Prostaglandin E(2) in tick saliva regulates macrophage cell migration and cytokine profile

Differential phagocytic expression of IC-21 macrophages and their scavenging receptors during inflammatory induction by oxysterol: A microscopic approach

Phagocytosis by macrophages dates back to a long history in science, this present study deals with new approaches that have been analyzed and standardized towards the interesting aspects of primary and secondary macrophages. The distinct morphological differences in primary and secondary phagocytic cells were observed and the phagocytic response of secondary macrophages under the influence of 7-ketocholesterol and lipopolysaccharide was analyzed. The primary peritoneal and secondary IC-21 cells unveiled explicit differences in nuclear numbers shapes and sizes of the granules present within the cytoplasmic region. Further, potent inducers 7KCh and LPS influenced an effective activation of IC-21 macrophages and resulted in ROS generation, irregulated protein expressions of CD86, CD68, and CD206 with enhanced phagocytic responses towards goat, cow, and human RBC targets with significant phagocytic rate and index were observed. Moreover, a remarkable observation of target specificity and aggregations with IC-21 phagocytic macrophages revealed the notion that specific membrane receptors and secretory molecules (lysosomes) are primarily involved in their phagocytic mechanism. RESEARCH HIGHLIGHTS: IC-21 macrophages are peritoneal origin from mice but the primary peritoneal macrophages and cell line show distinct differences. IC-21 macrophages express target-specific phagocytosis. Phagocytosis in IC-21 macrophages is regulated by CD markers (68, 86, and 206).

Proteases and protease inhibitors in saliva of hard ticks: Biological role and pharmacological potential

Hard ticks (family Ixodidae) are significant vectors of pathogens affecting humans and animals. This review explores the composition of tick saliva, focusing on proteases and protease inhibitors, their biological roles, and their potential in vaccines and therapies. Tick saliva contains various proteases, mostly metalloproteases, serpins, cystatins, and Kunitz-type inhibitors, which modulate host hemostatic, immune, and wound healing responses to facilitate blood feeding and pathogen transmission. Proteases inhibit blood clotting, degrade extracellular matrix components, and modulate immune responses. Serpins, cystatins, and Kunitz-type inhibitors further inhibit key proteases involved in coagulation and inflammation, making them promising candidates for anticoagulant, anti-inflammatory, and immunomodulatory therapies. Several tick proteases and protease inhibitors have shown potential as vaccine targets, reducing tick feeding success and pathogen transmission. Future research should focus on comprehensive proteomic and genomic analyses, detailed structural and functional studies, and vaccine trials. Advanced omics approaches and bioinformatics tools will be crucial in uncovering the complex interactions between ticks, hosts, and pathogens, improving tick control strategies and public health outcomes.

Genetic factors underlying host resistance to Rhipicephalus microplus tick infestation in Braford cattle: a systems biology perspective

Approximately 80% of the world's cattle are raised in regions with a high risk of tick-borne diseases, resulting in significant economic losses due to parasitism by Rhipicephalus (Boophilus) microplus. However, the lack of a systemic biology approach hampers a comprehensive understanding of tick-host interactions that mediate tick resistance phenotypes. Here, we conducted a genome-wide association study (GWAS) of 2933 Braford cattle and found 340 single-nucleotide polymorphisms (SNPs) associated with tick counts. Gene expression analyses were performed on skin samples obtained from previously tick-exposed heifers with extremely high or low estimated breeding values for R. microplus counts. Evaluations were performed both before and after artificial infestation with ticks. Differentially expressed genes were found within 1-Mb windows centered at significant SNPs from GWAS. A total of 330 genes were related to the breakdown of homeostasis that was induced by larval attachment to bovine skin. Enrichment analysis pointed to a key role of proteolysis and signal transduction via JAK/STAT, NFKB and WNT/beta catenin signaling pathways. Integrative analysis on matrixEQTL revealed two cis-eQTLs and four significant SNPs in the genes peptidyl arginine deiminase type IV (PADI4) and LOC11449251. The integration of genomic data from QTL maps and transcriptome analyses has identified a set of twelve key genes that show significant associations with tick loads. These genes could be key candidates to improve the accuracy of genomic predictions for tick resistance in Braford cattle.

Tick bite-induced alpha-gal syndrome and immunologic responses in an alpha-gal deficient murine model

Introduction

Alpha-Gal Syndrome (AGS) is a delayed allergic reaction due to specific IgE antibodies targeting galactose-α-1,3-galactose (α-gal), a carbohydrate found in red meat. This condition has gained significant attention globally due to its increasing prevalence, with more than 450,000 cases estimated just in the United States alone. Previous research has established a connection between AGS and tick bites, which sensitize individuals to α-gal antigens and elevate the levels of specific IgE. However, the precise mechanism by which tick bites influence the host's immune system and contribute to the development of AGS remains poorly understood. This study investigates various factors related to ticks and the host associated with the development of AGS following a tick bite, using mice with a targeted disruption of alpha-1,3-galactosyltransferase (AGKO) as a model organism.

Methods

Lone-star tick (Amblyomma americanum) and gulf-coast tick (Amblyomma maculatum) nymphs were used to sensitize AGKO mice, followed by pork meat challenge. Tick bite site biopsies from sensitized and non-sensitized mice were subjected to mRNA gene expression analysis to assess the host immune response. Antibody responses in sensitized mice were also determined.

Results

Our results showed a significant increase in the total IgE, IgG1, and α-gal IgG1 antibodies titers in the lone-star tick-sensitized AGKO mice compared to the gulf-coast tick-sensitized mice. Pork challenge in Am. americanum -sensitized mice led to a decline in body temperature after the meat challenge. Gene expression analysis revealed that Am. americanum bites direct mouse immunity toward Th2 and facilitate host sensitization to the α-gal antigen.

Conclusion

This study supports the hypothesis that specific tick species may increase the risk of developing α-gal-specific IgE and hypersensitivity reactions or AGS, thereby providing opportunities for future research on the mechanistic role of tick and host-related factors in AGS development.

Spatial Metabolomics Reveals the Multifaceted Nature of Lamprey Buccal Gland and Its Diverse Mechanisms for Blood-Feeding

Lampreys are blood-sucking vampires in marine environments. From a survival perspective, it is expected that the lamprey buccal gland exhibits a repository of pharmacologically active components to modulate the host's homeostasis, inflammatory and immune responses. By analyzing the metabolic profiles of 14 different lamprey tissues, we show that two groups of metabolites in the buccal gland of lampreys, prostaglandins and the kynurenine pathway metabolites, can be injected into the host fish to assist lamprey blood feeding. Prostaglandins are well-known blood-sucking-associated metabolites that act as vasodilators and anticoagulants to maintain vascular homeostasis and are involved in inflammatory responses. The vasomotor reactivity test on catfish aortic ring showed that kynurenine can also relax the blood vessels of the host fish, thus improving the blood flow of the host fish at the bite site. Finally, a lamprey spatial metabolomics database ( https://www.lampreydb.com ) was constructed to assist studies using lampreys as animal model.

Transcriptomic and targeted immune transcript analyses confirm localized skin immune responses in Atlantic salmon towards the salmon louse

Atlantic salmon (Salmo salar) are highly susceptible to infestations with the ectoparasite Lepeophtheirus salmonis, the salmon louse. Infestations elicit an immune response in the fish, but the response does not lead to parasite clearance, nor does it protect against subsequent infestations. It is, however, not known why the immune response is not adequate, possibly because the local response directly underneath the louse has been poorly evaluated. The present study describes the transcriptomic response by RNA sequencing of skin at the site of copepodid attachment. Analysing differentially expressed genes, 2864 were higher and 1357 were lower expressed at the louse attachment site compared to uninfested sites in the louse infested fish, while gene expression at uninfested sites were similar to uninfested control fish. The transcriptional patterns of selected immune genes were further detailed in three skin compartments/types: Whole skin, scales only and fin tissue. The elevation of pro-inflammatory cytokines and immune cell marker transcripts observed in whole skin and scale samples were not induced in fin, and a higher cytokine transcript level in scale samples suggest it can be used as a nonlethal sampling method to enhance selective breeding trials. Furthermore, the immune response was followed in both skin and anterior kidney as the infestation developed. Here, newly moulted preadult 1 stage lice induced a higher immune response than chalimi and adult lice. Overall, infestation with salmon louse induce a modest but early immune response with an elevation of mainly innate immune transcripts, with the response primarily localized to the site of attachment.

Salivary macrophage chemokines as potential biomarkers of gingivitis

OBJECTIVE

The present study aimed to analyze the salivary levels of macrophage-activating factor (MAF), macrophage-chemotactic factor (MCF), and macrophage migration inhibitory factor (MIF) in healthy and gingivitis patients, and to correlate between the concentrations of these chemo attractants with the intensity of gingival inflammation clinically.

METHODS

Sixty saliva specimens were collected from periodontally healthy (n = 30), and gingivitis patients (n = 30). Bleeding on probing (BOP), Visible Plaque Index (VPI), and Simplified Modified Gingival Index (SMGI) were recorded through clinical examination. Salivary MAF, MCF, and MIF concentrations were assayed using enzyme-linked immunosorbent assays (ELISA). Statistical analysis was performed using SPSS (version 28). Total mean score for each biomarker was determined, and descriptive bivariate statistics were conducted to characterize the levels of biomarkers among the study groups. The difference in the biomarker levels among the study groups were analyzed by independent sample t test and one-way ANOVA. The diagnostic ability of the biomarkers was further tested by ROC curve analysis.

RESULTS

Salivary levels of MAF was not significantly different between periodontally healthy individuals and gingivitis patients. The difference in MCF and MIF levels between patients with gingivitis and those with healthy periodontium was statistically significant (p 0.05 and p 0.001, respectively). When examined across the various stages of disease progression, MIF showed statistically significant difference among the three biomarkers (p 0.05). ROC curve analysis further revealed that area under the curve (AUC) for MIF has a better diagnostic capacity than MCF (AUC 0.981 vs. 0.673).

CONCLUSIONS

Our results suggest that MIF could be considered as a potential salivary biomarker for gingivitis.

Suppressive modulation of host immune responses by Dermanyssus gallinae infestation

The poultry red mite (Dermanyssus gallinae, PRM) is a blood-sucking ectoparasite in chickens and is one of the most serious threats to poultry farms. Mass infestation with PRMs causes various health problems in chickens, resulting in significant productivity reduction in the poultry industry. Infestation with hematophagous ectoparasites, such as ticks, induces host inflammatory and hemostatic reactions. On the other hand, several studies have reported that hematophagous ectoparasites secrete various immunosuppressants from their saliva to suppress host immune responses to maintain blood sucking. Here, we examined the expression of cytokines in peripheral blood cells to investigate whether PRM infestation affects immunological states in chickens. In PRM-infested chickens, anti-inflammatory cytokines, IL-10 and TGF-β1, and immune checkpoint molecules, CTLA-4 and PD-1, were highly expressed compared to noninfested chickens. PRM-derived soluble mite extracts (SME) upregulated the gene expression of IL-10 in peripheral blood cells and HD-11 chicken macrophages. In addition, SME suppressed the expression of interferons and inflammatory cytokines in HD-11 chicken macrophages. Moreover, SME induces the polarization of macrophages into anti-inflammatory phenotypes. Collectively, PRM infestation could affect host immune responses, especially suppress the inflammatory responses. Further studies are warranted to fully understand the influence of PRM infestation on host immunity.

Host Immune Responses to Salivary Components - A Critical Facet of Tick-Host Interactions

Tick sialome is comprised of a rich cocktail of bioactive molecules that function as a tool to disarm host immunity, assist blood-feeding, and play a vibrant role in pathogen transmission. The adaptation of the tick's blood-feeding behavior has lead to the evolution of bioactive molecules in its saliva to assist them to overwhelm hosts' defense mechanisms. During a blood meal, a tick secretes different salivary molecules including vasodilators, platelet aggregation inhibitors, anticoagulants, anti-inflammatory proteins, and inhibitors of complement activation; the salivary repertoire changes to meet various needs such as tick attachment, feeding, and modulation or impairment of the local dynamic and vigorous host responses. For instance, the tick's salivary immunomodulatory and cement proteins facilitate the tick's attachment to the host to enhance prolonged blood-feeding and to modulate the host's innate and adaptive immune responses. Recent advances implemented in the field of "omics" have substantially assisted our understanding of host immune modulation and immune inhibition against the molecular dynamics of tick salivary molecules in a crosstalk between the tick-host interface. A deep understanding of the tick salivary molecules, their substantial roles in multifactorial immunological cascades, variations in secretion, and host immune responses against these molecules is necessary to control these parasites. In this article, we reviewed updated knowledge about the molecular mechanisms underlying host responses to diverse elements in tick saliva throughout tick invasion, as well as host defense strategies. In conclusion, understanding the mechanisms involved in the complex interactions between the tick salivary components and host responses is essential to decipher the host defense mechanisms against the tick evasion strategies at tick-host interface which is promising in the development of effective anti-tick vaccines and drug therapeutics.

Tick Saliva and the Alpha-Gal Syndrome: Finding a Needle in a Haystack

Ticks and tick-borne diseases are significant public health concerns. Bioactive molecules in tick saliva facilitate prolonged blood-feeding and transmission of tick-borne pathogens to the vertebrate host. Alpha-gal syndrome (AGS), a newly reported food allergy, is believed to be induced by saliva proteins decorated with a sugar molecule, the oligosaccharide galactose-⍺-1,3-galactose (α-gal). This syndrome is characterized by an IgE antibody-directed hypersensitivity against α-gal. The α-gal antigen was discovered in the salivary glands and saliva of various tick species including, the Lone Star tick (Amblyomma americanum). The underlying immune mechanisms linking tick bites with α-gal-specific IgE production are poorly understood and are crucial to identify and establish novel treatments for this disease. This article reviews the current understanding of AGS and its involvement with tick species.

Roles of three putative salmon louse (Lepeophtheirus salmonis) prostaglandin E2 synthases in physiology and host-parasite interactions

BACKGROUND

The salmon louse (Lepeophtheirus salmonis) is a parasite of salmonid fish. Atlantic salmon (Salmo salar) exhibit only a limited and ineffective immune response when infested with this parasite. Prostaglandins (PGs) have many biological functions in both invertebrates and vertebrates, one of which is the regulation of immune responses. This has led to the suggestion that prostaglandin E₂ (PGE₂) is important in the salmon louse host-parasite interaction, although studies of a salmon louse prostaglandin E₂ synthase (PGES) 2 gene have not enabled conformation of this hypothesis. The aim of the present study was, therefore, to characterize two additional PGES-like genes.

METHODS

Lepeophtheirus salmonis microsomal glutathione S-transferase 1 like (LsMGST1L) and LsPGES3L were investigated by sequencing, phylogenetics, transcript localization and expression studies. Moreover, the function of these putative PGES genes in addition to the previously identified LsPGES2 gene was analyzed in double stranded (ds) RNA-mediated knockdown (KD) salmon louse.

RESULTS

Analysis of the three putative LsPGES genes showed a rather constitutive transcript level throughout development from nauplius to the adult stages, and in a range of tissues, with the highest levels in the ovaries or gut. DsRNA-mediated KD of these transcripts did not produce any characteristic changes in phenotype, and KD animals displayed a normal reproductive output. The ability of the parasite to infect or modulate the immune response of the host fish was also not affected by KD.

CONCLUSIONS

Salmon louse prostaglandins may play endogenous roles in the management of reproduction and oxidative stress and may be a product of salmon louse blood digestions.

Changing the Recipe: Pathogen Directed Changes in Tick Saliva Components

Ticks are obligate hematophagous parasites and are important vectors of a wide variety of pathogens. These pathogens include spirochetes in the genus Borrelia that cause Lyme disease, rickettsial pathogens, and tick-borne encephalitis virus, among others. Due to their prolonged feeding period of up to two weeks, hard ticks must counteract vertebrate host defense reactions in order to survive and reproduce. To overcome host defense mechanisms, ticks have evolved a large number of pharmacologically active molecules that are secreted in their saliva, which inhibits or modulates host immune defenses and wound healing responses upon injection into the bite site. These bioactive molecules in tick saliva can create a privileged environment in the host’s skin that tick-borne pathogens take advantage of. In fact, evidence is accumulating that tick-transmitted pathogens manipulate tick saliva composition to enhance their own survival, transmission, and evasion of host defenses. We review what is known about specific and functionally characterized tick saliva molecules in the context of tick infection with the genus Borrelia, the intracellular pathogen Anaplasma phagocytophilum, and tick-borne encephalitis virus. Additionally, we review studies analyzing sialome-level responses to pathogen challenge.

Tick saliva-induced programmed death-1 and PD-ligand 1 and its related host immunosuppression

The tick Rhipicephalus microplus is a harmful parasite of cattle that causes considerable economic losses to the cattle breeding industry. Although R. microplus saliva (Rm-saliva) contains several immunosuppressants, any association between Rm-saliva and the expression of immunoinhibitory molecules, such as programmed death (PD)-1 and PD-ligand 1 (PD-L1), has not been described. In this study, flow cytometric analyses revealed that Rm-saliva upregulated PD-1 expression in T cells and PD-L1 expression in CD14⁺ and CD11c⁺ cells in cattle. Additionally, Rm-saliva decreased CD69 expression in T cells and Th1 cytokine production from peripheral blood mononuclear cells. Furthermore, PD-L1 blockade increased IFN-γ production in the presence of Rm-saliva, suggesting that Rm-saliva suppresses Th1 responses via the PD-1/PD-L1 pathway. To reveal the upregulation mechanism of PD-1/PD-L1 by Rm-saliva, we analyzed the function of prostaglandin E₂ (PGE₂), which is known as an inducer of PD-L1 expression, in Rm-saliva. We found that Rm-saliva contained a high concentration of PGE₂, and PGE₂ treatment induced PD-L1 expression in CD14⁺ cells in vitro. Immunohistochemical analyses revealed that PGE₂ and PD-L1 expression was upregulated in tick-attached skin in cattle. These data suggest that PGE₂ in Rm-saliva has the potential to induce the expression of immunoinhibitory molecules in host immune cells.

Acquired tick resistance: The trail is hot

Acquired tick resistance is a phenomenon wherein the host elicits an immune response against tick salivary components upon repeated tick infestations. The immune responses, potentially directed against critical salivary components, thwart tick feeding, and the animal becomes resistant to subsequent tick infestations. The development of tick resistance is frequently observed when ticks feed on non-natural hosts, but not on natural hosts. The molecular mechanisms that lead to the development of tick resistance are not fully understood, and both host and tick factors are invoked in this phenomenon. Advances in molecular tools to address the host and the tick are beginning to reveal new insights into this phenomenon and to uncover a deeper understanding of the fundamental biology of tick-host interactions. This review will focus on the expanding understanding of acquired tick resistance and highlight the impact of this understanding on anti-tick vaccine development efforts.

Bone Marrow Mesenchymal Stem Cell-Derived Small Extracellular Vesicles Promote Periodontal Regeneration

Bone marrow mesenchymal stem cell-derived small extracellular vesicles (BMSC-sEVs) can be used as a potential cell-free strategy for periodontal tissue regeneration, and we aim to investigate the effect and possible mechanism of BMSC-sEV in periodontal tissue regeneration in this study. The BMSC-sEV was isolated by the Exosome Isolation™ reagent and identified by transmission electron microscopy, nanoparticle tracking analysis, and Western blotting. The human periodontal ligament cells (hPDLCs) were cocultured with BMSC-sEV in vitro to detect the effects of BMSC-sEV on hPDLC migration, proliferation, and differentiation. The BMSC-sEV loaded by hydrogel was injected into experimental periodontitis rats to verify the therapeutic effect and possible mechanism. The results showed that BMSC-sEVs were 30-150 nm vesicles and expressed the exosome protein CD63 and tumor susceptibility 101 (TSG101), which could promote the migration, proliferation, osteogenic differentiation of hPDLCs. The BMSC-sEV-hydrogel had a therapeutic effect on periodontitis rats. After administration for 4-8 weeks, microcomputed tomography and histological analysis showed that alveolar bone loss, inflammatory infiltration, and collagen destruction in the BMSC-sEV-hydrogel group were less than that in the phosphate-buffered saline (PBS)-hydrogel group and periodontitis group. Further immunohistochemical and immunofluorescent staining revealed that the number of tartrate-resistant acid phosphatase-positive cells and the expression ratio of osteoprotegerin (OPG) and receptor-activator of nuclear factor kappa beta ligand (RANKL) in the BMSC-sEV-hydrogel group were lower than that in the PBS-hydrogel group and periodontitis group, while the expression of transforming growth factor-beta 1 (TGF-β1) and the ratio of macrophage type 2 and macrophage type 1 (M2/M1) were opposite. Therefore, BMSC-sEV can promote the regeneration of periodontal tissues, and that may be partly due to BMSC-sEV involvement in the OPG-RANKL-RANK signaling pathway to regulate the function of osteoclasts and affect the macrophage polarization and TGF-β1 expression to modulate the inflammatory immune response, thereby inhibiting the development of periodontitis and immune damage of periodontal tissue. Impact statement Bone marrow mesenchymal stem cell-derived small extracellular vesicles (BMSCs-sEVs) have been proven to have similar functions to BMSCs, such as promoting the regeneration of heart, liver, kidney, and bone tissue and regulating immune responses. BMSCs are candidate seed cells of periodontal regeneration, but it is unclear about the role of BMSC-sEV on periodontal regeneration. In this study, we explored the effects and possible mechanism of BMSC-sEV on periodontal regeneration. The results of this study provide the evidence of BMSC-sEV as a cell-free strategy for periodontal regeneration.

Infection with Toxocara canis Inhibits the Production of IgE Antibodies to α-Gal in Humans: Towards a Conceptual Framework of the Hygiene Hypothesis?

α-Gal syndrome (AGS) is a type of anaphylactic reaction to mammalian meat characterized by an immunoglobulin (Ig)E immune response to the oligosaccharide α-Gal (Galα1-3Galβ1-4GlcNAc-R). Tick bites seems to be a prerequisite for the onset of the allergic disease in humans, but the implication of non-tick parasites in α-Gal sensitization has also been deliberated. In the present study, we therefore evaluated the capacity of helminths (Toxocara canis, Ascaris suum, Schistosoma mansoni), protozoa (Toxoplasma gondii), and parasitic fungi (Aspergillus fumigatus) to induce an immune response to α-Gal. For this, different developmental stages of the infectious agents were tested for the presence of α-Gal. Next, the potential correlation between immune responses to α-Gal and the parasite infections was investigated by testing sera collected from patients with AGS and those infected with the parasites. Our results showed that S. mansoni and A. fumigatus produce the terminal α-Gal moieties, but they were not able to induce the production of specific antibodies. By contrast, T. canis, A. suum and T. gondii lack the α-Gal epitope. Furthermore, the patients with T. canis infection had significantly decreased anti-α-Gal IgE levels when compared to the healthy controls, suggesting the potential role of this nematode parasite in suppressing the allergic response to the glycan molecule. This rather intriguing observation is discussed in the context of the 'hygiene hypothesis'. Taken together, our study provides new insights into the relationships between immune responses to α-Gal and parasitic infections. However, further investigations should be undertaken to identify T. canis components with potent immunomodulatory properties and to assess their potential to be used in immunotherapy and control of AGS.

Allergic Reactions and Immunity in Response to Tick Salivary Biogenic Substances and Red Meat Consumption in the Zebrafish Model

Ticks are arthropod ectoparasite vectors of pathogens and the cause of allergic reactions affecting human health worldwide. In humans, tick bites can induce high levels of immunoglobulin E antibodies against the carbohydrate Galα1-3Galβ1-(3)4GlcNAc-R (α-Gal) present in glycoproteins and glycolipids from tick saliva that mediate anaphylactic reactions known as the alpha-Gal syndrome (AGS) or red meat allergy. In this study, a new animal model was developed using zebrafish for the study of allergic reactions and the immune mechanisms in response to tick salivary biogenic substances and red meat consumption. The results showed allergic hemorrhagic anaphylactic-type reactions and abnormal behavior patterns likely in response to tick salivary toxic and anticoagulant biogenic compounds different from α-Gal. However, the results showed that only zebrafish previously exposed to tick saliva developed allergic reactions to red meat consumption with rapid desensitization and tolerance. These allergic reactions were associated with tissue-specific Toll-like receptor-mediated responses in types 1 and 2 T helper cells (T_H1 and T_H2) with a possible role for basophils in response to tick saliva. These results support previously proposed immune mechanisms triggering the AGS and provided evidence for new mechanisms also potentially involved in the AGS. These results support the use of the zebrafish animal model for the study of the AGS and other tick-borne allergies.

Network analysis uncovers putative genes affecting resistance to tick infestation in Braford cattle skin

Background

Genetic resistance in cattle is considered a suitable way to control tick burden and its consequent losses for livestock production. Exploring tick-resistant (R) and tick-susceptible (S) hosts, we investigated the genetic mechanisms underlying the variation of Braford resistance to tick infestation. Skin biopsies from four-times-artificially infested R (n = 20) and S (n = 19) hosts, obtained before the first and 24 h after the fourth tick infestation were submitted to RNA-Sequencing. Differential gene expression, functional enrichment, and network analysis were performed to identify genetic pathways and transcription factors (TFs) affecting host resistance.

Results

Intergroup comparisons of hosts before (Rpre vs. Spre) and after (Rpost vs. Spost) tick infestation found 51 differentially expressed genes (DEGs), of which almost all presented high variation (TopDEGs), and 38 were redundant genes. Gene expression was consistently different between R and S hosts, suggesting the existence of specific anti-tick mechanisms. In the intragroup comparisons, Rpost vs. Rpre and Spost vs. Spre, we found more than two thousand DEGs in response to tick infestation in both resistance groups. Redundant and non-redundant TopDEGs with potential anti-tick functions suggested a role in the development of different levels of resistance within the same breed. Leukocyte chemotaxis was over-represented in both hosts, whereas skin degradation and remodeling were only found in TopDEGs from R hosts. Also, these genes indicated the participation of cytokines, such as IL6 and IL22, and the activation of Wingless (WNT)-signaling pathway. A central gene of this pathway, WNT7A, was consistently modulated when hosts were compared. Moreover, the findings based on a genome-wide association study (GWAS) corroborate the prediction of the WNT-signaling pathway as a candidate mechanism of resistance. The regulation of immune response was the most relevant pathway predicted for S hosts. Members of Ap1 and NF-kB families were the most relevant TFs predicted for R and S, respectively.

Conclusion

This work provides indications of genetic mechanisms presented by Braford cattle with different levels of resistance in response to tick infestation, contributing to the search of candidate genes for tick resistance in bovine.

Amblyomma americanum ticks utilizes countervailing pro and anti-inflammatory proteins to evade host defense

Feeding and transmission of tick-borne disease (TBD) agents by ticks are facilitated by tick saliva proteins (TSP). Thus, defining functional roles of TSPs in tick evasion is expected to reveal potential targets in tick-antigen based vaccines to prevent TBD infections. This study describes two types of Amblyomma americanum TSPs: those that are similar to LPS activate macrophage (MΦ) to express pro-inflammation (PI) markers and another set that suppresses PI marker expression by activated MΦ. We show that similar to LPS, three recombinant (r) A. americanum insulin-like growth factor binding-related proteins (rAamIGFBP-rP1, rAamIGFBP-rP6S, and rAamIGFBP-rP6L), hereafter designated as PI-rTSPs, stimulated both PBMC -derived MΦ and mice RAW 267.4 MΦ to express PI co-stimulatory markers, CD40, CD80, and CD86 and cytokines, TNFα, IL-1, and IL-6. In contrast, two A. americanum tick saliva serine protease inhibitors (serpins), AAS27 and AAS41, hereafter designated as anti-inflammatory (AI) rTSPs, on their own did not affect MΦ function or suppress expression of PI markers, but enhanced expression of AI cytokines (IL-10 and TGFβ) in MΦ that were pre-activated by LPS or PI-rTSPs. Mice paw edema test demonstrated that in vitro validated PI- and AI-rTSPs are functional in vivo since injection of HEK293-expressed PI-rTSPs (individually or as a cocktail) induced edema comparable to carrageenan-induced edema and was characterized by upregulation of CD40, CD80, CD86, TNF-α, IL-1, IL-6, and chemokines: CXCL1, CCL2, CCL3, CCL5, and CCL11, whereas the AI-rTSPs (individually and cocktail) were suppressive. We propose that the tick may utilize countervailing PI and AI TSPs to regulate evasion of host immune defenses whereby TSPs such as rAamIGFBP-rPs activate host immune cells and proteins such as AAS27 and AAS41 suppress the activated immune cells.

Several studies have documented immuno-suppressive activities in whole tick saliva and salivary gland protein extracts. We have made contribution toward understanding the molecular basis of tick feeding, as we have described functions of defined tick saliva immuno-modulatory proteins. We have shown that A. americanum injects two groups of functionally opposed tick saliva proteins: those that could counter-intuitively be characterized as pro-host defense, and those that are expected to have anti-host immune defense functions. Based on our data, we propose that the tick evades host defense using countervailing pro- and anti- inflammatory proteins in which the pro-host defense tick saliva proteins stimulate host immune cells such as macrophages, and the anti-host defense tick saliva proteins suppress functions of the activated immune cells.

Synergistic effect of phosphodiesterase 4 inhibitor and serum on migration of endotoxin-stimulated macrophages

Macrophage migration is an essential step in host defense against infection and wound healing. Elevation of cAMP by inhibiting phosphodiesterase 4 (PDE4), enzymes that specifically degrade cAMP, is known to suppress various inflammatory responses in activated macrophages, but the role of PDE4 in macrophage migration is poorly understood. Here we show that the migration of Raw 264.7 macrophages stimulated with LPS was markedly and dose-dependently induced by the PDE4 inhibitor rolipram as assessed by scratch wound healing assay. Additionally, this response required the involvement of serum in the culture medium as serum starvation abrogated the effect. Further analysis revealed that rolipram and serum exhibited synergistic effect on the migration, and the influence of serum was independent of PDE4 mRNA expression in LPS-stimulated macrophages. Moreover, the enhanced migration by rolipram was mediated by activating cAMP/exchange proteins directly activated by cAMP (Epac) signaling, presumably via interaction with LPS/TLR4 signaling with the participation of unknown serum components. These results suggest that PDE4 inhibitors, together with serum components, may serve as positive regulators of macrophage recruitment for more efficient pathogen clearance and wound repair.

Environmental and Molecular Drivers of the α-Gal Syndrome

The α-Gal syndrome (AGS) is a type of allergy characterized by an IgE antibody (Ab) response against the carbohydrate Galα1-3Galβ1-4GlcNAc-R (α-Gal), which is present in glycoproteins from tick saliva and tissues of non-catarrhine mammals. Recurrent tick bites induce high levels of anti-α-Gal IgE Abs that mediate delayed hypersensitivity to consumed red meat products in humans. This was the first evidence that tick glycoproteins play a major role in allergy development with the potential to cause fatal delayed anaphylaxis to α-Gal-containing foods and drugs and immediate anaphylaxis to tick bites. Initially, it was thought that the origin of tick-derived α-Gal was either residual blood meal mammalian glycoproteins containing α-Gal or tick gut bacteria producing this glycan. However, recently tick galactosyltransferases were shown to be involved in α-Gal synthesis with a role in tick and tick-borne pathogen life cycles. The tick-borne pathogen Anaplasma phagocytophilum increases the level of tick α-Gal, which potentially increases the risk of developing AGS after a bite by a pathogen-infected tick. Two mechanisms might explain the production of anti-α-Gal IgE Abs after tick bites. The first mechanism proposes that the α-Gal antigen on tick salivary proteins is presented to antigen-presenting cells and B-lymphocytes in the context of Th₂ cell-mediated immunity induced by tick saliva. The second mechanism is based on the possibility that tick salivary prostaglandin E2 triggers Immunoglobulin class switching to anti-α-Gal IgE-producing B cells from preexisting mature B cells clones producing anti-α-Gal IgM and/or IgG. Importantly, blood group antigens influence the capacity of the immune system to produce anti-α-Gal Abs which in turn impacts individual susceptibility to AGS. The presence of blood type B reduces the capacity of the immune system to produce anti-α-Gal Abs, presumably due to tolerance to α-Gal, which is very similar in structure to blood group B antigen. Therefore, individuals with blood group B and reduced levels of anti-α-Gal Abs have lower risk to develop AGS. Specific immunity to tick α-Gal is linked to host immunity to tick bites. Basophil activation and release of histamine have been implicated in IgE-mediated acquired protective immunity to tick infestations and chronic itch. Basophil reactivity was also found to be higher in patients with AGS when compared to asymptomatic α-Gal sensitized individuals. In addition, host resistance to tick infestation is associated with resistance to tick-borne pathogen infection. Anti-α-Gal IgM and IgG Abs protect humans against vector-borne pathogens and blood group B individuals seem to be more susceptible to vector-borne diseases. The link between blood groups and anti-α-Gal immunity which in turn affects resistance to vector-borne pathogens and susceptibility to AGS, suggests a trade-off between susceptibility to AGS and protection to some infectious diseases. The understanding of the environmental and molecular drivers of the immune mechanisms involved in AGS is essential to developing tools for the diagnosis, control, and prevention of this growing health problem.

Effects of inflammatory cytokines on bone/cartilage repair

Many inflammatory factors can affect cell behaviors and work as a form of inter-regulatory networks through the inflammatory pathway. Inflammatory cytokines are critical for triggering bone regeneration after fracture or bone injury. Also, inflammatory cytokines play an important role in cartilage repair. The synergistic or antagonistic effects of both proinflammatory and anti-inflammatory cytokines have a great influence on fracture healing. This review discusses key inflammatory cytokines and signaling pathways involved in bone or cartilage repair.

Host immunogenetics in tick-borne encephalitis virus infection-The CCR5 crossroad

The human Tick-borne encephalitis virus (TBEV) infection is a complex event encompassing factors derived from the virus itself, the vectors, the final host, and the environment as well. Classically, genetic traits stand out among the human factors that modify the susceptibility and progression of infectious diseases. However, and although this is a changing scenario, studies evaluating the genetic factors that affect the susceptibility specifically to TBEV infection and TBEV-related diseases are still scarce. There are already some interesting pieces of evidence showing that some genes and polymorphisms have a real impact on TBEV infection. Also, the inflammatory processes involving tick-human interactions began to be understood in greater detail. This review focuses on the immunogenetic and inflammatory aspects concerning tick-host interactions, TBEV infections, and tick-borne encephalitis. Of note, it has been described that polymorphisms in CD209, GSTM1, IL-10, IL-28B, MMP9, OAS2, OAS3, and TLR3 have a statistically significant impact on TBEV infection. Besides, CCR5, its ligands, and the CCR5Δ32 genetic variant seem to have a very important influence on the infection and its immune responses. Taking this information into consideration, a special discussion regarding the effects of CCR5 on TBEV infection and tick-borne encephalitis will be presented. Emerging topics (such as exosomes, evasins, and CCR5 blockers) involving immunological and inflammatory aspects of TBEV-human interactions will also be addressed. Lastly, the current picture of TBEV infection and the importance to address the TBEV-associated problems through the One Health perspective will be discussed.

Grading system for periodontitis by analyzing levels of periodontal pathogens in saliva

Periodontitis is an infectious disease that is associated with microorganisms that colonize the tooth surface. Clinically, periodontal condition stability reflects dynamic equilibrium between bacterial challenge and host response. Therefore, periodontal pathogen assessment can assist in the early detection of periodontitis. Here we developed a grading system called the periodontal pathogen index (PPI) by analyzing the copy numbers of multiple pathogens both in healthy and chronic periodontitis patients. We collected 170 mouthwash samples (64 periodontally healthy controls and 106 chronic periodontitis patients) and analyzed the salivary 16S rRNA levels of nine pathogens using multiplex, quantitative real-time polymerase chain reaction. Except for Aggregatibacter actinomycetemcomitans, copy numbers of all pathogens were significantly higher in chronic periodontitis patients. We classified the samples based on optimal cut-off values with maximum sensitivity and specificity from receiver operating characteristic curve analyses (AUC = 0.91, 95% CI: 0.87-0.96) into four categories of PPI: Healthy (1-40), Moderate (41-60), At Risk (61-80), and Severe (81-100). PPI scores were significantly higher in all chronic periodontitis patients than in the controls (odds ratio: 31.7, 95% CI: 13.41-61.61) and were associated with age, scaling as well as clinical characteristics including clinical attachment level and plaque index. Our PPI grading system can be clinically useful for the early assessment of pathogenic bacterial burden and follow-up monitoring after periodontitis treatment.

[Saliva of periodontitis patients promotes macrophage differentiation and activation]

OBJECTIVE

The aim of this study was to investigate the effect of saliva of patients with chronic periodontitis (CPD) on the differentiation, activation, and secretion of osteoclast-maturing mediators of macrophages.

METHODS

A total of 40 saliva samples were collected from healthy donors (n=20) and severe periodontitis patients (n=20). Peripheral blood mononuclear cells (PBMCs) and THP-1 monocyte line cells were challenged with 15% saliva for 5 days. The phenotype, surface marker, and phagocytosis of macrophages were analyzed by flow cytometry and microscopy. Osteoclast-maturing mediators were assayed by using enzyme-linked immunosorbent assay (ELISA) kits.

RESULTS

When PBMCs were treated with CPD saliva for 5 days, 61.25%±11.33% of cells were transformed into large granular cells; 86.78%±13.69% of large granular cells were identified as CD14⁺⁺CD16⁺ macrophages. When THP-1 cells were treated with CPD saliva, most cells attached to the bottom of cell culture plates, thereby exhibiting macrophage morphology and releasing additional osteoclast-maturing mediators. Furthermore, the phagocytosis of THP-1 cells considerably increased in the presence of CPD saliva (66.35%±9.67%) compared with medium control (33.33%±7.52%), or healthy saliva (40.71%±3.52%).

CONCLUSIONS

Saliva from patients with CPD can induce macrophage differentiation, activate phagocytose microorganisms, and secrete osteoclast-maturing mediators.

Ticks and Tick-Borne Infections: Complex Ecology, Agents, and Host Interactions

Ticks transmit the most diverse array of infectious agents of any arthropod vector. Both ticks and the microbes they transmit are recognized as significant threats to human and veterinary public health. This article examines the potential impacts of climate change on the distribution of ticks and the infections they transmit; the emergence of novel tick-borne pathogens, increasing geographic range and incidence of tick-borne infections; and advances in the characterization of tick saliva mediated modulation of host defenses and the implications of those interactions for transmission, establishment, and control of tick infestation and tick-borne infectious agents.

Mosquito Saliva Reshapes Alphavirus Infection and Immunopathogenesis

Alphaviruses are transmitted to humans via bites of infected mosquitoes. Although alphaviruses have caused a wide range of outbreaks and crippling disease, the availability of licensed vaccines or antiviral therapies remains limited. Mosquito vectors such as Aedes and Culex are the main culprits in the transmission of alphaviruses. This review explores how mosquito saliva may promote alphavirus infection. Identifying the roles of mosquito-derived factors in alphavirus pathogenesis will generate novel tools to circumvent and control mosquito-borne alphavirus infections in humans.

Immunomodulatory Effects of Amblyomma variegatum Saliva on Bovine Cells: Characterization of Cellular Responses and Identification of Molecular Determinants

The tropical bont tick, Amblyomma variegatum, is a tick species of veterinary importance and is considered as one of major pest of ruminants in Africa and in the Caribbean. It causes direct skin lesions, transmits heartwater, and reactivates bovine dermatophilosis. Tick saliva is reported to affect overall host responses through immunomodulatory and anti-inflammatory molecules, among other bioactive molecules. The general objective of this study was to better understand the role of saliva in interaction between the Amblyomma tick and the host using cellular biology approaches and proteomics, and to discuss its impact on disease transmission and/or activation. We first focused on the immuno-modulating effects of semi-fed A. variegatum female saliva on bovine peripheral blood mononuclear cells (PBMC) and monocyte-derived macrophages in vitro. We analyzed its immuno-suppressive properties by measuring the effect of saliva on PBMC proliferation, and observed a significant decrease in ConA-stimulated PBMC lymphoproliferation. We then studied the effect of saliva on bovine macrophages using flow cytometry to analyze the expression of MHC-II and co-stimulation molecules (CD40, CD80, and CD86) and by measuring the production of nitric oxide (NO) and pro- or anti-inflammatory cytokines. We observed a significant decrease in the expression of MHC-II, CD40, and CD80 molecules, associated with decreased levels of IL-12-p40 and TNF-α and increased level of IL-10, which could explain the saliva-induced modulation of NO. To elucidate these immunomodulatory effects, crude saliva proteins were analyzed using proteomics with an Orbitrap Elite mass spectrometer. Among the 336 proteins identified in A. variegatum saliva, we evidenced bioactive molecules exhibiting anti-inflammatory, immuno-modulatory, and anti-oxidant properties (e.g., serpins, phospholipases A2, heme lipoprotein). We also characterized an intriguing ubiquitination complex that could be involved in saliva-induced immune modulation of the host. We propose a model for the interaction between A. variegatum saliva and host immune cells that could have an effect during tick feeding by favoring pathogen dissemination or activation by reducing the efficiency of host immune response to the corresponding tick-borne diseases.

Hyalomma dromedarii (Acari: Ixodidae) Salivary Gland Extract Inhibits Angiogenesis and Exhibits In Vitro Antitumor Effects

Hard ticks (Acari: Ixodidae) are blood-sucking ectoparasites characterized by the extended period of their attachment to their host. To access their bloodmeal, ticks secrete saliva containing a range of molecules that target the host's inflammation, immune system, and hemostatic components. Some of these molecules reportedly possess antiangiogenic and antitumor properties. The present study describes our investigation, the first of its kind, of the antiangiogenic and antitumoral effects of the Hyalomma dromedarii Koch, 1844 (Acari: Ixodidae), salivary gland extract (SGE), which inhibited the adhesion and migration of Human Umbilical Vein Endothelial Cells (HUVECs) in a dose-dependent manner, as well as angiogenesis in the Chick Chorioallantoic Membrane model. Interestingly, H. dromedarii SGE exerted an antiproliferative effect on U87 glioblastoma cells and inhibited their adhesion and migration to fibrinogen. These results open up new possibilities for characterizing and developing new molecules involved in the key steps of tumor progression.

Interaction between saliva's adenosine and tick parasitism: effects on feeding and reproduction

Background

It has recently been demonstrated that saliva from Rhipicephalus sanguineus ticks contains adenosine (ADO) and prostaglandin E2 (PGE2), two non-protein molecules that have significant immunomodulatory properties. These molecules can inhibit cytokine production by dendritic cells (DCs), while also reducing the expression of CD40 in these cells. However, more studies are needed for a better understanding of their participation in the feeding of ticks in vivo. This work, therefore, evaluated the importance of ADO during tick infestations. Mice were infested with adult ticks (3 couples/mouse), and their skin was collected at the tick-infested site (3rd and 7th day), and mRNA for receptors of ADO was quantified by real-time PCR.

Results

Tick infestation increased by four and two times the expression of the A2b and A3v1 receptors on day 3, respectively, while expression of other ADO receptors was unaltered. In addition, we treated mice (n = 10/group) daily with 8-(p-Sulfophenyl)theophylline, 8-pSPT, 20 mg/kg, i.p.), a non-selective antagonist of ADO receptors, and evaluated the performance of ticks during infestations. Female ticks fed on 8-pSPT-treated mice presented a reduction in their engorgement, weight and hatching rates of egg masses, and survival times of larvae compared to the same parameters presented by ticks in the control group. To investigate if these 8-pSPT-treated mice presented altered immune responses, we performed three tick infestations and collected their lymph node cells to determine the percentages and activation state of DCs and cytokine production by lymphocytes by flow cytometry (Cytometric Bead Array technique, CBA). Our data showed that 8-pSPT-treated mice presented an increase in the percentage of DCs as well as of their stimulatory and co-stimulatory molecules (CD40, CD80 and MHCII). Regarding production of T cell cytokines, we observed a significant increase in the levels of IL-2 and a significant decrease in IL-10, IL-17, TNF-α and IFN-γ cytokines.

Conclusions

These results suggest that ADO produced by ticks helps them feed and reproduce and that this effect may be due to modulation of host DCs and T cells.

The Essential Role of Tick Salivary Glands and Saliva in Tick Feeding and Pathogen Transmission

As long-term pool feeders, ticks have developed myriad strategies to remain discreetly but solidly attached to their hosts for the duration of their blood meal. The critical biological material that dampens host defenses and facilitates the flow of blood-thus assuring adequate feeding-is tick saliva. Saliva exhibits cytolytic, vasodilator, anticoagulant, anti-inflammatory, and immunosuppressive activity. This essential fluid is secreted by the salivary glands, which also mediate several other biological functions, including secretion of cement and hygroscopic components, as well as the watery component of blood as regards hard ticks. When salivary glands are invaded by tick-borne pathogens, pathogens may be transmitted via saliva, which is injected alternately with blood uptake during the tick bite. Both salivary glands and saliva thus play a key role in transmission of pathogenic microorganisms to vertebrate hosts. During their long co-evolution with ticks and vertebrate hosts, microorganisms have indeed developed various strategies to exploit tick salivary molecules to ensure both acquisition by ticks and transmission, local infection and systemic dissemination within the vertebrate host.

Enhanced activity of macrophage M1/M2 phenotypes in periodontitis

OBJECTIVE

Monocytes/macrophages play a key role in mobilizing host defense against microbial infection. The selectivity of gene expression can turn macrophages into M1- or M2-type and the plasticity and differentiation of both M1 and M2 macrophages may play important roles in the development of periodontal disease. Our research aimed to study the association between the ratio of M1/M2 macrophage and inflammatory cytokines IL-1β, MMP-9, and investigate the expressions of M1-and M2-type macrophages in gingivitis and chronic periodontitis.

METHODS

Forty specimens were collected from gingivitis individuals (n=20) and chronic periodontitis (n=20). Probing depth (PD), clinical attachment level (CAL), plaque index (PI) and bleeding on probing (BOP) were recorded. The expressions of M1- and M2-type macrophages are detected with immunohistochemical method and the relative expressions of M1-, M2-type macrophage, IL-1β and MMP-9 were assayed using real-time polymerase chain reactions.

RESULTS

The M1 and M2 peptide were mainly observed in the cytoplasm of gingival connective tissue. The ratio of M1/M2 was significant higher in chronic periodontitis group compared with that in gingivitis one. In addition, the relative expressions of IL-1β and MMP-9 also increased in periodontitis group and was correlated with the ratios of M1/M2. Meanwhile, PD was positively correlated with ratios of M1/M2.

CONCLUSIONS

Periodontal inflammation associates with an enhancement of ratio of M1/M2 phenotypes of macrophages. M1/M2 ratio could provide useful information on the periodontal tissue health status.

Effect of Amblyomma maculatum (Acari: Ixodidae) Saliva on the Acute Cutaneous Immune Response to Rickettsia parkeri Infection in a Murine Model

Rickettsia parkeri Luckman (Rickettsiales: Rickettsiaceae) is a pathogenic spotted fever group Rickettsia transmitted by Amblyomma maculatum Koch (Acari: Ixodidae) in the United States. The acute innate immune response to this pathogen and the effect of tick feeding or salivary components on this response is largely unknown. We hypothesized that A. maculatum saliva enhances R. parkeri infection via downregulation of the acute cellular and cytokine immune response. C3H/HeN mice were intradermally inoculated with R. parkeri both with and without A. maculatum saliva. Flow cytometry and microscopic evaluation of inoculation site skin suspensions revealed that neutrophils and macrophages predominated at 6 and 24 h post R. parkeri inoculation, respectively. This cellular influx was significantly downregulated when A. maculatum saliva was inoculated along with R. parkeri Inflammatory cytokines (interferon γ and interleukins 6 and 10) were significantly elevated after R. parkeri inoculation. However, cytokine concentration and rickettsial load were not significantly modified by A. maculatum saliva during the acute phase of infection. These results revealed that tick saliva inhibits the cutaneous cellular influx during the acute phase of rickettsial infection. Further study is needed to determine the overall impact of this effect on the establishment of rickettsiosis in the host and development of disease.

Deviant Behavior: Tick-Borne Pathogens and Inflammasome Signaling

In the face of an assault, host cells mount an immediate response orchestrated by innate immunity. Two of the best described innate immune signaling networks are the Toll- and the Nod-like receptor pathways. Extensive work has been done characterizing both signaling cascades with several recent advances on the forefront of inflammasome biology. In this review, we will discuss how more commonly-studied pathogens differ from tick-transmitted microbes in the context of Nod-like receptor signaling and inflammasome formation. Because pathogens transmitted by ticks have unique characteristics, we offer the opinion that these microbes can be used to uncover novel principles of Nod-like receptor biology.

Modulation of host immunity by tick saliva

Next generation sequencing and proteomics have helped to comprehensively characterize gene expression in tick salivary glands at both the transcriptome and the proteome level. Functional data are, however, lacking. Given that tick salivary secretions are critical to the success of the tick transmission lifecycle and, as a consequence, for host colonization by the pathogens they spread, we thoroughly review here the literature on the known interactions between tick saliva (or tick salivary gland extracts) and the innate and adaptive vertebrate immune system. The information is intended to serve as a reference for functional characterization of the numerous genes and proteins expressed in tick salivary glands with an ultimate goal to develop novel vector and pathogen control strategies.

SIGNIFICANCE

We overview all the known interactions of tick saliva with the vertebrate immune system. The provided information is important, given the recent developments in high-throughput transcriptomic and proteomic analysis of gene expression in tick salivary glands, since it may serve as a guideline for the functional characterization of the numerous newly-discovered genes expressed in tick salivary glands.

Host-feeding behaviour of Dermacentor reticulatus and Dermacentor marginatus in mono-specific and inter-specific infestations

Background

Given the sympatric occurrence in some regions of Europe and the great epidemiological significance of D. reticulatus and D. marginatus species, we investigated the behaviour of these ticks during inter-specific and mono-specific host infestations.

Findings

The investigations were conducted on rabbits at 20 ± 3 °C and humidity of 38 ± 1 %. The inter-specific infestations groups consisted of 20 females and ten males of D. marginatus and 20 females and ten males of D. reticulatus on each host, whereas mono-specific infestations involved 40 females and 20 males of each species.

The investigations have demonstrated competition between the two tick species resulting in modification of the behaviour on the host and the feeding course in D. marginatus females by the presence of D. reticulatus. In the inter-specific group, D. marginatus females attached for a longer time (mean 2.74 ± 1.12 h) than in the mono-specific group (mean 1.24 ± 0.97 h) (p < 0.0001). The feeding period of these females was shorter (9.45 ± 1.30 days) than in the mono-specific group (13.15 ± 2.53 days) (p < 0.0001), but they exhibited a statistically significantly higher body weight in comparison with the females from the mono-specific infestation (p = 0.0155). In D. reticulatus females, no significant difference was found in the host attachment and feeding rates between the mono-specific and inter-specific groups.

Conclusions

The differences in the behaviour of the females from both species during co-feeding reflect physiological adaptation to environmental conditions, which enables them to ingest blood and reproduce. During co-feeding of D. reticulatus and D. marginatus on the same host, two inter-specific systems with different physiological features are formed, which may influence the transmission of tick-borne pathogens.

Immunosuppressive effects of Amblyomma cajennense tick saliva on murine bone marrow-derived dendritic cells

Background

Dendritic cells (DCs) are professional antigen-presenting cells with vital roles in the activation of host immunity. Ticks are bloodsucking arthropods that secrete bioactive compounds with immunomodulatory properties via their saliva. It is known that some tick species modulate the biology of DCs with different intensities; however, studies on Amblyomma cajennense, the Cayenne tick, have not yet been performed, although this species is considered one of the most capable of modulating immune responses of different hosts.

Methods

Engorged female ticks were stimulated with dopamine to induce salivation, and saliva was pooled. The effects of tick saliva on the biology of dendritic cells were assessed by examining DC differentiation, maturation, migration, cellular viability, cytokine production and expression of surface markers by flow cytometry and ELISA. Competitive enzyme immunoassays (EIA) were used to measure saliva prostaglandin-E₂ (PGE₂). Statistical significance was determined by ANOVA followed by Tukey’s post-test or by the Kruskal-Wallis test with the Dunns post-test.

Results

In this work, we demonstrated that the presence of A. cajennense saliva to bone marrow cultures inhibit DC differentiation. This inhibition was not accompanied by inhibition or induction of stimulatory and co-stimulatory molecules such as MHC-II, CD40, CD80 or CD86. Immature and mature DCs that were pre-exposed to saliva showed reduced migration toward the chemokines RANTES and MIP-3β. This inhibition was associated to a reduced expression of CCR5 (the receptor for RANTES) or CCR7 (the receptor for MIP-3β) induced by the presence of saliva in the cultures. Tick saliva also inhibited IL-12p40, IL-6 and TNF-α in a concentration-dependent manner while potentiating IL-10 cytokine production by DCs stimulated with Toll-like receptor-4 ligand. Additionally, A. cajennense tick saliva inhibited the expression of CD40 and CD86 in mature DCs while potentiating the expression of PD-L1. PGE₂ was detected as one of the constituents of saliva at a concentration of ~ 80 ng/ml, and we believe that most of the results reported herein are due to the presence of PGE₂.

Conclusions

These results help to understand the tick-host interaction and demonstrate that A. cajennense ticks appear to have mechanisms for modulating host immune cells, including DCs.

A 24-48 h fed Amblyomma americanum tick saliva immuno-proteome

BACKGROUND

Multiple tick saliva proteins, the majority of which are unknown, confer tick resistance in repeatedly infested animals. The objective of this study was to identify the 24-48 h fed Amblyomma americanum tick saliva immuno-proteome. The 24-48 h tick-feeding phase is critical to tick parasitism as it precedes important events in tick biology, blood meal feeding and disease agent transmission. Fed male, 24 and 96 h fed female phage display cDNA expression libraries were biopanned using rabbit antibodies to 24 and 48 h fed A. americanum female tick saliva proteins. Biopanned immuno-cDNA libraries were subjected to next generation sequencing, de novo assembly, and bioinformatic analysis.

RESULTS

More than 800 transcripts that code for 24-48 h fed A. americanum immuno-proteins are described. Of the 895 immuno-proteins, 52% (464/895) were provisionally identified based on matches in GenBank. Of these, ~19% (86/464) show high level of identity to other tick hypothetical proteins, and the rest include putative proteases (serine, cysteine, leukotriene A-4 hydrolase, carboxypeptidases, and metalloproteases), protease inhibitors (serine and cysteine protease inhibitors, tick carboxypeptidase inhibitor), and transporters and/or ligand binding proteins (histamine binding/lipocalin, fatty acid binding, calreticulin, hemelipoprotein, IgG binding protein, ferritin, insulin-like growth factor binding proteins, and evasin). Others include enzymes (glutathione transferase, cytochrome oxidase, protein disulfide isomerase), ribosomal proteins, and those of miscellaneous functions (histamine release factor, selenoproteins, tetraspanin, defensin, heat shock proteins).

CONCLUSIONS

Data here demonstrate that A. americanum secretes a complex cocktail of immunogenic tick saliva proteins during the first 24-48 h of feeding. Of significance, previously validated immunogenic tick saliva proteins including AV422 protein, calreticulin, histamine release factor, histamine binding/lipocalins, selenoproteins, and paramyosin were identified in this screen, supporting the specificity of the approach in this study. While descriptive, this study opens opportunities for in-depth tick feeding physiology studies.

Effects of Aedes aegypti salivary components on dendritic cell and lymphocyte biology

Background

Saliva is a key element of interaction between hematophagous mosquitoes and their vertebrate hosts. In addition to allowing a successful blood meal by neutralizing or delaying hemostatic responses, the salivary cocktail is also able to modulate the effector mechanisms of host immune responses facilitating, in turn, the transmission of several types of microorganisms. Understanding how the mosquito uses its salivary components to circumvent host immunity might help to clarify the mechanisms of transmission of such pathogens and disease establishment.

Methods

Flow cytometry was used to evaluate if increasing concentrations of A. aegypti salivary gland extract (SGE) affects bone marrow-derived DC differentiation and maturation. Lymphocyte proliferation in the presence of SGE was estimated by a colorimetric assay. Western blot and Annexin V staining assays were used to assess apoptosis in these cells. Naïve and memory cells from mosquito-bite exposed mice or OVA-immunized mice and their respective controls were analyzed by flow cytometry.

Results

Concentration-response curves were employed to evaluate A. aegypti SGE effects on DC and lymphocyte biology. DCs differentiation from bone marrow precursors, their maturation and function were not directly affected by A. aegypti SGE (concentrations ranging from 2.5 to 40 μg/mL). On the other hand, lymphocytes were very sensitive to the salivary components and died in the presence of A. aegypti SGE, even at concentrations as low as 0.1 μg/mL. In addition, A. aegypti SGE was shown to induce apoptosis in all lymphocyte populations evaluated (CD4⁺ and CD8⁺ T cells, and B cells) through a mechanism involving caspase-3 and caspase-8, but not Bim. By using different approaches to generate memory cells, we were able to verify that these cells are resistant to SGE effects.

Conclusion

Our results show that lymphocytes, and not DCs, are the primary target of A. aegypti salivary components. In the presence of A. aegypti SGE, naïve lymphocyte populations die by apoptosis in a caspase-3- and caspase-8-dependent pathway, while memory cells are selectively more resistant to its effects. The present work contributes to elucidate the activities of A. aegypti salivary molecules on the antigen presenting cell-lymphocyte axis and in the biology of these cells.