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

Immunity to a salivary protein of a sand fly vector protects against the fatal outcome of visceral leishmaniasis in a hamster model

Visceral leishmaniasis (VL) is a fatal disease for humans, and no vaccine is currently available. Sand fly salivary proteins have been associated with protection against cutaneous leishmaniasis. To test whether vector salivary proteins can protect against VL, a hamster model was developed involving intradermal inoculation in the ears of 100,000 Leishmania infantum chagasi parasites together with Lutzomyia longipalpis saliva to mimic natural transmission by sand flies. Hamsters developed classical signs of VL rapidly, culminating in a fatal outcome 5-6 months postinfection. Saliva had no effect on the course of infection in this model. Immunization with 16 DNA plasmids coding for salivary proteins of Lu. longipalpis resulted in the identification of LJM19, a novel 11-kDa protein, that protected hamsters against the fatal outcome of VL. LJM19-immunized hamsters maintained a low parasite load that correlated with an overall high IFN-gamma/TGF-beta ratio and inducible NOS expression in the spleen and liver up to 5 months postinfection. Importantly, a delayed-type hypersensitivity response with high expression of IFN-gamma was also noted in the skin of LJM19-immunized hamsters 48 h after exposure to uninfected sand fly bites. Induction of IFN-gamma at the site of bite could partly explain the protection observed in the viscera of LJM19-immunized hamsters through direct parasite killing and/or priming of anti-Leishmania immunity. We have shown that immunity to a defined salivary protein (LJM19) confers powerful protection against the fatal outcome of a parasitic disease, which reinforces the concept of using components of arthropod saliva in vaccine strategies against vector-borne diseases.

An immunoregulatory peptide from salivary glands of the horsefly, Hybomitra atriperoides

Horseflies are economically important blood-feeding arthropods and also a nuisance for humans, and vectors for filariasis. They rely heavily on the pharmacological propriety of their saliva to get blood meal and suppress immune reactions of hosts. Little information is available on horsefly immune suppressants. By high-performance liquid chromatography (HPLC) purification coupling with pharmacological testing, an immunoregulatory peptide named immunoregulin HA has been identified and characterized from salivary glands of the horsefly of Hybomitra atriperoides (Diptera, Tabanidae). Immunoregulin HA could inhibit the secretion of interferon-gamma (IFN-gamma) and monocyte chemoattractant protein (MCP-1) and increase the secretion of interleukin-10 (IL-10) induced by lipopolysaccharide (LPS) in rat splenocytes. IL-10 is a suppressor cytokine of T-cell proliferative and cytokine responses. IL-10 can inhibit the elaboration of pro-inflammatory cytokines. Immunoregulin HA possibly unregulated the IL-10 production to inhibit IFN-gamma and MCP-1 secretion in the current experiments. This immunosuppression may facilitate the blood feeding of this horsefly. The current works will facilitate to understand the molecular mechanisms of the ectoparasite-host relationship.

Changes in amounts of total salivary gland proteins of Lutzomyia longipallpis (Diptera: Psychodidae) according to age and diet

Saliva plays important roles in facilitation of a bloodmeal, lubrication of mouthparts, and parasite transmission for some vector insects. Salivary composition changes during the lifetime of an insect, and differences in the salivary profile may influence its functions. In this report, the amount and profile of salivary gland protein of the American visceral leishmaniasis vector Lutzomyia longipalpis (Lutz & Neiva, 1912) were analyzed at different times of insect development and diet. Protein content from unfed female sand flies increased significantly with age, and a significant difference was observed in sugar-fed females during the first 10 d of adult life. Salivary protein content sharply decreased 1 d after blood feeding, with gradual increase in concentration the following days. SDS-polyacrylamide gel electrophoresis analysis revealed that most polypeptides present in the saliva of sugar-fed also were present in the saliva of blood-fed females. Understanding changes in sand fly's saliva contents at distinct days after emergence and the influence of a bloodmeal in this aspect may reveal the role played by saliva during leishmaniasis transmission.

Glycolytic and chitinolytic activities of Phlebotomus papatasi (Diptera: Psychodidae) from diverse ecological habitats

The sand fly Phlebotomus papatasi Scopoli, 1786, the vector of Leishmania major Yakimoff et Schokhor, 1914, is found in desert areas where sugars are scarce but also in habitats that abound in sugar sources. The sand flies require sugar meals from plant sources for their energy requirements and to hydrolyze these complex sugars, they need a repertoire of glycosidases. We presumed that there are differences in the levels of glycosidase activities in flies from such habitats and also assumed that they may be instrumental in modulating the flies' susceptibility to L. major infections. Phlebotomus papatasi originating from diverse ecological habitats ranging from an oasis to desert sites were colonized. They were analyzed for weight changes and glycosidase activities before and after feeding on 1M sucrose solution. Oasis flies were smaller than desert flies but took larger sugar meals. Homogenates of these flies hydrolyzed 16 synthetic and 2 natural glycoside substrates to varying degrees. The arid-region flies tended to produce more glycosidase activity than those originating in sugar-rich environments, especially sucrase, alpha- and beta-glucosidase, aalpha-fucosidase, alpha-mannosidase, and alpha- and beta-N-acetylgalactosaminidase. However, chitinolytic enzyme activities and particularly the beta-N-acetylhexosaminidase activity of oasis flies were higher than other flies tested. In comparing the desert flies, there were also significant differences in glycolytic enzyme activities between the spring-line (flowering season) of flies and the autumn-line (end of dry season) flies. A range of saccharide inhibitors was tested to demonstrate the specificity of the enzymes.

Proteomic approaches for discovery of new targets for vaccine and therapeutics against visceral leishmaniasis

Visceral leishmaniasis (VL) is the most devastating type caused by Leishmania donovani, Leishmania infantum, and Leishmania chagasi. The therapeutic mainstay is still based on the antiquated pentavalent antimonial against which resistance is now increasing. Unfortunately, due to the digenetic life cycle of parasite, there is significant antigenic diversity. There is an urgent need to develop novel drug/vaccine targets against VL for which the primary goal should be to identify and characterize the structural and functional proteins. Proteomics, being widely employed in the study of Leishmania seems to be a suitable strategy as the availability of annotated sequenced genome of Leishmania major has opened the door for dissection of both protein expression/regulation and function. Advances in clinical proteomic technologies have enable to enhance our mechanistic understanding of virulence/pathogenicity/host-pathogen interactions, drug resistance thereby defining novel therapeutic/vaccine targets. Expression proteomics exploits the differential expression of leishmanial proteins as biomarkers for application towards early diagnosis. Further using immunoproteomics efforts were also focused on evaluating responses to define parasite T-cell epitopes as vaccine/diagnostic targets. This review has highlighted some of the relevant developments in the rapidly emerging field of leishmanial proteomics and focus on its future applications in drug and vaccine discovery against VL.

Engineered human soluble calcium-activated nucleotidase inhibits coagulation in vitro and thrombosis in vivo

Human soluble calcium-activated nucleotidase (human SCAN) is a homologue of the salivary anti-coagulant apyrases injected by insects into their hosts to allow blood feeding. However, the human enzyme, unlike its insect counterparts, does not efficiently hydrolyze the platelet agonist, ADP. By site-directed mutagenesis, two mutant human SCANs were constructed and expressed in bacteria. Following refolding from inclusion bodies and purification, these enzymes were assessed for anti-coagulant and anti-thrombotic efficacy. These engineered proteins include both active site mutations and a dimer interface mutation to increase the stability and ADPase activity of the modified human nucleotidase. The ADPase activity of these mutants increased more than ten fold. The E130Y/K201M/E216M SCAN mutant efficiently inhibited platelet aggregation in vitro. In addition, the E130Y/K201M/T206K/T207E/E216M mutant inhibited jugular vein thrombosis in the murine ferric chloride-induced model of thrombosis, as assessed by laser Doppler blood flow measurements. The bed bug insect homologue of human SCAN was also expressed and purified, and used in these in vivo experiments as a benchmark to assess the therapeutic potential of the engineered human enzymes. The most active modified human enzyme was able to completely inhibit the thrombosis induced by ferric chloride at roughly double the protein dose used for the bed bug enzyme. Thus, for the first time, we show that an engineered form of this human protein is efficacious in an in vivo model of thrombosis, demonstrating that suitably modified human SCAN enzymes have therapeutic potential as anti-coagulant and anti-thrombotic therapeutic agents. This suggests their utility in future treatment strategies for thrombotic cardiovascular diseases, including myocardial infarctions and ischemic strokes.

APY-1, a novel Caenorhabditis elegans apyrase involved in unfolded protein response signalling and stress responses

Protein glycosylation modulates a wide variety of intracellular events and dysfunction of the glycosylation pathway has been reported in a variety of human pathologies. Endo-apyrases have been suggested to have critical roles in protein glycosylation and sugar metabolism. However, deciphering the physiological relevance of Endo-apyrases activity has actually proved difficult, owing to their complexity and the functional redundancy within the family. We report here that a UDP/GDPase, homologous to the human apyrase Scan-1, is present in the membranes of Caenorhabditis elegans, encoded by the ORF F08C6.6 and hereinafter-named APY-1. We showed that ER stress induced by tunicamycin or high temperature resulted in increased transcription of apy-1. This increase was not observed in C. elegans mutants defective in ire-1 or atf-6, demonstrating the requirement of both ER stress sensors for up-regulation of apy-1. Depletion of APY-1 resulted in constitutively activated unfolded protein response. Defects in the pharynx and impaired organization of thin fibers in muscle cells were observed in adult worms depleted of APY-1. Some of the apy-1(RNAi) phenotypes are suggestive of premature aging, because these animals also showed accumulation of lipofuscin and reduced lifespan that was not dependent on the functioning of DAF-2, the receptor of the insulin/IGF-1 signaling pathway.

Cloning and characterization of a V-ATPase subunit C from the American visceral leishmaniasis vector Lutzomyia longipalpis modulated during development and blood ingestion

Visceral leishmaniasis (VL) is a serious tropical disease that affects approximately 500 thousand people worldwide every year. In the Americas, VL is caused by the parasite Leishmania (Leishmania) infantum chagasi mainly transmitted by the bite of the sand fly vector Lutzomyia longipalpis. Despite recent advances in the study of interaction between Leishmania and sand flies, very little is known about sand fly protein expression profiles. Understanding how the expression of proteins may be affected by blood feeding and/or presence of parasite in the vector's midgut might allow us to devise new strategies for controlling the spread of leishmaniasis. In this work, we report the characterization of a vacuolar ATPase subunit C from L. longipalpis by screening of a midgut cDNA library with a 220 bp fragment identified by means of differential display reverse transcriptase-polymerase chain reaction analysis. The expression of the gene varies along insect development and is upregulated in males and bloodfed L. longipalpis, compared to unfed flies.

Human anti-saliva immune response following experimental exposure to the visceral leishmaniasis vector, Lutzomyia longipalpis

Experiments in animals verified that phlebotomine saliva enhances Leishmania infection, and vaccination with saliva prevents disease. We have shown that individuals from an endemic area of visceral leishmaniasis displayed robust antibody responses to saliva from the vector Lutzomyia longipalpis, which correlated with anti-parasite cell-mediated immunity. Here, we explored human anti-saliva responses following exposure to sand flies, using an in vivo bite model in which normal volunteers were exposed four times to 30 laboratory-reared Lu. longipalpis. Following the third exposure, normal volunteers developed diverse dermatological reactions at the site of insect bite. Serum from normal volunteers displayed high levels of anti-salivary gland sonicate IgG1, IgG4 and IgE as well as several salivary gland proteins. Furthermore, following in vitro stimulation with salivary gland sonicate, there was an increased frequency of CD4(+)CD25(+) and CD8(+)CD25(+) T cells as well as IFN-gamma and IL-10 synthesis. Strikingly, 1 year after the first exposure, PBMC from the volunteers displayed recall IFN-gamma responses that correlated with a significant reduction in infection rates using a macrophage-lymphocyte autologous culture. Together, these data suggest that human immunization against sand fly saliva is feasible and recall responses are obtained even 1 year after exposure, opening perspectives for vaccination in man.

Toward an understanding of the molecular mechanism for successful blood feeding by coupling proteomics analysis with pharmacological testing of horsefly salivary glands

Horseflies are economically important blood-feeding arthropods and also a nuisance for humans and vectors for filariasis. They 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; especially no horsefly immune suppressants have been reported. By proteomics or peptidomics and coupling transcriptome analysis with pharmacological testing, several families of proteins or peptides, which act mainly on the hemostatic system or immune system of the host, were identified and characterized from 30,000 pairs salivary glands of the horsefly Tabanus yao (Diptera, Tabanidae). They are: (i) a novel family of inhibitors of platelet aggregation including two members, which possibly inhibit platelet aggregation by a novel mechanism and act on platelet membrane, (ii) a novel family of immunosuppressant peptides including 12 members, which can inhibit interferon-gamma production and increase interleukin-10 secretion, (iii) a serine protease inhibitor with 56 amino acid residues containing anticoagulant activity, (iv) a serine protease with anticoagulant activity, (v) a protease with fibrinogenolytic activity, (vi) three families of antimicrobial peptides including six members, (vii) a hyaluronidase, (viii) a vasodilator peptide, which is an isoform of vasotab identified from Hybomitra bimaculata, and interestingly (ix) two metallothioneins, which are the first metallothioneins reported from invertebrate salivary glands. The current work will facilitate the understanding of the molecular mechanisms of the ectoparasite-host relationship and help in identifying novel vaccine targets and novel leading pharmacological compounds.

A killed Leishmania vaccine with sand fly saliva extract and saponin adjuvant displays immunogenicity in dogs

A vaccine against canine visceral leishmaniasis (CVL), comprising Leishmania braziliensis promastigote protein, sand fly gland extract (SGE) and saponin adjuvant, was evaluated in dog model, in order to analyse the immunogenicity of the candidate vaccine. The vaccine candidate elicited strong antigenicity in dogs in respect of specific SGE and Leishmania humoral immune response. The major saliva proteins recognized by serum from immunized dogs exhibited molecular weights of 35 and 45 kDa, and were related to the resistance pattern against Leishmania infection. Immunophenotypic analysis revealed increased circulating CD21⁺ B-cells and CD5⁺ T-cells, reflected by higher counts of CD4⁺ and CD8⁺ T-cells. The observed interaction between potential antigen-presenting cells (evaluated as CD14⁺ monocytes) and lymphocyte activation status indicated a relationship between innate and adaptive immune responses. The higher frequency in L. chagasi antigen-specific CD8⁺ T-lymphocytes, and their positive association with intense cell proliferation, in addition to the progressively higher production of serum nitric oxide levels, showed a profile compatible with anti-CVL vaccine potential. Further studies on immunological response after challenge with L. chagasi may provide important information that will lead to a better understanding on vaccine trial and efficacy.

The Glossina morsitans tsetse fly saliva: general characteristics and identification of novel salivary proteins

The tsetse fly (Glossina spp.) is an obligate blood-sucking insect that transmits different human-pathogenic and livestock threatening trypanosome species in Africa. To obtain more insight in the tsetse salivary function, some general aspects of the tsetse fly saliva and its composition were studied. Direct pH and protein content measurements revealed a moderately alkaline (pH approximately 8.0) salivary environment with approximately 4.3 microg soluble proteins per gland and a constant representation of the major saliva proteins throughout the blood-feeding cycle. Although major salivary genes are constitutively expressed, upregulation of salivary protein synthesis within 48 h after the blood meal ensures complete protein replenishment from day 3 onwards. Screening of a non-normalised Glossina morsitans morsitans lambdagt11 salivary gland expression library with serum from a saliva-immunized rabbit identified three full-length cDNAs encoding for novel salivary proteins with yet unknown functions: a 8.3 kDa glycine/glutamate-rich protein (G. morsitans morsitans salivary gland protein Gmmsgp1), a 12.0 kDa proline-rich protein (Gmmsgp2), and a 97.4 kDa protein composed of a metallophosphoesterase/5'nucleotidase region with a glutamate/aspartate/asparagines-rich region (Gmmsgp3).

Leishmania and the leishmaniases: a parasite genetic update and advances in taxonomy, epidemiology and pathogenicity in humans

Leishmaniases remain a major public health problem today despite the vast amount of research conducted on Leishmania pathogens. The biological model is genetically and ecologically complex. This paper explores the advances in Leishmania genetics and reviews population structure, taxonomy, epidemiology and pathogenicity. Current knowledge of Leishmania genetics is placed in the context of natural populations. Various studies have described a clonal structure for Leishmania but recombination, pseudo-recombination and other genetic processes have also been reported. The impact of these different models on epidemiology and the medical aspects of leishmaniases is considered from an evolutionary point of view. The role of these parasites in the expression of pathogenicity in humans is also explored. It is important to ascertain whether genetic variability of the parasites is related to the different clinical expressions of leishmaniasis. The review aims to put current knowledge of Leishmania and the leishmaniases in perspective and to underline priority questions which 'leishmaniacs' must answer in various domains: epidemiology, population genetics, taxonomy and pathogenicity. It concludes by presenting a number of feasible ways of responding to these questions.

Role of Sand Fly Saliva in Human and Experimental Leishmaniasis: Current Insights

Leishmaniases are wide spread diseases transmitted to their vertebrate host by infected sand fly. The saliva from these arthropods contains a vast repertoire of pharmacologically active molecules that hampers the host's haemostatic, inflammatory and immune responses. The early interactions between Leishmania and the host's immune response are closely linked to disease evolution or protection against the protozoan, and the ectoparasite saliva contributes directly to these interactions. Current studies have depicted these features, and these relations are being widely explored. There are concrete indications that the host response against sand fly saliva influences disease outcome in leishmaniasis. Additionally, there are demonstrations that immunization with whole sand fly saliva, or its components, leads to protection against leishmaniasis in different host species. The combination of these evidences opens up optimistic perspectives for improving vaccine development against Leishmania infection.

The sialotranscriptome of the blood-sucking bug Triatoma brasiliensis (Hemiptera, Triatominae)

Triatoma brasiliensis is the most important autochthon vector of Trypanosoma cruzi in Brazil, where it is widely distributed in the semiarid areas of the Northeast. In order to advance the knowledge of the salivary biomolecules of Triatominae, a salivary gland cDNA library of T. brasiliensis was mass sequenced and analyzed. Polypeptides were sequenced by HPLC/Edman degradation experiments. Then 1712 cDNA sequences were obtained and grouped in 786 clusters. The housekeeping category had 24.4% and 17.8% of the clusters and sequences, respectively. The putatively secreted category contained 47.1% of the clusters and 68.2% of the sequences. Finally, 28.5% of the clusters, containing 14% of all sequences, were classified as unknown. The sialoma of T. brasiliensis showed a high amount and great variety of different lipocalins (93.8% of secreted proteins). Remarkably, a great number of serine proteases that were not observed in previous blood-sucking sialotranscriptomes were found. Nine Kazal peptides were identified, among them one with high homology to the tabanid vasodilator vasotab, suggesting that the Triatoma vasodilator could be a Kazal protein.

Antibodies against Lutzomyia longipalpis saliva in the fox Cerdocyon thous and the sylvatic cycle of Leishmania chagasi

Sera of 11 wild Cerdocyon thous foxes from an endemic area for American visceral leishmaniasis were tested for the presence of antibodies against salivary gland homogenates (SGH) of Lutzomyia longipalpis. All foxes had higher levels of anti-Lu. longipalpis SGH antibodies than foxes from non-endemic areas, suggesting contact between foxes and the vector of visceral leishmaniasis. Sera of humans and dogs living in the same area were also tested for reactivity against Lu. longipalpis SGHs and had a lower proportion of reactivity than foxes. Antibodies against Leishmania chagasi were not detected in any of the foxes, but three foxes showed the presence of parasites in the bone marrow by direct examination, PCR or by infecting the vector. Both humans and dogs had higher levels of anti-Le. chagasi IgG antibodies than C. thous. The finding of an antibody response against saliva of Lu. longipalpis among C. thous together with the broad distribution of the vector in resting areas of infected foxes suggests that the natural foci of transmission of Le. chagasi exists independently of the transmission among dogs and humans.

An annotated catalogue of salivary gland transcripts in the adult female mosquito, Aedes aegypti

Background

Saliva of blood-sucking arthropods contains a cocktail of antihemostatic agents and immunomodulators that help blood feeding. Mosquitoes additionally feed on sugar meals and have specialized regions of their glands containing glycosidases and antimicrobials that might help control bacterial growth in the ingested meals. To expand our knowledge on the salivary cocktail of Ædes ægypti, a vector of dengue and yellow fevers, we analyzed a set of 4,232 expressed sequence tags from cDNA libraries of adult female mosquitoes.

Results

A nonredundant catalogue of 614 transcripts (573 of which are novel) is described, including 136 coding for proteins of a putative secretory nature. Additionally, a two-dimensional gel electrophoresis of salivary gland (SG) homogenates followed by tryptic digestion of selected protein bands and MS/MS analysis revealed the expression of 24 proteins. Analysis of tissue-specific transcription of a subset of these genes revealed at least 31 genes whose expression is specific or enriched in female SG, whereas 24 additional genes were expressed in female SG and in males but not in other female tissues. Most of the 55 proteins coded by these SG transcripts have no known function and represent high-priority candidates for expression and functional analysis as antihemostatic or antimicrobial agents. An unexpected finding is the occurrence of four protein families specific to SG that were probably a product of horizontal transfer from prokaryotic organisms to mosquitoes.

Conclusion

Overall, this paper contributes to the novel identification of 573 new transcripts, or near 3% of the Æ. ægypti proteome assuming a 20,000-protein set, and to the best-described sialome of any blood-feeding insect.

Antibodies from dogs with canine visceral leishmaniasis recognise two proteins from the saliva of Lutzomyia longipalpis

The saliva of the sand fly Lutzomyia longipalpis, a major vector of Leishmania, exhibits pharmacological and immunomodulatory activities that may facilitate entry and establishment of parasites into the vertebrate host. Salivary gland components of the sand fly are, therefore, potential candidates in the development of a vaccine against human leishmaniasis. With the objective of identifying sand fly saliva proteins that could be used to immunise animals against canine visceral leishmaniasis, we have evaluated anti-saliva antibody reactivity using serum samples collected from dogs naturally infected with Leishmania chagasi. Two proteins with molecular weights of 28.6 and 47.3 kDa were recognised by dog antibodies in Western blot assays. Protein bands were excised from an SDS-PAGE gel and the sequences determined by mass spectrometry. The proteins were identified as LuLo-D7 and Lulo YELLOW, respectively. The significance of these findings in the context of the development of multi-component vaccination experiments is discussed.

Characterization of BGTG-1, a tergal gland-secreted alpha-amylase, from the German cockroach, Blattella germanica (L.)

The protein fraction of the German cockroach, Blattella germanica (L.), tergal gland secretion was examined. SDS-PAGE separation of proteins present in B. germanica tergal gland secretion revealed a tergal gland-secreted protein, BGTG-1, at approximately 63 kDa. BGTG-1 first appeared in tergal gland secretion at 2 days postimaginal moult and the amount of protein observed increased through day 5. A 2051 bp cDNA sequence, bgtg-1, was obtained by RACE polymerase chain reaction and contains a 1494 bp ORF encoding a predicted protein of 498 amino acids. In a Northern hybridization experiment using total RNA from B. germanica tergal gland tissue, a (32)P-labelled bgtg-1 probe hybridized to an RNA approximately 2000 bp and confirmed the 2051 bp cDNA size obtained by RACE PCR. Using the BLASTx sequence similarity search tool, the top match to the bgtg-1 ORF was found to be an alpha-amylase from Drosophila kikkawai (e-value = 1 x 10(-178)). Alignment of the bgtg-1 deduced protein sequence with alpha-amylases from fruit fly, Drosophila melanogaster, honey bee, Apis mellifera (L.) and yellow mealworm, Tenebrio molitor (L.), revealed conserved residues throughout the ORF and sequence identities ranging from 58.4 to 58.2%. Using a gel-based assay, degradation of starch by native BGTG-1 was demonstrated in vitro and we propose that BGTG-1 may be involved in processing phagostimulatory sugars present in B. germanica tergal gland secretion.

Salivary apyrases of Triatoma infestans are assembled into homo-oligomers

Apyrase activity is present in the saliva of haematophagous arthropods. It is related to blood-feeding because of the apyrase ability to hydrolyse ADP, a key component of platelet aggregation. Five apyrases with apparent molecular masses of 88, 82, 79, 68 and 67 kDa were identified in the saliva of the vector of Chagas disease, Triatoma infestans. The large size observed during purification of these enzymes suggested oligomerization. In the present study, we confirmed, using gel-filtration and analytical ultracentrifugation, the presence of apyrase oligomers with molecular masses of 200 kDa in the saliva. Electrophoretic analyses showed that disulphide bonds were involved in homo-oligomerization. In addition, heterogeneity in disulphide bonds and in pI was detected, with the pI ranging from 4.9 to 5.4. The present study gives the first insights into the quaternary structure of soluble apyrases.

The calcium activated nucleotidases: A diverse family of soluble and membrane associated nucleotide hydrolyzing enzymes

It has long been known that the salivary glands of hematophagous (blood-feeding) arthropods secrete soluble apyrases, which are potent nucleotide hydrolyzing enzymes capable of hydrolyzing extracellular ATP and ADP, the latter being a major agonist contributing to platelet aggregation. Only recently, however, has the identification of proteins homologous to these apyrases been reported in non-blood-feeding organisms such as rodents and humans. In this review, we present an overview of the diverse family of apyrases first described in the blood-feeding arthropods, including the identification and characterization of the soluble and membrane-bound vertebrate enzymes homologous to these arthropod apyrases. We also describe the enzymatic properties and nucleotide specificities of the expressed enzymes, and insights gained into the structure and function of this calcium activated nucleotidase (CAN) family from biophysical, mutagenesis and crystallography studies. The potential therapeutic value of these proteins is also discussed.

Antihemostatic Molecules from Saliva of Blood-Feeding Arthropods

The ability to feed on vertebrate blood has evolved many times in various arthropod clades. Each time this trait evolves, novel solutions to the problem posed by vertebrate hemostasis are generated. Consequently, saliva of blood-feeding arthropods has proven to be a rich source of antihemostatic molecules. Vasodilators include nitrophorins (nitric oxide storage and transport heme proteins), a variety of peptides that mimic endogenous vasodilatory neuropeptides, and proteins that catabolize or sequester endogenous vasoconstrictors. A variety of platelet aggregation inhibitors antagonize platelet responses to wound-generated signals, including ADP, thrombin, and collagen. Anticoagulants disrupt elements of both the intrinsic and extrinsic pathways. Molecular approaches (termed 'sialomics') to characterize the full inventory of mRNAs transcribed in salivary glands have revealed a surprising level of complexity within a single species. Multiple salivary proteins may be directed against each component of hemostasis, resulting in both redundancy and in some cases cooperative interactions between antihemostatic proteins, as in the case of the Rhodnius prolixus apyrase (which hydrolyzes ADP) and Rhodnius platelet aggregation inhibitor 1 (which sequesters ADP). The complexity and redundancy of saliva ensures an efficient blood meal for the arthropod, but it also provides a diverse array of novel antihemostatic molecules for the pharmacologist.

Tick troponin I-like molecule is a potent inhibitor for angiogenesis

This is the first report identifying the anti-angiogenesis saliva molecule of the ixodid tick. In our previous study, we identified a troponin I-like molecule (HLTnI) of the ixodid hard tick Haemaphysalis longicornis, a vector for various pathogens. To investigate its potential inhibitory effects for angiogenesis, we expressed and purified recombinant HLTnI in Escherichia coli. In a vascular endothelial growth factor (VEGF) competitive angiogenesis assay, the recombinant HLTnI significantly inhibited the capillary formation of human vascular endothelial cells (HUVEC) in vitro. The inhibition was dose-dependent with an IC(50) of 18.95 nM. These results indicated that HLTnI is a potent angiogenesis inhibitor.

Comparative salivary gland transcriptomics of sandfly vectors of visceral leishmaniasis

Background

Immune responses to sandfly saliva have been shown to protect animals against Leishmania infection. Yet very little is known about the molecular characteristics of salivary proteins from different sandflies, particularly from vectors transmitting visceral leishmaniasis, the fatal form of the disease. Further knowledge of the repertoire of these salivary proteins will give us insights into the molecular evolution of these proteins and will help us select relevant antigens for the development of a vector based anti-Leishmania vaccine.

Results

Two salivary gland cDNA libraries from female sandflies Phlebotomus argentipes and P. perniciosus were constructed, sequenced and proteomic analysis of the salivary proteins was performed. The majority of the sequenced transcripts from the two cDNA libraries coded for secreted proteins. In this analysis we identified transcripts coding for protein families not previously described in sandflies. A comparative sandfly salivary transcriptome analysis was performed by using these two cDNA libraries and two other sandfly salivary gland cDNA libraries from P. ariasi and Lutzomyia longipalpis, also vectors of visceral leishmaniasis. Full-length secreted proteins from each sandfly library were compared using a stand-alone version of BLAST, creating formatted protein databases of each sandfly library. Related groups of proteins from each sandfly species were combined into defined families of proteins. With this comparison, we identified families of salivary proteins common among all of the sandflies studied, proteins to be genus specific and proteins that appear to be species specific. The common proteins included apyrase, yellow-related protein, antigen-5, PpSP15 and PpSP32-related protein, a 33-kDa protein, D7-related protein, a 39- and a 16.1- kDa protein and an endonuclease-like protein. Some of these families contained multiple members, including PPSP15-like, yellow proteins and D7-related proteins suggesting gene expansion in these proteins.

Conclusion

This comprehensive analysis allows us the identification of genus- specific proteins, species-specific proteins and, more importantly, proteins common among these different sandflies. These results give us insights into the repertoire of salivary proteins that are potential candidates for a vector-based vaccine.

Caste-based differences in gene expression in the polyembryonic wasp Copidosoma floridanum

The polyembryonic parasitoid Copidosoma floridanum produces two larval castes, soldiers and reproductives, during development within its host. Soldier larvae defend the brood against competitors while reproductive larvae develop into adult wasps. As with other caste-forming insects, the distinct morphological and behavioral features of soldier and reproductive larvae likely involve differential gene expression. In this study we used a bi-directional suppression subtractive hybridization (SSH) approach to isolate differentially expressed genes from C. floridanum soldier and reproductive larvae. We isolated 230 novel expressed sequence tags (ESTs) from the two subtractions (114 soldier/116 reproductive ESTs). Among these ESTs were sequences with significant similarity to genes coding for serine proteinases, proteinase inhibitors, odorant-binding and chemosensory proteins, and cuticular proteins. Also, three novel genes were isolated that resemble one another in conceptual translation and share the cysteine spacing pattern of short scorpion toxins and insect defensins. Reverse transcription-polymerase chain reaction (RT-PCR) analysis of 20 ESTs from the two libraries indicated that 85% were differentially expressed in one caste or the other. We conclude that our SSH strategy was effective in identifying a number of genes differentially expressed in soldier and reproductive larvae and that several of these genes will be useful in characterizing caste-specific gene networks in C. floridanum.

Haematophagous arthropod saliva and host defense system: a tale of tear and blood

The saliva from blood-feeding arthropod vectors is enriched with molecules that display diverse functions that mediate a successful blood meal. They function not only as weapons against host's haemostatic, inflammatory and immune responses but also as important tools to pathogen establishment. Parasites, virus and bacteria taking advantage of vectors' armament have adapted to facilitate their entry in the host. Today, many salivary molecules have been identified and characterized as new targets to the development of future vaccines. Here we focus on current information on vector's saliva and the molecules responsible to modify host's hemostasis and immune response, also regarding their role in disease transmission.

Xenopus apyrase (xapy), a secreted nucleotidase that is expressed during early development

We have characterized a cDNA encoding a Xenopus laevis apyrase (XAPY) that is expressed during embryogenesis. XAPY is highly homologous to two recently described mammalian apyrases, human SCAN-1 and rat Ca2+-NDPase, and to a lesser extent the salivary apyrase of the blood-feeding arthropod Cimex lectularis. RT-PCR analysis shows that Xapy is expressed at all the developmental stages tested, from oocytes through to tadpoles. Xapy transcripts are widely distributed in the embryo, but from late neurulae through to late tailbud stages they are highly enriched in the cement gland, an adhesive organ in the epidermis of the head. When expressed in HEK 293 cells, XAPY is largely retained in the endoplasmic reticulum, although some is also secreted. XAPY conditioned media hydrolyses UDP and UTP, confirming that it is a functional apyrase.

Effect of salivary gland extract of Leishmania vector, Lutzomyia longipalpis, on leukocyte migration in OVA-induced immune peritonitis

Salivary gland extracts (SGE) from Lutzomyia longipalpis potentate L. major infection by inducing a Th2 immune response. However, the effect of SGE on the effector phase of immune response is not known. Herein, we demonstrate that SGE inhibited neutrophil migration in ovalbumin (OVA)-induced peritonitis in immunized mice. SGE pretreatment of mice inhibited OVA-induced CD4+ and CD8+ T lymphocyte migration. The OVA-induced production of TNF-alpha, IL-1beta and leukotriene B4 (LTB4), neutrophil chemotactic mediators in this model, were inhibited by SGE. On the other hand, SGE enhanced production of IL-10 and IL-4. In naive mice, SGE also blocked LTB4-induced neutrophil migration, but not that induced fMLP. Moreover, co-incubation of LTB4 (but not fMLP, TNF-alpha and MIP-1alpha) with SGE inhibited the ability of LTB4 to induce neutrophil migration in vivo and in vitro. Altogether, the results suggest that SGE has anti-inflammatory properties that are associated with inhibition of TNF-alpha and LTB4 production and/or with the neutrophil chemotactic activity of LTB4. The effectiveness of SGE in inhibiting neutrophil migration and inflammatory mediators release in a Th1 immune inflammatory response model reinforces the need for isolation of the compounds responsible for these activities, which could be used as prototypes for the development new anti-inflammatory drugs.

The transcriptome of the salivary glands of the female western black-legged tick Ixodes pacificus (Acari: Ixodidae)

Sequencing of an Ixodes pacificus salivary gland cDNA library yielded 1068 sequences with an average undetermined nucleotide of 1.9% and an average length of 487 base pairs. Assembly of the expressed sequence tags yielded 557 contigs, 138 of which appear to code for secreted peptides or proteins based on translation of a putative signal peptide. Based on the BLASTX similarity of these contigs to 66 matches of Ixodes scapularis peptide sequences, only 58% sequence identity was found, indicating a rapid divergence of salivary proteins as observed previously for mosquito and triatomine bug salivary proteins. Here we report 106 mostly full-length sequences that clustered in 16 different families: Basic-tail proteins rich in lysine in the carboxy-terminal, Kunitz-containing proteins (monolaris, ixolaris and penthalaris families), proline-rich peptides, 5-, 9.4- and 18.7-kDa proteins of unknown functions, in addition to metalloproteases (class PIII-like) similar to reprolysins. We also have found a family of disintegrins, named ixodegrins that display homology to variabilin, a GPIIb/IIIa antagonist from the tick Dermacentor variabilis. In addition, we describe peptides (here named ixostatins) that display remarkable similarities to the cysteine-rich domain of ADAMST-4 (aggrecanase). Many molecules were assigned in the lipocalin family (histamine-binding proteins); others appear to be involved in oxidant metabolism, and still others were similar to ixodid proteins such as the anticomplement ISAC. We also identified for the first time a neuropeptide-like protein (nlp-31) with GGY repeats that may have antimicrobial activity. In addition, 16 novel proteins without significant similarities to other tick proteins and 37 housekeeping proteins that may be useful for phylogenetic studies are described. Some of these proteins may be useful for studying vascular biology or the immune system, for vaccine development, or as immunoreagents to detect prior exposure to ticks. Electronic version of the manuscript can be found at.

From transcriptome to immunome: identification of DTH inducing proteins from a Phlebotomus ariasi salivary gland cDNA library

Delayed-type hypersensitivity (DTH) response to arthropod vector salivary proteins is associated with protection against pathogen transmission. Massive cDNA sequencing, high-throughput DNA plasmid construction and DNA immunisation were used to identify twelve DTH inducing proteins isolated from a Phlebotomus ariasi salivary gland cDNA library. Additionally, nine P. ariasi DNA plasmids produced specific anti-saliva antibodies, four of these showed a Th1 immune response while the other two exhibited a Th2 profile as determined by IgG2a and IgG1 isotype switching, respectively. In order to validate the specificity of sand fly DNA plasmids, mice previously exposed to sand fly saliva were intradermally injected once with selected P. ariasi plasmids and a specific DTH response consisting of infiltration of mononuclear cells in varying proportions was observed at 24 and 48 h. This approach can help to identify DTH inducing proteins that may be related to host protection against vector-borne diseases or other disease agents where cellular immune response is protective.

Characterization of the SCP/TAPS gene family in Drosophila melanogaster

The SCP/Tpx-1/Ag5/PR-1/Sc7 (SCP/TAPS) gene family encodes proteins found in many eukaryotes. SCP/TAPS proteins are defined by the presence of an SCP/TAPS domain, and many participate in important physiological processes. Five SCP/TAPS genes were previously identified in Drosophila melanogaster and are expressed in the digestive tract or in the testes. Sequence databases were searched to determine if other SCP/TAPS genes were present in D. melanogaster, and an additional 21 SCP/TAPS genes were identified. To further define the roles of these genes, the structures of each gene and protein were analyzed. Based on these analyses, 25 SCP/TAPS genes could be placed into one of two groups. Each group contained conserved intron positions that were not shared with the other group. Proteins encoded by group 1 genes also shared additional sequence motifs and conserved cysteines not found in group 2 proteins. To determine if the two groups were expressed differently, reverse transcriptase (RT)-polymerase chain reaction (PCR) was used to examine expression in adult flies. The results indicated that most genes were preferentially expressed in adult males, suggesting a role for these genes in male reproduction. Members of both groups displayed this preferential expression, so it was not group-specific. The two groups may differ in localization rather than function.

Leishmania chagasi/infantum: further investigations on Leishmania tropisms in atypical cutaneous and visceral leishmaniasis foci in Central America

In Central America, apparently genetically identical Leishmania chagasi/infantum parasites cause cutaneous (CL) and visceral leishmaniasis (VL), the latter being more frequent in young children. The present study investigated if there were pathology-related differences in virulence between Honduran CL and VL strains using Mediterranean L. infantum strains as a reference. Macrophage infectivity and serum sensitivity, properties thought to be associated with virulence, were similar between CL and VL strains from both regions. Attention focused on the genome organisation of genes for two candidate virulence factors: Leishmania mitogen activated protein kinase (LMPK) and cysteine proteinase b (Cpb). Interestingly, the Mediterranean strains exhibited restriction enzyme polymorphisms associated with tropism for both LMPK and Cpb genes whereas no differences were observed for the Honduran strains. We also report relative genetic homogeneity of the Honduran strains as compared to the Mediterranean strains and discuss it in terms of the probable origin for the Central American L. chagasi/infantum.

Midgut and salivary gland transcriptomes of the arbovirus vector Culicoides sonorensis (Diptera: Ceratopogonidae)

Numerous Culicoides spp. are important vectors of livestock or human disease pathogens. Transcriptome information from midguts and salivary glands of adult female Culicoides sonorensis provides new insight into vector biology. Of 1719 expressed sequence tags (ESTs) from adult serum-fed female midguts harvested within 5 h of feeding, twenty-eight clusters of serine proteases were derived. Four clusters encode putative iron binding proteins (FER1, FERL, PXDL1, PXDL2), and two clusters encode metalloendopeptidases (MDP6C, MDP6D) that probably function in bloodmeal catabolism. In addition, a diverse variety of housekeeping cDNAs were identified. Selected midgut protease transcripts were analysed by quantitative real-time PCR (q-PCR): TRY1_115 and MDP6C mRNAs were induced in adult female midguts upon feeding, whereas TRY1_156 and CHYM1 were abundant in midguts both before and immediately after feeding. Of 708 salivary gland ESTs analysed, clusters representing two new classes of protein families were identified: a new class of D7 proteins and a new class of Kunitz-type protease inhibitors. Additional cDNAs representing putative immunomodulatory proteins were also identified: 5' nucleotidases, antigen 5-related proteins, a hyaluronidase, a platelet-activating factor acetylhydrolase, mucins and several immune response cDNAs. Analysis by q-PCR showed that all D7 and Kunitz domain transcripts tested were highly enriched in female heads compared with other tissues and were generally absent from males. The mRNAs of two additional protease inhibitors, TFPI1 and TFPI2, were detected in salivary glands of paraffin-embedded females by in situ hybridization.

Identification of the most abundant secreted proteins from the salivary glands of the sand fly Lutzomyia longipalpis, vector of Leishmania chagasi

Using massive cDNA sequencing, proteomics and customized computational biology approaches, we have isolated and identified the most abundant secreted proteins from the salivary glands of the sand fly Lutzomyia longipalpis. Out of 550 randomly isolated clones from a full-length salivary gland cDNA library, we found 143 clusters or families of related proteins. Out of these 143 families, 35 were predicted to be secreted proteins. We confirmed, by Edman degradation of Lu. longipalpis salivary proteins, the presence of 17 proteins from this group. Full-length sequence for 35 cDNA messages for secretory proteins is reported, including an RGD-containing peptide, three members of the yellow-related family of proteins, maxadilan, a PpSP15-related protein, six members of a family of putative anticoagulants, an antigen 5-related protein, a D7-related protein, a cDNA belonging to the Cimex apyrase family of proteins, a protein homologous to a silk protein with amino acid repeats resembling extracellular matrix proteins, a 5'-nucleotidase, a peptidase, a palmitoyl-hydrolase, an endonuclease, nine novel peptides and four different groups of proteins with no homologies to any protein deposited in accessible databases. Sixteen of these proteins appear to be unique to sand flies. With this approach, we have tripled the number of isolated secretory proteins from this sand fly. Because of the relationship between the vertebrate host immune response to salivary proteins and protection to parasite infection, these proteins are promising markers for vector exposure and attractive targets for vaccine development to control Leishmania chagasi infection.

Kinetics of expression of the salivary apyrases in Triatoma infestans

Apyrases are nucleoside triphosphate-diphosphohydrolases that remove Pi from ATP and ADP. The blood feeding reduviid Triatoma infestans, which transmits the Trypanosoma cruzi agent of Chagas disease to animals and man, presents in its salivary glands five apyrases with molecular masses of 88, 82, 79, 68 and 67 kDa. These triatomine apyrases have been associated with the prevention of ADP induced platelet aggregation in the host. Here we provide biochemical data showing that these apyrases are stored in the lumen of the salivary gland D1 pairs, and that about one half of the pool of the enzyme is consumed during feeding. After the feeding recovery of apyrases to maximal activity level takes days, thus suggesting de novo protein synthesis. This hypothesis is supported by quantitative RT-PCR analysis which shows an upregulation of the 79 kDa apyrase mRNA level after feeding.

A nucleotidase with unique catalytic properties is secreted by Trichinella spiralis

We have isolated and expressed a cDNA from the parasitic nematode Trichinella spiralis encoding a novel secreted nucleotidase which catalyses the hydrolysis of nucleoside 5'-diphosphates and 5'-monophosphates, but not 5'-triphosphates. The full length cDNA encodes a protein of 550 amino acids with an N-terminal signal peptide, but lacking a C-terminal signature sequence for addition of a glycosyl phosphatidylinositol (GPI) anchor. Expression in Pichia pastoris resulted in the secretion of an active enzyme with the catalytic properties of both a Mg2+-dependent diphosphohydrolase/apyrase and a 5'-nucleotidase. The protein sequence is homologous to 5'-nucleotidases from a wide variety of organisms but contains no sequences specifically conserved in apyrases, suggesting that it is a representative of a new class of secreted nucleotidase. The enzyme was essentially monospecific for AMP among the nucleoside 5'-monophosphates and catalysed the hydrolysis of nucleoside 5'-diphosphates in the order of UDP >> ADP. The diphosphatase activity was dependent on the presence of magnesium ions and a reducing agent, while the 5'-nucleotidase activity was enhanced by these additions. Kinetic analyses indicated that the enzyme exhibits allosteric behaviour. Determination of the number of active sites suggested that catalysis of the two different reactions occurs at the same active site. The data are discussed in terms of regulation of host purinergic signalling during infection.

An insight into the salivary transcriptome and proteome of the adult female mosquito Culex pipiens quinquefasciatus

To obtain an insight into the salivary transcriptome and proteome (sialome) of the adult female mosquito Culex quinquefasciatus, a cDNA library was randomly sequenced, and aminoterminal information for selected proteins and peptides was obtained. cDNA sequence clusters coding for secreted proteins were further analyzed. The transcriptome revealed messages coding for several proteins of known families previously reported in the salivary glands of other blood-feeding insects as well as immune-related products such as C-type lectin, gambicin, and members of the prophenol oxidase cascade. Additionally, several transcripts coding for low-complexity proteins were found, some clearly coding for mucins. Many novel transcripts were found, including a novel endonuclease previously described in crabs and shrimps but not in insects; a hyaluronidase, not described before in mosquito salivary glands but found in venom glands and in salivary glands of sand flies and black flies; several cysteine-rich peptides with possible anticlotting function, including one similar to a previously described nematode family of anti-proteases; and a completely novel family of cysteine- and tryptophane-rich proteins (CWRC family) for which 12 full-length sequences are described. Also described are 14 additional novel proteins and peptides whose function and/or family affiliation are unknown. In total, 54 transcripts coding for full-length proteins are described. That several of these are translated into proteins was confirmed by finding the corresponding aminoterminal sequences in the SDS-PAGE/Edman degradation experiments. Electronic versions of all tables and sequences can be found at http://www.ncbi.nlm.nih.gov/projects/Mosquito/C_quinquefasciatus_sialome.

Triatoma infestans apyrases belong to the 5'-nucleotidase family

Apyrases are nucleoside triphosphate-diphosphohydrolases (EC 3.6.1.5) present in a variety of organisms. The apyrase activity found in the saliva of hematophagous insects is correlated with the prevention of ADP-induced platelet aggregation of the host during blood sucking. Purification of apyrase activity from the saliva of the triatomine bug Triatoma infestans was achieved by affinity chromatography on oligo(dT)-cellulose and gel filtration chromatography. The isolated fraction includes five N-glycosylated polypeptides of 88, 82, 79, 68 and 67 kDa apparent molecular masses. The isolated apyrase mixture completely inhibited aggregation of human blood platelets. Labeling with the ATP substrate analogue 5'-p-fluorosulfonylbenzoyladenosine showed that the five species have ATP-binding characteristic of functional apyrases. Furthermore, tandem mass spectroscopy peptide sequencing showed that the five species share sequence similarities with the apyrase from Aedes aegypti and with 5'-nucleotidases from other species. The complete cDNA of the 79-kDa enzyme was cloned, and its sequence confirmed that it encodes for an apyrase belonging to the 5'-nucleotidase family. The gene multiplication leading to the unusual salivary apyrase diversity in T. infestans could represent an important mechanism amplifying the enzyme expression during the insect evolution to hematophagy, in addition to an escape from the host immune response, thus enhancing acquisition of a meal by this triatomine vector of Chagas' disease.

The transcriptome of adult female Anopheles darlingi salivary glands

Anopheles (Nyssorhynchus) darlingi is an important malaria vector in South and Central America; however, little is known about molecular aspects of its biology. Genomic and proteomic analyses were performed on the salivary gland products of Anopheles darlingi. A total of 593 randomly selected, salivary gland-derived cDNAs were sequenced and assembled based on their similarities into 288 clusters. The putative translated proteins were classified into three categories: (S) secretory products, (H) housekeeping products and (U) products with unknown cell location and function. Ninety-three clusters encode putative secreted proteins and several of them, such as an anophelin, a thrombin inhibitor, apyrases and several new members of the D7 protein family, were identified as molecules involved in haematophagy. Sugar-feeding related enzymes (alpha-glucosidases and alpha-amylase) also were found among the secreted salivary products. Ninety-nine clusters encode housekeeping proteins associated with energy metabolism, protein synthesis, signal transduction and other cellular functions. Ninety-seven clusters encode proteins with no similarity with known proteins. Comparison of the sequence divergence of the S and H categories of proteins of An. darlingi and An. gambiae revealed that the salivary proteins are less conserved than the housekeeping proteins, and therefore are changing at a faster evolutionary rate. Tabular and supplementary material containing the cDNA sequences and annotations are available at http://www.ncbi.nlm.nih.gov/projects/Mosquito/A_darlingi_sialome/

Exploring the sialome of the blood-sucking bug Rhodnius prolixus

Rhodnius prolixus is a Hemiptera that feeds exclusively on vertebrate blood in all life stages. Its salivary glands produce potent pharmacological substances that counteract host hemostasis, including anti-clotting, anti-platelet, and vasodilatory substances. To obtain a further insight into the salivary biochemical and pharmacological complexity of this insect, a cDNA library was randomly sequenced, and salivary gland homogenates were fractionated by HPLC to obtain aminoterminal sequences of abundantly expressed proteins. Results indicate a remarkable expansion of the lipocalin family in Rhodnius salivary glands, among other protein sequences described. A summary of 31 new full length proteins deducted from their mRNA sequence is described, including several new members of the nitrophorin, triabin, and pallidipin families. The electronic version of the complete tables is available at http://www.ncbi.nlm.nih.gov/projects/vectors/rhodnius_prolixus.

The MRJP/YELLOW protein family of Apis mellifera: identification of new members in the EST library

Major royal jelly proteins (named MRJP1-5) of honeybee (Apis mellifera), yellow proteins of Drosophila, together with putative proteins found in several bacteria, form a protein family termed the MRJP/yellow family. Members of the family exert diverse physiological functions and amongst eukaryotes appear to be restricted to the order Insecta. MRJPs constitute about 90% of total protein of royal jelly, which is secreted by nurse bees to feed the queen and growing larvae. We looked for mrjp and yellow homologues in a honeybee brain expressed sequence tags (EST) library. In addition to the five mrjp cDNAs previously characterized, we found three additional cDNAs encoding novel MRJPs and importantly, two cDNAs coding for orthologues of Drosophila yellow proteins. One yellow cDNA and all three cDNAs coding for the novel MRJPs were assembled completely, the sequence of the other yellow homologue was partially assembled. The data we present here supports the view that repeated duplications and functional divergence occurred during the evolution of MRJPs in honeybees, with even closely related MRJPs appearing to perform diverse physiological functions. Conversely, yellow protein orthologues appear to be conserved and thus candidates for maintaining the former function(s) of yellow proteins.

Leishmanial infection: analysis of its first steps. A review

The first steps in leishmaniasis are critical in determining the evolution of the disease. Major advances have recently been done in understanding this crucial moment. Fundamental research in parasite-vector interaction, parasite biology, insect saliva, and vertebrate host response have shed new light and uncovered a most fascinating and complex moment in leishmaniasis. We review here some of these aspects and we try to connect them in a logical framework.

A mammalian-like lipase gene is expressed in the female reproductive accessory glands of the sand fly Phlebotomus papatasi (Diptera, Psychodidae)

A lipase-like protein (PhpaLIP) was identified as the major protein component in the secretion of the female reproductive accessory glands of the sand fly Phlebotomus papatasi. The full-length cDNA encoding this protein was isolated and its nucleotide sequence determined. The deduced translational product of the gene contains a GFSFG motif, consistent with a GXSXG consensus, which is shared by most bacterial and eukaryotic hydrolases. Transcriptional analysis of the PhpaLIP gene showed that its expression is female-specific, and is also detectable in districts other than accessory glands, suggesting that it might play different functions. Taken together with the observation of sequence similarity shared by PhpaLIP and mammalian lipases, the demonstration of the presence of lipase activity in the accessory gland secretion suggests a possible biological role of PhpaLIP gene product.

Lutzomyia longipalpis (Diptera: Psychodidae: Phlebotominae): a review

Lutzomyia longipalpis is the most important vector of AmericanVisceral Leishmaniasis (AVL) due to Leishmania chagasi in the New World. Despite its importance, AVL, a disease primarily of rural areas, has increased its prevalence and became urbanized in some large cities in Brazil and other countries in Latin America. Although the disease is treatable, other control measures include elimination of infected dogs and the use of insecticides to kill the sand flies. A better understanding of vector biology could also account as one more tool for AVL control. A wide variety of papers about L. longipalpis have been published in the recent past years. This review summarizes our current information of this particular sand fly regarding its importance, biology, morphology, pheromones genetics, saliva, gut physiology and parasite interactions.

Exploring the salivary gland transcriptome and proteome of the Anopheles stephensi mosquito

Anopheles stephensi is the main urban mosquito vector of malaria in the Indian subcontinent, and belongs to the same subgenus as Anopheles gambiae, the main malaria vector in Africa. Recently the genome and proteome sets of An. gambiae have been described, as well as several protein sequences expressed in its salivary glands, some of which had their expression confirmed by amino terminal sequencing. In this paper, we randomly sequenced a full-length cDNA library of An. stephensi and performed Edman degradation of polyvinylidene difluoride (PVDF)-transferred protein bands from salivary homogenates. Twelve of 13 proteins found by aminoterminal degradation were found among the cDNA clusters of the library. Thirty-three full-length novel cDNA sequences are reported, including a novel secreted galectin; the homologue of anophelin, a thrombin inhibitor; a novel trypsin/chymotrypsin inhibitor; an apyrase; a lipase; and several new members of the D7 protein family. Most of the novel proteins have no known function. Comparison of the putatively secreted and putatively housekeeping proteins of An. stephensi with An. gambiae proteins indicated that the salivary gland proteins are at a faster evolutionary pace. The possible role of these proteins in blood and sugar feeding by the mosquito is discussed. The electronic tables and supplemental material are available at http://www.ncbi.nlm.nih.gov/projects/Mosquito/A_stephensi_sialome/ .

The salivary purine nucleosidase of the mosquito, Aedes aegypti

A cDNA clone originating from adult female Aedes aegypti mosquitoes was found with substantial similarity to nucleosidases of the EC 3.2.2.1 enzyme class. Although this type of enzyme is unusual in animals, abundant enzyme activity was found in salivary homogenates of this mosquito, but not in salivary homogenates of the mosquitoes Anopheles gambiae and Culex quinquefasciatus, or the sand fly Lutzomyia longipalpis. Aedes salivary homogenate hydrolyses inosine and guanosine to hypoxanthine and xanthine plus the ribose moiety, but does not hydrolyse the pyrimidines uridine and cytidine, thus characterizing the presence of a purine nucleosidase activity. The enzyme is present in oil-induced saliva, indicating that it is secreted. Male Ae. aegypti salivary gland homogenates (SGH) have very low purine nucleosidase activity, suggesting that the enzyme plays a role in mosquito blood feeding. A novel isocratic HPLC method to separate nucleosides and their bases is described.

Salivary gland hyaluronidase in various species of phlebotomine sand flies (Diptera: psychodidae)

Hyaluronidase activity was detected and partially characterized in salivary gland extracts of females of six sand fly species. In Phlebotomus papatasi and Lutzomyia longipalpis the enzyme was active over a broad pH range; the pH optimum was 5.0. Besides high cleaving activity towards hyaluronic acid, it hydrolyzed chondroitin sulfates A and C. Hyaluronidases of various sand fly species differed in structure and sensitivity to reducing conditions. In the subgenera Phlebotomus (P. papatasi and P. duboscqi) and Adlerius (P. halepensis) the predominant active form of the enzyme was monomeric with the same apparent molecular weight under nonreducing and reducing conditions (around 65 kDa for P. papatasi and P. duboscqi and 110 kDa for P. halepensis). In P. sergenti the enzyme occurred as a putative homodimer but remained active under reducing conditions when separated into 60 kDa subunits. In L. longipalpis and P. perniciosus the activity was detectable under non-reducing conditions only. In P. duboscqi, low enzyme activity was found also in males. Salivary gland hyaluronidases of sand flies share characteristics with endo-N-acetyl-hexosaminidases of mammalian sperm cells and corresponding venom enzymes of Hymenoptera. Hypothetically, they facilitate blood meal acquisition but also may modulate immune reactions of the host and promote pathogen transmission.

Molecular cloning and sequencing of salivary gland-specific cDNAs of the blood-sucking bug Triatoma brasiliensis (Hemiptera: Reduviidae)

Haematophagous insects produce pharmacological substances in their saliva to counteract vertebrate host haemostasis events such as coagulation, vasoconstriction and platelet aggregation. To investigate the bioactive salivary molecules of the triatomine bug Triatoma brasiliensis, we produced subtraction-enriched cDNAs of salivary-gland specific genes using suppression subtractive hybridization. Six full-length differentially expressed cDNAs (Tb113, Tb125, Tb152, Tb169, Tb180 and Tb198) were selected, cloned and sequenced. Sequence similarity searches of the databases using the putative amino acid sequence of our clones gave the following results: Tb152 - Triabin, an antithrombin induced platelet aggregation factor found in salivary gland extracts of T. pallidipennis. Tb169 - Pallidipin, an anticollagen induced platelet aggregation factor also found in T. pallidipennis salivary homogenates. Tb180 - Procalin, the major allergen of T. protracta saliva. The other three salivary-gland specific cDNAs produced no obvious homologies. Comparison of these salivary gland-specific cDNAs of with those of other triatomines combined with functional studies using recombinant proteins will allow a better understanding of the co-evolutionary process occurring between these insects and their vertebrate hosts, and may also lead to the discovery of novel antihaemostatic agents.