Abstract
BackgroundSand fly saliva plays an important role in blood feeding and Leishmania transmission as it was shown to increase parasite virulence. On the other hand, immunity to salivary components impedes the establishment of infection. Therefore, it is most desirable to gain a deeper insight into the composition of saliva in sand fly species which serve as vectors of various forms of leishmaniases. In the present work, we focused on Phlebotomus (Adlerius) arabicus, which was recently shown to transmit Leishmania tropica, the causative agent of cutaneous leishmaniasis in Israel.ResultsA cDNA library from salivary glands of P. arabicus females was constructed and transcripts were sequenced and analyzed. The most abundant protein families identified were SP15-like proteins, ParSP25-like proteins, D7-related proteins, yellow-related proteins, PpSP32-like proteins, antigen 5-related proteins, and 34 kDa-like proteins. Sequences coding for apyrases, hyaluronidase and other putative secreted enzymes were also represented, including endonuclease, phospholipase, pyrophosphatase, amylase and trehalase. Mass spectrometry analysis confirmed the presence of 20 proteins predicted to be secreted in the salivary proteome. Humoral response of mice bitten by P. arabicus to salivary antigens was assessed and many salivary proteins were determined to be antigenic.ConclusionThis transcriptomic analysis of P. arabicus salivary glands is the first description of salivary proteins of a sand fly in the subgenus Adlerius. Proteomic analysis of P. arabicus salivary glands produced the most comprehensive account in a single sand fly species to date. Detailed information and phylogenetic relationships of the salivary proteins are provided, expanding the knowledge base of molecules that are likely important factors of sand fly-host and sand fly-Leishmania interactions. Enzymatic and immunological investigations further demonstrate the value of functional transcriptomics in advancing biological and epidemiological research that can impact leishmaniasis.
Highlights
Sand fly saliva plays an important role in blood feeding and Leishmania transmission as it was shown to increase parasite virulence
Sequencing of salivary gland cDNA library A cDNA library was constructed from salivary glands of Phlebotomus arabicus females dissected one day after emergence
Predicted proteins containing retention signals for endoplasmic reticulum and/or transmembrane domains were not treated as putatively secreted. An example of such proteins is the translocon-associated protein complex, subunit (PabSP91; GenBank accession number FJ427208), which has homologs previously designated as 16 kDa or 16.1 kDa salivary protein in P. ariasi or L. longipalpis, respectively
Summary
Sand fly saliva plays an important role in blood feeding and Leishmania transmission as it was shown to increase parasite virulence. Phlebotomine sand flies are the arthropod vectors of Leishmania parasites, the causative agents of leishmaniasis. During the feeding process sand flies inject saliva into the site of the bite to facilitate successful acquisition of a blood meal [1]. Sand fly saliva facilitates the transmission of Leishmania parasites to mammalian hosts; at the same time, immune response to salivary components was shown to partially protect the host from Leishmania infection [2]. Salivary components essential for parasite transmission and/or eliciting protective immune response are sought-after. CDNA libraries from several other sand fly species were characterized and include other sand flies that vector L. major (P. duboscqi), L. infantum (P. ariasi and P. perniciosus) and L. donovani (P. argentipes)
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