Evasin-4, a tick-derived chemokine-binding protein with broad selectivity can be modified for use in preclinical disease models

Structural basis of chemokine recognition by the class A3 tick evasin EVA-ACA1001

Ticks produce chemokine-binding proteins, known as evasins, in their saliva to subvert the host's immune response. Evasins bind to chemokines and thereby inhibit the activation of their cognate chemokine receptors, thus suppressing leukocyte recruitment and inflammation. We recently described subclass A3 evasins, which, like other class A evasins, exclusively target CC chemokines but appear to use a different binding site architecture to control target selectivity among CC chemokines. We now describe the structural basis of chemokine recognition by the class A3 evasin EVA-ACA1001. EVA-ACA1001 binds to almost all human CC chemokines and inhibits receptor activation. Truncation mutants of EVA-ACA1001 showed that, unlike class A1 evasins, both the N- and C-termini of EVA-ACA1001 play minimal roles in chemokine binding. To understand the structural basis of its broad chemokine recognition, we determined the crystal structure of EVA-ACA1001 in complex with the human chemokine CCL16. EVA-ACA1001 forms backbone-backbone interactions with the CC motif of CCL16, a conserved feature of all class A evasin-chemokine complexes. A hydrophobic pocket in EVA-ACA1001, formed by several aromatic side chains and the unique disulfide bond of class A3 evasins, accommodates the residue immediately following the CC motif (the "CC + 1 residue") of CCL16. This interaction is shared with EVA-AAM1001, the only other class A3 evasins characterized to date, suggesting it may represent a common mechanism that accounts for the broad recognition of CC chemokines by class A3 evasins.

Discovery and pharmacophoric characterization of chemokine network inhibitors using phage-display, saturation mutagenesis and computational modelling

CC and CXC-chemokines are the primary drivers of chemotaxis in inflammation, but chemokine network redundancy thwarts pharmacological intervention. Tick evasins promiscuously bind CC and CXC-chemokines, overcoming redundancy. Here we show that short peptides that promiscuously bind both chemokine classes can be identified from evasins by phage-display screening performed with multiple chemokines in parallel. We identify two conserved motifs within these peptides and show using saturation-mutagenesis phage-display and chemotaxis studies of an exemplar peptide that an anionic patch in the first motif and hydrophobic, aromatic and cysteine residues in the second are functionally necessary. AlphaFold2-Multimer modelling suggests that the peptide occludes distinct receptor-binding regions in CC and in CXC-chemokines, with the first and second motifs contributing ionic and hydrophobic interactions respectively. Our results indicate that peptides with broad-spectrum anti-chemokine activity and therapeutic potential may be identified from evasins, and the pharmacophore characterised by phage display, saturation mutagenesis and computational modelling.

Swapping N-terminal regions among tick evasins reveals cooperative interactions influencing chemokine binding and selectivity

Class A tick evasins are natural chemokine-binding proteins that block the signaling of multiple chemokines from the CC subfamily through their cognate receptors, thus suppressing leukocyte recruitment and inflammation. Development of tick evasins as chemokine-targeted anti-inflammatory therapeutics requires an understanding of the factors controlling their chemokine recognition and selectivity. To investigate the role of the evasin N-terminal region for chemokine recognition, we prepared chimeric evasins by interchanging the N-terminal regions of four class A evasins, including a newly identified evasin, EVA-RPU02. We show through chemokine binding analysis of the parental and chimeric evasins that the N-terminal region is critical for chemokine binding affinity and selectivity. Notably, we found some chimeras were unable to bind certain cognate chemokine ligands of both parental evasins. Moreover, unlike any natural evasins characterized to date, some chimeras exhibited specific binding to a single chemokine. These results indicate that the evasin N terminus interacts cooperatively with the “body” of the evasin to enable optimum chemokine recognition. Furthermore, the altered chemokine selectivity of the chimeras validates the approach of engineering the N termini of evasins to yield unique chemokine recognition profiles.

The tick and I: Parasite-host interactions between ticks and humans

Ticks, particularly hard ticks (Ixodidae), which are among the most important vectors of dangerous infectious agents, feed on their hosts for extended periods of time. With this lifestyle, numerous adaptations have evolved in ticks and their hosts, the pharmacological importance of which is increasingly being recognized. Many bioactive substances in tick saliva are being considered as the basis of new drugs. For example, components of tick cement can be developed into tissue adhesives or wound closures. Analgesic and antipruritic salivary components inhibit histamine or bradykinin, while other tick-derived molecules bind opioid or cannabinoid receptors. Tick saliva inhibits the extrinsic, intrinsic, or common pathway of blood coagulation with implications for the treatment of thromboembolic diseases. It contains vasodilating substances and affects wound healing. The broad spectrum of immunomodulatory and immunosuppressive effects of tick saliva, such as inhibition of chemokines or cellular immune responses, allows development of drugs against inflammation in autoimmune diseases and/or infections. Finally, modern vaccines against ticks can curb the spread of serious infections. The medical importance of the complex tick-host interactions is increasingly being recognized and translated into first clinical applications. Using selected examples, an overview of the mutual adaptations of ticks and hosts is given here, focusing on their significance to medical advance.

Phylogenetic Analysis Indicates That Evasin-Like Proteins of Ixodid Ticks Fall Into Three Distinct Classes

Chemokines are structurally related proteins that activate leucocyte migration in response to injury or infection. Tick saliva contains chemokine-binding proteins or evasins which likely neutralize host chemokine function and inflammation. Biochemical characterisation of 50 evasins from Ixodes, Amblyomma and Rhipicephalus shows that they fall into two functional classes, A and B, with exclusive binding to either CC- or CXC- chemokines, respectively. Class A evasins, EVA1 and EVA4 have a four-disulfide-bonded core, whereas the class B evasin EVA3 has a three-disulfide-bonded “knottin” structure. All 29 class B evasins have six cysteine residues conserved with EVA3, arrangement of which defines a Cys6-motif. Nineteen of 21 class A evasins have eight cysteine residues conserved with EVA1/EVA4, the arrangement of which defines a Cys8-motif. Two class A evasins from Ixodes (IRI01, IHO01) have less than eight cysteines. Many evasin-like proteins have been identified in tick salivary transcriptomes, but their phylogenetic relationship with respect to biochemically characterized evasins is not clear. Here, using BLAST searches of tick transcriptomes with biochemically characterized evasins, we identify 292 class A and 157 class B evasins and evasin-like proteins from Prostriate (Ixodes), and Metastriate (Amblyomma, Dermacentor, Hyalomma, Rhipicephalus) ticks. Phylogenetic analysis shows that class A evasins/evasin-like proteins segregate into two classes, A1 and A2. Class A1 members are exclusive to Metastriate ticks and typically have a Cys8-motif and include EVA1 and EVA4. Class A2 members are exclusive to Prostriate ticks, lack the Cys8-motif, and include IHO01 and IRI01. Class B evasins/evasin-like proteins are present in both Prostriate and Metastriate lineages, typically have a Cys6-motif, and include EVA3. Most evasins/evasin-like proteins in Metastriate ticks belong to class A1, whereas in Prostriate species they are predominantly class B. In keeping with this, the majority of biochemically characterized Metastriate evasins bind CC-chemokines, whereas the majority of Prostriate evasins bind CXC-chemokines. While the origin of the structurally dissimilar classes A1 and A2 is yet unresolved, these results suggest that class B evasin-like proteins arose before the divergence of Prostriate and Metastriate lineages and likely functioned to neutralize CXC-chemokines and support blood feeding.

Immunomodulatory Proteins in Tick Saliva From a Structural Perspective

To feed successfully, ticks must bypass or suppress the host’s defense mechanisms, particularly the immune system. To accomplish this, ticks secrete specialized immunomodulatory proteins into their saliva, just like many other blood-sucking parasites. However, the strategy of ticks is rather unique compared to their counterparts. Ticks’ tendency for gene duplication has led to a diverse arsenal of dozens of closely related proteins from several classes to modulate the immune system’s response. Among these are chemokine-binding proteins, complement pathways inhibitors, ion channels modulators, and numerous poorly characterized proteins whose functions are yet to be uncovered. Studying tick immunomodulatory proteins would not only help to elucidate tick-host relationships but would also provide a rich pool of potential candidates for the development of immunomodulatory intervention drugs and potentially new vaccines. In the present review, we will attempt to summarize novel findings on the salivary immunomodulatory proteins of ticks, focusing on biomolecular targets, structure-activity relationships, and the perspective of their development into therapeutics.

A Cornflower Extract Containing N-Feruloylserotonin Reduces Inflammation in Human Skin by Neutralizing CCL17 and CCL22 and Inhibiting COX-2 and 5-LOX

Thymus and Activation-Regulated Chemokine (TARC/CCL17) and Macrophage-Derived Chemokine (MDC/CCL22) are two key chemokines exerting their biological effect via binding and activating a common receptor CCR4, expressed at the surface of type 2 helper T (Th2) cells. By recruiting Th2 cells in the dermis, CCL17 and CCL22 promote the development of inflammation in atopic skin. The aim of this research was to develop a plant extract whose biological properties, when applied topically, could be beneficial for people with atopic-prone skin. The strategy which was followed consisted in identifying ligands able to neutralize the biological activity of CCL17 and CCL22. Thus, an in silico molecular modeling and a generic screening assay were developed to screen natural molecules binding and blocking these two chemokines. N-Feruloylserotonin was identified as a neutraligand of CCL22 in these experiments. A cornflower extract containing N-feruloylserotonin was selected for further in vitro tests: the gene expression modulation of inflammation biomarkers induced by CCL17 or CCL22 in the presence or absence of this extract was assessed in the HaCaT keratinocyte cell line. Additionally, the same cornflower extract in another vehicle was evaluated in parallel with N-feruloylserotonin for cyclooxygenase-2 (COX-2) and 5-lipoxygenase (5-LOX) enzymatic cellular inhibition. The cornflower extract was shown to neutralize the two chemokines in vitro, inhibited COX-2 and 5-LOX, and demonstrated anti-inflammatory activities due mainly to the presence of N-feruloylserotonin. Although these findings would need to be confirmed in an in vivo study, the in vitro studies lay the foundation to explain the benefits of the cornflower extract when applied topically to individuals with atopic-prone skin.

Structural characterization of anti-CCL5 activity of the tick salivary protein evasin-4

Ticks, as blood-sucking parasites, have developed a complex strategy to evade and suppress host immune responses during feeding. The crucial part of this strategy is expression of a broad family of salivary proteins, called Evasins, to neutralize chemokines responsible for cell trafficking and recruitment. However, structural information about Evasins is still scarce, and little is known about the structural determinants of their binding mechanism to chemokines. Here, we studied the structurally uncharacterized Evasin-4, which neutralizes a broad range of CC-motif chemokines, including the chemokine CC-motif ligand 5 (CCL5) involved in atherogenesis. Crystal structures of Evasin-4 and E66S CCL5, an obligatory dimeric variant of CCL5, were determined to a resolution of 1.3–1.8 Å. The Evasin-4 crystal structure revealed an L-shaped architecture formed by an N- and C-terminal subdomain consisting of eight β-strands and an α-helix that adopts a substantially different position compared with closely related Evasin-1. Further investigation into E66S CCL5–Evasin-4 complex formation with NMR spectroscopy showed that residues of the N terminus are involved in binding to CCL5. The peptide derived from the N-terminal region of Evasin-4 possessed nanomolar affinity to CCL5 and inhibited CCL5 activity in monocyte migration assays. This suggests that Evasin-4 derivatives could be used as a starting point for the development of anti-inflammatory drugs.

Using evasins to target the chemokine network in inflammation

Inflammation, is driven by a network comprising cytokines, chemokines, their target receptors and leukocytes, and is a major pathologic mechanism that adversely affects organ function in diverse human diseases. Despite being supported by substantial target validation, no successful anti-chemokine therapeutic to treat inflammatory disease has yet been developed. This is in part because of the robustness of the chemokine network, which emerges from a large total chemokine load in disease, promiscuous expression of receptors on leukocytes, promiscuous and synergistic interactions between chemokines and receptors, and feedforward loops created by secretion of chemokines by leukocytes themselves. Many parasites, including viruses, helminths and ticks, evade the chemokine network by producing proteins that bind promiscuously to chemokines or their receptors. Evasins - three small glycoproteins identified in the saliva of the brown dog tick - bind multiple chemokines, and are active in several animal models of inflammatory disease. Over 50 evasin homologs have recently been identified from diverse tick species. Characterization of the chemokine binding patterns of evasins show that several have anti-chemokine activities that extend substantially beyond those previously described. These studies indicate that evasins function at the site of the tick bite by reducing total chemokine load. This not only reduces chemokine signaling to receptors, but also interrupts feedforward loops, thus disabling the chemokine network. Taking the lead from nature, a goal for the development of new anti-chemokine therapeutics would be to reduce the total chemokine load in disease. This could be achieved by administering appropriate evasin combinations or by smaller peptides that mimic evasin action.

Evasins: Tick Salivary Proteins that Inhibit Mammalian Chemokines

Ticks are hematophagous arachnids that parasitize mammals and other hosts, feeding on their blood. Ticks secrete numerous salivary factors that enhance host blood flow or suppress the host inflammatory response. The recruitment of leukocytes, a hallmark of inflammation, is regulated by chemokines, which activate chemokine receptors on the leukocytes. Ticks target this process by secreting glycoproteins called Evasins, which bind to chemokines and prevent leukocyte recruitment. This review describes the recent discovery of numerous Evasins produced by ticks, their classification into two structural and functional classes, and the efficacy of Evasins in animal models of inflammatory diseases. The review also proposes a standard nomenclature system for Evasins and discusses the potential of repurposing or engineering Evasins as therapeutic anti-inflammatory agents.

The Use of Tick Salivary Proteins as Novel Therapeutics

The last three decades of research into tick salivary components have revealed several proteins with important pharmacological and immunological activities. Two primary interests have driven research into tick salivary secretions: the search for suitable pathogen transmission blocking or “anti-tick” vaccine candidates and the search for novel therapeutics derived from tick salivary components. Intensive basic research in the field of tick salivary gland transcriptomics and proteomics has identified several major protein families that play important roles in tick feeding and overcoming vertebrate anti-tick responses. Moreover, these families contain members with unrealized therapeutic potential. Here we review the major tick salivary protein families exploitable in medical applications such as immunomodulation, inhibition of hemostasis and inflammation. Moreover, we discuss the potential, opportunities, and challenges in searching for novel tick-derived drugs.

Tick saliva protein Evasin-3 modulates chemotaxis by disrupting CXCL8 interactions with glycosaminoglycans and CXCR2

Chemokines are a group of chemotaxis proteins that regulate cell trafficking and play important roles in immune responses and inflammation. Ticks are blood-sucking parasites that secrete numerous immune-modulatory agents in their saliva to evade host immune responses. Evasin-3 is a small salivary protein that belongs to a class of chemokine-binding proteins isolated from the brown dog tick, Rhipicephalus sanguineus. Evasin-3 has been shown to have a high affinity for chemokines CXCL1 and CXCL8 and to diminish inflammation in mice. In the present study, solution NMR spectroscopy was used to investigate the structure of Evasin-3 and its CXCL8–Evasin-3 complex. Evasin-3 is found to disrupt the glycosaminoglycan-binding site of CXCL8 and inhibit the interaction of CXCL8 with CXCR2. Structural data were used to design two novel CXCL8-binding peptides. The linear tEv3 17–56 and cyclic tcEv3 16–56 dPG Evasin-3 variants were chemically synthesized by solid-phase peptide synthesis. The affinity of these newly synthesized variants to CXCL8 was measured by surface plasmon resonance biosensor analysis. The K_d values of tEv3 17–56 and tcEv3 16–56 dPG were 27 and 13 nm, respectively. Both compounds effectively inhibited CXCL8-induced migration of polymorphonuclear neutrophils. The present results suggest utility of synthetic Evasin-3 variants as scaffolds for designing and fine-tuning new chemokine-binding agents that suppress immune responses and inflammation.

A knottin scaffold directs the CXC-chemokine-binding specificity of tick evasins

Tick evasins (EVAs) bind either CC- or CXC-chemokines by a poorly understood promiscuous or "one-to-many" mechanism to neutralize inflammation. Because EVAs potently inhibit inflammation in many preclinical models, highlighting their potential as biological therapeutics for inflammatory diseases, we sought to further unravel the CXC-chemokine-EVA interactions. Using yeast surface display, we identified and characterized 27 novel CXC-chemokine-binding evasins homologous to EVA3 and defined two functional classes. The first, which included EVA3, exclusively bound ELR⁺ CXC-chemokines, whereas the second class bound both ELR⁺ and ELR^- CXC-chemokines, in several cases including CXC-motif chemokine ligand 10 (CXCL10) but, surprisingly, not CXCL8. The X-ray crystal structure of EVA3 at a resolution of 1.79 Å revealed a single antiparallel β-sheet with six conserved cysteine residues forming a disulfide-bonded knottin scaffold that creates a contiguous solvent-accessible surface. Swapping analyses identified distinct knottin scaffold segments necessary for different CXC-chemokine-binding activities, implying that differential ligand positioning, at least in part, plays a role in promiscuous binding. Swapping segments also transferred chemokine-binding activity, resulting in a hybrid EVA with dual CXCL10- and CXCL8-binding activities. The solvent-accessible surfaces of the knottin scaffold segments have distinctive shape and charge, which we suggest drives chemokine-binding specificity. These studies provide structural and mechanistic insight into how CXC-chemokine-binding tick EVAs achieve class specificity but also engage in promiscuous binding.

Chemical Equilibrium at the Tick-Host Feeding Interface:A Critical Examination of Biological Relevance in Hematophagous Behavior

Ticks secrete hundreds to thousands of proteins into the feeding site, that presumably all play important functions in the modulation of host defense mechanisms. The current review considers the assumption that tick proteins have functional relevance during feeding. The feeding site may be described as a closed system and could be treated as an ideal equilibrium system, thereby allowing modeling of tick-host interactions in an equilibrium state. In this equilibrium state, the concentration of host and tick proteins and their affinities will determine functional relevance at the tick-host interface. Using this approach, many characterized tick proteins may have functional relevant concentrations and affinities at the feeding site. Conversely, the feeding site is not an ideal closed system, but is dynamic and changing, leading to possible overestimation of tick protein concentration at the feeding site and consequently an overestimation of functional relevance. Ticks have evolved different possible strategies to deal with this dynamic environment and overcome the barrier that equilibrium kinetics poses to tick feeding. Even so, cognisance of the limitations that equilibrium binding place on deductions of functional relevance should serve as an important incentive to determine both the concentration and affinity of tick proteins proposed to be functional at the feeding site.

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.

Genetically engineered two-warhead evasins provide a method to achieve precision targeting of disease-relevant chemokine subsets

Both CC and CXC-class chemokines drive inflammatory disease. Tick salivary chemokine-binding proteins (CKBPs), or evasins, specifically bind subsets of CC- or CXC-chemokines, and could precisely target disease-relevant chemokines. Here we have used yeast surface display to identify two tick evasins: a CC-CKBP, P1243 from Amblyomma americanum and a CXC-CKBP, P1156 from Ixodes ricinus. P1243 binds 11 CC-chemokines with Kd < 10 nM, and 10 CC-chemokines with Kd between 10 and 100 nM. P1156 binds two ELR + CXC-chemokines with Kd < 10 nM, and four ELR + CXC-chemokines with Kd between 10 and 100 nM. Both CKBPs neutralize chemokine activity with IC50 < 10 nM in cell migration assays. As both CC- and CXC-CKBP activities are desirable in a single agent, we have engineered "two-warhead" CKBPs to create single agents that bind and neutralize subsets of CC and CXC chemokines. These results show that tick evasins can be linked to create non-natural proteins that target subsets of CC and CXC chemokines. We suggest that "two-warhead" evasins, designed by matching the activities of parental evasins to CC and CXC chemokines expressed in disease, would achieve precision targeting of inflammatory disease-relevant chemokines by a single agent.

The N-terminal domain of a tick evasin is critical for chemokine binding and neutralization and confers specific binding activity to other evasins

Tick chemokine-binding proteins (evasins) are an emerging class of biologicals that target multiple chemokines and show anti-inflammatory activities in preclinical disease models. Using yeast surface display, we identified a CCL8-binding evasin, P672, from the tick Rhipicephalus pulchellus We found that P672 binds CCL8 and eight other CC-class chemokines with a Kd < 10 nm and four other CC chemokines with a Kd between 10 and 100 nm and neutralizes CCL3, CCL3L1, and CCL8 with an IC50 < 10 nm The CC chemokine-binding profile was distinct from that of evasin 1 (EVA1), which does not bind CCL8. We also show that P672's binding activity can be markedly modulated by the location of a StrepII-His purification tag. Combining native MS and bottom-up proteomics, we further demonstrated that P672 is glycosylated and forms a 1:1 complex with CCL8, disrupting CCL8 homodimerization. Homology modeling of P672 using the crystal structure of the EVA1 and CCL3 complex as template suggested that 44 N-terminal residues of P672 form most of the contacts with CCL8. Replacing the 29 N-terminal residues of EVA1 with the 44 N-terminal residues of P672 enabled this hybrid evasin to bind and neutralize CCL8, indicating that the CCL8-binding properties of P672 reside, in part, in its N-terminal residues. This study shows that the function of certain tick evasins can be manipulated simply by adding a tag. We conclude that homology modeling helps identify regions with transportable chemokine-binding functions within evasins, which can be used to construct hybrid evasins with altered properties.

Beyond migration-Chemokines in lymphocyte priming, differentiation, and modulating effector functions

Chemokines and their receptors coordinate the positioning of leukocytes, and lymphocytes in particular, in space and time. Discrete lymphocyte subsets, depending on their activation and differentiation status, express various sets of chemokine receptors to be recruited to distinct tissues. Thus, the network of chemokines and their receptors ensures the correct localization of specialized lymphocyte subsets within the appropriate microenvironment enabling them to search for cognate antigens, to become activated, and to fulfill their effector functions. The chemokine system therefore is vital for the initiation as well as the regulation of immune responses to protect the body from pathogens while maintaining tolerance towards self. Besides the well investigated function of orchestrating directed cell migration, chemokines additionally act on lymphocytes in multiple ways to shape immune responses. In this review, we highlight and discuss the role of chemokines and chemokine receptors in controlling cell-to-cell contacts required for lymphocyte arrest on endothelial cells and immunological synapse formation, in lymphocyte priming and differentiation, survival, as well as in modulating effector functions.

Ticks from diverse genera encode chemokine-inhibitory evasin proteins

To prolong residence on their hosts, ticks secrete many salivary factors that target host defense molecules. In particular, the tick Rhipicephalus sanguineus has been shown to produce three salivary glycoproteins named "evasins," which bind to host chemokines, thereby inhibiting the recruitment of leukocytes to the location of the tick bite. Using sequence similarity searches, we have identified 257 new putative evasin sequences encoded by the genomes or salivary or visceral transcriptomes of numerous hard ticks, spanning the genera Rhipicephalus, Amblyomma, and Ixodes of the Ixodidae family. Nine representative sequences were successfully expressed in Escherichia coli, and eight of the nine candidates exhibited high-affinity binding to human chemokines. Sequence alignments enabled classification of the evasins into two subfamilies: C₈ evasins share a conserved set of eight Cys residues (four disulfide bonds), whereas C₆ evasins have only three of these disulfide bonds. Most of the identified sequences contain predicted secretion leader sequences, N-linked glycosylation sites, and a putative site of tyrosine sulfation. We conclude that chemokine-binding evasin proteins are widely expressed among tick species of the Ixodidae family, are likely to play important roles in subverting host defenses, and constitute a valuable pool of anti-inflammatory proteins for potential future therapeutic applications.

Evasin-displaying lactic acid bacteria bind different chemokines and neutralize CXCL8 production in Caco-2 cells

Chemokines are key signals in the immune system and play an important role as proinflammatory mediators in the pathology of inflammatory bowel disease and colorectal cancer, making them an important target for therapy. Recombinant lactic acid bacteria (LAB) were engineered to bind CC and CXC chemokines by displaying chemokine‐binding proteins evasin‐1, evasin‐3 and evasin‐4 on their surface. Evasin genes were cloned into lactococcal surface display vector and overexpressed in L. lactis NZ9000 and NZ9000ΔhtrA in fusion with secretion signal and surface anchor. Evasin‐displaying bacteria removed from 15% to 90% of 11 different chemokines from the solution as determined with ELISA and Luminex multiplexing assays, whereby L. lactis NZ9000ΔhtrA proved more efficient. Lactobacillus salivarius ATCC 11741 was coated with L. . lactis‐expressed evasin fusion protein, and its ability to bind chemokines was also confirmed. Evasin‐3‐displaying L. lactis removed 76.0% of IL‐1β‐induced CXCL8 from the supernatant of Caco‐2 epithelial cells. It also prevented secretion of CXCL8 from Caco‐2 cells in a time‐dependent manner when added before induction with IL‐1β. Evasin‐displaying LAB have the ability to bind multiple chemokines simultaneously and exert synergistic activity. This innovative treatment approach therefore has the potential for mucosal therapy of inflammatory bowel disease or colorectal cancer.

Yeast surface display identifies a family of evasins from ticks with novel polyvalent CC chemokine-binding activities

Chemokines function via G-protein coupled receptors in a robust network to recruit immune cells to sites of inflammation. Due to the complexity of this network, targeting single chemokines or receptors has not been successful in inflammatory disease. Dog tick saliva contains polyvalent CC-chemokine binding peptides termed evasins 1 and 4, that efficiently disrupt the chemokine network in models of inflammatory disease. Here we develop yeast surface display as a tool for functionally identifying evasins, and use it to identify 10 novel polyvalent CC-chemokine binding evasin-like peptides from salivary transcriptomes of eight tick species in Rhipicephalus and Amblyomma genera. These evasins have unique binding profiles compared to evasins 1 and 4, targeting CCL2 and CCL13 in addition to other CC-chemokines. Evasin binding leads to neutralisation of chemokine function including that of complex chemokine mixtures, suggesting therapeutic efficacy in inflammatory disease. We propose that yeast surface display is a powerful approach to mine potential therapeutics from inter-species protein interactions that have arisen during evolution of parasitism in ticks.

Functional role of CCL5/RANTES for HCC progression during chronic liver disease

BACKGROUND & AIMS

During liver inflammation, triggering fibrogenesis and carcinogenesis immune cells play a pivotal role. In the present study we investigated the role of CCL5 in human and in murine models of chronic liver inflammation leading to hepatocellular carcinoma (HCC) development.

METHODS

CCL5 expression and its receptors were studied in well-defined patients with chronic liver disease (CLD) and in two murine inflammation based HCC models. The role of CCL5 in inflammation, fibrosis, tumor initiation and progression was analyzed in different cell populations of NEMO^Δhepa/CCL5^-/- animals and after bone marrow transplantation (BMT). For therapeutic intervention Evasin-4 was injected for 24h or 8weeks.

RESULTS

In CLD patients, CCL5 and its receptor CCR5 are overexpressed - an observation confirmed in the Mdr2^-/- and NEMO^Δhepa model. CCL5 deletion in NEMO^Δhepa mice diminished hepatocyte apoptosis, compensatory proliferation and fibrogenesis due to reduced immune cell infiltration. Especially, CD45⁺/Ly6G⁺ granulocytes, CD45⁺/CD11b⁺/Gr1.1⁺/F4/80⁺ pro-inflammatory monocytes, CD4⁺ and CD8⁺ T cells were decreased. One year old NEMO^Δhepa/CCL5^-/- mice displayed smaller and less malignant tumors, characterized by reduced proliferative capacity and less pronounced angiogenesis. We identified hematopoietic cells as the main source of CCL5, while CCL5 deficiency did not sensitise NEMO^Δhepa hepatocytes towards TNFα induced apoptosis. Finally, therapeutic intervention with Evasin-4 over a period of 8weeks ameliorated liver disease progression.

CONCLUSION

We identified an important role of CCL5 in human and functionally in mice with disease progression, especially HCC development. A novel approach to inhibit CCL5 in vivo thus appears encouraging for patients with CLD.

LAY SUMMARY

Our present study identifies the essential role of the chemoattractive cytokine CCL5 for liver disease progression and especially hepatocellular carcinoma development in men and mice. Finally, the inhibition of CCL5 appears to be encouraging for therapy of human chronic liver disease.

Evasins: Therapeutic Potential of a New Family of Chemokine-Binding Proteins from Ticks

Blood-sucking parasites, such as ticks, remain attached to their hosts for relatively long periods of time in order to obtain their blood meal without eliciting an immune response. One mechanism used to avoid rejection is the inhibition of the recruitment of immune cells, which can be achieved by a class of chemokine-binding proteins (CKBPs) known as Evasins. We have identified three distinct Evasins produced by the salivary glands of the common brown dog tick, Rhipicephalus sanguineus. They display different selectivities for chemokines, the first two identified show a narrow selectivity profile, while the third has a broader binding spectrum. The Evasins showed efficacy in animal models of inflammatory disease. Here, we will discuss the potential of their development for therapeutic use, addressing both the advantages and disadvantages that this entails.

Partial characterization of a novel anti-inflammatory protein from salivary gland extract of Hyalomma anatolicum anatolicum 77Acari: Ixodidae) ticks

Aim:

Hyalomma anatolicum anatolicum ticks transmit Theileria annulata, causative agent of tropical theileriosis to cattle and buffaloes causing a major economic loss in terms of production and mortality in tropical countries. Ticks have evolved several immune evading strategies to circumvent hosts’ rejection and achieve engorgement. Successful feeding of ticks relies on a pharmacy of chemicals located in their complex salivary glands and secreted saliva. These chemicals in saliva could inhibit host inflammatory responses through modulating cytokine secretion and detoxifying reactive oxygen species. Therefore, the present study was aimed to characterize anti-inflammatory peptides from salivary gland extract (SGE) of H. a. anatolicum ticks with a view that this information could be utilized in raising vaccines, designing synthetic peptides or peptidomimetics which can further be developed as novel therapeutics.

Materials and Methods:

Salivary glands were dissected out from partially fed adult female H. a. anatolicum ticks and homogenized under the ice to prepare SGE. Gel filtration chromatography was performed using Sephadex G-50 column to fractionate the crude extract. Protein was estimated in each fraction and analyzed for identification of anti-inflammatory activity. Sodium dodecyl sulfate - polyacrylamide gel electrophoresis (SDS-PAGE) was run for further characterization of protein in desired fractions.

Results:

A novel 28 kDa protein was identified in H. a. anatolicum SGE with pronounced anti-inflammatory activity.

Conclusion:

Purification and partial characterization of H. a. anatolicum SGE by size-exclusion chromatography and SDS-PAGE depicted a 28 kDa protein with prominent anti-inflammatory activity.

A strategy to discover decoy chemokine ligands with an anti-inflammatory activity

Excessive signaling by chemokines has been associated with chronic inflammation or cancer, thus attracting substantial attention as promising therapeutic targets. Inspired by chemokine-clearing molecules shaped by pathogens to escape the immune system, we designed a generic screening assay to discover chemokine neutralizing molecules (neutraligands) and unambiguously distinguish them from molecules that block the receptor (receptor antagonists). This assay, called TRIC-r, combines time-resolved intracellular calcium recordings with pre-incubation of bioactive compounds either with the chemokine or the receptor-expressing cells. We describe here the identification of high affinity neutraligands of CCL17 and CCL22, two chemokines involved in the Th2-type of lung inflammation. The decoy molecules inhibit in vitro CCL17- or CCL22-induced intracellular calcium responses, CCR4 endocytosis and human T cell migration. In vivo, they inhibit inflammation in a murine model of asthma, in particular the recruitment of eosinophils, dendritic cells and CD4⁺T cells. Altogether, we developed a successful strategy to discover as new class of pharmacological tools to potently control cell chemotaxis in vitro and in vivo.

Targeting chemokines: Pathogens can, why can't we?

Chemoattractant cytokines, or chemokines, are the largest sub-family of cytokines. About 50 distinct chemokines have been identified in humans. Their principal role is to stimulate the directional migration of leukocytes, which they achieve through activation of their receptors, following immobilization on cell surface glycosaminoglycans (GAGs). Chemokine receptors belong to the G protein-coupled 7-transmembrane receptor family, and hence their identification brought great promise to the pharmaceutical industry, since this receptor class is the target for a large percentage of marketed drugs. Unfortunately, the development of potent and efficacious inhibitors of chemokine receptors has not lived up to the early expectations. Several approaches to targeting this system will be described here, which have been instrumental in establishing paradigms in chemokine biology. Whilst drug discovery programs have not yet elucidated how to make successful drugs targeting the chemokine system, it is now known that certain parasites have evolved anti-chemokine strategies in order to remain undetected by their hosts. What can we learn from them?

Treatment with Evasin-3 abrogates neutrophil-mediated inflammation in mouse acute pancreatitis

BACKGROUND

Acute pancreatitis is characterized by inflammatory processes affecting not only the pancreas, but also the lung. Here, we investigated timing of leucocyte infiltration and chemokine expression within lung and pancreas during pancreatitis and whether treatments selectively inhibiting chemokines (using Evasins) could improve organ injury.

MATERIAL AND METHODS

C57Bl/6 mice were submitted in vivo to 10-h intraperitoneal injections of cerulein and followed for up to 168 h. Five minutes after the first cerulein injection, a single intraperitoneal injection of 10 μg Evasin-3, 1 μg Evasin-4 or an equal volume of vehicle (PBS) was performed. Leucocytes, reactive oxygen species (ROS), necrosis and chemokine/cytokine mRNA expression were assessed in different organs by immunohistology and real-time RT-PCR, respectively.

RESULTS

In the lung, neutrophil infiltration and macrophage infiltration peaked at 12 h and were accompanied by increased CXCL2 mRNA expression. CCL2, CXCL1 and TNF-alpha significantly increased after 24 h as compared to baseline. No increase in CCL3 and CCL5 was observed. In the pancreas, neutrophil infiltration peaked at 6 h, while macrophages increased only after 72 h. Treatment with Evasin-3 decreased neutrophil infiltration, ROS production and apoptosis in the lung and reduced neutrophils, macrophages apoptosis and necrosis in the pancreas. Evasin-4 only reduced macrophage content in the lung and did not provide any benefit at the pancreas level.

CONCLUSION

Chemokine production and leucocyte infiltration are timely regulated in lung and pancreas during pancreatitis. CXC chemokine inhibition with Evasin-3 improved neutrophil inflammation and injury, potentially interfering with damages in acute pancreatitis and related pulmonary complications.

Identification of the pharmacophore of the CC chemokine-binding proteins Evasin-1 and -4 using phage display

To elucidate the ligand-binding surface of the CC chemokine-binding proteins Evasin-1 and Evasin-4, produced by the tick Rhipicephalus sanguineus, we sought to identify the key determinants responsible for their different chemokine selectivities by expressing Evasin mutants using phage display. We first designed alanine mutants based on the Evasin-1·CCL3 complex structure and an in silico model of Evasin-4 bound to CCL3. The mutants were displayed on M13 phage particles, and binding to chemokine was assessed by ELISA. Selected variants were then produced as purified proteins and characterized by surface plasmon resonance analysis and inhibition of chemotaxis. The method was validated by confirming the importance of Phe-14 and Trp-89 to the inhibitory properties of Evasin-1 and led to the identification of a third crucial residue, Asn-88. Two amino acids, Glu-16 and Tyr-19, were identified as key residues for binding and inhibition of Evasin-4. In a parallel approach, we identified one clone (Y28Q/N60D) that showed a clear reduction in binding to CCL3, CCL5, and CCL8. It therefore appears that Evasin-1 and -4 use different pharmacophores to bind CC chemokines, with the principal binding occurring through the C terminus of Evasin-1, but through the N-terminal region of Evasin-4. However, both proteins appear to target chemokine N termini, presumably because these domains are key to receptor signaling. The results also suggest that phage display may offer a useful approach for rapid investigation of the pharmacophores of small inhibitory binding proteins.

The Activity of CCL18 is Principally Mediated through Interaction with Glycosaminoglycans

The CC chemokine ligand 18 (CCL18) was first identified as a chemoattractant for naïve T cells. It has been reported to recruit T and B lymphocytes, and we show here, natural killer (NK) cells, but with low efficacy. Investigation of its ability to elicit G-protein-coupled signaling showed that it does not involve extracellular signal-regulated kinase (ERK) phosphorylation, and it is not able to induce receptor internalization, as assessed on CCR3. CCL18 has recently been reported to possess activities unrelated to cellular recruitment, but it had no effect on T lymphocyte proliferation. We postulated that a more potent chemoattractant may be produced under inflammatory conditions but only minor truncations were observed, with the major form being the full-length protein. In view of the lack of potent immunomodulatory properties, we wondered if binding to CCL18 by the tick chemokine binding proteins Evasin-1 and -4 was an artifact of the methods used, but complex formation was confirmed by size exclusion chromatography, and abrogation of its binding to, and antagonism of, CCR3. Its receptor has remained elusive since its cloning in 1997, although it has been reported to induce migration of breast cancer cells by signaling through PITPNM3, but we show that this receptor is not expressed on lymphocytes. We have developed a radiolabeled equilibrium competition binding assay and demonstrated that it bound with high affinity to peripheral blood leukocytes (PBLs), but the binding was displaced similarly by both unlabelled CCL18 as well as heparin. Both heparin binding and binding to PBLs are considerably abrogated by mutation of the BBXB motif in the 40s loop suggesting an essential role of the CCL18-glycosaminoglycan interaction.