in six study sites with distinct malaria infection prevalence and blood sample from cattle, we tried to assess the influence of malaria-trypanosomiasis co-endemicity on the vectorial capacity of Anopheles.

Results: Overall, all animal infections were due to Trypanosoma vivax (infection rates from 2.6 to 10.5%) in villages where the lowest Plasmodium prevalence were observed at the beginning of the study. An. gambiae s.l. displayed trophic preferences for human-animal hosts. Over 84 mosquitoes, only one was infected by Plasmodium falciparum (infection rate: 4.5%) in a site that displayed the highest prevalence at the beginning of the study. Thus, Anopheles could be exposed to Trypanosoma when they feed on infected animals. No Plasmodium infection was observed in the Trypanosoma-infected animals sites. This can be due to an interaction between both parasites as observed in mice and highlights the need of further studies considering Trypanosoma/Plasmodium mixed infections to better characterize the role of these infections in the dynamic of malaria transmission and the mechanisms involved.
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http://dx.doi.org/10.1186/s13104-020-04977-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7057563PMC
March 2020

Differential Susceptibility and Innate Immune Response of and to the Haitian Strain of the Mayaro Virus.

Viruses 2019 10 9;11(10). Epub 2019 Oct 9.

MIVEGEC-IRD, Univ. Montpellier, CNRS, 34394 Montpellier, France.

Mayaro (MAYV) is an emerging arthropod-borne virus belonging to the Alphavirus genus of the family. Although forest-dwelling mosquitoes have been considered as its main vector, the virus has also been detected in circulating mosquitoes. Here we assess the susceptibility of and to infection with MAYV and their innate immune response at an early stage of infection. was more susceptible to infection with MAYV than Analysis of transcript levels of twenty immunity-related genes by real-time PCR in the midgut of both mosquitoes infected with MAYV revealed increased expression of several immune genes, including CLIP-domain serine proteases, the anti-microbial peptides defensin A, E, cecropin E, and the virus inducible gene. The regulation of certain genes appeared to be species-dependent. Infection of with MAYV resulted in increased levels of myeloid differentiation2-related lipid recognition protein () transcripts, as compared to . Increased expression levels of thio-ester-containing protein 22 () and Niemann-Pick type C1 () gene transcripts were observed in infected , but not . The differences in these gene expression levels during MAYV infection could explain the variation in susceptibility observed in both mosquito species.
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http://dx.doi.org/10.3390/v11100924DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6832402PMC
October 2019

Mayaro Virus Infects Human Chondrocytes and Induces the Expression of Arthritis-Related Genes Associated with Joint Degradation.

Viruses 2019 08 29;11(9). Epub 2019 Aug 29.

MIVEGEC, IRD, Univ. Montpellier, CNRS, 34394 Montpellier, France.

Mayaro virus (MAYV) is an emerging arthritogenic alphavirus belonging to the Togaviridae family. Infection leads to a dengue-like illness accompanied by severe polyarthralgia. However, the molecular and cellular mechanisms of arthritis as a result of MAYV infection remain poorly understood. In the present study, we assess the susceptibility of human chondrocytes (HC), fibroblast-like synoviocytes and osteoblasts that are the major cell types involved in osteoarthritis, to infection with MAYV. We show that these cells are highly permissive to MAYV infection and that viral RNA copy number and viral titers increase over time in infected cells. Knowing that HC are the primary cells in articular cartilage and are essential for maintaining the cartilaginous matrix, gene expression studies were conducted in MAYV-infected primary HC using polymerase chain reaction (PCR) arrays. The infection of the latter cells resulted in an induction in the expression of several matrix metalloproteinases (MMP) including MMP1, MMP7, MMP8, MMP10, MMP13, MMP14 and MMP15 which could be involved in the destruction of articular cartilage. Infected HC were also found to express significantly increased levels of various IFN-stimulated genes and arthritogenic mediators such as TNF-α and IL-6. In conclusion, MAYV-infected primary HC overexpress arthritis-related genes, which may contribute to joint degradation and pathogenesis.
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http://dx.doi.org/10.3390/v11090797DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6783875PMC
August 2019

Development, validation and clinical evaluation of a broad-range pan-filovirus RT-qPCR.

J Clin Virol 2019 05 19;114:26-31. Epub 2019 Mar 19.

Helsinki University and Helsinki University Hospital (HUSLAB), Department of Virology, Finland; University of Helsinki, Department of Virology, Helsinki, Finland; Faculty of Veterinary Medicine, Department of Veterinary Biosciences, University of Helsinki, Finland.

Background: During the five decades since their discovery, filoviruses of four species have caused human hemorrhagic fever outbreaks: Marburg (MARV) marburgvirus, and Zaire (EBOV), Sudan (SUDV) and Bundybugyo (BDBV) ebolaviruses. The largest, devastating EBOV epidemic in West Africa in 2014-16, has been followed by outbreaks of MARV in Uganda, 2017, and EBOV in Democratic Republic of Congo, 2018, emphasizing the need to develop preparedness to diagnose all filoviruses.

Objectives: The aim of this study was to optimize a new filovirus RT-qPCR to detect all filoviruses, define its limits of detection (LOD) and perform a field evaluation with outbreak samples.

Study Design: A pan-filovirus RT-qPCR targeting the L gene was developed and evaluated within the EbolaMoDRAD (Ebola virus: modern approaches for developing bedside rapid diagnostics) project. Specificity and sensitivity were determined and the effect of inactivation and PCR reagents (liquid and lyophilized format) were tested.

Results: The LODs for the lyophilized pan-filovirus L-RT-qPCR assay were 9.4 copies per PCR reaction for EBOV, 9.9 for MARV, 1151 for SUDV, 65 for BDBV and 289 for Taï Forest virus. The test was set at the Pasteur Institute, Dakar, Senegal, and 83 Ebola patient samples, with viral load ranging from 5 to 5 million copies of EBOV per reaction, were screened. The results for the patient samples were in 100% concordance with the reference EBOV-specific assay.

Discussion: Overall, the assay showed good sensitivity and specificity, covered all filoviruses known to be human pathogens, performed well both in lyophilized and liquid-phase formats and with EBOV outbreak clinical samples.
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http://dx.doi.org/10.1016/j.jcv.2019.03.010DOI Listing
May 2019

Dengue epidemic in Touba, Senegal: implications for the Grand Magal Pilgrimage for travellers.

J Travel Med 2019 Oct;26(7)

Institut Pasteur de Dakar, Pôle de Virologie, 36 avenue Pasteur BP 220 Dakar, Senegal.

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http://dx.doi.org/10.1093/jtm/tay123DOI Listing
October 2019

Metallic Conductive Nanowires Elaborated by PVD Metal Deposition on Suspended DNA Bundles.

Small 2017 09 5;13(33). Epub 2017 Jul 5.

Université Grenoble Alpes, F-38000, Grenoble, France.

Metallic conductive nanowires (NWs) with DNA bundle core are achieved, thanks to an original process relying on double-stranded DNA alignment and physical vapor deposition (PVD) metallization steps involving a silicon substrate. First, bundles of DNA are suspended with a repeatable process between 2 µm high parallel electrodes with separating gaps ranging from 800 nm to 2 µm. The process consists in the drop deposition of a DNA lambda-phage solution on the electrodes followed by a naturally evaporation step. The deposition process is controlled by the DNA concentration within the buffer solution, the drop volume, and the electrode hydrophobicity. The suspended bundles are finally metallized with various thicknesses of titanium and gold by a PVD e-beam evaporation process. The achieved NWs have a width ranging from a few nanometers up to 100 nm. The electrical behavior of the achieved 60 and 80 nm width metallic NWs is shown to be Ohmic and their intrinsic resistance is estimated according to different geometrical models of the NW section area. For the 80 nm width NWs, a resistance of about few ohms is established, opening exploration fields for applications in microelectronics.
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http://dx.doi.org/10.1002/smll.201700956DOI Listing
September 2017

Perspectives and Challenges in Entomological Risk Assessment and Vector Control of Chikungunya.

J Infect Dis 2016 Dec;214(suppl 5):S459-S465

Control of Epidemic Diseases, Pandemic and Epidemic Diseases, World Health Organization, Geneva, Switzerland.

Chikungunya virus (CHIKV) is primarily spread by the Aedes aegypti and Aedes albopictus mosquito vectors. Because there is no licensed vaccine for CHIKV, identifying ways to reduce or eliminate mosquito populations is the most effective strategy to immediately halt transmission to man. Strategies to assess the entomological risk and to control the vector are absolutely crucial to demolishing the rise of CHIKV. This review provides perspectives in entomological risk assessment and vector control, challenges for both, and gaps in knowledge that need to be addressed through rigorous research and multidisciplinary collaborations.
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http://dx.doi.org/10.1093/infdis/jiw397DOI Listing
December 2016

DNA Origami Mask for Sub-Ten-Nanometer Lithography.

ACS Nano 2016 07 10;10(7):6458-63. Epub 2016 Jun 10.

University Grenoble Alpes , F-38000 Grenoble, France.

DNA nanotechnology is currently widely explored and especially shows promises for advanced lithography due to its ability to define nanometer scale features. We demonstrate a 9 × 14 nm(2) hole pattern transfer from DNA origami into an SiO2 layer with a sub-10-nm resolution using anhydrous HF vapor in a semiconductor etching machine. We show that the resulting SiO2 pattern inherits its shape from the DNA structure within a process time ranging from 30 to 60 s at an etching rate of 0.2 nm/s. At 600 s of etching, the SiO2 pattern meets corrosion and the overall etching reaction is blocked. These results, in addition to the entire surface coverage by magnesium occurring on the substrate at a density of 1.1 × 10(15) atom/cm(2), define a process window, fabrication rules, and limits for DNA-based lithography.
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http://dx.doi.org/10.1021/acsnano.6b00413DOI Listing
July 2016

Vector competence of Aedes vexans (Meigen), Culex poicilipes (Theobald) and Cx. quinquefasciatus Say from Senegal for West and East African lineages of Rift Valley fever virus.

Parasit Vectors 2016 Feb 20;9:94. Epub 2016 Feb 20.

Unité d'Entomologie Médicale, Institut Pasteur de Dakar, 36 Avenue Pasteur, BP 220, Dakar, Senegal.

Background: Rift Valley fever virus (RVFV; Phlebovirus, Bunyaviridae) is a mosquito-borne, zoonotic pathogen. In Senegal, RVFV was first isolated in 1974 from Aedes dalzieli (Theobald) and thereafter from Ae. fowleri (de Charmoy), Ae. ochraceus Theobald, Ae. vexans (Meigen), Culex poicilipes (Theobald), Mansonia africana (Theobald) and Ma. uniformis (Theobald). However, the vector competence of these local species has never been demonstrated making hypothetical the transmission cycle proposed for West Africa based on serological data and mosquito isolates.

Methods: Aedes vexans and Cx. poicilipes, two common mosquito species most frequently associated with RVFV in Senegal, and Cx. quinquefasciatus, the most common domestic species, were assessed after oral feeding with three RVFV strains of the West and East/central African lineages. Fully engorged mosquitoes (420 Ae. vexans, 563 Cx. quinquefasciatus and 380 Cx. poicilipes) were maintained at 27 ± 1 °C and 70-80% relative humidity. The saliva, legs/wings and bodies were tested individually for the RVFV genome using real-time RT-PCR at 5, 10, 15 and 20 days post exposure (dpe) to estimate the infection, dissemination, and transmission rates. Genotypic characterisation of the 3 strains used were performed to identify factors underlying the different patterns of transmission.

Results: The infection rates varied between 30.0-85.0% for Ae. vexans, 3.3-27% for Cx. quinquefasciatus and 8.3-46.7% for Cx. poicilipes, and the dissemination rates varied between 10.5-37% for Ae. vexans, 9.5-28.6% for Cx. quinquefasciatus and 3.0-40.9% for Cx. poicilipes. However only the East African lineage was transmitted, with transmission rates varying between 13.3-33.3% in Ae. vexans, 50% in Cx. quinquefasciatus and 11.1% in Cx. poicilipes. Culex mosquitoes were less susceptible to infection than Ae. vexans. Compared to other strains, amino acid variation in the NSs M segment proteins of the East African RVFV lineage human-derived strain SH172805, might explain the differences in transmission potential.

Conclusion: Our findings revealed that all the species tested were competent for RVFV with a significant more important role of Ae. vexans compared to Culex species and a highest potential of the East African lineage to be transmitted.
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http://dx.doi.org/10.1186/s13071-016-1383-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4761212PMC
February 2016

Potential of selected Senegalese Aedes spp. mosquitoes (Diptera: Culicidae) to transmit Zika virus.

BMC Infect Dis 2015 Nov 2;15:492. Epub 2015 Nov 2.

Unité d'Entomologie Médicale, Institut Pasteur de Dakar, 36 Avenue Pasteur, BP 220,, Dakar, Senegal.

Background: Zika virus (ZIKV; genus Flavivirus, family Flaviviridae) is an emerging virus of medical importance maintained in a zoonotic cycle between arboreal Aedes spp. mosquitoes and nonhuman primates in African and Asian forests. Serological evidence and virus isolations have demonstrated widespread distribution of the virus in Senegal. Several mosquito species have been found naturally infected by ZIKV but little is known about their vector competence.

Methods: We assessed the vector competence of Ae. aegypti from Kedougou and Dakar, Ae. unilineatus, Ae. vittatus and Ae. luteocephalus from Kedougou in Senegal for 6 ZIKV strains using experimental oral infection. Fully engorged female mosquitoes were maintained in an environmental chamber set at 27 ± 1 °C and 80 ± 5% Relative humidity. At day 5, 10 and 15 days post infection (dpi), individual mosquito saliva, legs/wings and bodies were tested for the presence of ZIKV genome using real time RT-PCR to estimate the infection, dissemination, and transmission rates.

Results: All the species tested were infected by all viral strains but only Ae. vittatus and Ae. luteocephalus were potentially capable of transmitting ZIKV after 15 dpi with 20 and 50% of mosquitoes, respectively, delivering epidemic (HD 78788) and prototype (MR 766) ZIKV strains in saliva.

Conclusion: All the species tested here were susceptible to oral infection of ZIKV but only a low proportion of Ae. vittatus and Ae. luteocephalus had the viral genome in their saliva and thus the potential to transmit the virus. Further investigations are needed on the vector competence of other species associated with ZIKV for better understanding of the ecology and epidemiology of this virus in Senegal.
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http://dx.doi.org/10.1186/s12879-015-1231-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4629289PMC
November 2015

TPM analyses reveal that FtsK contributes both to the assembly and the activation of the XerCD-dif recombination synapse.

Nucleic Acids Res 2014 Feb 8;42(3):1721-32. Epub 2013 Nov 8.

CNRS; IPBS (Institut de Pharmacologie et de Biologie Structurale); 205 route de Narbonne BP 64182, F-31077 Toulouse, France, Université de Toulouse; UPS; IPBS; F-31077 Toulouse, France, Université de Toulouse; UPS; LMGM (Laboratoire de Microbiologie et Génétique Moléculaires); F-31062 Toulouse, France and CNRS; LMGM; F-31062 Toulouse, France.

Circular chromosomes can form dimers during replication and failure to resolve those into monomers prevents chromosome segregation, which leads to cell death. Dimer resolution is catalysed by a highly conserved site-specific recombination system, called XerCD-dif in Escherichia coli. Recombination is activated by the DNA translocase FtsK, which is associated with the division septum, and is thought to contribute to the assembly of the XerCD-dif synapse. In our study, direct observation of the assembly of the XerCD-dif synapse, which had previously eluded other methods, was made possible by the use of Tethered Particle Motion, a single molecule approach. We show that XerC, XerD and two dif sites suffice for the assembly of XerCD-dif synapses in absence of FtsK, but lead to inactive XerCD-dif synapses. We also show that the presence of the γ domain of FtsK increases the rate of synapse formation and convert them into active synapses where recombination occurs. Our results represent the first direct observation of the formation of the XerCD-dif recombination synapse and its activation by FtsK.
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http://dx.doi.org/10.1093/nar/gkt1024DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3919580PMC
February 2014

Insecticide susceptibility of Aedes aegypti populations from Senegal and Cape Verde Archipelago.

Parasit Vectors 2012 Oct 22;5:238. Epub 2012 Oct 22.

Unité d'entomologie médicale, Institut Pasteur de Dakar, 36 Avenue Pasteur, Dakar BP 220, Sénégal.

Background: Two concomitant dengue 3 (DEN-3) epidemics occurred in Cape Verde Archipelago and Senegal between September and October 2009. Aedes aegypti was identified as the vector of these epidemics as several DEN-3 virus strains were isolated from this species in both countries. The susceptibility to pyrethroids, organochlorine, organophosphates and carbamate was investigated in two field strains of Aedes aegypti from both countries using WHO diagnostic bioassay kits in order to monitor their the current status of insecticide susceptibility.

Findings: The two tested strains were highly resistant to DDT. The Cape Verde strain was found to be susceptible to all others tested insecticides except for propoxur 0.1%, which needs further investigation. The Dakar strain was susceptible to fenitrothion 1% and permethrin 0.75%, but displayed reduced susceptibility to deltamethrin, lambda-cyhalothrin and propoxur.

Conclusions: As base-line results, our observations stress a careful management of insecticide use for the control of Ae. aegypti. Indeed, they indicate that DDT is no longer efficient for the control of Ae. aegypti populations in Cape Verde and Dakar and further suggest a thorough follow-up of propoxur susceptibility status in both sites and that of deltamethrin and lambda-cyhalothrin in Ae. aegypti populations in Dakar. Thus, regular monitoring of susceptibility is greatly needed as well as the knowing if this observed resistance/susceptibility is focal or not and for observed resistance, the use of biochemical methods is needed with detailed comparison of resistance levels over a large geographic area.

Keywords: Aedes aegypti, Insecticides, Susceptibility, Cape Verde, Senegal.
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http://dx.doi.org/10.1186/1756-3305-5-238DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3485106PMC
October 2012