Toward an understanding of the biochemical and pharmacological complexity of the saliva of a hematophagous sand fly Lutzomyia longipalpis

A potent anti-thrombosis peptide (vasotab TY) from horsefly salivary glands

Vasotab TY is a KGD (Lys-Gly-Asp)-containing peptide identified from salivary glands of the horsefly of Tabanus yao. We have previously reported that vasotab TY showed a strong vasodilator activity. In the present study, vasotab TY was found to inhibit platelet aggregation effectively. It completely inhibited platelet aggregation induced by adenosine diphosphate (ADP) at the concentration of 9.6μg/ml. Vasotab TY significantly reduced thrombus weight in rat arteriovenous shunt model and inhibited thrombosis in carrageenan-induced mouse tail thrombosis model in vivo. Vasotab TY competitively bound to glycoprotein IIb/IIIa (GPIIb/IIIa) with eptifibatide, a well-known KGD-containing cyclic heptapeptide containing high specificity and high affinity for GPIIb/IIIa, suggesting that it is an antagonist of the fibrinogen receptor GPIIb/IIIa on the surface of platelet. The KGD motif in vasotab TY may facilitate the binding of it to GPIIb/IIIa. Vasotab TY showed a half-life of more than 1h in vivo. It showed little side effects including little bleeding, no hemolytic activity on human blood red cells and no cytotoxicity on human keratinocyte and THP-1 cells. Combined its vasodilator and platelet inhibitory functions, vasotab TY might be an excellent candidate for the development of clinical anti-thrombosis medicines.

Cloning and expression of apyrase gene from Ancylostoma caninum in Escherechia coli

Apyrase encoding metal-ions activated plasma membrane protease is present in animal and plant tissues. This enzyme can hydrolyze ADP and ATP pyrophosphate bond, resulting in AMP and free phosphate groups, and plays an important role for insects and parasites to evade host immune system. However localization and function of apyrase in the canine hookworm, Ancylostoma caninum, remains unknown. To analyze apyrase gene in A. caninum (a eukaryotic parasitic hookworm), a pair of primers was designed according to the previous EST data. The full-length cDNA of apyrase gene was amplified from A. caninum by RT-PCR. The partial cDNA of apyrase encodes 249 amino acid protein was expressed in Escherechia coli. The recombinant protein was induced to express under proper conditions and the molecular size was as expected. The recombinant protein was purified. The transcripts of apyrase in different stages of A. caninum were analyzed by the Real-time PCR assay, and Immuno-localization assays were used to research the protein expression in different stages of A. caninum.

Comparative analysis of salivary gland transcriptomes of Phlebotomus orientalis sand flies from endemic and non-endemic foci of visceral leishmaniasis

Background

In East Africa, Phlebotomus orientalis serves as the main vector of Leishmania donovani, the causative agent of visceral leishmaniasis (VL). Phlebotomus orientalis is present at two distant localities in Ethiopia; Addis Zemen where VL is endemic and Melka Werer where transmission of VL does not occur. To find out whether the difference in epidemiology of VL is due to distant compositions of P. orientalis saliva we established colonies from Addis Zemen and Melka Werer, analyzed and compared the transcriptomes, proteomes and enzymatic activity of the salivary glands.

Methodology/Principal Findings

Two cDNA libraries were constructed from the female salivary glands of P. orientalis from Addis Zemen and Melka Werer. Clones of each P. orientalis library were randomly selected, sequenced and analyzed. In P. orientalis transcriptomes, we identified members of 13 main protein families. Phylogenetic analysis and multiple sequence alignments were performed to evaluate differences between the P. orientalis colonies and to show the relationship with other sand fly species from the subgenus Larroussius. To further compare both colonies, we investigated the humoral antigenicity and cross-reactivity of the salivary proteins and the activity of salivary apyrase and hyaluronidase.

Conclusions

This is the first report of the salivary components of P. orientalis, an important vector sand fly. Our study expanded the knowledge of salivary gland compounds of sand fly species in the subgenus Larroussius. Based on the phylogenetic analysis, we showed that P. orientalis is closely related to Phlebotomus tobbi and Phlebotomus perniciosus, whereas Phlebotomus ariasi is evolutionarily more distinct species. We also demonstrated that there is no significant difference between the transcriptomes, proteomes or enzymatic properties of the salivary components of Addis Zemen (endemic area) and Melka Werer (non-endemic area) P. orientalis colonies. Thus, the different epidemiology of VL in these Ethiopian foci cannot be attributed to the salivary gland composition.

Phlebotomus orientalis is the vector of visceral leishmaniasis (VL) caused by Leishmania donovani in Northeast Africa. Immunization with sand fly saliva or with individual salivary proteins has been shown to protect against leishmaniasis in different hosts, warranting the intensive study of salivary proteins of sand fly vectors. In our study, we characterize the salivary compounds of P. orientalis, thereby broadening the repertoire of salivary proteins of sand fly species belonging to the subgenus Larroussius. In order to find out whether there is any connection between the composition of P. orientalis saliva and the epidemiology of VL in two distinct Ethiopian foci, Addis Zemen and Melka Werer, we studied the transcriptomes, proteomes, enzymatic activities, and the main salivary antigens in two P. orientalis colonies originating from these areas. We did not detect any significant difference between the saliva of female sand flies originating in Addis Zemen (endemic area) and Melka Werer (non-endemic area). Therefore, the different epidemiology of VL in these Ethiopian foci cannot be related to the distant salivary gland protein composition. Identifying the sand fly salivary gland compounds will be useful for future research focused on characterizing suitable salivary proteins as potential anti-Leishmania vaccine candidates.

A deep insight into the sialotranscriptome of the mosquito, Psorophora albipes

Background

Psorophora mosquitoes are exclusively found in the Americas and have been associated with transmission of encephalitis and West Nile fever viruses, among other arboviruses. Mosquito salivary glands represent the final route of differentiation and transmission of many parasites. They also secrete molecules with powerful pharmacologic actions that modulate host hemostasis, inflammation, and immune response. Here, we employed next generation sequencing and proteome approaches to investigate for the first time the salivary composition of a mosquito member of the Psorophora genus. We additionally discuss the evolutionary position of this mosquito genus into the Culicidae family by comparing the identity of its secreted salivary compounds to other mosquito salivary proteins identified so far.

Results

Illumina sequencing resulted in 13,535,229 sequence reads, which were assembled into 3,247 contigs. All families were classified according to their in silico-predicted function/ activity. Annotation of these sequences allowed classification of their products into 83 salivary protein families, twenty (24.39%) of which were confirmed by our subsequent proteome analysis. Two protein families were deorphanized from Aedes and one from Ochlerotatus, while four protein families were described as novel to Psorophora genus because they had no match with any other known mosquito salivary sequence. Several protein families described as exclusive to Culicines were present in Psorophora mosquitoes, while we did not identify any member of the protein families already known as unique to Anophelines. Also, the Psorophora salivary proteins had better identity to homologs in Aedes (69.23%), followed by Ochlerotatus (8.15%), Culex (6.52%), and Anopheles (4.66%), respectively.

Conclusions

This is the first sialome (from the Greek sialo = saliva) catalog of salivary proteins from a Psorophora mosquito, which may be useful for better understanding the lifecycle of this mosquito and the role of its salivary secretion in arboviral transmission.

Molecular and immunogenic properties of apyrase SP01B and D7-related SP04 recombinant salivary proteins of Phlebotomus perniciosus from Madrid, Spain

Sand fly salivary proteins are on the spotlight to become vaccine candidates against leishmaniasis and to markers of exposure to sand fly bites due to the host immune responses they elicit. Working with the whole salivary homogenate entails serious drawbacks such as the need for maintaining sand fly colonies and the laborious task of glands dissection. In order to overcome these difficulties, producing recombinant proteins of different vectors has become a major task. In this study, a cDNA library was constructed with the salivary glands of Phlebotomus perniciosus from Madrid, Spain, the most widespread vector of Leishmania infantum in the Mediterranean basin. Analysis of the cDNA sequences showed several polymorphisms among the previously described salivary transcripts. The apyrase SP01B and the D7-related protein SP04 were successfully cloned, expressed in Escherichia coli, and purified. Besides, recombinant proteins were recognized by sera of hamsters and mice previously immunized with saliva through the exposure to uninfected sand fly bites. These results suggest that these two recombinant proteins conserved their immunogenic properties after expression in a prokaryote system. Therefore, this work contributes to expand the knowledge of P. perniciosus saliva that would be eventually used for the development of tools for vector control programs.

Origin and function of the major royal jelly proteins of the honeybee (Apis mellifera) as members of the yellow gene family

In the honeybee, Apis mellifera, the queen larvae are fed with a diet exclusively composed of royal jelly (RJ), a secretion of the hypopharyngeal gland of young worker bees that nurse the brood. Up to 15% of RJ is composed of proteins, the nine most abundant of which have been termed major royal jelly proteins (MRJPs). Although it is widely accepted that RJ somehow determines the fate of a female larva and in spite of considerable research efforts, there are surprisingly few studies that address the biochemical characterisation and functions of these MRJPs. Here we review the research on MRJPs not only in honeybees but in hymenopteran insects in general and provide metadata analyses on genome organisation of mrjp genes, corroborating previous reports that MRJPs have important functions for insect development and not just a nutritional value for developing honeybee larvae.

Evolution of the salivary apyrases of blood-feeding arthropods

Phylogenetic analyses of three families of arthropod apyrases were used to reconstruct the evolutionary relationships of salivary-expressed apyrases, which have an anti-coagulant function in blood-feeding arthropods. Members of the 5'nucleotidase family were recruited for salivary expression in blood-feeding species at least five separate times in the history of arthropods, while members of the Cimex-type apyrase family have been recruited at least twice. In spite of these independent events of recruitment for salivary function, neither of these families showed evidence of convergent amino acid sequence evolution in salivary-expressed members. On the contrary, in the 5'-nucleotide family, salivary-expressed proteins conserved ancestral amino acid residues to a significantly greater extent than related proteins without salivary function, implying parallel evolution by conservation of ancestral characters. This unusual pattern of sequence evolution suggests the hypothesis that purifying selection favoring conservation of ancestral residues is particularly strong in salivary-expressed members of the 5'-nucleotidase family of arthropods because of constraints arising from expression within the vertebrate host.

Functional transcriptomics of wild-caught Lutzomyia intermedia salivary glands: identification of a protective salivary protein against Leishmania braziliensis infection

Background

Leishmania parasites are transmitted in the presence of sand fly saliva. Together with the parasite, the sand fly injects salivary components that change the environment at the feeding site. Mice immunized with Phlebotomus papatasi salivary gland (SG) homogenate are protected against Leishmania major infection, while immunity to Lutzomyia intermedia SG homogenate exacerbated experimental Leishmania braziliensis infection. In humans, antibodies to Lu. intermedia saliva are associated with risk of acquiring L. braziliensis infection. Despite these important findings, there is no information regarding the repertoire of Lu. intermedia salivary proteins.

Methods and Findings

A cDNA library from the Salivary Glands (SGs) of wild-caught Lu. intermedia was constructed, sequenced, and complemented by a proteomic approach based on 1D SDS PAGE and mass/mass spectrometry to validate the transcripts present in this cDNA library. We identified the most abundant transcripts and proteins reported in other sand fly species as well as novel proteins such as neurotoxin-like proteins, peptides with ML domain, and three small peptides found so far only in this sand fly species. DNA plasmids coding for ten selected transcripts were constructed and used to immunize BALB/c mice to study their immunogenicity. Plasmid Linb-11—coding for a 4.5-kDa protein—induced a cellular immune response and conferred protection against L. braziliensis infection. This protection correlated with a decreased parasite load and an increased frequency of IFN-γ-producing cells.

Conclusions

We identified the most abundant and novel proteins present in the SGs of Lu. intermedia, a vector of cutaneous leishmaniasis in the Americas. We also show for the first time that immunity to a single salivary protein from Lu. intermedia can protect against cutaneous leishmaniasis caused by L. braziliensis.

Sand fly saliva contains potent, biologically active proteins that allow the insect to stop host responses to acquire a blood meal. After repeated exposures, a number of these salivary proteins also induce a response in the host such as antibody production and/or cellular-mediated immunity. In animal models, these immune responses affect Leishmania infection. On one hand, immunity to Phlebotomus papatasi saliva protected animals against cutaneous leishmaniasis, while on the other hand, immunity to Lutzomyia intermedia saliva did not protect but exacerbated this disease. These differences are probably due to the types of proteins present in the saliva of these different sand fly species. The present work focused on isolation and identification of the secreted proteins present in the salivary glands of Lu. intermedia, an important vector of L. braziliensis, the agent of mucocutaneous leishmaniasis. Saliva from this sand fly contains a number of proteins not present in P. papatasi saliva and, with some exceptions; proteins that are homologous between the two species are very divergent. Furthermore, we identified one protein that, after vaccination, induced a cellular immune response able to protect mice against Leishmania braziliensis infection. This is the first evidence that a single salivary protein from Lu. intermedia can protect mice against this cutaneous leishmaniasis.

Vaccination with L. infantum chagasi nucleosomal histones confers protection against new world cutaneous leishmaniasis caused by Leishmania braziliensis

Background

Nucleosomal histones are intracellular proteins that are highly conserved among Leishmania species. After parasite destruction or spontaneous lysis, exposure to these proteins elicits a strong host immune response. In the present study, we analyzed the protective capability of Leishmania infantum chagasi nucleosomal histones against L. braziliensis infection using different immunization strategies.

Methodology/Principal Findings

BALB/c mice were immunized with either a plasmid DNA cocktail (DNA) containing four Leishmania nucleosomal histones or with the DNA cocktail followed by the corresponding recombinant proteins plus CpG (DNA/Protein). Mice were later challenged with L. braziliensis, in the presence of sand fly saliva. Lesion development, parasite load and the cellular immune response were analyzed five weeks after challenge. Immunization with either DNA alone or with DNA/Protein was able to inhibit lesion development. This finding was highlighted by the absence of infected macrophages in tissue sections. Further, parasite load at the infection site and in the draining lymph nodes was also significantly lower in vaccinated animals. This outcome was associated with increased expression of IFN-γ and down regulation of IL-4 at the infection site.

Conclusion

The data presented here demonstrate the potential use of L. infantum chagasi nucleosomal histones as targets for the development of vaccines against infection with L. braziliensis, as shown by the significant inhibition of disease development following a live challenge.

Salivary proteomics in biomedical research

Proteins that are important indicators of physiological or pathological states, can provide information for the identification of early and differential markers for disease. Saliva, contains an abundance of proteins, offers an easy, inexpensive, safe, and non-invasive approach for disease detection, and possesses a high potential to revolutionize the diagnostics. Discovery of salivary biomarkers could be used to scrutinize health and disease surveillance. The impact of human saliva proteome analysis in the search for clinically relevant disease biomarkers will be realized through advances made using proteomic technologies. The advancements of emerging proteomic techniques have benefited biomarker research to the point where saliva is now recognized as an excellent diagnostic medium for the detection of disease. This review presents an overview of the value of saliva as a credible diagnostic tool and we aim to summarize the proteomic technologies currently used for global analysis of saliva proteins and to elaborate on the application of saliva proteomics to the discovery of disease biomarkers, and discuss some of the critical challenges and perspectives in this field.

Transcriptional profiles of mating-responsive genes from testes and male accessory glands of the Mediterranean fruit fly, Ceratitis capitata

BACKGROUND

Insect seminal fluid is a complex mixture of proteins, carbohydrates and lipids, produced in the male reproductive tract. This seminal fluid is transferred together with the spermatozoa during mating and induces post-mating changes in the female. Molecular characterization of seminal fluid proteins in the Mediterranean fruit fly, Ceratitis capitata, is limited, although studies suggest that some of these proteins are biologically active.

METHODOLOGY/PRINCIPAL FINDINGS

We report on the functional annotation of 5914 high quality expressed sequence tags (ESTs) from the testes and male accessory glands, to identify transcripts encoding putative secreted peptides that might elicit post-mating responses in females. The ESTs were assembled into 3344 contigs, of which over 33% produced no hits against the nr database, and thus may represent novel or rapidly evolving sequences. Extraction of the coding sequences resulted in a total of 3371 putative peptides. The annotated dataset is available as a hyperlinked spreadsheet. Four hundred peptides were identified with putative secretory activity, including odorant binding proteins, protease inhibitor domain-containing peptides, antigen 5 proteins, mucins, and immunity-related sequences. Quantitative RT-PCR-based analyses of a subset of putative secretory protein-encoding transcripts from accessory glands indicated changes in their abundance after one or more copulations when compared to virgin males of the same age. These changes in abundance, particularly evident after the third mating, may be related to the requirement to replenish proteins to be transferred to the female.

CONCLUSIONS/SIGNIFICANCE

We have developed the first large-scale dataset for novel studies on functions and processes associated with the reproductive biology of Ceratitis capitata. The identified genes may help study genome evolution, in light of the high adaptive potential of the medfly. In addition, studies of male recovery dynamics in terms of accessory gland gene expression profiles and correlated remating inhibition mechanisms may permit the improvement of pest management approaches.

Analysis of salivary gland transcripts of the sand fly Lutzomyia ayacuchensis, a vector of Andean-type cutaneous leishmaniasis

The saliva of blood sucking insects contains potent pharmacologically active components that assist them in counteracting the host hemostatic and inflammatory systems during blood feeding. In addition, sand fly salivary proteins affect host immunity and have the potential to be a vaccine against Leishmania infection. In the present study, the salivary gland transcripts of Lutzomyia ayacuchensis, a vector of cutaneous leishmaniasis in Ecuadorian and Peruvian Andes, were analyzed by sequencing randomly selected clones of the salivary gland cDNA library of this sand fly. This resulted in the identification of the most abundant transcripts coding for secreted proteins. These proteins were homologous to the salivary molecules present in other sand flies including the RGD-containing peptide, PpSP15/SL1 family protein, yellow-related protein, putative apyrase, antigen 5-related protein, D7 family protein, and 27 kDa salivary protein. Of note, homologues of maxadilan, an active vasodilator abundantly present in saliva of Lutzomyia longipalpis, were not identified. This analysis is the first description of salivary proteins from a sand fly of the subgenus Helcocyrtomyia and from vector of cutaneous leishmaniasis in the New World. The present analysis will provide further insights into the evolution of salivary components in blood sucking arthropods.

Cellular function and molecular structure of ecto-nucleotidases

Ecto-nucleotidases play a pivotal role in purinergic signal transmission. They hydrolyze extracellular nucleotides and thus can control their availability at purinergic P2 receptors. They generate extracellular nucleosides for cellular reuptake and salvage via nucleoside transporters of the plasma membrane. The extracellular adenosine formed acts as an agonist of purinergic P1 receptors. They also can produce and hydrolyze extracellular inorganic pyrophosphate that is of major relevance in the control of bone mineralization. This review discusses and compares four major groups of ecto-nucleotidases: the ecto-nucleoside triphosphate diphosphohydrolases, ecto-5'-nucleotidase, ecto-nucleotide pyrophosphatase/phosphodiesterases, and alkaline phosphatases. Only recently and based on crystal structures, detailed information regarding the spatial structures and catalytic mechanisms has become available for members of these four ecto-nucleotidase families. This permits detailed predictions of their catalytic mechanisms and a comparison between the individual enzyme groups. The review focuses on the principal biochemical, cell biological, catalytic, and structural properties of the enzymes and provides brief reference to tissue distribution, and physiological and pathophysiological functions.

Proteomics and transcriptome analysis coupled with pharmacological test reveals the diversity of anti-thrombosis proteins from the medicinal insect, Eupolyphaga sinensis

The insect of Eupolyphaga sinensis Walker has been used as traditional anti-thrombosis medicine without bleeding risk for several hundreds years in eastern countries. Our previous work has identified a bi-functional anti-thrombosis protein containing both direct-acting fibrin(ogen)olytic and plasminogen-activating activities from the insect. By proteomics and transcriptome analysis, 105 serine proteases belonging to four families were identified from the ground beetle, E. sinensis and the classification is for serine proteases of this organism. Pharmacological test indicated that 5 (eupolytin 1-5) of them have the abilities to hydrolyze fibrin(ogen) and/or activate plasminogen. The current work revealed the extreme diversity of anti-thrombosis components in E. sinensis and anti-thrombosis molecular mechanisms of the traditional medicinal insect, and provided many templates for the development of new thrombolytic agents. Especially, these proteins, which contain both plasmin- and PA (plasminogen-activating)-like activities, are excellent candidates for anti-thrombosis medicines.

Lufaxin, a novel factor Xa inhibitor from the salivary gland of the sand fly Lutzomyia longipalpis blocks protease-activated receptor 2 activation and inhibits inflammation and thrombosis in vivo

OBJECTIVE

Blood-sucking arthropods' salivary glands contain a remarkable diversity of antihemostatics. The aim of the present study was to identify the unique salivary anticoagulant of the sand fly Lutzomyia longipalpis, which remained elusive for decades.

METHODS AND RESULTS

Several L. longipalpis salivary proteins were expressed in human embryonic kidney 293 cells and screened for inhibition of blood coagulation. A novel 32.4-kDa molecule, named Lufaxin, was identified as a slow, tight, noncompetitive, and reversible inhibitor of factor Xa (FXa). Notably, Lufaxin's primary sequence does not share similarity to any physiological or salivary inhibitors of coagulation reported to date. Lufaxin is specific for FXa and does not interact with FX, Dansyl-Glu-Gly-Arg-FXa, or 15 other enzymes. In addition, Lufaxin blocks prothrombinase and increases both prothrombin time and activated partial thromboplastin time. Surface plasmon resonance experiments revealed that FXa binds Lufaxin with an equilibrium constant ≈3 nM, and isothermal titration calorimetry determined a stoichiometry of 1:1. Lufaxin also prevents protease-activated receptor 2 activation by FXa in the MDA-MB-231 cell line and abrogates edema formation triggered by injection of FXa in the paw of mice. Moreover, Lufaxin prevents FeCl(3)-induced carotid artery thrombus formation and prolongs activated partial thromboplastin time ex vivo, implying that it works as an anticoagulant in vivo. Finally, salivary gland of sand flies was found to inhibit FXa and to interact with the enzyme.

CONCLUSIONS

Lufaxin belongs to a novel family of slow-tight FXa inhibitors, which display antithrombotic and anti-inflammatory activities. It is a useful tool to understand FXa structural features and its role in prohemostatic and proinflammatory events.

Salivary gland transcriptomes and proteomes of Phlebotomus tobbi and Phlebotomus sergenti, vectors of leishmaniasis

Background

Phlebotomus tobbi is a vector of Leishmania infantum, and P. sergenti is a vector of Leishmania tropica. Le. infantum and Le. tropica typically cause visceral or cutaneous leishmaniasis, respectively, but Le. infantum strains transmitted by P. tobbi can cause cutaneous disease. To better understand the components and possible implications of sand fly saliva in leishmaniasis, the transcriptomes of the salivary glands (SGs) of these two sand fly species were sequenced, characterized and compared.

Methodology/Principal Findings

cDNA libraries of P. tobbi and P. sergenti female SGs were constructed, sequenced, and analyzed. Clones (1,152) were randomly picked from each library, producing 1,142 high-quality sequences from P. tobbi and 1,090 from P. sergenti. The most abundant, secreted putative proteins were categorized as antigen 5-related proteins, apyrases, hyaluronidases, D7-related and PpSP15-like proteins, ParSP25-like proteins, PpSP32-like proteins, yellow-related proteins, the 33-kDa salivary proteins, and the 41.9-kDa superfamily of proteins. Phylogenetic analyses and multiple sequence alignments of putative proteins were used to elucidate molecular evolution and describe conserved domains, active sites, and catalytic residues. Proteomic analyses of P. tobbi and P. sergenti SGs were used to confirm the identification of 35 full-length sequences (18 in P. tobbi and 17 in P. sergenti). To bridge transcriptomics with biology P. tobbi antigens, glycoproteins, and hyaluronidase activity was characterized.

Conclusions

This analysis of P. sergenti is the first description of the subgenus Paraphlebotomus salivary components. The investigation of the subgenus Larroussius sand fly P. tobbi expands the repertoire of salivary proteins in vectors of Le. infantum. Although P. tobbi transmits a cutaneous form of leishmaniasis, its salivary proteins are most similar to other Larroussius subgenus species transmitting visceral leishmaniasis. These transcriptomic and proteomic analyses provide a better understanding of sand fly salivary proteins across species and subgenera that will be vital in vector-pathogen and vector-host research.

Phlebotomine female sand flies require a blood meal for egg development, and it is during the blood feeding that pathogens can be transmitted to a host. Leishmania parasites are among these pathogens and can cause disfiguring cutaneous or even possibly fatal visceral disease. The Leishmania parasites are deposited into the bite wound along with the sand fly saliva. The components of the saliva have many pharmacologic and immune functions important in blood feeding and disease establishment. In this article, the authors identify and investigate the protein components of saliva of two important vectors of leishmaniasis, Phlebotomus tobbi and P. sergenti, by sequencing the transcriptomes of the salivary glands. We then compared the predicted protein sequences of these salivary proteins to those of other bloodsucking insects to elucidate the similarity in composition, structure, and enzymatic activity. Finally, this descriptive analysis of P. tobbi and P. sergenti transcriptomes can aid future research in identifying molecules for epidemiologic assays and in investigating sand fly-host interactions.

The immune response to sand fly salivary proteins and its influence on leishmania immunity

Leishmaniasis is a vector-borne disease transmitted by bites of phlebotomine sand flies. During Leishmania transmission, sand fly saliva is co-inoculated with parasites into the skin of the mammalian host. Sand fly saliva consists of roughly thirty different salivary proteins, many with known roles linked to blood feeding facilitation. Apart from the anti-hemostatic capacity of saliva, several sand fly salivary proteins have been shown to be immunogenic. Immunization with a single salivary protein or exposure to uninfected bites was shown to result in a protective immune response against leishmaniasis. Antibodies to saliva were not required for this protection. A strong body of evidence points to the role for saliva-specific T cells producing IFN-γ in the form of a delayed-type hypersensitivity reaction at the bite site as the main protective response. Herein, we review the immunity to sand fly salivary proteins in the context of its vector-parasite-host combinations and their vaccine potential, as well as some recent advances to shed light on the mechanism of how an immune response to sand fly saliva protects against leishmaniasis.

The protein LJM 111 from Lutzomyia longipalpis salivary gland extract (SGE) accounts for the SGE-inhibitory effects upon inflammatory parameters in experimental arthritis model

Several studies have pointed out the immunomodulatory properties of the Salivary Gland Extract (SGE) from Lutzomyia longipalpis. We aimed to identify the SGE component (s) responsible for its effect on ovalbumin (OVA)-induced neutrophil migration (NM) and to evaluate the effect of SGE and components in the antigen-induced arthritis (AIA) model. We tested the anti-arthritic activities of SGE and the recombinant LJM111 salivary protein (rLJM111) by measuring the mechanical hypernociception and the NM into synovial cavity. Furthermore, we measured IL-17, TNF-α and IFN-γ released by lymph nodes cells stimulated with mBSA or anti-CD3 using enzyme-linked immunosorbent assay (ELISA). Additionally, we tested the effect of SGE and rLJM111 on co-stimulatory molecules expression (MHC-II and CD-86) by flow cytometry, TNF-α and IL-10 production (ELISA) of bone marrow-derived dendritic cells (BMDCs) stimulated with LPS, chemotaxis and actin polymerization from neutrophils. Besides, the effect of SGE on CXCR2 and GRK-2 expression on neutrophils was investigated. We identified one plasmid expressing the protein LJM111 that prevented NM in OVA-challenged immunized mice. Furthermore, both SGE and rLJM111 inhibited NM and pain sensitivity in AIA and reduced IL-17, TNF-α and IFN-γ. SGE and rLJM111 also reduced MHC-II and CD-86 expression and TNF-α whereas increased IL-10 release by LPS-stimulated BMDCs. SGE, but not LJM 111, inhibited neutrophils chemotaxis and actin polymerization. Additionally, SGE reduced neutrophil CXCR2 expression and increased GRK-2. Thus, rLJM111 is partially responsible for SGE mechanisms by diminishing DC function and maturation but not chemoattraction of neutrophils.

Morphometrics and protein profiles of the salivary glands of Phlebotomus papatasi and Phlebotomus langeroni sand flies

Sand fly salivary fluid contains numerous proteins that modulate host immune responses to infection and facilitate blood-feeding and establishing Leishmania infection. Salivary proteins are differentially expressed in adaptation to the host, the meal type and ecological factors. We report on the morphometrics and protein composition of salivary glands of colonised Phlebotomus papatasi and P. langeroni sand flies from Egypt. Female glands were dissected at day 1 (D1, unfed), day 2 (D2, sugar-fed), day 3 (D3, blood-fed) and day 7 (D7, blood-digested). The salivary glands are composed of two lobes: heterogeneous in P. papatasi and homogeneous in P. langeroni. Lobe sizes varied considerably with fly age and feeding state; D3 flies had the largest lobe sizes and protein content. The P. papatasi flies had larger lobes and higher protein content than the P. langeroni flies. The P. papatasi D1 flies had 15 protein bands that decreased in the D2, D3 and D7 flies to 10 bands in the Sinai flies and 9 bands in the Alexandria flies. All P. langeroni flies had 12 protein bands but with different intensities. The results reveal inter-specific variation between P. papatasi and P. langeroni, while no intra-specific variation between P. papatasi strains. These results increase our understanding of salivary gland protein composition and blood-feeding behaviour in Old World sand flies with implications for leishmaniasis epidemiology and control.

New Insights on the Inflammatory Role of Lutzomyia longipalpis Saliva in Leishmaniasis

When an haematophagous sand fly vector insect bites a vertebrate host, it introduces its mouthparts into the skin and lacerates blood vessels, forming a hemorrhagic pool which constitutes an intricate environment of cell interactions. In this scenario, the initial performance of host, parasite, and vector “authors” will heavily influence the course of Leishmania infection. Recent advances in vector-parasite-host interaction have elucidated “co-authors” and “new roles” not yet described. We review here the stimulatory role of Lutzomyia longipalpis saliva leading to inflammation and try to connect them in an early context of Leishmania infection.

Identification and characterization of a novel calcium-activated apyrase from Cryptosporidium parasites and its potential role in pathogenesis

Herein, we report the biochemical and functional characterization of a novel Ca²⁺-activated nucleoside diphosphatase (apyrase), CApy, of the intracellular gut pathogen Cryptosporidium. The purified recombinant CApy protein displayed activity, substrate specificity and calcium dependency strikingly similar to the previously described human apyrase, SCAN-1 (soluble calcium-activated nucleotidase 1). CApy was found to be expressed in both Cryptosporidium parvum oocysts and sporozoites, and displayed a polar localization in the latter, suggesting a possible co-localization with the apical complex of the parasite. In vitro binding experiments revealed that CApy interacts with the host cell in a dose-dependent fashion, implying the presence of an interacting partner on the surface of the host cell. Antibodies directed against CApy block Cryptosporidium parvum sporozoite invasion of HCT-8 cells, suggesting that CApy may play an active role during the early stages of parasite invasion. Sequence analyses revealed that the capy gene shares a high degree of homology with apyrases identified in other organisms, including parasites, insects and humans. Phylogenetic analysis argues that the capy gene is most likely an ancestral feature that has been lost from most apicomplexan genomes except Cryptosporidium, Neospora and Toxoplasma.

An insight into the sialome of Simulium guianense (DIPTERA:SIMulIIDAE), the main vector of River Blindness Disease in Brazil

BACKGROUND

Little is known about the composition and function of the saliva in black flies such as Simulium guianense, the main vector of river blindness disease in Brazil. The complex salivary potion of hematophagous arthropods counteracts their host's hemostasis, inflammation, and immunity.

RESULTS

Transcriptome analysis revealed ubiquitous salivary protein families--such as the Antigen-5, Yellow, Kunitz domain, and serine proteases--in the S. guianense sialotranscriptome. Insect-specific families were also found. About 63.4% of all secreted products revealed protein families found only in Simulium. Additionally, we found a novel peptide similar to kunitoxin with a structure distantly related to serine protease inhibitors. This study revealed a relative increase of transcripts of the SVEP protein family when compared with Simulium vittatum and S. nigrimanum sialotranscriptomes. We were able to extract coding sequences from 164 proteins associated with blood and sugar feeding, the majority of which were confirmed by proteome analysis.

CONCLUSIONS

Our results contribute to understanding the role of Simulium saliva in transmission of Onchocerca volvulus and evolution of salivary proteins in black flies. It also consists of a platform for mining novel anti-hemostatic compounds, vaccine candidates against filariasis, and immuno-epidemiologic markers of vector exposure.

A novel allergen Tab y 1 with inhibitory activity of platelet aggregation from salivary glands of horseflies

BACKGROUND

Horsefly sting causes allergic reactions in human body. However, our knowledge on horsefly allergens remains poor.

OBJECTIVES

To identify the novel horsefly allergens and characterize their properties.

METHODS

A native allergen protein Tab y 1 (apyrase) was purified from the salivary glands of the horsefly Tabanus yao Macquart by gel filtration and ion exchange chromatography. Its sequence was determined by Edman degradation and cDNA cloning. Its allergenicity was assessed by immunoblotting for specific IgE, basophil activation test, skin prick test (SPT), and competitive enzyme-linked immunosorbent assay (ELISA).

RESULTS

Tab y 1 showed a single diffusion band of 70 kDa on SDS-PAGE. Seventy percent (7/10) of patients with horsefly allergy tested positive to Tab y 1 in SPT; sera from 81% (30/37) of patients reacted to Tab y 1 on western blots. Purified Tab y 1 reduced approximately 42% sera IgE reactivity to horsefly salivary gland extract on a competitive ELISA. Tab y 1 upregulated the expression of CD63 and CCR3 on passively sensitized basophils by up to approximately 4.9-fold. Tab y 1 also showed enzymatic activity to hydrolyze ATP and ADP, and potent antiplatelet aggregation and antithrombotic activities.

CONCLUSION

The current work identified a novel major allergen of horsefly, Tab y 1, with antiplatelet aggregation and antithrombotic activities, which implicates Tab y 1 in helping horseflies suck host blood, meanwhile causing allergy in their human hosts.

Human cellular immune response to the saliva of Phlebotomus papatasi is mediated by IL-10-producing CD8+ T cells and Th1-polarized CD4+ lymphocytes

BACKGROUND

The saliva of sand flies strongly enhances the infectivity of Leishmania in mice. Additionally, pre-exposure to saliva can protect mice from disease progression probably through the induction of a cellular immune response.

METHODOLOGY/PRINCIPAL FINDINGS

We analysed the cellular immune response against the saliva of Phlebotomus papatasi in humans and defined the phenotypic characteristics and cytokine production pattern of specific lymphocytes by flow cytometry. Additionally, proliferation and IFN-γ production of activated cells were analysed in magnetically separated CD4+ and CD8+ T cells. A proliferative response of peripheral blood mononuclear cells against the saliva of Phlebotomus papatasi was demonstrated in nearly 30% of naturally exposed individuals. Salivary extracts did not induce any secretion of IFN-γ but triggered the production of IL-10 primarily by CD8+ lymphocytes. In magnetically separated lymphocytes, the saliva induced the proliferation of both CD4+ and CD8+ T cells which was further enhanced after IL-10 blockage. Interestingly, when activated CD4+ lymphocytes were separated from CD8+ cells, they produced high amounts of IFN-γ.

CONCLUSION

Herein, we demonstrated that the overall effect of Phlebotomus papatasi saliva was dominated by the activation of IL-10-producing CD8+ cells suggesting a possible detrimental effect of pre-exposure to saliva on human leishmaniasis outcome. However, the activation of Th1 lymphocytes by the saliva provides the rationale to better define the nature of the salivary antigens that could be used for vaccine development.

Characterization of two closely related α-amylase paralogs in the bark beetle, Ips typographus (L.)

Ips typographus (L.), the eight-spined spruce bark beetle, causes severe damage throughout Eurasian spruce forests and suitable nuclear markers are needed in order to study its population structure on a genetic level. Two closely related genes encoding α-amylase in I. typographus were characterized and named AmyA and AmyB. Both α-amylase paralogs consisted of six exons and five introns. AmyA encodes a polypeptide of 483 amino acids, whereas AmyB has two alternative transcripts encoding polypeptides of 483 and 370 amino acids. The expression levels of both genes were high during larval stage and adulthood. The AmyB transcripts were absent in the pupal stage. A modification of the allozyme staining method allowed us to detect two clusters of bands on the electrophoretic gel that may correspond to the two α-amylase genes. There was a correlation between the lack of AmyB expression in pupa and the absence of the fast migrating isozyme cluster at this stage, suggesting that the faster migrating isoforms are products of the AmyB gene, whereas the slowly migrating bands are derived from the AmyA.

Toxins in thrombosis and haemostasis: potential beyond imagination

Exogenous factors isolated from venoms of snakes and saliva of haematophagous animals that affect thrombosis and haemostasis have contributed significantly to the development of diagnostic agents, research tools and life-saving drugs. Here, I discuss recent advances in the discovery, structural and functional characterisation, and mechanism of action of new procoagulant and anti-haemostatic proteins. In nature, these factors have evolved to target crucial 'bottlenecks' in the coagulation cascade and platelet aggregation. Several simple protein scaffolds are used to target a wide variety of target proteins and receptors exhibiting functional divergence. Different protein scaffolds have also evolved to target identical, physiologically relevant key enzymes or receptors exhibiting functional convergence. At times, exogenous factors bind to the same target protein, but at distinct sites, to differentially attenuate their functions exhibiting mechanistic divergence within the same family of proteins. The structure-function relationships of these factors are subtle and complicated but represent an exciting challenge. These studies provide ample opportunities to design highly specific and precise ligands to achieve desired biological target function. Although only a small number of them have been characterised to date, the molecular and mechanical diversities of these exogenous factors and their contributions to understanding molecular and cellular events in thrombosis and haemostasis as well as developing diagnostic and research tools and therapeutic agents, is outstanding. Based on the current status, I have attempted to identify future potential and prospects in this area of research.

A calcium-activated nucleotidase secreted from Ostertagia ostertagi 4th-stage larvae is a member of the novel salivary apyrases present in blood-feeding arthropods

Apyrases (ATP-diphosphohydrolase) comprise a ubiquitous class of glycosylated nucleotidases that hydrolyse extracellular ATP and ADP to orthophosphate and AMP. One class of newly-described, Ca2+-dependent, salivary apyrases known to counteract blood-clotting, has been identified in haematophagous arthropods. Herein, we have identified a gene (Oos-apy-1) encoding a protein that structurally conforms to the Ca2+-activated apyrase from the bed bug, Cimex lectularius, by immunologically screening an Ostertagia L4 cDNA expression library. The expressed protein (rOos-APY-1) was biochemically functional in the presence of Ca2+ only, with greatest activity on ATP, ADP, UTP and UDP. Host antibodies to the fusion protein appeared as early as 14 days post-infection (p.i.) and increased through 30 days p.i. Immunohistochemical and Western blot analyses demonstrated that the native Oos-APY-1 protein is present in the glandular bulb of the oesophagus and is confined to the L4. A putative signal sequence at the N-terminus and near 100% identity with a Teladorsagia circumcincta L4 secreted protein is consistent with the native protein being secreted at the cellular level. Predicated upon substrate specificity, the native protein may be used by the parasite to control the levels of host extracellular nucleotides released by locally-damaged tissues in an effort to modulate immune intervention and inflammation.

A bi-functional anti-thrombosis protein containing both direct-acting fibrin(ogen)olytic and plasminogen-activating activities

Direct-acting fibrin(ogen)olytic agents such as plasmin have been proved to contain effective and safety thrombolytic potential. Unfortunately, plasmin is ineffective when administered by the intravenous route because it was neutralized by plasma antiplasmin. Direct-acting fibrin(ogen)olytic agents with resistance against antiplasmin will brighten the prospect of anti-thrombosis. As reported in 'Compendium of Materia Medica', the insect of Eupolyphaga sinensis Walker has been used as traditional anti-thrombosis medicine without bleeding risk for several hundreds years. Currently, we have identified a fibrin(ogen)olytic protein (Eupolytin1) containing both fibrin(ogen)olytic and plasminogen-activating (PA) activities from the beetle, E. sinensis.

OBJECTIVES

To investigate the role of native and recombinant eupolytin1 in fibrin(ogen)olytic and plasminogen-activating processes.

METHODS AND RESULTS

Using thrombus animal model, eupolytin1 was proved to contain strong and rapid thrombolytic ability and safety in vivo, which are better than that of urokinase. Most importantly, no bleeding complications were appeared even the intravenous dose up to 0.12 µmol/kg body weight (3 times of tested dose which could completely lyse experimental thrombi) in rabbits. It is the first report of thrombolytic agents containing both direct-acting fibrin(ogen)olytic and plasminogen-activating activities.

CONCLUSIONS

The study identified novel thrombolytic agent with prospecting clinical potential because of its bi-functional merits containing both plasmin- and PA-like activities and unique pharmacological kinetics in vivo.

Ecological genomics of sand fly salivary gland genes: an overview

Sand fly saliva contains an array of bioactive molecules that facilitate blood feeding and also function as modulators of the vertebrate immune response. Such a complex of biologically active molecules was shown to be both conserved and divergent among sand fly species. It is likely that expression of sand fly salivary molecules could be modulated by environmental factors, both biotic and abiotic, that ultimately dictate the quality, and possibly quantity, of the secreted saliva. Carbohydrates are an integral part of the sand fly diet, and sugar-sources found in natural habitats are potentially involved in defining the profile of sand fly saliva, and may influence vectorial capacity. Saliva can drive the outcome of Leishmania infection in animal models, and salivary molecules are potential targets for development of vaccines to control Leishmania infection. Thus, identifying what environmental factors effectively modulate sand fly saliva in the field is a critical step towards the development of meaningful protection strategies against leishmaniasis that are based on salivary compounds from sand fly vectors.

Purification and characterization of two new allergens from the salivary glands of the horsefly, Tabanus yao

BACKGROUND

Horsefly bite can cause allergic reactions in humans. There is no information about allergenic horsefly proteins.

OBJECTIVES

The current work aims to purify and characterize IgE-binding proteins from horsefly salivary glands.

METHODS

Two IgE-binding proteins, Tab a 1 and Tab a 2 with molecular weight of 26 and 35 kd, respectively, were purified and characterized from 60,000 pairs of horsefly salivary glands of Tabanus yao, respectively. Their primary sequences were determined by Edman degradation and cDNA cloning. Their allergenicity was examined using enzyme-linked immunosorbent assay (ELISA), ELISA inhibition tests, and immunoblots.

RESULTS

Immunoblotting demonstrated IgE binding by 32 and 34 of 37 (86.5% and 91.8%) subjects' sera to Tab a 1 and Tab a 2, respectively. They were identified as an antigen 5-related (Ag 5) protein and hyaluronidase, respectively. ELISA inhibitions of serum IgE reactivity to the horsefly salivary gland extract (SGE) using purified Tab a 1 and Tab a 2 were significant (about 45%). In addition, these proteins showed some IgE-binding capacity to sera of subjects with wasp sting allergy.

CONCLUSIONS

We have first identified and characterized two IgE-binding proteins, Tab a 1, an Ag 5-like protein and Tab a 2, a hyaluronidase, from the horsefly salivary glands. They appear to be of importance for the allergic reactions induced by horsefly bite. These allergens are thus not only found in stinging but also found in hematophagous insects. These results also provided support for the presence of the so-called wasp-horsefly syndrome (WHS).

An insight into the sialome of blood-feeding Nematocera

Within the Diptera and outside the suborder Brachycera, the blood-feeding habit occurred at least twice, producing the present day sand flies, and the Culicomorpha, including the mosquitoes (Culicidae), black flies (Simulidae), biting midges (Ceratopogonidae) and frog feeding flies (Corethrellidae). Alternatives to this scenario are also discussed. Successful blood-feeding requires adaptations to antagonize the vertebrate's mechanisms of blood clotting, platelet aggregation, vasoconstriction, pain and itching, which are triggered by tissue destruction and immune reactions to insect products. Saliva of these insects provides a complex pharmacological armamentarium to block these vertebrate reactions. With the advent of transcriptomics, the sialomes (from the Greek word sialo = saliva) of at least two species of each of these families have been studied (except for the frog feeders), allowing an insight into the diverse pathways leading to today's salivary composition within the Culicomorpha, having the sand flies as an outgroup. This review catalogs 1288 salivary proteins in 10 generic classes comprising over 150 different protein families, most of which we have no functional knowledge. These proteins and many sequence comparisons are displayed in a hyperlinked spreadsheet that hopefully will stimulate and facilitate the task of functional characterization of these proteins, and their possible use as novel pharmacological agents and epidemiological markers of insect vector exposure.

The enigmatic autoimmune response in endemic pemphigus foliaceus

Endemic pemphigus foliaceus, known as Fogo Selvagem (FS) in Brazil, is a disease characterized by subcorneal blisters and IgG4 anti-dermoglein 1 (Dsg1) autoantibodies. Epidemiological studies of FS strongly an environmental etiology. A 15-year surveillance of the Limao Verde Amerindian reservation in Brazil has uncovered information on the transition of the autoimmune response from the pre-clinical stage to disease state. This incubation time may evolve over several years. The serological markers of the pre-clinical state of FS are IgM anti-Dsg1, IgE and non-IgG4 autoantibodies against Dsg1. The disease stage of FS is characterized by the rise of pathogenic IgG4 anti-Dsg1 autoantibodies. In this review, the authors reviewed the literature on the relevance of the humoral autoimmune response of FS as well as the possible environmental triggers of anti-Dsg1 autoantibody formation. Based on epidemiological observations, the authors hypothesize that the pathogenic IgG4 response in FS may be triggered by hematophagous insect bites.

An insight into the sialome of Glossina morsitans morsitans

BACKGROUND

Blood feeding evolved independently in worms, arthropods and mammals. Among the adaptations to this peculiar diet, these animals developed an armament of salivary molecules that disarm their host's anti-bleeding defenses (hemostasis), inflammatory and immune reactions. Recent sialotranscriptome analyses (from the Greek sialo = saliva) of blood feeding insects and ticks have revealed that the saliva contains hundreds of polypeptides, many unique to their genus or family. Adult tsetse flies feed exclusively on vertebrate blood and are important vectors of human and animal diseases. Thus far, only limited information exists regarding the Glossina sialome, or any other fly belonging to the Hippoboscidae.

RESULTS

As part of the effort to sequence the genome of Glossina morsitans morsitans, several organ specific, high quality normalized cDNA libraries have been constructed, from which over 20,000 ESTs from an adult salivary gland library were sequenced. These ESTs have been assembled using previously described ESTs from the fat body and midgut libraries of the same fly, thus totaling 62,251 ESTs, which have been assembled into 16,743 clusters (8,506 of which had one or more EST from the salivary gland library). Coding sequences were obtained for 2,509 novel proteins, 1,792 of which had at least one EST expressed in the salivary glands. Despite library normalization, 59 transcripts were overrepresented in the salivary library indicating high levels of expression. This work presents a detailed analysis of the salivary protein families identified. Protein expression was confirmed by 2D gel electrophoresis, enzymatic digestion and mass spectrometry. Concurrently, an initial attempt to determine the immunogenic properties of selected salivary proteins was undertaken.

CONCLUSIONS

The sialome of G. m. morsitans contains over 250 proteins that are possibly associated with blood feeding. This set includes alleles of previously described gene products, reveals new evidence that several salivary proteins are multigenic and identifies at least seven new polypeptide families unique to Glossina. Most of these proteins have no known function and thus, provide a discovery platform for the identification of novel pharmacologically active compounds, innovative vector-based vaccine targets, and immunological markers of vector exposure.

Platelet aggregation inhibitors from hematophagous animals

Salivary glands from blood-sucking animals (e.g., mosquitoes, bugs, sand flies, fleas, ticks, leeches, hookworms, bats) are a rich source of bioactive molecules that counteract hemostasis in a redundant and synergistic manner. This review discusses recent progress in the identification of salivary inhibitors of platelet aggregation, their molecular characterization, and detailed mechanism of action. Diversity of inhibitors is remarkable, with distinct families of proteins characterized as apyrases that enzymatically degrade ADP or as collagen-binding proteins that prevent its interaction with vWF, or platelet integrin α2β1 or GPVI. Molecules that bind ADP, TXA(2), epinephrine, or serotonin with high affinity have also been cloned, expressed, and their structure determined. In addition, a repertoire of antithrombins and an increasingly number of RGD and non-RGD disintegrins targeting platelet αIIbβ3 have been reported. Moreover, metalloproteases with fibrinogen(olytic) activity and PAF phosphorylcholine hydrolase are enzymes that have been recruited to the salivary gland to block platelet aggregation. Platelet inhibitory prostaglandins, lysophosphatydilcholine, adenosine, and nitric oxide (NO)-carrying proteins are other notable examples of molecules from hematophagous salivary secretions (herein named sialogenins) with antihemostatic properties. Sialogenins have been employed as tools in biochemistry and cell biology and also display potential therapeutic applications.

Functional characterization of a salivary apyrase from the sand fly, Phlebotomus duboscqi, a vector of Leishmania major

Two transcripts coding for proteins homologous to apyrases were identified by massive sequencing of a Phlebotomus (P.) duboscqi salivary gland cDNA library. The sequence analysis revealed that the amino acids important for enzymatic activity including nucleotidase activity and the binding of calcium and nucleotides were well conserved in these molecules. A recombinant P. duboscqi salivary apyrase was expressed in Escherichia coli and purified. The resulting protein efficiently hydrolyzed ADP and ATP, but not AMP, GDP, CDP or UDP, in a calcium-dependent manner. Further, the recombinant protein inhibited ADP- and collagen-induced platelet aggregation. The results indicated that this salivary protein plays an important role in the blood-feeding process in P. duboscqi. Its unique enzymatic activity makes the salivary apyrase an attractive candidate as a therapeutic agent for the treatment of thrombotic pathologies as well as a reagent for a wide variety of research purposes.

Anti-thrombosis repertoire of blood-feeding horsefly salivary glands

Blood-feeding arthropods rely heavily on the pharmacological properties of their saliva to get a blood meal and suppress immune reactions of hosts. Little information is available on antihemostatic substances in horsefly salivary glands although their saliva has been thought to contain wide range of physiologically active molecules. In traditional Eastern medicine, horseflies are used as anti-thrombosis material for hundreds of years. By proteomics coupling transcriptome analysis with pharmacological testing, several families of proteins or peptides, which exert mainly on anti-thrombosis functions, were identified and characterized from 60,000 pairs of salivary glands of the horsefly Tabanus yao Macquart (Diptera, Tabanidae). They are: (I) ten fibrin(ogen)olytic enzymes, which hydrolyze specially alpha chain of fibrin(ogen) and are the first family of fibrin(ogen)olytic enzymes purified and characterized from arthropods; (II) another fibrin(ogen)olytic enzyme, which hydrolyzes both alpha and beta chain of fibrin(ogen); (III) ten Arg-Gly-Asp-motif containing proteins acting as platelet aggregation inhibitors; (IV) five thrombin inhibitor peptides; (V) three vasodilator peptides; (VI) one apyrase acting as platelet aggregation inhibitor; (VII) one peroxidase with both platelet aggregation inhibitory and vasodilator activities. The first three families are belonging to antigen five proteins, which show obvious similarity with insect allergens. They are the first members of the antigen 5 family found in salivary glands of blood sucking arthropods to have anti-thromobosis function. The current results imply a possible evolution from allergens of blood-sucking insects to anti-thrombosis agents. The extreme diversity of horsefly anti-thrombosis components also reveals the anti-thrombosis molecular mechanisms of the traditional Eastern medicine insect material.

The Toxicogenomic Multiverse: Convergent Recruitment of Proteins Into Animal Venoms

Throughout evolution, numerous proteins have been convergently recruited into the venoms of various animals, including centipedes, cephalopods, cone snails, fish, insects (several independent venom systems), platypus, scorpions, shrews, spiders, toxicoferan reptiles (lizards and snakes), and sea anemones. The protein scaffolds utilized convergently have included AVIT/colipase/prokineticin, CAP, chitinase, cystatin, defensins, hyaluronidase, Kunitz, lectin, lipocalin, natriuretic peptide, peptidase S1, phospholipase A2, sphingomyelinase D, and SPRY. Many of these same venom protein types have also been convergently recruited for use in the hematophagous gland secretions of invertebrates (e.g., fleas, leeches, kissing bugs, mosquitoes, and ticks) and vertebrates (e.g., vampire bats). Here, we discuss a number of overarching structural, functional, and evolutionary generalities of the protein families from which these toxins have been frequently recruited and propose a revised and expanded working definition for venom. Given the large number of striking similarities between the protein compositions of conventional venoms and hematophagous secretions, we argue that the latter should also fall under the same definition.

A horsefly saliva antigen 5-like protein containing RTS motif is an angiogenesis inhibitor

The Ag5 proteins are the most abundant and immunogenic proteins in the venom secretory ducts of stinging insects. An antigen 5-like protein (named tabRTS) composed of 221 amino acid residues was purified and characterized from the salivary glands of the horsefly, Tabanus yao (Diptera, Tabanidae). Its cDNA was cloned from the cDNA library of the horsefly's salivary gland. TabRTS containing the SCP domain (Sc7 family of extracellular protein domain) was found in insect antigen 5 proteins. More interestingly, there is an Arg-Thr-Ser (RTS) disintegrin motif at the C-terminus of tabRTS. The RTS motif is positioned in a loop bracketed by cysteine residues as those found in RTS-disintegrins of Crotalidae and Viperidae snake venoms, which act as angiogenesis inhibitors. Endothelial Cell Tube formation assay in vitro and chicken chorioallantoic membrane (CAM) angiogenesis assay in vivo were performed as to investigate the effect of tabRTS on angiogenesis. It was found that tabRTS could significantly inhibit angiogenesis in vitro and in vivo. Anti-alpha(1)beta(1) monoclonal antibody could dose-dependently inhibit the anti-angiogenic activity of tabRTS. This result indicated that tabRTS possibly targets the alpha(1)beta(1) integrin to exert the anti-angiogenic activity as snake venom RTS-/KTS-disintegrins do. The current work revealed the first angiogenesis inhibitor protein containing RTS motif from invertebrates, a possible novel type of RTS-disintegrin.

Insight into the sialome of the Black Fly, Simulium vittatum

Adaptation to vertebrate blood feeding includes development of a salivary "magic potion" that can disarm host hemostasis and inflammatory reactions. Within the lower Diptera, a vertebrate blood-sucking mode evolved in the Psychodidae (sand flies), Culicidae (mosquitoes), Ceratopogonidae (biting midges), Simuliidae (black flies), and the frog-feeding Corethrellidae. Sialotranscriptome analyses from several species of mosquitoes and sand flies and from one biting midge indicate divergence in the evolution of the blood-sucking salivary potion, manifested in the finding of many unique proteins within each insect family, and even genus. Gene duplication and divergence events are highly prevalent, possibly driven by vertebrate host immune pressure. Within this framework, we describe the sialome (from Greek sialo, saliva) of the black fly Simulium vittatum and discuss the findings within the context of the protein families found in other blood-sucking Diptera. Sequences and results of Blast searches against several protein family databases are given in Supplemental Tables S1 and S2, which can be obtained from http://exon.niaid.nih.gov/transcriptome/S_vittatum/T1/SV-tb1.zip and http://exon.niaid.nih.gov/transcriptome/S_vittatum/T2/SV-tb2.zip .

EST sequencing of blood-fed and Leishmania-infected midgut of Lutzomyia longipalpis, the principal visceral leishmaniasis vector in the Americas

Leishmaniasis is an important worldwide public health problem. Visceral leishmaniasis caused by Leishmania infantum chagasi is mainly transmitted by Lutzomyia longipalpis in the Americas. Leishmania development within the sand fly vector is mostly restricted to the midgut. Thus, a comparative analysis of blood-fed versus infected midguts may provide an invaluable insight into various aspects of sand fly immunity, physiology of blood digestion, and, more importantly, of Leishmania development. To that end, we have engaged in a study to identify expressed sequenced tags (ESTs) from L. longipalpis cDNA libraries produced from midguts dissected at different times post blood meal and also after artificial infection with L. i. chagasi. A total of 2,520 ESTs were obtained and, according to the quality of the sequencing data obtained, assembled into 378 clusters and 1,526 individual sequences or singletons totalizing 1,904 sequences. Several sequences associated with defense, apoptosis, RNAi, and digestion processes were annotated. The data presented here increases current knowledge on the New World sand fly transcriptome, contributing to the understanding of various aspects of the molecular physiology of L. longipalpis, and mechanisms underlying the relationship of this sand fly species with L. i. chagasi.

Analysis of salivary transcripts and antigens of the sand fly Phlebotomus arabicus

BACKGROUND

Sand 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.

RESULTS

A 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.

CONCLUSION

This 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.

Ornithodoros savignyi: soft tick apyrase belongs to the 5'-nucleotidase family

Salivary apyrases are nucleotide-metabolising enzymes that blood-feeding parasites utilise for modulation of extracellular nucleotides to prevent platelet activation and aggregation. In this study a 5'-nucleotidase specific degenerate primer was used to identify homologous transcripts from Ornithodoros savignyi salivary gland cDNA. Two 5'-nucleotidase isoforms that share significant sequence identity to putative apyrases from Rhipicephalus appendiculatus and Ixodes scapularis were identified. Structure prediction showed a tertiary structure similar to periplasmic ecto-5'-nucleotidase from Escherichia coli, with high conservation of functional residues. The O. savignyi 5'-nucleotidase isoform I was recombinantly expressed in Pichia pastoris. Cross-reactivity was demonstrated with polyclonal anti-apyrase antisera produced against O. savignyi apyrase. Subsequent Edman sequencing and MS/MS analysis of purified O. savignyi apyrase identified peptide sequence fragments that shared sequence identity with both newly identified 5'-nucleotidase isoforms. It was concluded that wild-type apyrase is a mixture of the isoforms identified from the salivary glands of O. savignyi. These results represent the first confirmation of a soft (argasid) tick apyrase that belongs to the 5'-nucleotidase family of enzymes.

A portrait of the "SCP/TAPS" proteins of eukaryotes--developing a framework for fundamental research and biotechnological outcomes

A wide range of proteins belonging to the SCP/TAPS "family" has been described for various eukaryotic organisms, including plants and animals (vertebrates and invertebrates, such as helminths). Although SCP/TAPS proteins have been proposed to play key roles in a number of fundamental biological processes, such as host-pathogen interactions and defence mechanisms, there is a paucity of information on their genetic relationships, structures and functions, and there is no standardised nomenclature for these proteins. A detailed analysis of the relationships of members of the SCP/TAPS family of proteins, based on key protein signatures, could provide a foundation for investigating these areas. In this article, we review the current state of knowledge of key SCP/TAPS proteins of eukaryotes, with an emphasis on those from parasitic helminths, and undertake a comprehensive, systematic phylogenetic analysis of currently available full-length protein sequence data (considering characteristic protein signatures or motifs) to infer relationships and provide a framework (based on statistical support) for the naming of these proteins. This framework is intended to guide genomic and molecular biological explorations of key SCP/TAPS molecules associated with infectious diseases of plants and animals. In particular, fundamental investigations of these molecules in parasites and the integration of structural and functional data could lead to new and innovative approaches for the control of parasitic diseases, with important biotechnological outcomes.

The role of saliva in tick feeding

When attempting to feed on their hosts, ticks face the problem of host hemostasis (the vertebrate mechanisms that prevent blood loss), inflammation (that can produce itching or pain and thus initiate defensive behavior on their hosts) and adaptive immunity (by way of both cellular and humoral responses). Against these barriers, ticks evolved a complex and sophisticated pharmacological armamentarium, consisting of bioactive lipids and proteins, to assist blood feeding. Recent progress in transcriptome research has uncovered that hard ticks have hundreds of different proteins expressed in their salivary glands, the majority of which have no known function, and include many novel protein families (e.g., their primary structure is unique to ticks). This review will address the vertebrate mechanisms of these barriers as a guide to identify the possible targets of these large numbers of known salivary proteins with unknown function. We additionally provide a supplemental Table that catalogues over 3,500 putative salivary proteins from various tick species, which might assist the scientific community in the process of functional identification of these unique proteins. This supplemental file is accessble fromhttp://exon.niaid.nih.gov/transcriptome/tick_review/Sup-Table-1.xls.gz.

The CAP superfamily: cysteine-rich secretory proteins, antigen 5, and pathogenesis-related 1 proteins--roles in reproduction, cancer, and immune defense

The cysteine-rich secretory proteins, antigen 5, and pathogenesis-related 1 proteins (CAP) superfamily members are found in a remarkable range of organisms spanning each of the animal kingdoms. Within humans and mice, there are 31 and 33 individual family members, respectively, and although many are poorly characterized, the majority show a notable expression bias to the reproductive tract and immune tissues or are deregulated in cancers. CAP superfamily proteins are most often secreted and have an extracellular endocrine or paracrine function and are involved in processes including the regulation of extracellular matrix and branching morphogenesis, potentially as either proteases or protease inhibitors; in ion channel regulation in fertility; as tumor suppressor or prooncogenic genes in tissues including the prostate; and in cell-cell adhesion during fertilization. This review describes mammalian CAP superfamily gene expression profiles, phylogenetic relationships, protein structural properties, and biological functions, and it draws into focus their potential role in health and disease. The nine subfamilies of the mammalian CAP superfamily include: the human glioma pathogenesis-related 1 (GLIPR1), Golgi associated pathogenesis related-1 (GAPR1) proteins, peptidase inhibitor 15 (PI15), peptidase inhibitor 16 (PI16), cysteine-rich secretory proteins (CRISPs), CRISP LCCL domain containing 1 (CRISPLD1), CRISP LCCL domain containing 2 (CRISPLD2), mannose receptor like and the R3H domain containing like proteins. We conclude that overall protein structural conservation within the CAP superfamily results in fundamentally similar functions for the CAP domain in all members, yet the diversity outside of this core region dramatically alters target specificity and, therefore, the biological consequences.

Hyaluronidase of bloodsucking insects and its enhancing effect on leishmania infection in mice

BACKGROUND

Salivary hyaluronidases have been described in a few bloodsucking arthropods. However, very little is known about the presence of this enzyme in various bloodsucking insects and no data are available on its effect on transmitted microorganisms. Here, we studied hyaluronidase activity in thirteen bloodsucking insects belonging to four different orders. In addition, we assessed the effect of hyaluronidase coinoculation on the outcome of Leishmania major infection in BALB/c mice.

PRINCIPAL FINDINGS

High hyaluronidase activity was detected in several Diptera tested, namely deer fly Chrysops viduatus, blackflies Odagmia ornata and Eusimilium latipes, mosquito Culex quinquefasciatus, biting midge Culicoides kibunensis and sand fly Phlebotomus papatasi. Lower activity was detected in cat flea Ctenocephalides felis. No activity was found in kissing bug Rhodnius prolixus, mosquitoes Anopheles stephensi and Aedes aegypti, tse-tse fly Glossina fuscipes, stable fly Stomoxys calcitrans and human louse Pediculus humanus. Hyaluronidases of different insects vary substantially in their molecular weight, the structure of the molecule and the sensitivity to reducing conditions or sodium dodecyl sulphate. Hyaluronidase exacerbates skin lesions caused by Leishmania major; more severe lesions developed in mice where L. major promastigotes were coinjected with hyaluronidase.

CONCLUSIONS

High hyaluronidase activities seem to be essential for insects with pool-feeding mode, where they facilitate the enlargement of the feeding lesion and serve as a spreading factor for other pharmacologically active compounds present in saliva. As this enzyme is present in all Phlebotomus and Lutzomyia species studied to date, it seems to be one of the factors responsible for enhancing activity present in sand fly saliva. We propose that salivary hyaluronidase may facilitate the spread of other vector-borne microorganisms, especially those transmitted by insects with high hyaluronidase activity, namely blackflies (Simuliidae), biting midges (Ceratopogonidae) and horse flies (Tabanidae).