BACKGROUND: Ticks, hematophagous Acari, pose a significant threat by transmitting various pathogens to their vertebrate hosts during feeding. Despite advances in tick genomics, high-quality genomes were lacking until recently, particularly in the genus Ixodes, which includes the main vectors of Lyme disease. RESULTS: Here, we present the genome sequences of four tick species, derived from a single female individual, with a particular focus on the European species Ixodes ricinus, achieving a chromosome-level assembly. Additionally, draft assemblies were generated for the three other Ixodes species, I. persulcatus, I. pacificus, and I. hexagonus. The quality of the four genomes and extensive annotation of several important gene families have allowed us to study the evolution of gene repertoires at the level of the genus Ixodes and of the tick group. We have determined gene families that have undergone major amplifications during the evolution of ticks, while an expression atlas obtained for I. ricinus reveals striking patterns of specialization both between and within gene families. Notably, several gene family amplifications are associated with a proliferation of single-exon genes-most strikingly for fatty acid elongases and sulfotransferases. CONCLUSIONS: The integration of our data with existing genomes establishes a solid framework for the study of gene evolution, improving our understanding of tick biology. In addition, our work lays the foundations for applied research and innovative control targeting these organisms.

• Keywords
• Comparative genomics, Duplication, Hematophagy, Parasite, Retroposition,
• MeSH
• Biological Evolution * MeSH
• Phylogeny MeSH
• Genome * MeSH
• Ixodes * genetics   classification   MeSH
• Evolution, Molecular * MeSH
• Animals MeSH
• Check Tag
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH

Ticks are ectoparasites that feed on blood and have an impressive ability to consume and process enormous amounts of host blood, allowing extremely long periods of starvation between blood meals. The central role in the parasitic lifestyle of ticks is played by the midgut. This organ efficiently stores and digests ingested blood and serves as the primary interface for the transmission of tick-borne pathogens. In this study, we used a label-free quantitative approach to perform a novel dynamic proteomic analysis of the midgut of Ixodesricinus nymphs, covering their development from unfed to pre-molt stages. We identified 1534 I. ricinus-specific proteins with a relatively low proportion of host proteins. This proteome dataset, which was carefully examined by manual scrutiny, allowed precise annotation of proteins important for blood meal processing and their dynamic changes during nymphal ontogeny. We focused on midgut molecules related to lipid hydrolysis, storage, and transport, opening a yet unexplored avenue for studying lipid metabolism in ticks. Further dynamic profiling of the tick's multi-enzyme digestive network, protease inhibitors, enzymes involved in redox homeostasis and detoxification, antimicrobial peptides, and proteins responsible for midgut colonization by Borrelia spirochetes promises to uncover new targets for targeting tick nymphs, the most critical life stage for transmission the pathogens that cause tick-borne diseases.

• Keywords
• Borrelia, Ixodes, antimicrobial peptides, label-free quantification, lipid metabolism, midgut, protease inhibitors, proteases, proteome, ticks,
• MeSH
• Ixodes * parasitology   MeSH
• Proteome MeSH
• Proteomics MeSH
• Digestive System MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Proteome MeSH

Dermanyssus gallinae is a blood-feeding mite that parasitises wild birds and farmed poultry. Its remarkably swift processing of blood, together with the capacity to blood-feed during most developmental stages, makes this mite a highly debilitating pest. To identify specific adaptations to digestion of a haemoglobin-rich diet, we constructed and compared transcriptomes from starved and blood-fed stages of the parasite and identified midgut-enriched transcripts. We noted that midgut transcripts encoding cysteine proteases were upregulated with a blood meal. Mapping the full proteolytic apparatus, we noted a reduction in the suite of cysteine proteases, missing homologues for Cathepsin B and C. We have further identified and phylogenetically analysed three distinct transcripts encoding vitellogenins that facilitate the reproductive capacity of the mites. We also fully mapped transcripts for haem biosynthesis and the ferritin-based system of iron storage and inter-tissue trafficking. Additionally, we identified transcripts encoding proteins implicated in immune signalling (Toll and IMD pathways) and activity (defensins and thioester-containing proteins), RNAi, and ion channelling (with targets for commercial acaricides such as Fluralaner, Fipronil, and Ivermectin). Viral sequences were filtered from the Illumina reads and we described, in part, the RNA-virome of D. gallinae with identification of a novel virus, Red mite quaranjavirus 1.

• MeSH
• Poultry MeSH
• Mite Infestations * veterinary   parasitology   MeSH
• Chickens MeSH
• Poultry Diseases * MeSH
• Mites * genetics   MeSH
• RNA-Seq MeSH
• Virome MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Research Support, N.I.H., Intramural MeSH

Many animals are dependent on microbial partners that provide essential nutrients lacking from their diet. Ticks, whose diet consists exclusively on vertebrate blood, rely on maternally inherited bacterial symbionts to supply B vitamins. While previously studied tick species consistently harbor a single lineage of those nutritional symbionts, we evidence here that the invasive tick Hyalomma marginatum harbors a unique dual-partner nutritional system between an ancestral symbiont, Francisella, and a more recently acquired symbiont, Midichloria. Using metagenomics, we show that Francisella exhibits extensive genome erosion that endangers the nutritional symbiotic interactions. Its genome includes folate and riboflavin biosynthesis pathways but deprived functional biotin biosynthesis on account of massive pseudogenization. Co-symbiosis compensates this deficiency since the Midichloria genome encompasses an intact biotin operon, which was primarily acquired via lateral gene transfer from unrelated intracellular bacteria commonly infecting arthropods. Thus, in H. marginatum, a mosaic of co-evolved symbionts incorporating gene combinations of distant phylogenetic origins emerged to prevent the collapse of an ancestral nutritional symbiosis. Such dual endosymbiosis was never reported in other blood feeders but was recently documented in agricultural pests feeding on plant sap, suggesting that it may be a key mechanism for advanced adaptation of arthropods to specialized diets.

• Keywords
• Francisella, Hyalomma, Midichloria, endosymbiosis, evolutionary biology, hematophagy,
• MeSH
• Francisella genetics   metabolism   MeSH
• Ixodidae microbiology   physiology   MeSH
• Gene Transfer, Horizontal MeSH
• Rickettsiales genetics   metabolism   MeSH
• Symbiosis physiology   MeSH
• Vitamin B Complex biosynthesis   MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Vitamin B Complex MeSH

Ticks, notorious blood-feeders and disease-vectors, have lost a part of their genetic complement encoding haem biosynthetic enzymes and are, therefore, dependent on the acquisition and distribution of host haem. Solute carrier protein SLC48A1, aka haem-responsive gene 1 protein (HRG1), has been implicated in haem transport, regulating the availability of intracellular haem. HRG1 transporter has been identified in both free-living and parasitic organisms ranging from unicellular kinetoplastids, nematodes, up to vertebrates. However, an HRG1 homologue in the arthropod lineage has not yet been identified. We have identified a single HRG1 homologue in the midgut transcriptome of the tick Ixodes ricinus, denoted as IrHRG, and have elucidated its role as a haem transporter. Data from haem biosynthesis-deficient yeast growth assays, systemic RNA interference and the evaluation of gallium protoporphyrin IX-mediated toxicity through tick membrane feeding clearly show that IrHRG is the bona fide tetrapyrrole transporter. We argue that during evolution, ticks profited from retaining a functional hrg1 gene in the genome because its protein product facilitates host haem escort from intracellularly digested haemoglobin, rendering haem bioavailable for a haem-dependent network of enzymes.

• Keywords
• HRG, auxotrophy, haem, ticks, transporter,
• MeSH
• Phylogeny MeSH
• Heme metabolism   MeSH
• Hemoglobins metabolism   MeSH
• Hemeproteins genetics   metabolism   MeSH
• Tick Infestations parasitology   MeSH
• Ixodes metabolism   MeSH
• Arthropod Proteins genetics   metabolism   MeSH
• Amino Acid Sequence MeSH
• Sequence Homology MeSH
• Transcriptome MeSH
• Digestive System metabolism   parasitology   MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Heme MeSH
• Hemoglobins MeSH
• Hemeproteins MeSH
• Arthropod Proteins MeSH

As opposed to pathogens passively circulating in the body fluids of their host, pathogenic species within the Spirochetes phylum are able to actively coordinate their movement in the host to cause systemic infections. Based on the unique morphology and high motility of spirochetes, we hypothesized that their surface adhesive molecules might be suitably adapted to aid in their dissemination strategies. Designing a system that mimics natural environmental signals, which many spirochetes face during their infectious cycle, we observed that a subset of their surface proteins, particularly Decorin binding protein (Dbp) A/B, can strongly enhance the motility of spirochetes in the extracellular matrix of the host. Using single-molecule force spectroscopy, we disentangled the mechanistic details of DbpA/B and decorin/laminin interactions. Our results show that spirochetes are able to leverage a wide variety of adhesion strategies through force-tuning transient molecular binding to extracellular matrix components, which concertedly enhance spirochetal dissemination through the host.

• MeSH
• Bacterial Adhesion * MeSH
• Adhesins, Bacterial genetics   metabolism   MeSH
• Borrelia burgdorferi genetics   metabolism   pathogenicity   MeSH
• Decorin metabolism   MeSH
• Extracellular Matrix metabolism   microbiology   MeSH
• Host-Pathogen Interactions MeSH
• Kinetics MeSH
• Ixodes microbiology   MeSH
• Rabbits MeSH
• Laminin metabolism   MeSH
• Lyme Disease metabolism   microbiology   MeSH
• Movement MeSH
• Protein Binding MeSH
• Single Molecule Imaging MeSH
• Animals MeSH
• Check Tag
• Rabbits MeSH
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Adhesins, Bacterial MeSH
• DCN protein, human MeSH Browser
• DdpB protein, Borrelia burgdorferi MeSH Browser
• Decorin MeSH
• Laminin MeSH

Host blood protein digestion plays a pivotal role in the ontogeny and reproduction of hematophagous vectors. The gut of hematophagous arthropods stores and slowly digests host blood and represents the primary gateway for transmitted pathogens. The initial step in blood degradation is induced lysis of host red blood cells (hemolysis), which releases hemoglobin for subsequent processing by digestive proteolytic enzymes. The activity cycles and characteristics of hemolysis in vectors are poorly understood. Hence, we investigated hemolysis in two evolutionarily distant blood-feeding arthropods: The mosquito Culex pipiens and the soft tick Argas persicus, both of which are important human and veterinary disease vectors. Hemolysis in both species was cyclical after blood meal ingestion. Maximum digestion occurs under slightly alkaline conditions in females. Hemolytic activity appears to be of lipoid origin in C. pipiens and enzymatic activity (proteolytic) in A. persicus. We have assessed the effect of pH, incubation time, and temperature on hemolytic activity and the hemolysin. The susceptibility of red blood cells from different hosts to the hemolysin and the effect of metabolic inhibition of hemolytic activity were assessed. We conclude that in C. pipiens and A. persicus midgut hemolysins control the amplitude of blood lysis step to guarantee an efficient blood digestion.

• MeSH
• Arthropod Vectors physiology   MeSH
• Arthropods MeSH
• Culex MeSH
• Culicidae MeSH
• Erythrocytes MeSH
• Hematologic Tests MeSH
• Hemolysis * MeSH
• Hemolysin Proteins MeSH
• Mosquito Vectors physiology   MeSH
• Humans MeSH
• Feeding Behavior physiology   MeSH
• Digestive System MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Hemolysin Proteins MeSH

Babesiosis is a tick-transmitted zoonosis caused by apicomplexan parasites of the genus Babesia. Treatment of this emerging malaria-related disease has relied on antimalarial drugs and antibiotics. The proteasome of Plasmodium, the causative agent of malaria, has recently been validated as a target for anti-malarial drug development and therefore, in this study, we investigated the effect of epoxyketone (carfilzomib, ONX-0914 and epoxomicin) and boronic acid (bortezomib and ixazomib) proteasome inhibitors on the growth and survival of Babesia. Testing the compounds against Babesia divergens ex vivo revealed suppressive effects on parasite growth with activity that was higher than the cytotoxic effects on a non-transformed mouse macrophage cell line. Furthermore, we showed that the most-effective compound, carfilzomib, significantly reduces parasite multiplication in a Babesia microti infected mouse model without noticeable adverse effects. In addition, treatment with carfilzomib lead to an ex vivo and in vivo decrease in proteasome activity and accumulation of polyubiquitinated proteins compared to untreated control. Overall, our results demonstrate that the Babesia proteasome is a valid target for drug development and warrants the design of potent and selective B. divergens proteasome inhibitors for the treatment of babesiosis.

• Keywords
• Babesia, Carfilzomib, Cytotoxicity, Epoxyketone, Proteasome,
• MeSH
• Babesia microti drug effects   genetics   growth & development   MeSH
• Babesia drug effects   genetics   growth & development   MeSH
• Babesiosis drug therapy   MeSH
• Cell Line MeSH
• Proteasome Inhibitors administration & dosage   adverse effects   pharmacology   therapeutic use   MeSH
• Boronic Acids pharmacology   MeSH
• Drug Delivery Systems * MeSH
• Macrophages drug effects   parasitology   MeSH
• Disease Models, Animal MeSH
• Mice MeSH
• Oligopeptides pharmacology   MeSH
• Proteasome Endopeptidase Complex drug effects   MeSH
• Proteome drug effects   genetics   MeSH
• Animals MeSH
• Check Tag
• Mice MeSH
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Research Support, N.I.H., Extramural MeSH
• Validation Study MeSH
• Names of Substances
• carfilzomib MeSH Browser
• epoxomicin MeSH Browser
• Proteasome Inhibitors MeSH
• Boronic Acids MeSH
• Oligopeptides MeSH
• Proteasome Endopeptidase Complex MeSH
• Proteome MeSH

Ticks salivate while feeding on their hosts. Saliva helps blood feeding through host anti-hemostatic and immunomodulatory components. Previous transcriptomic and proteomic studies revealed the complexity of tick saliva, comprising hundreds of polypeptides grouped in several multi-genic families such as lipocalins, Kunitz-domain containing peptides, metalloproteases, basic tail secreted proteins, and several other families uniquely found in ticks. These studies also revealed that the composition of saliva changes with time; expression of transcripts from the same family wax and wane as a function of feeding time. Here, we examined whether host immune factors could influence sialome switching by comparing sialomes of ticks fed naturally on a rabbit, to ticks artificially fed on defibrinated blood depleted of immune components. Previous studies were based on transcriptomes derived from pools of several individuals. To get an insight into the uniqueness of tick sialomes, we performed transcriptomic analyses of single salivary glands dissected from individual adult female I. ricinus ticks. Multivariate analysis identified 1,279 contigs differentially expressed as a function of time and/or feeding mode. Cluster analysis of these contigs revealed nine clusters of differentially expressed genes, four of which appeared consistently across several replicates, but five clusters were idiosyncratic, pointing to the uniqueness of sialomes in individual ticks. The disclosure of tick quantum sialomes reveals the unique salivary composition produced by individual ticks as they switch their sialomes throughout the blood meal, a possible mechanism of immune evasion.

• MeSH
• Ixodes genetics   metabolism   MeSH
• Rabbits MeSH
• Humans MeSH
• Sequence Analysis, RNA MeSH
• Salivary Glands metabolism   MeSH
• Saliva metabolism   MeSH
• Gene Expression Profiling MeSH
• Transcriptome * MeSH
• Computational Biology MeSH
• High-Throughput Nucleotide Sequencing methods   MeSH
• Animals MeSH
• Check Tag
• Rabbits MeSH
• Humans MeSH
• Male MeSH
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH

The present concept of the transmission of Lyme disease from Borrelia-infected Ixodes sp. ticks to the naïve host assumes that a low number of spirochetes that manage to penetrate the midgut epithelium migrate through the hemocoel to the salivary glands and subsequently infect the host with the aid of immunomodulatory compounds present in tick saliva. Therefore, humoral and/or cellular immune reactions within the tick hemocoel may play an important role in tick competence to act as a vector for borreliosis. To test this hypothesis we have examined complement-like reactions in the hemolymph of the hard tick Ixodes ricinus against Borrelia afzelii (the most common vector and causative agent of Lyme disease in Europe). We demonstrate that I. ricinus hemolymph does not exhibit borreliacidal effects comparable to complement-mediated lysis of bovine sera. However, after injection of B. afzelii into the tick hemocoel, the spirochetes were efficiently phagocytosed by tick hemocytes and this cellular defense was completely eliminated by pre-injection of latex beads. As tick thioester-containing proteins (T-TEPs) are components of the tick complement system, we performed RNAi-mediated silencing of all nine genes encoding individual T-TEPs followed by in vitro phagocytosis assays. Silencing of two molecules related to the C3 complement component (IrC3-2 and IrC3-3) significantly suppressed phagocytosis of B. afzelii, while knockdown of IrTep (insect type TEP) led to its stimulation. However, RNAi-mediated silencing of T-TEPs or elimination of phagocytosis by injection of latex beads in B. afzelii-infected I. ricinus nymphs had no obvious impact on the transmission of spirochetes to naïve mice, as determined by B. afzelii infection of murine tissues following tick infestation. This result supports the concept that Borrelia spirochetes are capable of avoiding complement-related reactions within the hemocoel of ticks competent to transmit Lyme disease.

• Keywords
• Borrelia, Ixodes, complement, phagocytosis, thioester-containing proteins,
• MeSH
• Arachnid Vectors immunology   microbiology   MeSH
• Borrelia burgdorferi Group immunology   MeSH
• Phagocytosis * MeSH
• Hemocytes immunology   MeSH
• Ixodes immunology   microbiology   MeSH
• Complement System Proteins metabolism   MeSH
• Lyme Disease transmission   MeSH
• Disease Models, Animal MeSH
• Mice MeSH
• Disease Transmission, Infectious MeSH
• Arthropod Proteins metabolism   MeSH
• Animals MeSH
• Check Tag
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Complement System Proteins MeSH
• Arthropod Proteins MeSH