Abstract
Culicoides biting midges (Diptera: Ceratopogonidae) are hematophagous insects with over 1400 species distributed throughout the world. Many of these species are of particular agricultural importance as primary vectors of bluetongue and Schmallenberg viruses, yet little is known about Culicoides genomics and proteomics. Detailed studies of members from other blood-feeding Dipteran families, including those of mosquito (Culicidae) and black fly (Simuliidae), have shown that protein components within the insect’s saliva facilitate the blood feeding process. To determine the protein components in Culicoides sonorensis midges, secreted saliva was collected for peptide sequencing by tandem mass spectrometry. Forty-five secreted proteins were identified, including members of the D7 odorant binding protein family, Kunitz-like serine protease inhibitors, maltase, trypsin, and six novel proteins unique to C. sonorensis. Identifying the complex myriad of proteins in saliva from blood-feeding Dipteran species is critical for understanding their role in blood feeding, arbovirus transmission, and possibly the resulting disease pathogenesis.
Highlights
Culicoides biting midges (Diptera: Ceratopogonidae) are hematophagous insects widely distributed throughout the world with over 1400 distinct species currently identified (Borkent & Wirth, 1997)
Previous reports have established these midges as important vectors for a number of animal-associated pathogens including bluetongue virus (BTV) (Foster, Jones & McCrory, 1963), epizootic hemorrhagic disease virus (EHDV) (Foster et al, 1977), vesicular stomatitis virus (VSV) (Drolet et al, 2005), Schmallenberg virus (SBV) (Lehmann et al, 2012), and African horse sickness virus (AHSV) (Mellor, Boorman & Baylis, 2000), as well as the transmission of Oropouche virus which causes acute disease in humans (Mourao et al, 2009)
Eight distinct Structural Classification of Proteins (SCOP) domains were identified among the remaining 20 proteins. Four of these domains are found in several of the most abundant C. sonorensis salivary proteins including alpha-glucosidase found in maltase, trypsin-like serine protease found in late trypsin, pheromone binding protein-general odorant binding protein (PBP-GOBP) found in the D7-family, and Kunitz-bovine pancreatic trypsin inhibitor (BPTI) found in the Kunitz-like serine protease inhibitor proteins
Summary
Culicoides biting midges (Diptera: Ceratopogonidae) are hematophagous insects widely distributed throughout the world with over 1400 distinct species currently identified (Borkent & Wirth, 1997). Both domesticated cattle and sheep are the primary blood feeding sources for midges, C. sonorensis females are opportunistic feeders targeting a wide range of wildlife including white-tail deer, rabbits and birds (Mullens & Dada, 1992; Tempelis & Nelson, 1971). Critical to this ability to feed from multiple sources is having a salivary output replete with an assortment of sugar digestion enzymes, as well as a wide variety of proteins designed to facilitate blood feeding from multiple hosts
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