Insight into the salivary transcriptome and proteome of Dipetalogaster maxima

Comparative proteomic analysis of the hemolymph and salivary glands of Rhodnius prolixus and R. colombiensis reveals candidates associated with differential lytic activity against Trypanosoma cruzi Dm28c and T. cruzi Y

BACKGROUND

Immune response of triatomines plays an important role in the success or failure of transmission of T. cruzi. Studies on parasite-vector interaction have shown the presence of trypanolytic factors and have been observed to be differentially expressed among triatomines, which affects the transmission of some T. cruzi strains or DTUs (Discrete Typing Units).

METHODOLOGY/PRINCIPAL FINDINGS

Trypanolytic factors were detected in the hemolymph and saliva of R. prolixus against epimastigotes and trypomastigotes of the Y strain (T. cruzi II). To identify the components of the immune response that could be involved in this lytic activity, a comparative proteomic analysis was carried out, detecting 120 proteins in the hemolymph of R. prolixus and 107 in R. colombiensis. In salivary glands, 1103 proteins were detected in R. prolixus and 853 in R. colombiensis. A higher relative abundance of lysozyme, prolixin, nitrophorins, and serpin as immune response proteins was detected in the hemolymph of R. prolixus. Among the R. prolixus salivary proteins, a higher relative abundance of nitrophorins, lipocalins, and triabins was detected. The higher relative abundance of these immune factors in R. prolixus supports their participation in the lytic activity on Y strain (T. cruzi II), but not on Dm28c (T. cruzi I), which is resistant to lysis by hemolymph and salivary proteins of R. prolixus due to mechanisms of evading oxidative stress caused by immune factors.

CONCLUSIONS/SIGNIFICANCE

The lysis resistance observed in the Dm28c strain would be occurring at the DTU I level. T. cruzi I is the DTU with the greatest geographic distribution, from the south of the United States to central Chile and Argentina, a distribution that could be related to resistance to oxidative stress from vectors. Likewise, we can say that lysis against strain Y could occur at the level of DTU II and could be a determinant of the vector inability of these species to transmit T. cruzi II. Future proteomic and transcriptomic studies on vectors and the interactions of the intestinal microbiota with parasites will help to confirm the determinants of successful or failed vector transmission of T. cruzi DTUs in different parts of the Western Hemisphere.

An Integrative Sialomic Analysis Reveals Molecules From Triatoma sordida (Hemiptera: Reduviidae)

Triatomines have evolved salivary glands that produce versatile molecules with various biological functions, including those leading their interactions with vertebrate hosts’ hemostatic and immunological systems. Here, using high-throughput transcriptomics and proteomics, we report the first sialome study on the synanthropic triatomine Triatoma sordida. As a result, 57,645,372 reads were assembled into 26,670 coding sequences (CDS). From these, a total of 16,683 were successfully annotated. The sialotranscriptomic profile shows Lipocalin as the most abundant protein family within putative secreted transcripts. Trialysins and Kazal-type protease inhibitors have high transcript levels followed by ubiquitous protein families and enzyme classes. Interestingly, abundant trialysin and Kazal-type members are highlighted in this triatomine sialotranscriptome. Furthermore, we identified 132 proteins in T. sordida salivary gland soluble extract through LC-MS/MS spectrometry. Lipocalins, Hemiptera specific families, CRISP/Antigen-5 and Kazal-type protein inhibitors proteins were identified. Our study provides a comprehensive description of the transcript and protein compositions of the salivary glands of T. sordida. It significantly enhances the information in the Triatominae sialome databanks reported so far, improving the understanding of the vector’s biology, the hematophagous behaviour, and the Triatominae subfamily’s evolution.

Salivary gland transcriptome of the Asiatic Triatoma rubrofasciata

Salivary gland transcriptome analysis of the Asiatic Triatoma rubrofasciata was performed by high-throughput RNA sequencing. This analysis showed that the majority of reads accounting for 85.38% FPKM (fragments per kilobase of exon per million mapped fragments) were mapped with a secreted class. Of these, the most abundant subclass accounting for 89.27% FPKM was the lipocalin family. In the lipocalin family, the most dominant molecules making up 70.49% FPKM were homologues of procalin, a major allergen identified from T. protracta saliva, suggesting an important role in blood-sucking of T. rubrofasciata. Other lipocalins showed similarities to pallidipin and triplatin, inhibitors of collagen-induced platelet aggregation identified from T. pallidipennis and T. infestans, respectively, Td38 from T. dimidiata with unknown function, triatin-like lipocalin with unknown function, and triafestin, an inhibitor of the activation of the kallikrein-kinin system, identified from T. infestans saliva. Other than lipocalin family proteins, homologues of antigen-5 (3.38% FPKM), Kazal-type serine protease inhibitor (1.36% FPKM), inositol polyphosphate 5-phosphatase (1.32% FPKM), and apyrase/5'-nucleotidase (0.64% FPKM) were identified as abundant molecules in T. rubrofasciata saliva. Through this study, de novo assembly of 42,580,822 trimmed reads generated 35,781 trinity transcripts, and a total of 1,272 coding sequences for the secreted class were deposited in GenBank. The results provide further insights into the evolution of salivary components in blood-sucking arthropods.

The Pharmacopea within Triatomine Salivary Glands

Triatomines are blood-feeding insects that prey on vertebrate hosts. Their saliva is largely responsible for their feeding success. The triatomine salivary content has been studied over the past decades, revealing multifunctional bioactive proteins targeting the host´s hemostasis and immune system. Recently, sequencing of salivary-gland mRNA libraries revealed increasingly complex and complete transcript databases that have been used to validate the expression of deduced proteins through proteomics. This review provides an insight into the journey of discovery and characterization of novel molecules in triatomine saliva.

Adaptations in energy metabolism and gene family expansions revealed by comparative transcriptomics of three Chagas disease triatomine vectors

Background

Chagas disease is a parasitic infection caused by Trypanosoma cruzi. It is an important public health problem affecting around seven to eight million people in the Americas. A large number of hematophagous triatomine insect species, occupying diverse natural and human-modified ecological niches transmit this disease. Triatomines are long-living hemipterans that have evolved to explode different habitats to associate with their vertebrate hosts. Understanding the molecular basis of the extreme physiological conditions including starvation tolerance and longevity could provide insights for developing novel control strategies. We describe the normalized cDNA, full body transcriptome analysis of three main vectors in North, Central and South America, Triatoma pallidipennis, T. dimidiata and T. infestans.

Results

Two-thirds of the de novo assembled transcriptomes map to the Rhodnius prolixus genome and proteome. A Triatoma expansion of the calycin family and two types of protease inhibitors, pacifastins and cystatins were identified. A high number of transcriptionally active class I transposable elements was documented in T. infestans, compared with T. dimidiata and T. pallidipennis. Sequence identity in Triatoma-R. prolixus 1:1 orthologs revealed high sequence divergence in four enzymes participating in gluconeogenesis, glycogen synthesis and the pentose phosphate pathway, indicating high evolutionary rates of these genes. Also, molecular evidence suggesting positive selection was found for several genes of the oxidative phosphorylation I, III and V complexes.

Conclusions

Protease inhibitors and calycin-coding gene expansions provide insights into rapidly evolving processes of protease regulation and haematophagy. Higher evolutionary rates in enzymes that exert metabolic flux control towards anabolism and evidence for positive selection in oxidative phosphorylation complexes might represent genetic adaptations, possibly related to prolonged starvation, oxidative stress tolerance, longevity, and hematophagy and flight reduction. Overall, this work generated novel hypothesis related to biological adaptations to extreme physiological conditions and diverse ecological niches that sustain Chagas disease transmission.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-4696-8) contains supplementary material, which is available to authorized users.

Ixonnexin from Tick Saliva Promotes Fibrinolysis by Interacting with Plasminogen and Tissue-Type Plasminogen Activator, and Prevents Arterial Thrombosis

Tick saliva is a rich source of modulators of vascular biology. We have characterized Ixonnexin, a member of the "Basic-tail" family of salivary proteins from the tick Ixodes scapularis. Ixonnexin is a 104 residues (11.8 KDa), non-enzymatic basic protein which contains 3 disulfide bonds and a C-terminal rich in lysine. It is homologous to SALP14, a tick salivary FXa anticoagulant. Ixonnexin was produced by ligation of synthesized fragments (51-104) and (1-50) followed by folding. Ixonnexin, like SALP14, interacts with FXa. Notably, Ixonnexin also modulates fibrinolysis in vitro by a unique salivary mechanism. Accordingly, it accelerates plasminogen activation by tissue-type plasminogen activator (t-PA) with Km 100 nM; however, it does not affect urokinase-mediated fibrinolysis. Additionally, lysine analogue ε-aminocaproic acid inhibits Ixonnexin-mediated plasmin generation implying that lysine-binding sites of Kringle domain(s) of plasminogen or t-PA are involved in this process. Moreover, surface plasmon resonance experiments shows that Ixonnexin binds t-PA, and plasminogen (KD 10 nM), but not urokinase. These results imply that Ixonnexin promotes fibrinolysis by supporting the interaction of plasminogen with t-PA through formation of an enzymatically productive ternary complex. Finally, in vivo experiments demonstrates that Ixonnexin inhibits FeCl3-induced thrombosis in mice. Ixonnexin emerges as novel modulator of fibrinolysis which may also affect parasite-vector-host interactions.

Exploring the molecular complexity of Triatoma dimidiata sialome

Triatoma dimidiata, a Chagas disease vector widely distributed along Central America, has great capability for domestic adaptation as the majority of specimens caught inside human dwellings or in peridomestic areas fed human blood. Exploring the salivary compounds that overcome host haemostatic and immune responses is of great scientific interest. Here, we provide a deeper insight into its salivary gland molecules. We used high-throughput RNA sequencing to examine in depth the T. dimidiata salivary gland transcriptome. From >51 million reads assembled, 92.21% are related to putative secreted proteins. Lipocalin is the most abundant gene family, confirming it is an expanded family in Triatoma genus salivary repertoire. Other putatively secreted members include phosphatases, odorant binding protein, hemolysin, proteases, protease inhibitors, antigen-5 and antimicrobial peptides. This work expands the previous set of functionally annotated sequences from T. dimidiata salivary glands available in NCBI from 388 to 3815. Additionally, we complemented the salivary analysis through proteomics (available data via ProteomeXchange with identifier PXD008510), disclosing the set complexity of 119 secreted proteins and validating the transcriptomic results. Our large-scale approach enriches the pharmacologically active molecules database and improves our knowledge about the complexity of salivary compounds from haematophagous vectors and their biological interactions.

SIGNIFICANCE

Several haematophagous triatomine species can transmit Trypanosoma cruzi, the etiological agent of Chagas disease. Due to the reemergence of this disease, new drugs for its prevention and treatment are considered priorities. For this reason, the knowledge of vector saliva emerges as relevant biological finding, contributing to the design of different strategies for vector control and disease transmission. Here we report the transcriptomic and proteomic compositions of the salivary glands (sialome) of the reduviid bug Triatoma dimidiata, a relevant Chagas disease vector in Central America. Our results are robust and disclosed unprecedented insights into the notable diversity of its salivary glands content, revealing relevant anti-haemostatic salivary gene families. Our work expands almost ten times the previous set of functionally annotated sequences from T. dimidiata salivary glands available in NCBI. Moreover, using an integrated transcriptomic and proteomic approach, we showed a correlation pattern of transcription and translation processes for the main gene families found, an important contribution to the research of triatomine sialomes. Furthermore, data generated here reinforces the secreted proteins encountered can greatly contribute for haematophagic habit, Trypanosoma cruzi transmission and development of therapeutic agent studies.

Salivary gland transcripts of the kissing bug, Panstrongylus chinai, a vector of Chagas disease

The saliva of hematophagous arthropods injected during blood feeding contains potent pharmacologically active components to counteract the host hemostatic and inflammatory systems. In the present study, dominant salivary gland transcripts of Panstrongylus chinai, a vector of Chagas disease, were analyzed by sequencing randomly selected clones of the salivary gland cDNA library. This analysis showed that 56.5% of the isolated transcripts coded for putative secreted proteins, of which 73.7% coded for proteins belonging to the lipocalin family. The most abundant transcript of lipocalin family proteins was a homologue of pallidipin 2, an inhibitor of collagen-induced platelet aggregation of Triatoma pallidipennis. In addition, homologues of triafestin, an inhibitor of the kallikrein-kinin system of T. infestans, were identified as the dominant transcript. Other salivary transcripts encoding lipocalin family proteins had homology to triplatin (an inhibitor of platelet aggregation) and others with unknown function. Other than lipocalin family proteins, homologues of a Kazal-type serine protease inhibitor (putative anticoagulant), a hemolysin-like protein (unknown function), inositol polyphosphate 5-related protein (a regulator of membrane phosphoinositide), antigen 5-related protein (unknown function) and apyrase (platelet aggregation inhibitor) were identified.

Proteases of haematophagous arthropod vectors are involved in blood-feeding, yolk formation and immunity - a review

Ticks, triatomines, mosquitoes and sand flies comprise a large number of haematophagous arthropods considered vectors of human infectious diseases. While consuming blood to obtain the nutrients necessary to carry on life functions, these insects can transmit pathogenic microorganisms to the vertebrate host. Among the molecules related to the blood-feeding habit, proteases play an essential role. In this review, we provide a panorama of proteases from arthropod vectors involved in haematophagy, in digestion, in egg development and in immunity. As these molecules act in central biological processes, proteases from haematophagous vectors of infectious diseases may influence vector competence to transmit pathogens to their prey, and thus could be valuable targets for vectorial control.

Structure and Ligand-Binding Mechanism of a Cysteinyl Leukotriene-Binding Protein from a Blood-Feeding Disease Vector

Blood-feeding disease vectors mitigate the negative effects of hemostasis and inflammation through the binding of small-molecule agonists of these processes by salivary proteins. In this study, a lipocalin protein family member (LTBP1) from the saliva of Rhodnius prolixus, a vector of the pathogen Trypanosoma cruzi, is shown to sequester cysteinyl leukotrienes during feeding to inhibit immediate inflammatory responses. Calorimetric binding experiments showed that LTBP1 binds leukotrienes C4 (LTC4), D4 (LTD4), and E4 (LTE4) but not biogenic amines, adenosine diphosphate, or other eicosanoid compounds. Crystal structures of ligand-free LTBP1 and its complexes with LTC4 and LTD4 reveal a conformational change during binding that brings Tyr114 into close contact with the ligand. LTC4 is cleaved in the complex, leaving free glutathione and a C20 fatty acid. Chromatographic analysis of bound ligands showed only intact LTC4, suggesting that cleavage could be radiation-mediated.

A Deep Insight into the Sialome of Rhodnius neglectus, a Vector of Chagas Disease

BACKGROUND

Triatomines are hematophagous insects that act as vectors of Chagas disease. Rhodnius neglectus is one of these kissing bugs found, contributing to the transmission of this American trypanosomiasis. The saliva of hematophagous arthropods contains bioactive molecules responsible for counteracting host haemostatic, inflammatory, and immune responses.

METHODS/PRINCIPAL FINDINGS

Next generation sequencing and mass spectrometry-based protein identification were performed to investigate the content of triatomine R. neglectus saliva. We deposited 4,230 coding DNA sequences (CDS) in GenBank. A set of 636 CDS of proteins of putative secretory nature was extracted from the assembled reads, 73 of them confirmed by proteomic analysis. The sialome of R. neglectus was characterized and serine protease transcripts detected. The presence of ubiquitous protein families was revealed, including lipocalins, serine protease inhibitors, and antigen-5. Metalloproteases, disintegrins, and odorant binding protein families were less abundant.

CONCLUSIONS/SIGNIFICANCE

The data presented improve our understanding of hematophagous arthropod sialomes, and aid in understanding hematophagy and the complex interplay among vectors and their vertebrate hosts.

An Insight into the Triabin Protein Family of American Hematophagous Reduviids: Functional, Structural and Phylogenetic Analysis

A transcriptomic analysis of the saliva of T. pallidipennis together with a short proteomic analysis were carried out to reveal novel primary structures of the lipocalin/triabin protein families in this reduviid. Although triabins share some structural characteristics to lipocalins and they are classified as in the calcyn/lipocalin superfamily, triabins differ from lipocalins in the direction of β-strands in the general conformation of the β-barrel. The triabin protein family encompasses a wide variety of proteins, which disrupt the hemostasis of warm-blooded animals. Likewise, the function of proteins classified as triabins includes proteins that are carriers of small molecules, protease inhibitors, binders of specific cell-surface receptors as well as proteins that form complexes with other macromolecules. For example, triabin and pallidipin from the saliva of T. pallidipennis are thrombin and platelet aggregation inhibitors, respectively; triplatin from T. infestans binds to thromboxane A2; and nitrophorin from Rhodnius prolixus carries nitric oxide. Therefore, based on 42 new transcriptome sequences of triabins from the salivary glands of T. pallidipennis reported at present, and on triabin sequences of other American hematophagous reduviids already reported in the literature, subfamilies of triabins were proposed following phylogenetic analyses and functional characterization of triabin members. Eight subfamilies of proteins were recognized with known functions, which were the nitrophorin and amine binding proteins, Rhodnius prolixus aggregation inhibitor, triafestin, triatin, dipetalodipin and pallidipin, triplatin and infestilin, dimiconin and triabin, and procalin subfamilies. Interestingly, 70% of the analyzed sequences came from these eight subfamilies because there was no biological function associated with them, implying the existence of a vast number of proteins with potential novel biological activities.

Venoms of Heteropteran Insects: A Treasure Trove of Diverse Pharmacological Toolkits

The piercing-sucking mouthparts of the true bugs (Insecta: Hemiptera: Heteroptera) have allowed diversification from a plant-feeding ancestor into a wide range of trophic strategies that include predation and blood-feeding. Crucial to the success of each of these strategies is the injection of venom. Here we review the current state of knowledge with regard to heteropteran venoms. Predaceous species produce venoms that induce rapid paralysis and liquefaction. These venoms are powerfully insecticidal, and may cause paralysis or death when injected into vertebrates. Disulfide-rich peptides, bioactive phospholipids, small molecules such as N,N-dimethylaniline and 1,2,5-trithiepane, and toxic enzymes such as phospholipase A2, have been reported in predatory venoms. However, the detailed composition and molecular targets of predatory venoms are largely unknown. In contrast, recent research into blood-feeding heteropterans has revealed the structure and function of many protein and non-protein components that facilitate acquisition of blood meals. Blood-feeding venoms lack paralytic or liquefying activity but instead are cocktails of pharmacological modulators that disable the host haemostatic systems simultaneously at multiple points. The multiple ways venom is used by heteropterans suggests that further study will reveal heteropteran venom components with a wide range of bioactivities that may be recruited for use as bioinsecticides, human therapeutics, and pharmacological tools.

Shared weapons of blood- and plant-feeding insects: Surprising commonalities for manipulating hosts

Insects that reprogram host plants during colonization remind us that the insect side of plant-insect story is just as interesting as the plant side. Insect effectors secreted by the salivary glands play an important role in plant reprogramming. Recent discoveries point to large numbers of salivary effectors being produced by a single herbivore species. Since genetic and functional characterization of effectors is an arduous task, narrowing the field of candidates is useful. We present ideas about types and functions of effectors from research on blood-feeding parasites and their mammalian hosts. Because of their importance for human health, blood-feeding parasites have more tools from genomics and other - omics than plant-feeding parasites. Four themes have emerged: (1) mechanical damage resulting from attack by blood-feeding parasites triggers "early danger signals" in mammalian hosts, which are mediated by eATP, calcium, and hydrogen peroxide, (2) mammalian hosts need to modulate their immune responses to the three "early danger signals" and use apyrases, calreticulins, and peroxiredoxins, respectively, to achieve this, (3) blood-feeding parasites, like their mammalian hosts, rely on some of the same "early danger signals" and modulate their immune responses using the same proteins, and (4) blood-feeding parasites deploy apyrases, calreticulins, and peroxiredoxins in their saliva to manipulate the "danger signals" of their mammalian hosts. We review emerging evidence that plant-feeding insects also interfere with "early danger signals" of their hosts by deploying apyrases, calreticulins and peroxiredoxins in saliva. Given emerging links between these molecules, and plant growth and defense, we propose that these effectors interfere with phytohormone signaling, and therefore have a special importance for gall-inducing and leaf-mining insects, which manipulate host-plants to create better food and shelter.

Cytogenetic Examination of South American Tapirs, Tapirus Terrestris (Perissodactyla, Tapiridae), from the Wroclaw Zoological Garden

Cytogenetic Examination of South American Tapirs, Tapirus terrestris (Perissodactyla, Tapiridae) from the Wroclaw Zoological Garden. Kosowska, B., Strzała, T., Moska, M., Ratajszczak, R., Dobosz, T. - Seven lowland tapirs (Tapirus terrestris) from Wrocław ZOO (three females and four males), differing from each other with exterior and sexual behaviour were verified with cytogenetic analysis in order to check their taxonomic status. Cytogenetic analysis was done using two alternative methods of blood collection: 1) conventionally with venepuncture, and 2) with blood sucking bugs from the Reduviidae family. Lymphocytes capable of growing were obtained only with conventional method of blood sampling. Karyotypes and karyograms of all analyzed tapirs were created using classical cytogenetic methods of chromosomes staining. All possessed karyograms had diploid chromosome number equal 80 (2n = 80). Homologous chromosomes did not differ between each other with quantity, size, centromeres location, length of arms, G bands and all were classified as proper karyograms of Tapirus terrestris species representatives. The X chromosomes as well as the first pair of chromosomes (both metacentric), were the largest among all analyzed, respectively. All remaining 38 pairs of chromosomes were acrocentric with Y chromosome as the smallest one (in males’ karyograms). Blood collected with blood sucking bugs proved to be unsuitable for cell culture. None of the seven established cultures was effective as lymphocytes obtained with this method did not show growth potential in prepared media. Thus, blood collected from the tapirs via Dipetalogaster maxima species did not show usefulness for cytogenetic studies due to the inability of cells to proliferation, even after a relatively short period of time elapsed since the blood sampling (1 to 2 hours).

The venomous cocktail of the vampire snail Colubraria reticulata (Mollusca, Gastropoda)

Background

Hematophagy arose independently multiple times during metazoan evolution, with several lineages of vampire animals particularly diversified in invertebrates. However, the biochemistry of hematophagy has been studied in a few species of direct medical interest and is still underdeveloped in most invertebrates, as in general is the study of venom toxins. In cone snails, leeches, arthropods and snakes, the strong target specificity of venom toxins uniquely aligns them to industrial and academic pursuits (pharmacological applications, pest control etc.) and provides a biochemical tool for studying biological activities including cell signalling and immunological response. Neogastropod snails (cones, oyster drills etc.) are carnivorous and include active predators, scavengers, grazers on sessile invertebrates and hematophagous parasites; most of them use venoms to efficiently feed. It has been hypothesized that trophic innovations were the main drivers of rapid radiation of Neogastropoda in the late Cretaceous.

We present here the first molecular characterization of the alimentary secretion of a non-conoidean neogastropod, Colubraria reticulata. Colubrariids successfully feed on the blood of fishes, throughout the secretion into the host of a complex mixture of anaesthetics and anticoagulants. We used a NGS RNA-Seq approach, integrated with differential expression analyses and custom searches for putative secreted feeding-related proteins, to describe in detail the salivary and mid-oesophageal transcriptomes of this Mediterranean vampire snail, with functional and evolutionary insights on major families of bioactive molecules.

Results

A remarkably low level of overlap was observed between the gene expression in the two target tissues, which also contained a high percentage of putatively secreted proteins when compared to the whole body. At least 12 families of feeding-related proteins were identified, including: 1) anaesthetics, such as ShK Toxin-containing proteins and turripeptides (ion-channel blockers), Cysteine-rich secretory proteins (CRISPs), Adenosine Deaminase (ADA); 2) inhibitors of primary haemostasis, such as novel vWFA domain-containing proteins, the Ectonucleotide pyrophosphatase/phosphodiesterase family member 5 (ENPP5) and the wasp Antigen-5; 3) anticoagulants, such as TFPI-like multiple Kunitz-type protease inhibitors, Peptidases S1 (PS1), CAP/ShKT domain-containing proteins, Astacin metalloproteases and Astacin/ShKT domain-containing proteins; 4) additional proteins, such the Angiotensin-Converting Enzyme (ACE: vasopressive) and the cytolytic Porins.

Conclusions

Colubraria feeding physiology seems to involve inhibitors of both primary and secondary haemostasis, anaesthetics, a vasoconstrictive enzyme to reduce feeding time and tissue-degrading proteins such as Porins and Astacins. The complexity of Colubraria venomous cocktail and the divergence from the arsenal of the few neogastropods studied to date (mostly conoideans) suggest that biochemical diversification of neogastropods might be largely underestimated and worth of extensive investigation.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1648-4) contains supplementary material, which is available to authorized users.

A Deep Insight Into the Sialotranscriptome of the Chagas Disease Vector, Panstrongylus megistus (Hemiptera: Heteroptera)

Saliva of blood-sucking arthropods contains a complex cocktail of pharmacologically active compounds that assists feeding by counteracting their hosts' hemostatic and inflammatory reactions. Panstrongylus megistus (Burmeister) is an important vector of Chagas disease in South America, but despite its importance there is only one salivary protein sequence publicly deposited in GenBank. In the present work, we used Illumina technology to disclose and publicly deposit 3,703 coding sequences obtained from the assembly of >70 million reads. These sequences should assist proteomic experiments aimed at identifying pharmacologically active proteins and immunological markers of vector exposure. A supplemental file of the transcriptome and deducted protein sequences can be obtained from http://exon.niaid.nih.gov/transcriptome/P_megistus/Pmeg-web.xlsx.

Identifying salivary antigens of Phlebotomus argentipes by a 2DE approach

In the Indian subcontinent visceral leishmaniasis, also known as kala-azar, is caused by the protozoa Leishmania donovani and is transmitted to humans by the bite of infected female sand flies Phlebotomus argentipes in an anthroponotic cycle. Sand fly saliva is known to play an important role in host infection outcome after an infective bite. Immunogenicity of P. argentipes saliva has already been described. However, specific antigens that can contribute to these immunogenic properties are unknown. This work focuses on the identification of antigens present in P. argentipes saliva through the combination of two-dimensional electrophoresis (2DE) and Western blot (WB). Analysis of the salivary protein profile showed a gradual increase of the protein content in relation to the age of sand flies, reaching the complete salivary protein pattern at day five, which marked the minimum age for dissections. The 2DE revealed a reproducible protein profile that matched the classic monodimensional SDS-PAGE pattern (1DE). The resulting salivary proteomic map consisted of at least 30 spots located between 10 and 60 kDa. According to their isoelectric points, spots were mostly distributed around pH ranges: 5-6 and 9-10. In the proteomic maps, the presence of isoforms or posttranslational modifications was also highlighted since several spots were identified as the same protein. Analysis by in silico prediction programs located several potential glycosylation and phosphorylation sites in the aminoacidic sequences. On the other hand, pooled sera of immunized hamsters through the bite of uninfected sand flies showed elevated anti-saliva IgG levels. These sera permitted the detection of 4 protein bands and at least 20 protein spots in 1DE and 2DE respectively, followed by WB. The antigens were identified by MALDI-TOF, MALDI-TOF/TOF and de novo sequencing as D7-related proteins, PpSP15-like proteins, antigen 5-related proteins, apyrases, and several proteins without assigned protein family. Absence of cross-reactivity between P. argentipes and Phlebotomus perniciosus saliva antibodies determined by ELISA and WB was highlighted in this study, confirming that specific salivary antigens from different sand fly vectors need to be sought when designing vector-borne vaccines and markers for vector exposure assays.

Salivary antigen-5/CAP family members are Cu2+-dependent antioxidant enzymes that scavenge O₂₋. and inhibit collagen-induced platelet aggregation and neutrophil oxidative burst

The function of the antigen-5/CAP family of proteins found in the salivary gland of bloodsucking animals has remained elusive for decades. Antigen-5 members from the hematophagous insects Dipetalogaster maxima (DMAV) and Triatoma infestans (TIAV) were expressed and discovered to attenuate platelet aggregation, ATP secretion, and thromboxane A2 generation by low doses of collagen (<1 μg/ml) but no other agonists. DMAV did not interact with collagen, glycoprotein VI, or integrin α2β1. This inhibitory profile resembles the effects of antioxidants Cu,Zn-superoxide dismutase (Cu,Zn-SOD) in platelet function. Accordingly, DMAV was found to inhibit cytochrome c reduction by O2[Symbol: see text] generated by the xanthine/xanthine oxidase, implying that it exhibits antioxidant activity. Moreover, our results demonstrate that DMAV blunts the luminescence signal of O2[Symbol: see text] generated by phorbol 12-myristate 13-acetate-stimulated neutrophils. Mechanistically, inductively coupled plasma mass spectrometry and fluorescence spectroscopy revealed that DMAV, like Cu,Zn-SOD, interacts with Cu(2+), which provides redox potential for catalytic removal of O2[Symbol: see text]. Notably, surface plasmon resonance experiments (BIAcore) determined that DMAV binds sulfated glycosaminoglycans (e.g. heparin, KD ~100 nmol/liter), as reported for extracellular SOD. Finally, fractions of the salivary gland of D. maxima with native DMAV contain Cu(2+) and display metal-dependent antioxidant properties. Antigen-5/CAP emerges as novel family of Cu(2+)-dependent antioxidant enzymes that inhibit neutrophil oxidative burst and negatively modulate platelet aggregation by a unique salivary mechanism.

Role of immune cell subsets in the establishment of vector-borne infections

Many of the pathogens responsible for diseases that result in both economic and global health burdens are transmitted by arthropod vectors in the course of a blood meal. In the past, these vectors were viewed mainly as simple delivery vehicles but the appreciation of the role that factors in the saliva of vectors play during pathogen transmission is increasing. Vector saliva proteins alter numerous physiological events in the skin; in addition, potent immunomodulatory properties are attributed to arthropod saliva. The description of specific factors responsible for these activities and their mechanisms of action have thus far remained mostly anecdotal. The National Institute of Allergy and Infectious Diseases (NIAID) sponsored a workshop in May 2012 to explore novel approaches aimed at identifying how vector saliva components affect the function of various immune cell subsets and the subsequent impact on the transmission of vector-borne pathogens. Such knowledge could guide the development of novel drugs, vaccines and other strategies to block the transmission of vector-borne pathogens. This meeting report summarizes the discussions of the gaps/challenges which represent attractive research opportunities with significant translational potential.

Application of RNA interference in triatomine (Hemiptera: Reduviidae) studies

Triatomines (Hemiptera: Reduviidae) are obligate hematophagous insects. They are of medical importance because they are vectors of Trypanosoma cruzi, the causative agent of Chagas disease in the Americas. In recent years, the RNA interference (RNAi) technology has emerged as a practical and useful alternative means of studying gene function in insects, including triatomine bugs. RNAi research in triatomines is still in its early stages, several issues still need to be elucidated, including the description of the molecules involved in the RNAi machinery and aspects related to phenotype evaluation and persistence of the knockdown in different tissues and organs. This review considers recent applications of RNAi to triatomine research, describing the major methods that have been applied during the knockdown process such as the double-stranded RNA delivery mechanism (injection, microinjection, or ingestion) and the phenotype characterization (mRNA and target protein levels) in studies conducted with the intent to provide greater insights into the biology of these insects. In addition to the characterization of insect biomolecules, some with biopharmacological potential, RNAi may provide a new view of the interaction between triatomine and trypanosomatids, enabling the development of new measures for vector control and transmission of the parasite.

Structure and ligand-binding properties of the biogenic amine-binding protein from the saliva of a blood-feeding insect vector of Trypanosoma cruzi

Proteins that bind small-molecule mediators of inflammation and hemostasis are essential for blood-feeding by arthropod vectors of infectious disease. In ticks and triatomine insects, the lipocalin protein family is greatly expanded and members have been shown to bind biogenic amines, eicosanoids and ADP. These compounds are potent mediators of platelet activation, inflammation and vascular tone. In this paper, the structure of the amine-binding protein (ABP) from Rhodnius prolixus, a vector of the trypanosome that causes Chagas disease, is described. ABP binds the biogenic amines serotonin and norepinephrine with high affinity. A complex with tryptamine shows the presence of a binding site for a single ligand molecule in the central cavity of the β-barrel structure. The cavity contains significant additional volume, suggesting that this protein may have evolved from the related nitrophorin proteins, which bind a much larger heme ligand in the central cavity.

Genome-wide transcriptome and proteome analysis on different developmental stages of Cordyceps militaris

BACKGROUND

Cordyceps militaris, an ascomycete caterpillar fungus, has been used as a traditional Chinese medicine for many years owing to its anticancer and immunomodulatory activities. Currently, artificial culturing of this beneficial fungus has been widely used and can meet the market, but systematic molecular studies on the developmental stages of cultured C. militaris at transcriptional and translational levels have not been determined.

METHODOLOGY/PRINCIPAL FINDINGS

We utilized high-throughput Illumina sequencing to obtain the transcriptomes of C. militaris mycelium and fruiting body. All clean reads were mapped to C. militaris genome and most of the reads showed perfect coverage. Alternative splicing and novel transcripts were predicted to enrich the database. Gene expression analysis revealed that 2,113 genes were up-regulated in mycelium and 599 in fruiting body. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis were performed to analyze the genes with expression differences. Moreover, the putative cordycepin metabolism difference between different developmental stages was studied. In addition, the proteome data of mycelium and fruiting body were obtained by one-dimensional gel electrophoresis (1-DGE) coupled with nano-electrospray ionization liquid chromatography tandem mass spectrometry (nESI-LC-MS/MS). 359 and 214 proteins were detected from mycelium and fruiting body respectively. GO, KEGG and Cluster of Orthologous Groups (COG) analysis were further conducted to better understand their difference. We analyzed the amounts of some noteworthy proteins in these two samples including lectin, superoxide dismutase, glycoside hydrolase and proteins involved in cordycepin metabolism, providing important information for further protein studies.

CONCLUSIONS/SIGNIFICANCE

The results reveal the difference in gene expression between the mycelium and fruiting body of artificially cultivated C. militaris by transcriptome and proteome analysis. Our study provides an effective resource for the further developmental and medicinal research of this promising fungus.

An insight into the sialotranscriptome of Triatoma matogrossensis, a kissing bug associated with fogo selvagem in South America

Triatoma matogrossensis is a Hemiptera that belongs to the oliveirai complex, a vector of Chagas' disease that feeds on vertebrate blood in all life stages. Hematophagous insects' salivary glands (SGs) produce potent pharmacologic compounds that counteract host hemostasis, including anticlotting, antiplatelet, and vasodilatory molecules. Exposure to T. matogrossensis was also found to be a risk factor associated with the endemic form of the autoimmune skin disease pemphigus foliaceus, which is described in the same regions where Chagas' disease is observed in Brazil. To obtain a further insight into the salivary biochemical and pharmacologic diversity of this kissing bug and to identify possible allergens that might be associated with this autoimmune disease, a cDNA library from its SGs was randomly sequenced. We present the analysis of a set of 2,230 (SG) cDNA sequences, 1,182 of which coded for proteins of a putative secretory nature.

Interactome: Smart hematophagous triatomine salivary gland molecules counteract human hemostasis during meal acquisition

Human populations are constantly plagued by hematophagous insects' bites, in particular the triatomine insects that are vectors of the Trypanosoma cruzi agent in Chagas disease. The pharmacologically-active molecules present in the salivary glands of hematophagous insects are injected into the human skin to initiate acquisition of blood meals. Sets of vasodilators, anti-platelet aggregators, anti-coagulants, immunogenic polypeptides, anesthetics, odorants, antibiotics, and detoxifying molecules have been disclosed with the aid of proteomics and recombinant cDNA techniques. These molecules can provide insights about the insect-pathogen-host interactions essential for understanding the physiopathology of the insect bite. The data and information presented in this review aim for the development of new drugs to prevent insect bites and the insect-transmitted endemic of Chagas disease.

An insight into the sialotranscriptome of Triatoma rubida (Hemiptera: Heteroptera)

The kissing bug Triatoma rubida (Uhler, 1894) is found in southwestern United States and parts of Mexico where it is found infected with Trypanosoma cruzi, invades human dwellings and causes allergies from their bites. Although the protein salivary composition of several triatomine species is known, not a single salivary protein sequence is known from T. rubida. Furthermore, the salivary diversity of related hematophagous arthropods is very large probably because of the immune pressure from their hosts. Here we report the sialotranscriptome analysis of T. rubida based on the assembly of 1,820 high-quality expressed sequence tags, 51% of which code for putative secreted peptides, including lipocalins, members of the antigen five family, apyrase, hemolysin, and trialysin families. Interestingly, T. rubida lipocalins are at best 40% identical in primary sequence to those of T. protracta, a kissing bug that overlaps its range with T. rubida, indicating the diversity of the salivary lipocalins among species of the same hematophagous genus. We additionally found several expressed sequence tags coding for proteins of clear Trypanosoma spp. origin. This work contributes to the future development of markers of human and pet exposure to T. rubida and to the possible development of desensitization therapies. Supp. Data 1 and 2 (online only) of the transcriptome and deducted protein sequences can be obtained from http://exon.niaid.nih.gov/transcriptome/Trubida/Triru-S1-web.xlsx and http://exon.niaid.nih.gov/transcriptome/Trubida/Triru-S2-web.xlsx.

Disintegrins from hematophagous sources

Bloodsucking arthropods are a rich source of salivary molecules (sialogenins) which inhibit platelet aggregation, neutrophil function and angiogenesis. Here we review the literature on salivary disintegrins and their targets. Disintegrins were first discovered in snake venoms, and were instrumental in our understanding of integrin function and also for the development of anti-thrombotic drugs. In hematophagous animals, most disintegrins described so far have been discovered in the salivary gland of ticks and leeches. A limited number have also been found in hookworms and horseflies, and none identified in mosquitoes or sand flies. The vast majority of salivary disintegrins reported display a RGD motif and were described as platelet aggregation inhibitors, and few others as negative modulator of neutrophil or endothelial cell functions. This notably low number of reported disintegrins is certainly an underestimation of the actual complexity of this family of proteins in hematophagous secretions. Therefore an algorithm was created in order to identify the tripeptide motifs RGD, KGD, VGD, MLD, KTS, RTS, WGD, or RED (flanked by cysteines) in sialogenins deposited in GenBank database. The search included sequences from various blood-sucking animals such as ticks (e.g., Ixodes sp., Argas sp., Rhipicephalus sp., Amblyommasp.), tabanids (e.g., Tabanus sp.), bugs (e.g., Triatoma sp., Rhodnius prolixus), mosquitoes (e.g., Anopheles sp., Aedes sp., Culex sp.), sand flies (e.g., Lutzomyia sp., Phlebotomus sp.), leeches (e.g., Macrobdella sp., Placobdella sp.) and worms (e.g., Ancylostoma sp.). This approach allowed the identification of a remarkably high number of novel putative sialogenins with tripeptide motifs typical of disintegrins (>450 sequences) whose biological activity remains to be verified. This database is accessible online as a hyperlinked worksheet and displays biochemical, taxonomic, and gene ontology aspects for each putative disintegrin. It is also freely available for download (right click with the mouse) at links http://exon.niaid.nih.gov/transcriptome/RGD/RGD-Peps-WEB.xlsx (web version) and http://exon.niaid.nih.gov/transcriptome/RGD/RGD-sialogenins.zip (stand alone version).

Dimiconin, a novel coagulation inhibitor from the kissing bug, Triatoma dimidiata, a vector of Chagas disease

Sequence analysis of Triatoma (T.) dimidiata salivary gland cDNA library resulted in the identification of two transcripts (Td60 and Td101) homologous to triabin, an inhibitor of thrombin in T. pallidipennis saliva. In the present study, a recombinant protein of Td60, designated dimiconin, was expressed in Escherichia coli and its activity was characterized. The resulting protein inhibited the intrinsic but not extrinsic blood coagulation pathway, suggesting that dimiconin is not a thrombin inhibitor. Measuring the enzymatic activity of coagulation factors using chromogenic substrates revealed that dimiconin efficiently inhibited factor XIIa (FXIIa) activity in a dose-dependent manner. In addition, pre-incubation of dimiconin with FXII effectively inhibited FXIIa activity whereas dimiconin did not affect already activated FXIIa, indicating that dimiconin inhibits the activation of FXII but not enzymatic activity of FXIIa. These results showed that dimiconin is an inhibitor of the contact phase initiated by FXII activation in the blood coagulation cascade, which differs from the bioactivity of triabin.

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.

Sialome of a generalist lepidopteran herbivore: identification of transcripts and proteins from Helicoverpa armigera labial salivary glands

Although the importance of insect saliva in insect-host plant interactions has been acknowledged, there is very limited information on the nature and complexity of the salivary proteome in lepidopteran herbivores. We inspected the labial salivary transcriptome and proteome of Helicoverpa armigera, an important polyphagous pest species. To identify the majority of the salivary proteins we have randomly sequenced 19,389 expressed sequence tags (ESTs) from a normalized cDNA library of salivary glands. In parallel, a non-cytosolic enriched protein fraction was obtained from labial salivary glands and subjected to two-dimensional gel electrophoresis (2-DE) and de novo peptide sequencing. This procedure allowed comparison of peptides and EST sequences and enabled us to identify 65 protein spots from the secreted labial saliva 2DE proteome. The mass spectrometry analysis revealed ecdysone, glucose oxidase, fructosidase, carboxyl/cholinesterase and an uncharacterized protein previously detected in H. armigera midgut proteome. Consistently, their corresponding transcripts are among the most abundant in our cDNA library. We did find redundancy of sequence identification of saliva-secreted proteins suggesting multiple isoforms. As expected, we found several enzymes responsible for digestion and plant offense. In addition, we identified non-digestive proteins such as an arginine kinase and abundant proteins of unknown function. This identification of secreted salivary gland proteins allows a more comprehensive understanding of insect feeding and poses new challenges for the elucidation of protein function.

A novel family of RGD-containing disintegrins (Tablysin-15) from the salivary gland of the horsefly Tabanus yao targets αIIbβ3 or αVβ3 and inhibits platelet aggregation and angiogenesis

A novel family of RGD-containing molecules (Tablysin-15) has been molecularly characterised from the salivary gland of the haematophagous horsefly Tabanus yao. Tablysin-15 does not share primary sequence homology to any disintegrin discovered so far, and displays an RGD motif in the N-terminus of the molecule. It is also distinct from disintegrins from Viperidae since its mature form is not released from a metalloproteinase precursor. Tablysin-15 exhibits high affinity binding for platelet αIIbβ3 and endothelial cell αVβ3 integrins, but not for α5β1 or α2β1. Accordingly, it blocks endothelial cell adhesion to vitronectin (IC50 ~1 nM) and marginally to fibronectin (IC50 ~1 μM), but not to collagen. It also inhibits fibroblast growth factor (FGF)-induced endothelial cell proliferation, and attenuates tube formation in vitro. In platelets, Tablysin-15 inhibits aggregation induced by collagen, ADP and convulxin, and prevents static platelet adhesion to immobilised fibrinogen. In addition, solid-phase assays and flow cytometry demonstrates that αIIbβ3 binds to Tablysin-15. Moreover, immobilised Tablysin-15 supports platelet adhesion by a mechanism which was blocked by anti-integrin αIIbβ3 monoclonal antibody (e.g. abciximab) or by EDTA. Furthermore, Tablysin-15 dose-dependently attenuates thrombus formation to collagen under flow. Consistent with these findings, Tablysin-15 displays antithrombotic properties in vivo suggesting that it is a useful tool to block αIIbβ3, or as a prototype to develop antithrombotics. The RGD motif in the unique sequence of Tablysin-15 represents a novel template for studying the structure-function relationship of the disintegrin family of inhibitors.

2-DE-based proteomic investigation of the saliva of the Amazonian triatomine vectors of Chagas disease: Rhodnius brethesi and Rhodnius robustus

The triatomine bugs are obligatory haematophagous organisms that act as vectors of Chagas disease by transmitting the protozoan Trypanosoma cruzi. Their feeding success is strongly related to salivary proteins that allow these insects to access blood by counteracting host haemostatic mechanisms. Proteomic studies were performed on saliva from the Amazonian triatomine bugs: Rhodnius brethesi and R. robustus, species epidemiologically relevant in the transmission of T. cruzi. Initially, salivary proteins were separated by two-dimensional gel electrophoresis (2-DE). The average number of spots of the R. brethesi and R. robustus saliva samples were 129 and 135, respectively. The 2-DE profiles were very similar between the two species. Identification of spots by peptide mass fingerprinting afforded limited efficiency, since very few species-specific salivary protein sequences are available in public sequence databases. Therefore, peptide fragmentation and de novo sequencing using a MALDI-TOF/TOF mass spectrometer were applied for similarity-driven identifications which generated very positive results. The data revealed mainly lipocalin-like proteins which promote blood feeding of these insects. The redundancy of saliva sequence identification suggested multiple isoforms caused by gene duplication followed by gene modification and/or post-translational modifications. In the first experimental assay, these proteins were predominantly phosphorylated, suggesting functional phosphoregulation of the lipocalins.