Proteomics of Anopheles gambiae

pas de résum

Reappraisal of Vipera aspis Venom Neurotoxicity

BACKGROUND: The variation of venom composition with geography is an important aspect of intraspecific variability in the Vipera genus, although causes of this variability remain unclear. The diversity of snake venom is important both for our understanding of venomous snake evolution and for the preparation of relevant antivenoms to treat envenomations. A geographic intraspecific variation in snake venom composition was recently reported for Vipera aspis aspis venom in France. Since 1992, cases of human envenomation after Vipera aspis aspis bites in south-east France involving unexpected neurological signs were regularly reported. The presence of genes encoding PLA(2) neurotoxins in the Vaa snake genome led us to investigate any neurological symptom associated with snake bites in other regions of France and in neighboring countries. In parallel, we used several approaches to characterize the venom PLA(2) composition of the snakes captured in the same areas. [br/] METHODOLOGY/PRINCIPAL FINDINGS: We conducted an epidemiological survey of snake bites in various regions of France. In parallel, we carried out the analysis of the genes and the transcripts encoding venom PLA(2)s. We used SELDI technology to study the diversity of PLA(2) in various venom samples. Neurological signs (mainly cranial nerve disturbances) were reported after snake bites in three regions of France: Languedoc-Roussillon, Midi-Pyrénées and Provence-Alpes-Côte d'Azur. Genomes of Vipera aspis snakes from south-east France were shown to contain ammodytoxin isoforms never described in the genome of Vipera aspis from other French regions. Surprisingly, transcripts encoding venom neurotoxic PLA(2)s were found in snakes of Massif Central region. Accordingly, SELDI analysis of PLA(2) venom composition confirmed the existence of population of neurotoxic Vipera aspis snakes in the west part of the Massif Central mountains. [br/] CONCLUSIONS/SIGNIFICANCE: The association of epidemiological studies to genetic, biochemical and immunochemical analyses of snake venoms allowed a good evaluation of the potential neurotoxicity of snake bites. A correlation was found between the expression of neurological symptoms in humans and the intensity of the cross-reaction of venoms with anti-ammodytoxin antibodies, which is correlated with the level of neurotoxin (vaspin and/or ammodytoxin) expression in the venom. The origin of the two recently identified neurotoxic snake populations is discussed according to venom PLA(2) genome and transcriptome data

Differential Expression of Salivary Proteins between Susceptible and Insecticide-Resistant Mosquitoes of Culex quinquefasciatus

Background: The Culex quinquefasciatus mosquito, a major pest and vector of filariasis and arboviruses in the tropics, has developed multiple resistance mechanisms to the main insecticide classes currently available in public health. Among them, the insensitive acetylcholinesterase (ace-1(R) allele) is widespread worldwide and confers cross-resistance to organophosphates and carbamates. Fortunately, in an insecticide-free environment, this mutation is associated with a severe genetic cost that can affect various life history traits. Salivary proteins are directly involved in human-vector contact during biting and therefore play a key role in pathogen transmission. Methods and Results: An original proteomic approach combining 2D-electrophoresis and mass spectrometry was adopted to compare the salivary expression profiles of two strains of C. quinquefasciatus with the same genetic background but carrying either the ace-1(R) resistance allele or not (wild type). Four salivary proteins were differentially expressed (> 2 fold, P < 0.05) in susceptible (SLAB) and resistant (SR) mosquito strains. Protein identification indicated that the D7 long form, a major salivary protein involved in blood feeding success, presented lower expression in the resistant strain than the susceptible strain. In contrast, three other proteins, including metabolic enzymes (endoplasmin, triosephosphate isomerase) were significantly over-expressed in the salivary gland of ace-1(R) resistant mosquitoes. A catalogue of 67 salivary proteins of C. quinquefasciatus sialotranscriptome was also identified and described. Conclusion: The "resistance"-dependent expression of salivary proteins in mosquitoes may have considerable impact on biting behaviour and hence on the capacity to transmit parasites/viruses to humans. The behaviour of susceptible and insecticide-resistant mosquitoes in the presence of vertebrate hosts and its impact on pathogen transmission urgently requires further investigation

Transcriptomic and functional analysis of the Anopheles gambiae salivary gland in relation to blood feeding

<p>Abstract</p> <p>Background</p> <p>The <it>Anopheles gambiae </it>salivary glands play a major role in malaria transmission and express a variety of bioactive components that facilitate blood-feeding by preventing platelet aggregation, blood clotting, vasodilatation, and inflammatory and other reactions at the probing site on the vertebrate host.</p> <p>Results</p> <p>We have performed a global transcriptome analysis of the <it>A. gambiae </it>salivary gland response to blood-feeding, to identify candidate genes that are involved in hematophagy. A total of 4,978 genes were found to be transcribed in this tissue. A comparison of salivary gland transcriptomes prior to and after blood-feeding identified 52 and 41 transcripts that were significantly up-regulated and down-regulated, respectively. Ten genes were further selected to assess their role in the blood-feeding process using RNAi-mediated gene silencing methodology. Depletion of the salivary gland genes encoding <it>D7L2</it>, <it>anophelin</it>, <it>peroxidase</it>, the <it>SG2 precursor</it>, and a <it>5'nucleotidase </it>gene significantly increased probing time of <it>A. gambiae </it>mosquitoes and thereby their capacity to blood-feed.</p> <p>Conclusions</p> <p>The salivary gland transcriptome comprises approximately 38% of the total mosquito transcriptome and a small proportion of it is dynamically changing already at two hours in response to blood feeding. A better understanding of the salivary gland transcriptome and its function can contribute to the development of pathogen transmission control strategies and the identification of medically relevant bioactive compounds.</p

Role of skin immune cells on the host susceptibility to mosquito-borne viruses

Due to climate change and the propagation of competent arthropods worldwide, arboviruses have become pathogens of major medical importance. Early transmission to vertebrates is initiated by skin puncture and deposition of virus together with arthropod saliva in the epidermis and dermis. Saliva components have the capacity to modulate skin cell responses by enhancing and/or counteracting initial replication and establishment of systemic viral infection. Here, we review the nature of the cells targeted by arboviruses at the skin level and discuss the type of cellular responses elicited by these pathogens in light of the immunomodulatory properties of arthropod vector-derived salivary factors injected at the inoculation site. Understanding cutaneous arbovirus&#8211;host interactions may provide new clues for the design of future therapeutics

Proteomic analysis of an Aedes albopictus cell line infected with Dengue serotypes 1 and 3 viruses

Background: Proteomic analysis was performed to identify proteins regulated during infection by Dengue serotypes 1 and 3 in an Aedes albopictus cell line. The potential of these viruses to cause severe disease at primary infection is of interest although few studies have been performed with these two Dengue serotypes. Results: The most relevant observation of our study is the significant overexpression of proteins involved in the cellular stress response and the glycolysis pathway after 48 hours of infection. Viral infection activates the translation of some host genes, which may result in stress due to responses involving unfolded proteins. Conclusions: Therefore, the oxidation reduction and glycolytic mechanisms could participate in the antiviral response against Dengue virus. The results of our study should help to improve our knowledge of the virus-mosquito interaction at a cellular level with the aim of designing efficient strategies for the control of Dengue virus

Native versus deglycosylated IgM in anti-MAG neuropathy: Correlation with clinical status - Study of 10 cases

International audienceBackground/purpose: In anti-myelin associated glycoprotein (anti-MAG) neuropathies, there is evidence that anti-MAG antibodies are pathogenic but numerous studies report the absence or a weak correlation between the titers of these antibodies and disease course. In this study we assessed the relationships between MAG and glycosylated moieties located on Fc fragment of IgM anti-MAG.Material and methods: IgM were extracted from the serum of 8 patients with anti-MAG neuropathy and in 2 patients with anti-MAG antibodies without anti-MAG neuropathy. Anti-MAG activity was performed with pre- and post-deglycosylated IgM extracts using indirect immunofluorescence (IIF) and ELISA. Sera from 49 patients with IgM monoclonal gammopathy without neurological disease were tested as control group (CG). Results were compared to clinical scores. For 4 patients the affinity constant of IgM with MAG was analyzed pre- and post-deglycosylated, using surface plasmon resonance technology (SPR).Results: The relationships between MAG and glycosylated moieties of IgM anti-MAG were confirmed by kinetic and immunological assays. Deglycosylation resulted in a decrease in anti-MAG titers. Post-deglycosylation anti-MAG titers trended with changes in IgM titers and allowed quantifying anti-MAG antibodies without a saturation of the testing method. After deglycosylation, the titers better represented pathogenic activity and help to follow a given patient's clinical status prospectively. Six patients from CG (12.2%) had anti-MAG antibody titers over positive threshold: 1000 Bühlmann-Titer-Units (BTU) supporting the hypothesis of neutral intermolecular interactions between IgM and MAG. Deglycosylation allowed distinguishing infra clinical forms from neutral relationships forms, when the titers are weak but this assay remains essentially a diagnostic tool

Midgut barriers prevent the replication and dissemination of the yellow fever vaccine in Aedes aegypti

International audienceBACKGROUND: To be transmitted to vertebrate hosts via the saliva of their vectors, arthropod-borne viruses have to cross several barriers in the mosquito body, including the midgut infection and escape barriers. Yellow fever virus (YFV) belongs to the genus Flavivirus, which includes human viruses transmitted by Aedes mosquitoes, such as dengue and Zika viruses. The live-attenuated YFV-17D vaccine has been used safely and efficiently on a large scale since the end of World War II. Early studies have shown, using viral titration from salivary glands of infected mosquitoes, that YFV-17D can infect Aedes aegypti midgut, but does not disseminate to other tissues.METHODOLOGY/PRINCIPAL FINDINGS: Here, we re-visited this issue using a panel of techniques, such as RT-qPCR, Western blot, immunofluorescence and titration assays. We showed that YFV-17D replication was not efficient in Aedes aegypti midgut, as compared to the clinical isolate YFV-Dakar. Viruses that replicated in the midgut failed to disseminate to secondary organs. When injected into the thorax of mosquitoes, viruses succeeded in replicating into midgut-associated tissues, suggesting that, during natural infection, the block for YFV-17D replication occurs at the basal membrane of the midgut.CONCLUSIONS/SIGNIFICANCE: The two barriers associated with Ae. aegypti midgut prevent YFV-17D replication. Our study contributes to our basic understanding of vector-pathogen interactions and may also aid in the development of non-transmissible live virus vaccines