An immunoglobulin binding protein (antigen 5) of the stable fly (Diptera: Muscidae) salivary gland stimulates bovine immune responses

An insight into the female and male Sabethes cyaneus mosquito salivary glands transcriptome

Mosquitoes are responsible for the death and debilitation of millions of people every year due to the pathogens they can transmit while blood feeding. While a handful of mosquitoes, namely those in the Aedes, Anopheles, and Culex genus, are the dominant vectors, many other species belonging to different genus are also involved in various pathogen cycles. Sabethes cyaneus is one of the many poorly understood mosquito species involved in the sylvatic cycle of Yellow Fever Virus. Here, we report the expression profile differences between male and female of Sa.cyaneus salivary glands (SGs). We find that female Sa.cyaneus SGs have 165 up-regulated and 18 down-regulated genes compared to male SGs. Most of the up-regulated genes have unknown functions, however, odorant binding proteins, such as those in the D7 protein family, and mucins were among the top 30 genes. We also performed various in vitro activity assays of female SGs. In the activity analysis we found that female SG extracts inhibit coagulation by blocking factor Xa and has endonuclease activity. Knowledge about mosquitoes and their physiology are important for understanding how different species differ in their ability to feed on and transmits pathogens to humans. These results provide us with an insight into the Sabethes SG activity and gene expression that expands our understanding of mosquito salivary glands.

The genome of the stable fly, Stomoxys calcitrans, reveals potential mechanisms underlying reproduction, host interactions, and novel targets for pest control

Background

The stable fly, Stomoxys calcitrans, is a major blood-feeding pest of livestock that has near worldwide distribution, causing an annual cost of over $2 billion for control and product loss in the USA alone. Control of these flies has been limited to increased sanitary management practices and insecticide application for suppressing larval stages. Few genetic and molecular resources are available to help in developing novel methods for controlling stable flies.

Results

This study examines stable fly biology by utilizing a combination of high-quality genome sequencing and RNA-Seq analyses targeting multiple developmental stages and tissues. In conjunction, 1600 genes were manually curated to characterize genetic features related to stable fly reproduction, vector host interactions, host-microbe dynamics, and putative targets for control. Most notable was characterization of genes associated with reproduction and identification of expanded gene families with functional associations to vision, chemosensation, immunity, and metabolic detoxification pathways.

Conclusions

The combined sequencing, assembly, and curation of the male stable fly genome followed by RNA-Seq and downstream analyses provide insights necessary to understand the biology of this important pest. These resources and new data will provide the groundwork for expanding the tools available to control stable fly infestations. The close relationship of Stomoxys to other blood-feeding (horn flies and Glossina) and non-blood-feeding flies (house flies, medflies, Drosophila) will facilitate understanding of the evolutionary processes associated with development of blood feeding among the Cyclorrhapha.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12915-021-00975-9.

An insight into the sialome, mialome and virome of the horn fly, Haematobia irritans

BACKGROUND

The horn fly (Haematobia irritans) is an obligate blood feeder that causes considerable economic losses in livestock industries worldwide. The control of this cattle pest is mainly based on insecticides; unfortunately, in many regions, horn flies have developed resistance. Vaccines or biological control have been proposed as alternative control methods, but the available information about the biology or physiology of this parasite is rather scarce.

RESULTS

We present a comprehensive description of the salivary and midgut transcriptomes of the horn fly (Haematobia irritans), using deep sequencing achieved by the Illumina protocol, as well as exploring the virome of this fly. Comparison of the two transcriptomes allow for identification of uniquely salivary or uniquely midgut transcripts, as identified by statistically differential transcript expression at a level of 16 x or more. In addition, we provide genomic highlights and phylogenetic insights of Haematobia irritans Nora virus and present evidence of a novel densovirus, both associated to midgut libraries of H. irritans.

CONCLUSIONS

We provide a catalog of protein sequences associated with the salivary glands and midgut of the horn fly that will be useful for vaccine design. Additionally, we discover two midgut-associated viruses that infect these flies in nature. Future studies should address the prevalence, biological effects and life cycles of these viruses, which could eventually lead to translational work oriented to the control of this economically important cattle pest.

An insight into the sialotranscriptome and virome of Amazonian anophelines

Background

Saliva of mosquitoes contains anti-platelet, anti-clotting, vasodilatory, anti-complement and anti-inflammatory substances that help the blood feeding process. The salivary polypeptides are at a fast pace of evolution possibly due to their relative lack of structural constraint and possibly also by positive selection on their genes leading to evasion of host immune pressure.

Results

In this study, we used deep mRNA sequence to uncover for the first time the sialomes of four Amazonian anophelines species (Anopheles braziliensis, A. marajorara, A. nuneztovari and A. triannulatus) and extend the knowledge of the A. darlingi sialome. Two libraries were generated from A. darlingi mosquitoes, sampled from two localities separated ~ 1100 km apart. A total of 60,016 sequences were submitted to GenBank, which will help discovery of novel pharmacologically active polypeptides and the design of specific immunological markers of mosquito exposure. Additionally, in these analyses we identified and characterized novel phasmaviruses and anpheviruses associated to the sialomes of A. triannulatus, A. marajorara and A. darlingi species.

Conclusions

Besides their pharmacological properties, which may be exploited for the development of new drugs (e.g. anti-thrombotics), salivary proteins of blood feeding arthropods may be turned into tools to prevent and/or better control vector borne diseases; for example, through the development of vaccines or biomarkers to evaluate human exposure to vector bites. The sialotranscriptome study reported here provided novel data on four New World anopheline species and allowed to extend our knowledge on the salivary repertoire of A. darlingi. Additionally, we discovered novel viruses following analysis of the transcriptomes, a procedure that should become standard within future RNAseq studies.

Electronic supplementary material

The online version of this article (10.1186/s12864-019-5545-0) contains supplementary material, which is available to authorized users.

Hematobin is a novel immunomodulatory protein from the saliva of the horn fly Haematobia irritans that inhibits the inflammatory response in murine macrophages

Background

The horn fly Haematobia irritans is a blood-sucking ectoparasite responsible for substantial economic loss of livestock. Like other hematophagous arthropods species, the successful blood-feeding of H. irritans is highly dependent on the modulation of the host’s hemostasis and immune system. Here, we evaluated the biological activity of hematobin (HTB), a protein recently identified in the H. irritans saliva, on macrophage biology. The goal was to understand the putative interactions between the components of H. irritans saliva and the early host immune responses.

Results

Thioglycolate-elicited peritoneal macrophages from BALB/c mice were stimulated by lipopolysaccharide (LPS) plus interferon-γ (IFN-γ) in the presence or absence of recombinant HTB. The presence of the salivary protein in the cultures inhibited nitric oxide production and decreased the inducible nitric oxide synthase (iNOS) expression induced by LPS plus IFN-γ. The tumor necrosis factor-α (TNF-α) and interleukin-12p40 (IL-12p40) levels were also reduced in the macrophages pre-incubated with HTB; these findings correlated to the decreased NF-κB expression. The biological activities described here were not associated with changes in annexin V binding to macrophages suggesting that HTB does not induce cell death. In addition, the activity of HTB seems to be specific to macrophages because no changes were observed in lymphocyte proliferation or cytokine production.

Conclusions

We describe here the first bioactive salivary protein of H. irritans. We characterized its ability to modulate macrophage inflammatory response, and the results can help explain how horn flies modulate the host immune system to feed on blood.

Electronic supplementary material

The online version of this article (10.1186/s13071-018-3017-z) contains supplementary material, which is available to authorized users.

Anopheline salivary protein genes and gene families: an evolutionary overview after the whole genome sequence of sixteen Anopheles species

BACKGROUND

Mosquito saliva is a complex cocktail whose pharmacological properties play an essential role in blood feeding by counteracting host physiological response to tissue injury. Moreover, vector borne pathogens are transmitted to vertebrates and exposed to their immune system in the context of mosquito saliva which, in virtue of its immunomodulatory properties, can modify the local environment at the feeding site and eventually affect pathogen transmission. In addition, the host antibody response to salivary proteins may be used to assess human exposure to mosquito vectors. Even though the role of quite a few mosquito salivary proteins has been clarified in the last decade, we still completely ignore the physiological role of many of them as well as the extent of their involvement in the complex interactions taking place between the mosquito vectors, the pathogens they transmit and the vertebrate host. The recent release of the genomes of 16 Anopheles species offered the opportunity to get insights into function and evolution of salivary protein families in anopheline mosquitoes.

RESULTS

Orthologues of fifty three Anopheles gambiae salivary proteins were retrieved and annotated from 18 additional anopheline species belonging to the three subgenera Cellia, Anopheles, and Nyssorhynchus. Our analysis included 824 full-length salivary proteins from 24 different families and allowed the identification of 79 novel salivary genes and re-annotation of 379 wrong predictions. The comparative, structural and phylogenetic analyses yielded an unprecedented view of the anopheline salivary repertoires and of their evolution over 100 million years of anopheline radiation shedding light on mechanisms and evolutionary forces that contributed shaping the anopheline sialomes.

CONCLUSIONS

We provide here a comprehensive description, classification and evolutionary overview of the main anopheline salivary protein families and identify two novel candidate markers of human exposure to malaria vectors worldwide. This anopheline sialome catalogue, which is easily accessible as hyperlinked spreadsheet, is expected to be useful to the vector biology community and to improve the capacity to gain a deeper understanding of mosquito salivary proteins facilitating their possible exploitation for epidemiological and/or pathogen-vector-host interaction studies.

Dengue Virus Infection of Aedes aegypti Requires a Putative Cysteine Rich Venom Protein

Dengue virus (DENV) is a mosquito-borne flavivirus that causes serious human disease and mortality worldwide. There is no specific antiviral therapy or vaccine for DENV infection. Alterations in gene expression during DENV infection of the mosquito and the impact of these changes on virus infection are important events to investigate in hopes of creating new treatments and vaccines. We previously identified 203 genes that were ≥5-fold differentially upregulated during flavivirus infection of the mosquito. Here, we examined the impact of silencing 100 of the most highly upregulated gene targets on DENV infection in its mosquito vector. We identified 20 genes that reduced DENV infection by at least 60% when silenced. We focused on one gene, a putative cysteine rich venom protein (SeqID AAEL000379; CRVP379), whose silencing significantly reduced DENV infection in Aedes aegypti cells. Here, we examine the requirement for CRVP379 during DENV infection of the mosquito and investigate the mechanisms surrounding this phenomenon. We also show that blocking CRVP379 protein with either RNAi or specific antisera inhibits DENV infection in Aedes aegypti. This work identifies a novel mosquito gene target for controlling DENV infection in mosquitoes that may also be used to develop broad preventative and therapeutic measures for multiple flaviviruses.

An insight into the sialome of the horse fly, Tabanus bromius

Blood feeding animals face their host's defenses against tissue injury and blood loss while attempting to feed. One adaptation to surmount these barriers involves the evolution of a salivary potion that disarms their host's inflammatory and anti-hemostatic processes. The composition of the peptide moiety of this potion, or sialome (from the Greek sialo = saliva), can be deducted in part by proper interpretation of the blood feeder' sialotranscriptome. In this work we disclose the sialome of the blood feeding adult female Tabanus bromius. Following assembly of over 75 million Illumina reads (101 nt long) 16,683 contigs were obtained from which 4078 coding sequences were extracted. From these, 320 were assigned as coding for putative secreted proteins. These 320 contigs mapped 85% of the reads. The antigen-5 proteins family was studied in detail, indicating three Tabanus specific clades with and without disintegrin domains, as well as with and without leukotriene binding domains. Defensins were also detailed; a clade of salivary tabanid peptides was found lacking the propeptide domain ending in the KR dipeptide signaling furin cleavage. Novel protein families were also disclosed. Viral transcripts were identified closely matching the Kotonkan virus capsid proteins. Full length Mariner transposases were also identified. A total of 3043 coding sequences and their protein products were deposited in Genbank. Hyperlinked excel spreadsheets containing the coding sequences and their annotation are available at http://exon.niaid.nih.gov/transcriptome/T_bromius/Tbromius-web.xlsx (hyperlinked excel spreadsheet, 11 MB) and http://exon.niaid.nih.gov/transcriptome/T_bromius/Tbromius-SA.zip (Standalone excel with all local links, 360 MB). These sequences provide for a platform from which further proteomic studies may be designed to identify salivary proteins from T. bromius that are of pharmacological interest or used as immunological markers of host exposure.

An HIV-1 envelope immunogen with W427S mutation in CD4 binding site induced more T follicular helper memory cells and reduced non-specific antibody responses

The CD4 binding site (CD4BS) of the HIV-1 envelope glycoprotein (Env) contains epitopes for broadly neutralizing antibody (nAb) and is the target for the vaccine development. However, the CD4BS core including residues 425-430 overlaps the B cell superantigen site and may be related to B cell exhaustion in HIV-1 infection. Furthermore, production of nAb and high-affinity plasma cells needs germinal center reaction and the help of T follicular helper (Tfh) cells. We believe that strengthening the ability of Env CD4BS in inducing Tfh response and decreasing the effects of the superantigen are the strategies for eliciting nAb and development of HIV-1 vaccine. We constructed a gp120 mutant W427S of an HIV-1 primary R5 strain and examined its ability in the elicitation of Ab and the production of Tfh by immunization of BALB/c mice. We found that the trimeric wild-type gp120 can induce more non-specific antibody-secreting plasma cells, higher serum IgG secretion, and more Tfh cells by splenocyte. The modified W427S gp120 elicits higher levels of specific binding antibodies as well as nAbs though it produces less Tfh cells. Furthermore, higher Tfh cell frequency does not correlate to the specific binding Abs or nAbs indicating that the wild-type gp120 induced some non-specific Tfh that did not contribute to the production of specific Abs. This gp120 mutant led to more memory Tfh production, especially, the effector memory Tfh cells. Taken together, W427S gp120 could induce higher level of specific binding and neutralizing Ab production that may be associated with the reduction of non-specific Tfh but strengthening of the memory Tfh.

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

BACKGROUND

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

METHODOLOGY/PRINCIPAL FINDINGS

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

CONCLUSIONS/SIGNIFICANCE

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

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.

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

Background

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

Methodology/Principal Findings

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

Conclusions

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

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

A deep insight into the sialotranscriptome of the gulf coast tick, Amblyomma maculatum

Background

Saliva of blood sucking arthropods contains compounds that antagonize their hosts' hemostasis, which include platelet aggregation, vasoconstriction and blood clotting; saliva of these organisms also has anti-inflammatory and immunomodullatory properties. Perhaps because hosts mount an active immune response against these compounds, the diversity of these compounds is large even among related blood sucking species. Because of these properties, saliva helps blood feeding as well as help the establishment of pathogens that can be transmitted during blood feeding.

Methodology/Principal Findings

We have obtained 1,626,969 reads by pyrosequencing a salivary gland cDNA library from adult females Amblyomma maculatum ticks at different times of feeding. Assembly of this data produced 72,441 sequences larger than 149 nucleotides from which 15,914 coding sequences were extracted. Of these, 5,353 had >75% coverage to their best match in the non-redundant database from the National Center for Biotechnology information, allowing for the deposition of 4,850 sequences to GenBank. The annotated data sets are available as hyperlinked spreadsheets. Putative secreted proteins were classified in 133 families, most of which have no known function.

Conclusions/Significance

This data set of proteins constitutes a mining platform for novel pharmacologically active proteins and for uncovering vaccine targets against A. maculatum and the diseases they carry.

A further insight into the sialome of the tropical bont tick, Amblyomma variegatum

Background

Ticks--vectors of medical and veterinary importance--are themselves also significant pests. Tick salivary proteins are the result of adaptation to blood feeding and contain inhibitors of blood clotting, platelet aggregation, and angiogenesis, as well as vasodilators and immunomodulators. A previous analysis of the sialotranscriptome (from the Greek sialo, saliva) of Amblyomma variegatum is revisited in light of recent advances in tick sialomes and provides a database to perform a proteomic study.

Results

The clusterized data set has been expertly curated in light of recent reviews on tick salivary proteins, identifying many new families of tick-exclusive proteins. A proteome study using salivary gland homogenates identified 19 putative secreted proteins within a total of 211 matches.

Conclusions

The annotated sialome of A. variegatum allows its comparison to other tick sialomes, helping to consolidate an emerging pattern in the salivary composition of metastriate ticks; novel protein families were also identified. Because most of these proteins have no known function, the task of functional analysis of these proteins and the discovery of novel pharmacologically active compounds becomes possible.

Insight into the Sialome of the Bed Bug, Cimex lectularius

The evolution of insects to a blood diet leads to the development of a saliva that antagonizes their hosts' hemostasis and inflammation. Hemostasis and inflammation are redundant processes, and thus a complex salivary potion composed of dozens or near 100 different polypeptides is commonly found by transcriptome or proteome analysis of these organisms. Several insect orders or families evolved independently to hematophagy, creating unique salivary potions in the form of novel pharmacological use of endogenous substances and in the form of unique proteins not matching other known proteins, these probably arriving by fast evolution of salivary proteins as they evade their hosts' immune response. In this work we present a preliminary description of the sialome (from the Greek Sialo = saliva) of the common bed bug Cimex lectularius, the first such work from a member of the Cimicidae family. This manuscript is a guide for the supplemental database files http://exon.niaid.nih.gov/transcriptome/C_lectularius/S1/Cimex-S1.zip and http://exon.niaid.nih.gov/transcriptome/C_lectularius/S2/Cimex-S2.xls.

An insight into the sialome of blood-feeding Nematocera

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

An insight into the sialotranscriptome of Simulium nigrimanum, a black fly associated with fogo selvagem in South America

Pemphigus foliaceus is a life threatening skin disease that is associated with autoimmunity to desmoglein, a skin protein involved in the adhesion of keratinocytes. This disease is endemic in certain areas of South America, suggesting the mediation of environmental factors triggering autoimmunity. Among the possible environmental factors, exposure to bites of black flies, in particular Simulium nigrimanum has been suggested. In this work, we describe the sialotranscriptome of adult female S. nigrimanum flies. It reveals the complexity of the salivary potion of this insect, comprised by over 70 distinct genes within over 30 protein families, including several novel families, even when compared with the previously described sialotranscriptome of the autogenous black fly, S. vittatum. The uncovering of this sialotranscriptome provides a platform for testing pemphigus patient sera against recombinant salivary proteins from S. nigrimanum and for the discovery of novel pharmacologically active compounds.

The salivary gland transcriptome of the eastern tree hole mosquito, Ochlerotatus triseriatus

Saliva of blood-sucking arthropods contains a complex mixture of peptides that affect their host's hemostasis, inflammation, and immunity. These activities can also modify the site of pathogen delivery and increase disease transmission. Saliva also induces hosts to mount an antisaliva immune response that can lead to skin allergies or even anaphylaxis. Accordingly, knowledge of the salivary repertoire, or sialome, of a mosquito is useful to provide a knowledge platform to mine for novel pharmacological activities, to develop novel vaccine targets for vector-borne diseases, and to develop epidemiological markers of vector exposure and candidate desensitization vaccines. The mosquito Ochlerotatus triseriatus is a vector of La Crosse virus and produces allergy in humans. In this work, a total of 1,575 clones randomly selected from an adult female O. triseriatus salivary gland cDNA library was sequenced and used to assemble a database that yielded 731 clusters of related sequences, 560 of which were singletons. Primer extension experiments were performed in selected clones to further extend sequence coverage, allowing for the identification of 159 protein sequences, 66 of which code for putative secreted proteins. Supplemental spreadsheets containing these data are available at http://exon.niaid.nih.gov/transcriptome/Ochlerotatus_triseriatus/S1/Ot-S1.xls and http://exon.niaid. nih.gov/transcriptome/Ochlerotatus_triseriatus/S2/Ot-S2.xls.

An insight into the sialome of Glossina morsitans morsitans

BACKGROUND

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

RESULTS

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

CONCLUSIONS

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

An insight into the sialotranscriptome of the West Nile mosquito vector, Culex tarsalis

BACKGROUND

Saliva of adult female mosquitoes help sugar and blood feeding by providing enzymes and polypeptides that help sugar digestion, control microbial growth and counteract their vertebrate host hemostasis and inflammation. Mosquito saliva also potentiates the transmission of vector borne pathogens, including arboviruses. Culex tarsalis is a bird feeding mosquito vector of West Nile Virus closely related to C. quinquefasciatus, a mosquito relatively recently adapted to feed on humans, and the only mosquito of the genus Culex to have its sialotranscriptome so far described.

RESULTS

A total of 1,753 clones randomly selected from an adult female C. tarsalis salivary glands (SG) cDNA library were sequenced and used to assemble a database that yielded 809 clusters of related sequences, 675 of which were singletons. Primer extension experiments were performed in selected clones to further extend sequence coverage, allowing for the identification of 283 protein sequences, 80 of which code for putative secreted proteins.

CONCLUSION

Comparison of the C. tarsalis sialotranscriptome with that of C. quinquefasciatus reveals accelerated evolution of salivary proteins as compared to housekeeping proteins. The average amino acid identity among salivary proteins is 70.1%, while that for housekeeping proteins is 91.2% (P < 0.05), and the codon volatility of secreted proteins is significantly higher than those of housekeeping proteins. Several protein families previously found exclusive of mosquitoes, including only in the Aedes genus have been identified in C. tarsalis. Interestingly, a protein family so far unique to C. quinquefasciatus, with 30 genes, is also found in C. tarsalis, indicating it was not a specific C. quinquefasciatus acquisition in its evolution to optimize mammal blood feeding.

An insight into the transcriptome and proteome of the salivary gland of the stable fly, Stomoxys calcitrans

Adult stable flies are blood feeders, a nuisance, and mechanical vectors of veterinary diseases. To enable efficient feeding, blood sucking insects have evolved a sophisticated array of salivary compounds to disarm their host's hemostasis and inflammatory reaction. While the sialomes of several blood sucking Nematocera flies have been described, no thorough description has been made so far of any Brachycera, except for a detailed proteome analysis of a tabanid (Xu et al., 2008). In this work we provide an insight into the sialome of the muscid Stomoxys calcitrans, revealing a complex mixture of serine proteases, endonucleases, Kazal-containing peptides, anti-thrombins, antigen 5 related proteins, antimicrobial peptides, and the usual finding of mysterious secreted peptides that have no known partners, and may reflect the very fast evolution of salivary proteins due to the vertebrate host immune pressure. Supplemental Tables S1 and S2 can be downloaded from http://exon.niaid.nih.gov/transcriptome/S_calcitrans/T1/Sc-tb1-web.xls and http://exon.niaid.nih.gov/transcriptome/S_calcitrans/T2/Sc-tb2-web.xls.

The Toxicogenomic Multiverse: Convergent Recruitment of Proteins Into Animal Venoms

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

Identification of a functional Antigen5-related allergen in the saliva of a blood feeding insect, the tsetse fly

Our previous screening of a Glossina morsitans morsitans lamdagt11 salivary gland expression library with serum of a tsetse fly exposed rabbit identified a cDNA encoding Tsetse Antigen5 (TAg5, 28.9 kDa), a homologue of Antigen5 sting venom allergens. Recombinant TAg5 was produced in Sf9 cells in order to assess its immunogenic properties in humans. Plasma from a patient that previously exhibited anaphylactic reactions against tsetse fly bites contained circulating anti-TAg5 and anti-saliva IgEs. In a significant proportion of plasma samples of African individuals, TAg5 and saliva binding IgEs (respectively 56 and 65%) can be detected. Saliva, harvested from flies that were subjected to TAg5- specific RNA interference (RNAi), displayed significantly reduced IgE binding potential. Allergenic properties of TAg5 and tsetse fly saliva were further illustrated in immunized mice, using an immediate cutaneous hypersensitivity and passive cutaneous anaphylaxis assay. Collectively, TAg5 was illustrated to be a tsetse fly salivary allergen, demonstrating that Antigen5-related proteins are represented as functional allergens not only in stinging but also in blood feeding insects.