Acquired tick resistance (ATR) is well characterized in tick-exposed animals, compromising tick fitness through antibody-mediated activation of basophils. Yet, anti-tick vaccines inducing ATR have had limited success. Here, we describe a neuroimmune event preceding ATR that leads to rapid host-mediated tick removal. Tick-sensitized guinea pigs mechanically remove ticks within 3-6 hours via an acquired neuroimmune-induced itch response that correlates with increased dermal expression of itch-associated genes like OSM and skin infiltration by T cells and macrophages, independently of IgG and IgE antibodies. When we expose humans to ticks, a similar immune response is observed. Blocking T cells before tick sensitization prevents immune cell infiltration to bite sites and abrogates scratching and tick removal. This neuroimmune response is independent of Trpv1 as tick-sensitized guinea pigs treated with resiniferatoxin remove ticks effectively. Itch-induced tick removal or IITR offers a novel approach to tick-borne disease prevention through early tick detection and removal.

BACKGROUND: The lone star tick, Amblyomma americanum, is a three-host species widely distributed across North America and a vector for multiple human pathogens. Bites from this tick is also associated with alpha-gal syndrome, underscoring its growing public health importance. Adult female ticks undergo a prolonged feeding cycle divided into preparatory, slow-feeding, and rapid-feeding phases. Tick salivary glands are essential for successful blood feeding, producing a complex mixture of molecules that modulate host hemostasis, immunity, and tissue repair. The dynamic remodeling of the salivary gland transcriptome and proteome, termed the sialome switch, is thought to support prolonged feeding and immune evasion. To investigate the molecular mechanisms underlying the sialome switch, we performed high-throughput transcriptomic profiling of salivary glands from A. americanum adult females across the feeding cycle. RESULTS: Unlike previous studies that described the sialome switch in A. americanum by pooling ticks according to time post-attachment, we classified individuals based on average body weight, defining seven feeding stages encompassing unfed, slow-feeding, and rapid-feeding ticks. We identified 18,704 putative coding sequences (CDS) and revealed five distinct transcriptional profiles corresponding to different feeding stages. Unsupervised clustering indicated that most CDS were stage-specifically expressed, with temporal shifts observed in different protein families, including Kunitz-type, lipocalins, metalloproteases, and evasins. The transition from unfed to the slow-feeding phase corresponded to expression of a distinct subset of CDS within the signal transduction class, suggesting potential signaling pathways responsible for regulating this dynamic process. CONCLUSIONS: This study provides a high-resolution view of transcriptional dynamics in A. americanum salivary glands and identifies candidate molecular pathways regulating the sialome switch. These findings advance understanding of tick feeding biology and shed light on strategies ticks use to evade host defenses during prolonged blood meals.

Human body lice, Pediculus humanus humanus, are blood-feeding parasites that live in clothing and feed several times per day. Saliva injected during louse feeding induces pruritis and local inflammation in the skin. If untreated, chronic Pediculosis can cause systemic negative health effects. Despite the medical importance of body lice and their longstanding association with humans, characterization of their saliva has been limited. To address this, we extracted RNA and protein from two of the body louse's morphologically distinct sets of salivary glands (Bean-shaped and U-shaped) and generated transcript and protein profiles for each. Additionally, we performed fluorescent staining and confocal microscopy on each gland type to enhance descriptions of their structure and gross cellular architecture. Analysis of body louse salivary gene products and proteins revealed that the overwhelming majority were not closely related to biomolecules of known function, highlighting the organism's unique and understudied saliva composition. Despite the contrasting morphology of the two gland types, there was a high degree of overlap in the salivary products produced. This finding suggests strong Darwinian selection pressure to maintain both salivary gland types, given that it would be simpler to have a single morphologically identical set of glands. Here we present the first next-generation sequencing and proteomic characterization of the human body louse sialome, discuss the potential physiological importance of louse salivary proteins, and consider possible explanations for why lice have a complex salivary gland system despite inordinate redundancy in the protein repertoire of the Bean- and U-shaped salivary glands.

The Oriental rat flea, Xenopsylla cheopis, is a main vector of plague caused by the bacterium Yersinia pestis. Transcriptomic analysis of this insect and the interaction between Yersinia and the flea digestive tract have been the subject of several studies. However, to develop more refined studies on this vector in the future, we sequence and describe a draft genome of the rat flea Xenopsylla cheopis, discuss the physiological implications of its genetic features, and compare them with the only other sequenced member of the Siphonaptera, the cat flea, Ctenocephalides felis. Sequencing data from both long and short reads were assembled into 7,694 contigs, from which 95,638 putative coding sequences (CDSs) were extracted and functionally annotated, providing insights into various aspects of flea physiology. This includes the identification of putative salivary proteins, such as acid phosphatases and FS-H/I, associated with blood acquisition; classification of multiple serine peptidases likely representing the primary digestive enzymes of X.cheopis; and the identification of all enzymes involved in heme biosynthesis, as well as heme oxygenases and unique heme-binding proteins potentially involved in heme detoxification. Comparison of detoxification-related genes—namely those in the cytochrome P450, carboxylesterase, and glutathione S-transferase families—with homologs from the cat flea (C. felis) revealed the presence of a platelet-activating factor (PAF) acetyl hydrolase that appears to be unique to rat fleas, cat fleas, and human head and body lice, but is absent in other blood-feeding arthropods. Additionally, we identified key components of immune-related pathways known from other arthropods, including the Toll, IMD, and JAK/STAT pathways. Finally, a contig encoding a novel bacterium was discovered within the assembled flea genome. Phylogenetic analysis of the Wolbachia endosymbiont in X. cheopis suggests it is closely related to the Wolbachia strain found in Drosophila melanogaster. The disclosure of the X. cheopis genome, together with its Wolbachia symbiont, should advance research on the biology of this vector.

The house fly, Musca domestica, serves as a mechanical vector for numerous pathogens, posing a significant risk to human and animal health. More than two decades ago, the Musca domestica salivary gland hypertrophy virus (MdSGHV) was discovered, infecting both males and females flies and disrupting mating and the reproductive process. While MdSGHV can infect various tissues, its primary replication site is the house fly salivary gland. It is well established that arthropod salivary glands play an important role not only in acquiring food but also in transmitting pathogens. Therefore, understanding the composition of vector salivary glands and the interactions between vector and pathogen components is essential for developing future control strategies. To this end, we conducted a comprehensive RNA-sequencing of salivary glands from both infected and non-infected house flies. Our analysis identified a total of 6,410 putative sequences, with 6,309 originating from M. domestica and 101 from the MdSGHV, categorized into 25 functional groups. Furthermore, differential expression analysis between infected and non-infected salivary glands revealed 2,852 significantly modulated transcripts, highlighting profound transcriptional changes triggered by MdSGHV infection. Overall, these findings not only deepen our understanding of the composition of M. domestica salivary glands but also provide valuable insight into the virus-vector interaction, which could serve as a model to understand other medically relevant interactions.

Plasmodium sporozoites, the infective stage of malaria, must invade the mosquito salivary glands (SGs) before being transmitted to a vertebrate host. However, the physiological and biochemical effects of this invasion remain largely unexplored. We examined the impact of Plasmodium infection on Anopheles gambiae salivary glands using high-resolution proteomics, gene expression, and morphological analysis. The data reveal differential expression of various proteins, including the enrichment of hemolymph-derived humoral proteins in infected salivary glands. These proteins diffuse into the SGs due to structural damage caused by the sporozoites during invasion, while saliva proteins diffuse out into the circulation. Moreover, proteomic analysis of saliva from P. berghei- or P. falciparum-infected mosquitoes revealed changes in composition, with a pronounced reduction of immune proteins relative to uninfected mosquitoes. This reduction is likely due to the association of these proteins with the surface of sporozoites and/or changes in the saliva's physical properties within the invaded salivary secretory cavities. The saliva protein profiles from mosquitoes infected with both Plasmodium species are remarkably similar, suggesting a conserved interaction between sporozoites and salivary glands. Our results provide a foundation for understanding the molecular interactions between Plasmodium sporozoites and mosquito salivary glands.

BackgroundFemale ticks remain attached to their host for multiple days to complete a blood meal. This prolonged feeding period is accompanied by a significant increase in the tick's size and body weight, paralleled by noteworthy changes to the tick midgut. While the midgut is recognized for its established role in blood storage and processing, its importance extends to playing a crucial role in the acquisition, survival, and proliferation of pathogens. Despite this, our overall understanding of tick midgut biology is limited.ResultsOur transcriptome analysis identified 15,599 putative DNA coding sequences (CDS), which were classified into 26 functional groups. Dimensional and differential expression analyses revealed four primary transcriptional profiles corresponding to unfed, slow-feeding, transitory (from slow- to rapid-feeding), and rapid-feeding stages. Additionally, comparing the current dataset with previously deposited transcriptome from other tick species allowed the identification of commonly expressed transcripts across different feeding stages.ConclusionOur findings provide a detailed temporal resolution of numerous metabolic pathways in the midgut of A. americanum adult females throughout the feeding process, highlighting the dynamic transcriptional regulation of the tick's midgut as feeding progresses. Furthermore, we identified conserved transcripts across three different tick species that exhibit similar expression patterns. This knowledge not only enhances our understanding of the physiological processes within the tick midgut but also opens up potential avenues for developing control methods that target multiple tick species.

Toxorhynchites mosquitoes have an exclusively phytophagous feeding habit as adults, which leads to significant differences in their morphophysiology compared with haematophagous mosquitoes. However, the molecular mechanisms of digestion in this mosquito are not well understood. In this study, RNA sequencing of the posterior midgut (PMG) of the mosquito Toxorhynchites theobaldi was undertaken, highlighting its significance in mosquito digestion. Subsequently, a comparison was made between the differential gene expression of the PMG and that of the anterior midgut. It was found that the most abundant proteases in the PMG were trypsin and chymotrypsin, and the level of gene expression for enzymes essential for digestion (such as serine protease, α-amylase and pancreatic triacylglycerol lipase) and innate immune response (including catalase, cecropin-A2 and superoxide dismutase) was like that of haematophagous mosquitoes. Peritrophin-1 was detected in the entire midgut, with an elevated expression level in the PMG. Based on our findings, it is hypothesized that a non-haematophagic habit might have been exhibited by the ancestor of Tx. theobaldi, and this trait may have been retained. This study represents a pioneering investigation at the molecular level of midgut contents in a non-haematophagous mosquito. The findings offer valuable insights into the evolutionary aspects of feeding habits in culicids.

Blood-feeding behavior has independently evolved in arthropods multiple times. Unlike hard ticks, soft ticks employ a rapid-feeding strategy for hematophagy, and there are comparatively limited studies on the transcriptomes of these organisms. This study investigates the soft tick Ornithodoros hermsi, conducting histopathological examinations at bitten skin sites and tick whole-body transcriptomic analyses across various developmental and feeding stages, including larvae, 1st-nymphal, and 2nd-nymphal stages. The results revealed the ability of O. hermsi to induce skin hemorrhage at the bite sites. Transcriptomic analyses identified three consistent transcriptional profiles: unfed, early-fed (6 h, 12 h, 24 h), and late-fed (5 days). The unfed profile exhibited high transcriptional activity across most of the functional classes annotated. In contrast, early-fed stages exhibited decreased expression of most functional classes, except for the unknown, which is highly expressed. Finally, transcriptional expression of most functional classes increased in the late-fed groups, resembling the baseline expression observed in the unfed groups. These findings highlight intense pre-feeding transcriptional activity in O. hermsi ticks, aligning with their rapid-feeding strategy. Moreover, besides shedding light on the temporal dynamics of key pathways during blood meal processing and tick development, this study contributes significantly to the transcriptome repertoire of a medically relevant soft tick species with relatively limited prior knowledge.

IntroductionTicks rely on robust cellular and humoral responses to control microbial infection. However, several aspects of the tick's innate immune system remain uncharacterized, most notably that of the immune cells (called hemocytes), which are known to play a significant role in cellular and humoral responses. Despite the importance of hemocytes in regulating microbial infection, our understanding of their basic biology and molecular mechanisms remains limited. Therefore, we believe that a more detailed understanding of the role of hemocytes in the interactions between ticks and tick-borne microbes is crucial to illuminating their function in vector competence and to help identify novel targets for developing new strategies to block tick-borne pathogen transmission.MethodsThis study examined hemocytes from the lone star tick (Amblyomma americanum) at the transcriptomic level using the 10X genomics single-cell RNA sequencing platform to analyze hemocyte populations from unfed, partially blood-fed, and Ehrlichia chaffeensis-infected ticks. The functional role of differentially expressed hemocyte markers in hemocyte proliferation and Ehrlichia dissemination was determined using an RNA interference approach.Results and discussionOur data exhibit the identification of fourteen distinct hemocyte populations. Our results uncover seven distinct lineages present in uninfected and Ehrlichia-infected hemocyte clusters. The functional characterization of hemocytin, cystatin, fibronectin, and lipocalin demonstrate their role in hemocyte population changes, proliferation, and Ehrlichia dissemination.ConclusionOur results uncover the tick immune responses to Ehrlichia infection and hematophagy at a single-cell resolution. This work opens a new field of tick innate immunobiology to understand the role of hemocytes, particularly in response to prolonged blood-feeding (hematophagy), and tick-microbial interactions.

Background:Female ticks remain attached to their host for multiple days to complete a blood meal. This prolonged feeding period is accompanied by a significant increase in the tick's size and body weight, paralleled by noteworthy changes to the tick midgut. While the midgut is recognized for its established role in blood storage and processing, its importance extends to playing a crucial role in the acquisition, survival, and proliferation of pathogens. Despite this, our overall understanding of tick midgut biology is limited. Results:We conducted a comprehensive longitudinal transcriptome analysis of the midgut in adult female A. americanum ticks across various feeding stages, including unfed, slow-feeding, and rapid-feeding phases. Our analysis revealed 15,599 putative DNA coding sequences (CDS) classified within 26 functional groups. Dimensional and differential expression analysis highlighted the dynamic transcriptional changes in the tick midgut as feeding progresses, particularly during the initial period of feeding and the transition from the slow-feeding to the rapid-feeding phase. Additionally, we performed an orthology analysis comparing our dataset with midgut transcriptomes from other hard ticks, such as Ixodes scapularis and Rhipicephalus microplus. This comparison allowed us to identify transcripts commonly expressed during different feeding phases across these three species. Conclusion:Our findings provide a detailed temporal resolution of numerous metabolic pathways in A. americanum, emphasizing the dynamic transcriptional changes occurring in the tick midgut throughout the feeding process. Furthermore, we identified conserved transcripts across three different tick species that exhibit similar expression patterns. This knowledge has significant implications for future research aimed at deciphering the physiological pathways relevant within the tick midgut. It also offers potential avenues for developing control methods that target multiple tick species.

In arthropods, hemolymph carries immune cells and solubilizes and transports nutrients, hormones, and other molecules that are involved in diverse physiological processes including immunity, metabolism, and reproduction. However, despite such physiological importance, little is known about its composition. We applied mass spectrometry-based label-free quantification approaches to study the proteome of hemolymph perfused from sugar-fed female and male Aedes aegypti mosquitoes. A total of 1403 proteins were identified, out of which 447 of them were predicted to be extracellular. In both sexes, almost half of these extracellular proteins were predicted to be involved in defense/immune response, and their relative abundances (based on their intensity-based absolute quantification, iBAQ) were 37.9 and 33.2%, respectively. Interestingly, among them, 102 serine proteases/serine protease-homologues were identified, with almost half of them containing CLIP regulatory domains. Moreover, proteins belonging to families classically described as chemoreceptors, such as odorant-binding proteins (OBPs) and chemosensory proteins (CSPs), were also highly abundant in the hemolymph of both sexes. Our data provide a comprehensive catalogue of A. aegypti hemolymph basal protein content, revealing numerous unexplored targets for future research on mosquito physiology and disease transmission. It also provides a reference for future studies on the effect of blood meal and infection on hemolymph composition.

[This corrects the article DOI: 10.3389/fimmu.2023.1305976.].

Salivary complement inhibitors occur in many of the blood feeding arthropod species responsible for transmission of pathogens. During feeding, these inhibitors prevent the production of proinflammatory anaphylatoxins, which may interfere with feeding, and limit formation of the membrane attack complex which could damage arthropod gut tissues. Salivary inhibitors are, in many cases, novel proteins which may be pharmaceutically useful or display unusual mechanisms that could be exploited pharmaceutically. Albicin is a potent inhibitor of the alternative pathway of complement from the saliva of the malaria transmitting mosquito, Anopheles albimanus. Here we describe the cryo-EM structure of albicin bound to C3bBb, the alternative C3 convertase, a proteolytic complex that is responsible for cleavage of C3 and amplification of the complement response. Albicin is shown to induce dimerization of C3bBb, in a manner similar to the bacterial inhibitor SCIN, to form an inactive complex unable to bind the substrate C3. Size exclusion chromatography and structures determined after 30 minutes of incubation of C3b, factor B (FB), factor D (FD) and albicin indicate that FBb dissociates from the inhibited dimeric complex leaving a C3b-albicin dimeric complex which apparently decays more slowly. Structural analysis using cryo-EM reveals that albicin, an inhibitor of the alternative pathway of complement from the saliva of a mosquito, binds the C3bBb complex through contacts with both chains of C3b as well as the protease factor B.

The hematophagy behavior has evolved independently several times within the Arthropoda phylum. Interestingly, the process of acquiring a blood meal in ticks is considerably distinct from that observed in other blood-feeding arthropods. Instead of taking seconds to minutes to complete a blood meal, an adult female Ixodes scapularis tick can remain attached to its host for numerous days. During this extended feeding period, the tick undergoes drastic morphological changes. It is well established that the tick midgut plays a pivotal role not only in blood meal digestion but also in pathogen acquisition and transmission. However, our understanding of the underlying molecular mechanisms involved in these events remains limited. To expedite tick research, we conducted a comprehensive longitudinal RNA-sequencing of the tick midgut before, during, and after feeding. By collecting ticks in different feeding stages (unfed, slow feeding, rapid feeding, and early post-detached), we obtained a comprehensive overview of the transcripts present in each stage and the dynamic transcriptional changes that occur between them. This provides valuable insights into tick physiology. Additionally, through unsupervised clustering, we identified transcripts with similar patterns and stage-specific sequences. These findings serve as a foundation for selecting targets in the development of anti-tick control strategies and facilitate a better understanding of how blood feeding and pathogen infection impact tick physiology.

Inhibitors of complement and coagulation are present in the saliva of a variety of blood feeding arthropods that transmit parasitic and viral pathogens. Here we describe the structure and mechanism of action of the sand fly salivary protein lufaxin, which inhibits formation of the central alternative C3 convertase (C3bBb) and inhibits coagulation factor Xa (fXa). Surface plasmon resonance experiments show that lufaxin stabilizes the binding of the serine protease factor B (FB) to C3b but does not detectably bind either C3b or FB alone. The crystal structure of the inhibitor reveals a novel all β-sheet fold containing two domains. A structure of the lufaxin-C3bB complex obtained by cryo-electron microscopy shows that lufaxin binds via its N-terminal domain at an interface containing elements of both C3b and FB. By occupying this spot, the inhibitor locks FB into a closed conformation where proteolytic activation of FB by FD cannot occur. C3bB-bound lufaxin binds fXa at a separate site in its C-terminal domain. In the cryo-EM structure of a C3bB-lufaxin-fXa complex the inhibitor binds both targets simultaneously and lufaxin inhibits fXa through substrate-like binding of a C-terminal peptide at the active site as well as other interactions in this region. Lufaxin inhibits complement activation in ex vivo models of atypical hemolytic uremic syndrome (aHUS) and paroxysmal nocturnal hemoglobinuria (PNH) as well as thrombin generation in plasma, providing rationale for the development of a bispecific inhibitor to treat complement-related diseases in which thrombosis is a prominent manifestation.

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.

Introduction:Blood-feeding arthropods rely on robust cellular and humoral immunity to control pathogen invasion and replication. Tick hemocytes produce factors that can facilitate or suppress microbial infection and pathogenesis. Despite the importance of hemocytes in regulating microbial infection, understanding of their basic biology and molecular mechanisms remains limited.Methods:Here we combined histomorphology and functional analysis to identify five distinct phagocytic and non-phagocytic hemocyte populations circulating within the Gulf Coast tick Amblyomma maculatum.Results and discussion:Depletion of phagocytic hemocytes using clodronate liposomes revealed their function in eliminating bacterial infection. We provide the first direct evidence that an intracellular tick-borne pathogen, Rickettsia parkeri, infects phagocytic hemocytes in Am. maculatum to modify tick cellular immune responses. A hemocyte-specific RNA-seq dataset generated from hemocytes isolated from uninfected and R. parkeri-infected partially blood-fed ticks generated ~40,000 differentially regulated transcripts, >11,000 of which were immune genes. Silencing two differentially regulated phagocytic immune marker genes (nimrod B2 and eater-two Drosophila homologs), significantly reduced hemocyte phagocytosis.Conclusion:Together, these findings represent a significant step forward in understanding how hemocytes regulate microbial homeostasis and vector competence.

Phlebotomine sand flies are of global significance as important vectors of human disease, transmitting bacterial, viral, and protozoan pathogens, including the kinetoplastid parasites of the genus Leishmania, the causative agents of devastating diseases collectively termed leishmaniasis. More than 40 pathogenic Leishmania species are transmitted to humans by approximately 35 sand fly species in 98 countries with hundreds of millions of people at risk around the world. No approved efficacious vaccine exists for leishmaniasis and available therapeutic drugs are either toxic and/or expensive, or the parasites are becoming resistant to the more recently developed drugs. Therefore, sand fly and/or reservoir control are currently the most effective strategies to break transmission. To better understand the biology of sand flies, including the mechanisms involved in their vectorial capacity, insecticide resistance, and population structures we sequenced the genomes of two geographically widespread and important sand fly vector species: Phlebotomus papatasi, a vector of Leishmania parasites that cause cutaneous leishmaniasis, (distributed in Europe, the Middle East and North Africa) and Lutzomyia longipalpis, a vector of Leishmania parasites that cause visceral leishmaniasis (distributed across Central and South America). We categorized and curated genes involved in processes important to their roles as disease vectors, including chemosensation, blood feeding, circadian rhythm, immunity, and detoxification, as well as mobile genetic elements. We also defined gene orthology and observed micro-synteny among the genomes. Finally, we present the genetic diversity and population structure of these species in their respective geographical areas. These genomes will be a foundation on which to base future efforts to prevent vector-borne transmission of Leishmania parasites.

Tick saliva helps blood feeding by its antihemostatic and immunomodulatory activities. Tick salivary gland transcriptomes (sialotranscriptomes) revealed thousands of transcripts coding for putative secreted polypeptides. Hundreds of these transcripts code for groups of similar proteins, constituting protein families, such as the lipocalins and metalloproteases. However, while many of these transcriptome-derived protein sequences matches sequences predicted by tick genome assemblies, the majority are not represented in these proteomes. The diversity of these transcriptome-derived transcripts could derive from artifacts generated during assembly of short Illumina reads or derive from polymorphisms of the genes coding for these proteins. To investigate this discrepancy, we collected salivary glands from blood-feeding ticks and, from the same homogenate, made and sequenced libraries following Illumina and PacBio protocols, with the assumption that the longer PacBio reads would reveal the sequences generated by the assembly of Illumina reads. Using both Rhipicephalus zambeziensis and Ixodes scapularis ticks, we have obtained more lipocalin transcripts from the Illumina library than the PacBio library. To verify whether these unique Illumina transcripts were real, we selected 9 uniquely Illumina-derived lipocalin transcripts from I. scapularis and attempted to obtain PCR products. These were obtained and their sequences confirmed the presence of these transcripts in the I. scapularis salivary homogenate. We further compared the predicted salivary lipocalins and metalloproteases from I. scapularis sialotranscriptomes with those found in the predicted proteomes of 3 publicly available genomes of I. scapularis. Results indicate that the discrepancy between the genome and transcriptome sequences for these salivary protein families is due to a high degree of polymorphism within these genes.