Helminth-derived proteins as immune system regulators: a systematic review of their promise in alleviating colitis

Helminth-derived proteins have immunomodulatory properties, influencing the host's immune response as an adaptive strategy for helminth survival. Helminth-derived proteins modulate the immune response by inducing anti-inflammatory cytokines, promoting regulatory T-cell development, and ultimately favouring a Th2-biased immune response. This systematic review focused on helminth-derived proteins and explored their impact on reducing inflammatory responses in mouse models of colitis. A systematic search across Medline, EMBASE, Web of Science, and Cochrane Library identified fourteen relevant studies. These studies reported immunomodulatory changes, including increased production of anti-inflammatory cells and cytokines. In mouse models of colitis treated with on helminth-derived proteins, significant improvements in pathological parameters such as body weight, colon length, and microscopic inflammatory scores were observed compared to control groups. Moreover, helminth-derived proteins can enhance the function of Tregs and alleviate the severity of inflammatory conditions. The findings underscore the pivotal role of helminth-derived proteins in immunomodulation, specifically in the axis of cytokine secretion and immune cell polarization. The findings offer new opportunities for treating chronic inflammatory conditions such Crohn's disease.

Strongyloides venezuelensis-derived venestatin ameliorates asthma pathogenesis by suppressing receptor for advanced glycation end-products-mediated signaling

INTRODUCTION

EF-hand Ca²⁺-binding proteins such as S100 protein family members are recognized by the receptor for advanced glycation end-products (RAGE) and are involved in the pathogenesis of asthma/allergic airway inflammation (AAI). Venestatin, an EF-hand Ca²⁺-binding protein, which is secreted by the parasitic helminth Strongyloides venezuelensis, binds with RAGE and suppresses RAGE-mediated inflammatory responses after parasite invasion. In this study, we evaluated the effect of venestatin on pathogenesis in a house dust mite (HDM) murine model of asthma/AAI.

METHODS

Mice were intranasally treated with HDM, HDM with recombinant venestatin, or HDM with synthetic peptides, which were designed based on the EF-hand Ca²⁺-binding domain of venestatin. Pro-inflammatory responses in the lungs of mice were assessed.

RESULTS

HDM treatment induced inflammatory cell infiltration, phosphorylation of the mitogen-activated protein kinase and inhibitor κB, and production of the cytokines tumor necrosis factor-α and interleukin-5 in the lungs. Co-administration of recombinant venestatin with HDM suppressed these pro-inflammatory responses. Treatment with synthetic peptides reduced inflammatory cell infiltration in a RAGE-dependent manner.

CONCLUSION

The EF-hand domain of venestatin may have potential therapeutic benefits in asthma.

The helminth glycoprotein omega-1 improves metabolic homeostasis in obese mice through type 2 immunity-independent inhibition of food intake

Type 2 immunity plays an essential role in the maintenance of metabolic homeostasis and its disruption during obesity promotes meta-inflammation and insulin resistance. Infection with the helminth parasite Schistosoma mansoni and treatment with its soluble egg antigens (SEA) induce a type 2 immune response in metabolic organs and improve insulin sensitivity and glucose tolerance in obese mice, yet, a causal relationship remains unproven. Here, we investigated the effects and underlying mechanisms of the T2 ribonuclease omega-1 (ω1), one of the major S mansoni immunomodulatory glycoproteins, on metabolic homeostasis. We show that treatment of obese mice with plant-produced recombinant ω1, harboring similar glycan motifs as present on the native molecule, decreased body fat mass, and improved systemic insulin sensitivity and glucose tolerance in a time- and dose-dependent manner. This effect was associated with an increase in white adipose tissue (WAT) type 2 T helper cells, eosinophils, and alternatively activated macrophages, without affecting type 2 innate lymphoid cells. In contrast to SEA, the metabolic effects of ω1 were still observed in obese STAT6-deficient mice with impaired type 2 immunity, indicating that its metabolic effects are independent of the type 2 immune response. Instead, we found that ω1 inhibited food intake, without affecting locomotor activity, WAT thermogenic capacity or whole-body energy expenditure, an effect also occurring in leptin receptor-deficient obese and hyperphagic db/db mice. Altogether, we demonstrate that while the helminth glycoprotein ω1 can induce type 2 immunity, it improves whole-body metabolic homeostasis in obese mice by inhibiting food intake via a STAT6-independent mechanism.

Mycobacterium-Induced Th1, Helminths-Induced Th2 Cells and the Potential Vaccine Candidates for Allergic Asthma: Imitation of Natural Infection

Bronchial asthma is one of the most chronic pulmonary diseases and major public health problems. In general, asthma prevails in developed countries than developing countries, and its prevalence is increasing in the latter. For instance, the hygiene hypothesis demonstrated that this phenomenon resulted from higher household hygienic standards that decreased the chances of infections, which would subsequently increase the occurrence of allergy. In this review, we attempted to integrate our knowledge with the hygiene hypothesis into beneficial preventive approaches for allergic asthma. Therefore, we highlighted the studies that investigated the correlation between allergic asthma and the two different types of infections that induce the two major antagonizing arms of T cells. This elucidation reflects the association between various types of natural infections and the immune system, which is predicted to support the main objective of the current research on investigating of the benefits of natural infections, regardless their immune pathways for the prevention of allergic asthma. We demonstrated that natural infection with Mycobacterium tuberculosis (Mtb) prevents the development of allergic asthma, thus Bacille Calmette-Guérin (BCG) vaccine is suggested at early age to mediate the same prevention particularly with increasing its efficiency through genetic engineering-based modifications. Likewise, natural helminth infections might inhabit the allergic asthma development. Therefore, helminth-derived proteins at early age are good candidates for designing vaccines for allergic asthma and it requires further investigation. Finally, we recommend imitation of natural infections as a general strategy for preventing allergic asthma that increased dramatically over the past decades.

Potential Influence of Helminth Molecules on COVID-19 Pathology

In recent months, the parasitology research community has been tasked with investigation of the influence of parasite coinfection on coronavirus disease 2019 (COVID-19) outcomes. Herein, we share our approach to analyze the effect of the trematode Fasciola hepatica as a modulator of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and of COVID-19 pathology.

A Novel Antithrombotic Protease from Marine Worm Sipunculus Nudus

Sipunculus nudus, an old marine species, has great potential for use as functional seafood due to its various bioactivities. Its potential antithrombotic activity pushed us to isolate the bio-active components bio-guided by tracking fibrinolytic activity. As a result, a novel protease named as SK (the kinase obtained from S. nudus) was obtained, which possessed a molecular weight of 28,003.67 Da and 15 N-terminal amino acid sequences of PFPVPDPFVWDTSFQ. SK exerted inhibitory effects on thrombus formation through improving the coagulation system with dose-effect relationship within a certain range. Furthermore, in most cases SK got obviously better effect than that of urokinase. With the help of untargeted mass spectrometry-based metabolomics profiling, arachidonic acid, sphingolipid, and nicotinate and nicotinamide mechanism pathways were found to be important pathways. They revealed that the effect mechanism of SK on common carotid arterial thrombosis induced by FeCl₃ was achieved by inhibiting vessel contraction, platelet aggregation, adhesion, and release, correcting endothelial cell dysfunction and retarding process of thrombus formation. This study demonstrated SK was a promising thrombolytic agent on the basis of its comprehensive activities on thrombosis, and it should get further exploitation and utilization.

Synthetic analogues of the parasitic worm product ES-62 reduce disease development in in vivo models of lung fibrosis

Parasitic worms are receiving much attention as a potential new therapeutic approach to treating autoimmune and allergic conditions but concerns remain regarding their safety. As an alternative strategy, we have focused on the use of defined parasitic worm products and recently taken this one step further by designing drug-like small molecule analogues of one such product, ES-62, which is anti-inflammatory by virtue of covalently attached phosphorylcholine moieties. Previously, we have shown that ES-62 mimics are efficacious in protecting against disease in mouse models of rheumatoid arthritis, systemic lupus erythematosus and skin and lung allergy. Given the potential role of chronic inflammation in fibrosis, in the present study we have focused our attention on lung fibrosis, a debilitating condition for which there is no cure and which in spite of treatment slowly gets worse over time. Two mouse models of fibrosis - bleomycin-induced and LPS-induced - in which roles for inflammation have been implicated were adopted. Four ES-62 analogues were tested - 11a and 12b, previously shown to be active in mouse models of allergic and autoimmune disease and 16b and AIK-29/62 both of which are structurally related to 11a. All four compounds were found to significantly reduce disease development in both fibrosis models, as shown by histopathological analysis of lung tissue, indicating their potential as treatments for this condition.

Brugia malayi abundant larval transcript 2 protein treatment attenuates experimentally-induced colitis in mice

Helminths are known to modulate host's immunity by suppressing host protective pro-inflammatory responses. Such immunomodulatory effects have been experimentally shown to have therapeutic implications in immune mediated disorders. In the present study, we have explored a filarial protein i.e. Brugia malayi recombinant abundant larval transcript 2 (rBmALT2) for its therapeutic effect in dextran sodium sulfate (DSS) induced colitis in mouse model. The immunomodulatory activity of rBmALT-2 was initially confirmed by demonstrating that it suppressed the lipopolysaccharide (LPS) induced nitric oxide synthesis and down-regulated the expression of pro-inflammatory cytokines in vitro by peritoneal exudate cells of mice. Treatment with rBmALT2 reduced severity of colitis associated with significant reduction in weight loss, disease activity, colon damage, mucosal edema and histopathological score including myeloperoxidase activity in colon tissues. rBmALT2 was comparatively more effective in attenuation of colitis when used in the preventive mode than when used for curative purpose. The therapeutic effect of rBmALT2 was found to be associated with downregulation of IFN-γ, IL-6, IL-17 and upregulation of IL-10 cytokines. These results provide strong experimental evidence that BmALT2 could be a potential alternative therapeutic agent in colitis.

ES-62 protects against collagen-induced arthritis by resetting interleukin-22 toward resolution of inflammation in the joints

OBJECTIVE

The parasitic worm-derived immunomodulator ES-62 protects against disease in the mouse collagen-induced arthritis (CIA) model of rheumatoid arthritis (RA) by suppressing pathogenic interleukin-17 (IL-17) responses. The Th17-associated cytokine IL-22 also appears to have a pathogenic role in autoimmune arthritis, particularly in promoting proinflammatory responses by synovial fibroblasts and osteoclastogenesis. The present study was undertaken to investigate whether the protection against joint damage afforded by ES-62 also reflects suppression of IL-22.

METHODS

The role(s) of IL-22 was assessed by investigating the effects of neutralizing anti-IL-22 antibodies and recombinant IL-22 (rIL-22) on proinflammatory cytokine production, synovial fibroblast responses, and joint damage in mice with CIA in the presence or absence of ES-62.

RESULTS

Neutralization of IL-22 during the initiation phase abrogated CIA, while administration of rIL-22 enhanced synovial fibroblast responses and exacerbated joint pathology. In contrast, after disease onset anti-IL-22 did not suppress progression, whereas administration of rIL-22 promoted resolution of inflammation. Consistent with these late antiinflammatory effects, the protection afforded by ES-62 was associated with elevated levels of IL-22 in the serum and joints that reflected a desensitization of the synovial fibroblast responses. Moreover, neutralization of IL-22 during the late effector stage of disease prevented ES-62-mediated desensitization of synovial fibroblast responses and protection against CIA.

CONCLUSION

IL-22 plays a dual role in CIA, being pathogenic during the initiation phase while acting to resolve inflammation and joint damage during established disease. Harnessing of the tissue repair properties of IL-22 by ES-62 highlights the potential for joint-targeted therapeutic modulation of synovial fibroblast responses and consequent protection against bone damage in RA.

[Studies on immunomodulation effect of recombinant Sj16 from Schistosoma japonicum on inflammation response of host]

OBJECTIVE

To study the immunomodulation effect of the recombination Sj16 from Schistosoma japonicum (reSj16) on inflammation response of host.

METHODS

reSj16 expressed in pGEX-4T-1 was purified by GST purification kit and detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and mass spectra (MS). The immunomodulation effect of reSj16 was observed by means of dimethylbenzene inducing mouse ear edema model, carrageenan inducing rat voix pedis swell model and acetic acid inducing mouse experiment peritonitis model.

RESULTS

The soluble protein of reSjl6 was obtained and identified by SDS-PAGE and MS. reSjl6 1.0, 5.0, 10.0 microg/kg evidently suppressed the mouse ear edema induced by dimethyl-benzene, significantly mitigated the rat voix pedis swelling induced by carrageenan, and remarkably suppressed the increase of the capillary permeability of abdominal cavity in experiment peritonitis mouse model.

CONCLUSION

The results further prove that Sj16 may be a potential immunosuppressive molecule and may have a notable effect on immunomodulation.

The phosphorycholine moiety of the filarial nematode immunomodulator ES-62 is responsible for its anti-inflammatory action in arthritis

OBJECTIVE

In countries where parasitic infections are endemic, autoimmune disease is relatively rare, leading to the hypothesis that parasite-derived immunomodulators may protect against its development. Consistent with this, we have previously demonstrated that ES-62, a 62 kDa phosphorylcholine (PC)-containing glycoprotein that is secreted by filarial nematodes, can exert anti-inflammatory action in the murine collagen-induced arthritis (CIA) model and human rheumatoid arthritis-derived synovial tissue cultures. As a first step to developing ES-62-based drugs, the aim of this study was to determine whether the PC-moiety of ES-62 was responsible for its anti-inflammatory actions.

METHODS

We compared the anti-inflammatory activity of a PC-free form of recombinant ES-62 (rES-62) and a synthetic PC-ovalbumin conjugate (OVA-PC) with that of native ES-62 in the CIA model and synovial tissues from patients with rheumatoid arthritis.

RESULTS

The anti-inflammatory actions of ES-62 in CIA appear to be dependent on the PC moiety as indicated by the reduction in severity of disease and also suppression of collagen-specific T helper 1 cytokine production observed when testing OVA-PC, but not rES-62. Interestingly, the anti-inflammatory activity of PC did not correlate with a reduction in anti-collagen IgG2a levels. Also, the ES-62-mediated suppression of interferon-gamma from human patient tissues could be mimicked by OVA-PC but not rES-62 or ovalbumin.

CONCLUSIONS

In countries where filariasis is endemic the reduced detection of inflammatory diseases, such as rheumatoid arthritis may be because of the anti-inflammatory action of the PC moieties of ES-62. PC may thus provide the starting point for the development of novel, safe immunomodulatory therapies.

Filarial nematode secreted product ES-62 is an anti-inflammatory agent: therapeutic potential of small molecule derivatives and ES-62 peptide mimetics

1. The 'hygiene hypothesis' postulates that the recent increased incidence of allergic or autoimmune diseases (e.g. asthma, type I diabetes) in the West reflects an absence of appropriate priming of the immune response by infectious agents, such as parasitic worms, during childhood. 2. Consistent with this, it has long been recognized that several autoimmune disorders, such as rheumatoid arthritis (RA), a T helper (Th) 1-mediated autoimmune disease characterized by excess production of pro-inflammatory cytokines, such as tumour necrosis factor-alpha, exhibit reduced incidence and severity in geographical regions with high parasite load, suggesting that environmental factors may subtly alter disease progression. 3. Infection with worms also appears to suppress Th2-biased inflammatory disorders, such as asthma, because there also appears to be an inverse correlation between parasite load and atopy. This is perhaps more surprising, given that helminths often induce strong Th2-type immune responses characterized by release of specific cytokines, such as interleukin (IL)-4, IL-5 and IL-13. 4. Therefore, these findings suggest that the co-evolution of helminths with hosts, which has resulted in the ability of worms to modulate inflammatory responses in order to promote parasite survival, may also have generated a predisposition for the host to develop autoimmunity and allergy in the absence of infection. 5. The mechanisms underlying such immunomodulation are not clear, but appear to involve the release of parasite-derived molecules that allow the worms to modulate or evade the host immune response by a number of mechanisms, including skewing of cytokine responses and the induction of T regulatory cells. 6. In the present review we discuss the properties of one such filarial nematode-derived immunomodulatory molecule, namely ES-62, its anti-inflammatory action and the therapeutic potential of small molecule derivatives and peptides that mimic its action.

Modulation of anaphylaxis by helminth-derived products in animal models

Helminths have a profound immunomodulatory effect upon the inductive and effector phases of inflammatory responses, including allergy. Several animal models of anaphylaxis have been established to investigate the mechanisms by which helminth infections or helminth-derived products interfere with the onset of allergic reactions. The focus of our studies was the immunosuppression induced by the intestinal roundworm Ascaris suum in the production of anaphylactic antibodies and the development of lung eosinophilic inflammation and hyperreactivity to its own allergens and to unrelated antigens. Thus, we identified a single protein affinity purified from the A. suum body extract, named PAS-1, which maintains all its immunosuppressive properties and promotes a significant increase in interleukin-10 production, an essential cytokine for the effectiveness of the suppressive mechanism. In addition, PAS-1 primes for regulatory T cells, which also mediate this mechanism. Therefore, this helminth molecule may be a promising target for therapeutic applications in allergic disorders.

The pathology of Plasmodium chabaudi infection is not ameliorated by the secreted filarial nematode immunomodulatory molecule, ES-62

ES-62 is a phosphorylcholine-containing glycoprotein secreted by filarial nematodes. This molecule has been shown to reduce the severity of inflammation in collagen-induced arthritis (CIA) in mice, a model of rheumatoid arthritis, via down-regulation of anti-collagen type 1 immune responses. Malaria parasites induce a pro-inflammatory host immune response and many of the symptoms of malaria are immune system-mediated. Therefore we have asked whether the immunomodulatory properties of ES-62 can down-regulate the severity of malaria infection in BALB/c mice infected with Plasmodium chabaudi. We have found that ES-62 has no significant effect on the course of P. chabaudi parasitaemia, and does not significantly affect any of the measures of malaria-induced pathology taken throughout infection.

New anticoagulants for the prevention and treatment of venous thromboembolism

Anticoagulant therapy is effective at preventing the development of venous thromboembolism in high-risk patients, and reduces morbidity and mortality in individuals with established thromboembolic disease. Vitamin K antagonists and heparins are currently the most commonly used anticoagulant drugs, but they have practical limitations. Therefore, new antithrombotic agents with predictable dose-responses (thereby decreasing the need for monitoring without compromising efficacy or safety), ideally available in an oral formulation and with a rapidly reversible anticoagulant effect, are needed. New drugs fulfilling some of the above criteria have been developed and have proven to be effective agents for the treatment and prevention of venous thromboembolism.

Progressive tissue injury in burns is reduced by rNAPc2

INTRODUCTION

Burn wounds are characterised by central necrosis surrounded by an area of stasis with compromised perfusion. Secondary aggravation of the burn wound due to ischaemia in the zone of stasis can also result in necrosis. This study aims to improve circulation in the zone of stasis by reducing microthrombus formation and thereby to reduce secondary aggravation.

MATERIAL AND METHODS

Recombinant nematode anticoagulant protein (rNAPc2) was administered to Wistar rats at 3 or 30 microg/kg as a single or daily dose. A comb pattern burn was induced on the dorsum of these rats and its evolution monitored by serial photography, planimetry, laser doppler flowmetry and immunohistochemistry.

RESULTS

In the 30 microg/kg daily group, extension of the burn wound was curbed, limiting the burn area to 1.99+/-0.67 cm(2) on day 28, compared to 3.51+/-0.37 cm(2) in the control group (p=0.015). Laser doppler evaluation showed a significant (p<0.001) increase in circulation in the first day post-burn. Significantly less (p<0.001) microvascular fibrin formation was observed by immunohistochemistry.

CONCLUSION

Anticoagulation with rNAPc2 improved perfusion of the burn wound. The resultant reduction in the area of the burn led to earlier healing and less scar contracture.

Mycobacterial codon optimization of the gene encoding the Sm14 antigen of Schistosoma mansoni in recombinant Mycobacterium bovis Bacille Calmette-Guérin enhances protein expression but not protection against cercarial challenge in mice

A mycobacterial codon-optimized gene encoding the Sm14 antigen of Schistosoma mansoni was generated using oligonucleotide assembly. This synthetic gene enhanced approximately fourfold the protein expression level in recombinant Mycobacterium bovis Bacille Calmette-Guérin (rBCG) when compared to that obtained using the native gene in the same expression vector. Immunization of mice with rBCG expressing Sm14 via the synthetic gene induced specific cellular Th1-predominant immune responses, as determined by interferon-gamma production of Sm14-stimulated splenocytes, which were comparable to those recorded in animals immunized with an rBCG strain expressing the native gene. Administration of a single dose of the rBCG-Sm14 construct carrying the synthetic gene conferred protection against cercarial challenge in outbred Swiss mice, at a level equivalent to those provided by either a single dose of rBCG expressing the native gene or three doses of Escherichia coli-derived recombinant Sm14. Our data demonstrated that despite improving the level of antigen expression, the codon optimization strategy did not result in enhanced immunity or protection against cercarial S. mansoni challenge.

Molecules of parasites as immunomodulatory drugs

Parasite molecules offer unique advantages for the treatment of immunologicical disorders, and several candidate molecules have been shown to be effective. In our studies, it was shown that a factor inducing immunoglobulin E from filarial nematode parasites was suppressive in animal models of immunological disorders such as allergy and insulin dependent diabetes mellitus (IDDM). The Th1/Th2 paradigm of CD4+ T helper cell subsets can provide the basis for the development of new types of drugs and of novel strategies for the treatment of allergic and autoimmune disorders by parasite molecules. In our experimental system, parasite molecules from a filarial nematode parasite led to the down-regulation of the allergic reaction in animal models. In the majority of hosts, infection with helminths is associated with markedly reduced cellular immune reactions and polarization of T cell responses to Th2 and Th3 types. Some studies have suggested that the stimulation of host immunoregulatory networks with parasite molecules leading to the synthesis of anti-inflammatory cytokines (interleukin10, transforming growth factor-beta (TGF-beta and others) can provide new therapy for immunological disorders. It is known that parasites produce some types of molecule that mimic host molecules such as CD40 ligand, TGF-beta and macrophage migration inhibitory factor. These molecules are also candidates for medicinal agents. This review describes many of the latest possibilities in this field and shows how they can be best put to use for the development of medicinal agents, molecular target identification, and for prioritization.

rNAPc2. Nuvelo

Recombinant nematode anticoagulant protein-2 (rNAPc2) is an antithrombotic protein under development by Nuvelo as a potential therapeutic agent for the treatment of major acute cardiovascular disease such as unstable angina and myocardial infarction. Phase II clinical trials were ongoing in January 2004, although development for deep vein thrombosis had been suspended by Dendreon due to a requirement for a partner to assist with additional phase II clinical trials.

Construction, expression, and characterization of a recombinant annexin B1-low molecular weight urokinase chimera in Escherichia coli

To produce a thrombi-targeting plasminogen activator, low molecular weight single-chain urokinase gene (scuPA32k) was spliced with the full-length cDNA of annexin B1 gene (anxB1) by overlap extension method. The fused gene anxB1scuPA was ligated into pET28a vector, transformed into E. coli BL21-RIL, and then induced to express under the control of T7 promoter. The AnxB1ScuPA protein expressed amounted to 22% of the total bacterial proteins. The product was refolded, and then purified by using DEAE Sepharose fast flow ion-exchange column and Superdex S-200 gel-filtration column. HPLC analysis revealed that the final purity is about 95%. The specific activity of AnxB1ScuPA, measured as amidolytic activity, reached 100,000 IU/mg. It had a similar S2444 catalytic efficiency (kcat/Km) to ScuPA32k, and also showed high activated-platelet membrane-binding activity and anticoagulant activity, indicating that the chimera fully retained the components of enzymatic and membrane-binding activities of the parent molecules. In vivo test revealed that, the dogs administered with AnxB1ScuPA had less reperfusion time, higher reperfusion ratio, and less bleeding effects than those with urokinase. These findings indicated that AnxB1ScuPA might have advantages over current available thrombolytic agents.

Recombinant factor VIIa as an antidote for anticoagulant treatment

Increasing knowledge on the function of the hemostatic system in vivo and limitations of currently available anticoagulant agents have led to the development of a new generation of anticoagulants. These new agents have a greater specificity towards activated coagulation pathways and factors and are presently being evaluated in clinical studies. The new generation anticoagulants include specific inhibitors of factor IIa (melagatran), factor Xa (pentasaccharides), and agents that interfere with tissue factor (TF) activity. A limitation of this new class of anticoagulants may be the lack of an appropriate strategy to reverse the effect if a bleeding event occurs. Recombinant factor VIIa (rFVIIa) is a potent prohemostatic agent and may represent an interesting option for consideration when an antidote is required. Indeed, rFVIIa has proven to be efficacious in the reversal of anticoagulant treatment with vitamin K antagonists. Studies in healthy subjects have also revealed that rFVIIa administration corrects coagulation time and can induce thrombin generation during anticoagulation with pentasaccharides or TF-inhibiting therapy. These results indicate that rFVIIa infusion results in a prohemostatic response in vivo in patients receiving treatment with factor Xa- or TF-specific anticoagulants. This suggests that rFVIIa may be a good candidate as an antidote for new anticoagulants in cases of (severe) bleeding or in patients scheduled for emergency surgery.

Treatment of Ebola virus infection with a recombinant inhibitor of factor VIIa/tissue factor: a study in rhesus monkeys

BACKGROUND

Infection with the Ebola virus induces overexpression of the procoagulant tissue factor in primate monocytes and macrophages, suggesting that inhibition of the tissue-factor pathway could ameliorate the effects of Ebola haemorrhagic fever. Here, we tested the notion that blockade of fVIIa/tissue factor is beneficial after infection with Ebola virus.

METHODS

We used a rhesus macaque model of Ebola haemorrhagic fever, which produces near 100% mortality. We administered recombinant nematode anticoagulant protein c2 (rNAPc2), a potent inhibitor of tissue factor-initiated blood coagulation, to the macaques either 10 min (n=6) or 24 h (n=3) after a high-dose lethal injection of Ebola virus. Three animals served as untreated Ebola virus-positive controls. Historical controls were also used in some analyses.

FINDINGS

Both treatment regimens prolonged survival time, with a 33% survival rate in each treatment group. Survivors are still alive and healthy after 9 months. All but one of the 17 controls died. The mean survival for the six rNAPc2-treated macaques that died was 11.7 days compared with 8.3 days for untreated controls (p=0.0184). rNAPc2 attenuated the coagulation response as evidenced by modulation of various important coagulation factors, including plasma D dimers, which were reduced in nearly all treated animals; less prominent fibrin deposits and intravascular thromboemboli were observed in tissues of some animals that succumbed to Ebola virus. Furthermore, rNAPc2 attenuated the proinflammatory response with lower plasma concentrations of interleukin 6 and monocyte chemoattractant protein-1 (MCP-1) noted in the treated than in the untreated macaques.

INTERPRETATION

Post-exposure protection with rNAPc2 against Ebola virus in primates provides a new foundation for therapeutic regimens that target the disease process rather than viral replication.

Recombinant nematode anticoagulant protein c2 and other inhibitors targeting blood coagulation factor VIIa/tissue factor

Originally isolated from a haematophagous hookworm, recombinant nematode anticoagulant protein c2 (rNAPc2) is an 85-amino acid protein with potent anticoagulant properties. Unlike conventional anticoagulants that attenuate blood coagulation via inhibition of thrombin or activated factor X (FXa) at the downstream portion of the cascade, rNAPc2 is a potent inhibitor of the activated factor VII/tissue factor complex (FVIIa/TF), the key physiological initiator of blood coagulation. Its mechanism of action requires prerequisite binding to circulating FXa or zymogen factor X (FX) to form a binary complex prior to its interaction and inhibition of membrane-bound FVIIa/TF. The binding of rNAPc2 to FX results in an elimination half-life of longer than 50 h following either subcutaneous or intravenous administration. Recombinant NAPc2, like other inhibitors of FVIIa/TF including tissue factor pathway inhibitor (TFPI) and active site-blocked FVIIa (ASIS, FFR-rFVIIa or FVIIai), may have a promising role in the prevention and treatment of venous and arterial thrombosis, as well as potential efficacy in the management of disseminated intravascular coagulopathies because of their potent and selective inhibition of FVIIa/TF.

A novel therapeutic approach targeting articular inflammation using the filarial nematode-derived phosphorylcholine-containing glycoprotein ES-62

Understanding modulation of the host immune system by pathogens offers rich therapeutic potential. Parasitic filarial nematodes are often tolerated in human hosts for decades with little evidence of pathology and this appears to reflect parasite-induced suppression of host proinflammatory immune responses. Consistent with this, we have previously described a filarial nematode-derived, secreted phosphorylcholine-containing glycoprotein, ES-62, with immunomodulatory activities that are broadly anti-inflammatory in nature. We sought to evaluate the therapeutic potential of ES-62 in vitro and in vivo in an autoimmune disease model, namely, collagen-induced arthritis in DBA/1 mice. ES-62 given during collagen priming significantly reduced initiation of inflammatory arthritis. Crucially, ES-62 was also found to suppress collagen-induced arthritis severity and progression when administration was delayed until after clinically evident disease onset. Ex vivo analyses revealed that in both cases, the effects were associated with inhibition of collagen-specific pro-inflammatory/Th1 cytokine (TNF-alpha, IL-6, and IFN-gamma) release. In parallel in vitro human tissue studies, ES-62 was found to significantly suppress macrophage activation via cognate interaction with activated T cells. Finally, ES-62 suppressed LPS-induced rheumatoid arthritis synovial TNF-alpha and IL-6 production. Evolutionary pressure has promoted the generation by pathogens of diverse mechanisms enabling host immune system evasion and induction of "tolerance." ES-62 represents one such mechanism. We now provide proof of concept that parasite-derived immunomodulatory strategies offer a novel therapeutic opportunity in inflammatory arthritis.

[Biology and physiopathology of tissue factor and its relevance for cardiovascular diseases]

Tissue factor (TF) is a transmembrane glycoprotein, currently considered as being the major regulator of the coagulation cascade and the initiator of thrombogenesis in vivo. When TF comes in contact with blood, it forms a high-affinity complex with factors VII/VIIa, activating factors IX and X and thus leading to the formation of an insoluble fibrin clot. The regulation of TF-VIIa activity plays a key role in blood-vessel wall interactions. Selective patterns of cellular expression of TF are observed in tissues. TF is constitutively localized only on the surface of cells anatomically separated from the blood, where it plays an essential role in hemostasis by limiting hemorrhage after vessel wall injury. A number of pathophysiologic stimuli are capable of inducing TF transcription and activity in endothelial cells and monocytes. An aberrant TF expression in contact with blood is implicated in thrombotic complications of atherosclerosis, including acute myocardial infarction. Recent findings have demonstrated cell-derived microparticles containing TF in the circulating blood of patients with acute coronary syndromes, capable of triggering and propagating thrombus growth. This observation suggests a new view of thrombosis that does not necessarily require the exposure of vessel wall-derived TF at the site of vascular injury to initiate and propagate thrombosis.

Effects of a selective CD11b/CD18 antagonist and recombinant human tissue plasminogen activator treatment alone and in combination in a rat embolic model of stroke

BACKGROUND AND PURPOSE

We evaluated the neuroprotective effect of UK-279,276 (also referred to as recombinant neutrophil inhibitory factor), a selective CD11b/CD18 antagonist, in combination with thrombolytic therapy on focal cerebral ischemia.

METHODS

Male Wistar rats (n=88) were subjected to embolic middle cerebral artery occlusion. Animals were randomly assigned to the following groups (n=11 in each group): vehicle treatment alone at 2 or 4 hours, UK-279,276 treatment alone at 2 or 4 hours, recombinant human tissue plasminogen activator (rhtPA) treatment alone at 2 or 4 hours, or the combination of UK-279,276 and rhtPA at 2 or 4 hours. Infarct volume, neurological function, hemorrhagic transformation, neutrophil accumulation, and parenchymal fibrin deposition were measured 7 days after middle cerebral artery occlusion.

RESULTS

Treatment with UK-279,276 significantly (P<0.05) improved neurological severity scores, an index of neurological functional deficit, but had no effect on infarct volume compared with vehicle-treated animals. Treatment with rhtPA alone at 2 but not 4 hours significantly (P<0.05) reduced infarct volume and improved neurological function compared with vehicle-treated animals. Combination treatment with UK-279,276 and rhtPA at 2 or 4 hours significantly (P<0.01) reduced infarct volume and enhanced recovery of neurological function compared with control. Neutrophil accumulation and fibrin deposition in the brain parenchyma of combination-treated rats at 2 and 4 hours after stroke were significantly reduced (P<0.05) compared with corresponding vehicle-treated control groups. The neuroprotective effect of the combined treatments was superior to the additive effects from each treatment of rhtPA or UK-279,276 alone.

CONCLUSIONS

These data suggest that the combination treatment with UK-279,276 and rhtPA may extend the window of thrombolytic therapy for the acute treatment of stroke.

Recombinant nematode anticoagulant protein c2, an inhibitor of the tissue factor/factor VIIa complex, in patients undergoing elective coronary angioplasty

OBJECTIVES

We investigated the safety and pharmacodynamics of escalating doses of recombinant nematode anticoagulant protein c2 (rNAPc2) in patients undergoing elective coronary angioplasty.

BACKGROUND

Recombinant NAPc2 is a potent inhibitor of the tissue factor/factor VIIa complex, which has the potential to reduce the risk of thrombotic complications in coronary artery disease.

METHODS

In a randomized, double-blinded, dose-escalation, multicenter trial, 154 patients received placebo or rNAPc2 at doses of 3.5, 5.0, 7.5, and 10.0 microg/kg body weight as a single subcutaneous administration 2 to 6 h before angioplasty. All patients received aspirin, unfractionated heparin during angioplasty, and clopidogrel in case of stent implantation.

RESULTS

Minor bleeding rates for the doses 3.5 to 7.5 microg/kg were comparable to that with placebo (6.7%), whereas an incidence of 26.9% was observed at the 10.0 microg/kg dose level (p < 0.01). Major bleedings occurred in the 5.0 microg/kg (n = 3) and 7.5 microg/kg (n = 1) dose groups. The three patients in the 5.0 microg/kg dose group also received a glycoprotein IIb/IIIa receptor inhibitor at the moment of major bleeding. Systemic thrombin generation, as measured by prothrombin fragment 1+2 (F(1+2)), was suppressed in all rNAPc2 dose groups to levels below pretreatment values for at least 36 h. In the placebo group, a distinct increase of F(1+2) levels was observed following cessation of heparin.

CONCLUSIONS

Inhibition of the tissue factor/factor VIIa complex with rNAPc2, at doses up to 7.5 microg/kg, in combination with aspirin, clopidogrel, and unfractionated heparin appears to be a safe and effective strategy to prevent thrombin generation during coronary angioplasty.

Vaccination of calves against Ostertagia ostertagi with cysteine proteinase enriched protein fractions

Cysteine proteinase enriched fractions obtained by thiol-sepharose chromatography of Ostertagia ostertagi membrane-bound protein extract (S3-thiol) or total adult excretory-secretory (ES-thiol) products were tested in a vaccination experiment to evaluate their protective efficacy against O. ostertagi in cattle. Calves were vaccinated three times and subsequently challenged with a trickled infection of 25,000 infective larvae in total over 25 days (1000 L3/day, 5 days/week). Geometric mean cumulative egg counts in the ES-thiol group were reduced by 60% during the 2-month period between the first challenge infection and necropsy, compared to the control group (P < 0.002). No reduction in egg output was observed in the S3-thiol group. At necropsy, calves immunized with ES-thiol had a significantly higher percentage of inhibited L4 larvae (9.8%) and had in total 18% less worms than the control calves, but this reduction was not statistically significant. Both the female and male adult worms were significantly smaller in the ES-thiol group than in the control group. Although no significant difference was observed in the number of eggs per female worm between the groups, there was a trend to less eggs per female worm in the ES-thiol group. Number of worms, size of adult worms and number of eggs per female worm were not significantly different between the S3-thiol group and the control group. Systemic immunization with QuilA as adjuvant induced a significant rise in Ostertagia-specific antibody levels in the abomasal mucosa. Ostertagia-specific local antibody levels showed a significant negative correlation with the size of the adult worms, the number of eggs per female worm and the cumulative faecal egg counts. However, these correlations were quite weak and did not appear to be isotype-specific.

Tissue factor - a therapeutic target for thrombotic disorders

Exposure of blood to tissue factor (TF) sets off the coagulation cascade. TF is a transmembrane protein that serves as an essential cofactor for activated coagulation factor VII (FVIIa). TF may be exposed locally by vascular injury (such as balloon angioplasty) or by spontaneous rupture of an atherosclerotic plaque. Expression of TF may also be induced on monocytes and endothelial cells in conditions like sepsis and cancer, causing a more generalised activation of clotting. TF may thus play a central role in thrombosis in a number of settings, and attention has turned to blocking TF as a means to prevent thrombosis. Inhibiting the inducible expression of TF by monocytes can be achieved by 'deactivating' cytokines, such as interleukin (IL)-4, -10 and -13, or by certain prostanoids; by drugs that modify signal transduction, such as pentoxifylline, retinoic acid or vitamin D(3), or by antisense oligonucleotides. Such approaches are for the most part at a preclinical stage. The function of TF can be blocked by antibodies that prevent the binding of FVIIa to TF; by active site-inhibited FVIIa, which competes with native FVIIa for binding; by antibodies or small molecules that block the function of the TF/FVIIa complex; and by molecules, such as TF pathway inhibitor or nematode anticoagulant peptide C2, which inhibit the active site of FVIIa in the TF/FVIIa complex after first binding to activated factor X. The latter two agents have entered Phase II clinical trials. Perhaps most intriguing is the use of anti-TF agents locally, which holds the promise of stopping thrombosis at a specific site of injury without the bleeding risk associated with systemic anticoagulation.

The role of tissue factor/factor VIIa in the pathophysiology of acute thrombotic formation

Tissue factor (TF) is the essential cofactor for the coagulation protease factor VIIa (FVIIa), initiating the coagulation cascade. The role of TF in thrombotic diseases is becoming increasingly evident. Recent findings suggest that inhibition of TF/FVIIa activity could be important in the prevention of clinical sequelae associated with plaque rupture or vessel damage that exposes TF to blood. Furthermore, selective inhibitors of TF/FVIIa may be associated with less bleeding risk than other antithrombotic agents. Several TF/FVIIa inhibitors are in development, including the protein-based inhibitors (such as NAPc2, Corsevin M, FFR-FVIIa, and Tifacogin). Research into the development of small molecule inhibitors is on-going, but is at a less advanced stage.

Novel inhibitors of factor X for use in cardiovascular diseases

The complementary roles of platelets and thrombin in the pathophysiology of acute coronary syndromes suggests that for treatment to be effective, both mediators must be targeted. Although great strides have been made in the development of antiplatelet therapies, attempts to inhibit thrombin have been less successful. Unfractionated heparin is limited by a number of pharmacologic shortcomings as well as an inability to meaningfully suppress thrombin generation. The low molecular weight heparins have yielded encouraging results in large-scale clinical trials, but it remains unclear whether their benefit stems from a superior pharmacologic profile to unfractionated heparin or is determined by an enhanced ability to suppress thrombin generation (by virtue of a direct anti-Xa effect). Regardless, investigators have become increasingly interested in factor Xa as a potential target for antithrombotic therapy. A number of naturally occurring Xa antagonists have been identified. Work with recombinant forms of these proteins confirms that factor Xa inhibition can suppress thrombin generation in a variety of animal thrombosis models. Accordingly, a number of synthetic direct and indirect Xa antagonists are under development for the prevention and treatment of thrombotic disorders. The following review summarizes the evolution of factor Xa antagonists.

Antithrombotic efficacy of single subcutaneous administration of a recombinant nematode anticoagulant peptide (rNAP5) in a canine model of coronary artery thrombolysis

We examined the adjunctive benefit of recombinant nematode anticoagulant peptide (rNAP5), a factor Xa inhibitor, in a canine model of recombinant (rt)-PA-induced thrombolysis. In anesthetized dogs, a stable occlusive thrombus was formed by electrolytic injury of the vessel wall, after which the animals were administered rt-PA (1.44 mg/kg, i.v.) and rNAP5 (0.1 mg/kg, s.c.: n=13), or rt-PA plus vehicle (1-2 ml, s.c.; n=13). Hemodynamic and coagulation parameters were monitored for 360 minutes. Single subcutaneous administration of rNAP5 resulted in a prolonged and sustained increase in the activated partial thromboplastin time (>100-fold), whereas prothrombin time was unchanged. The template bleeding time was not altered significantly throughout the protocol (maximum 1.4-fold). The incidence of reperfusion was similar in the two groups with a trend toward faster reperfusion in the rNAP5 group (34+/-4 minutes) compared to the vehicle group (63+/-15 minutes; p=0.07). After reperfusion, 80% of the vessels in the vehicle group reoccluded, whereas only 14% of vessels reoccluded in the rNAP5-treated group. Times to reocclusion were 65+/-21 minutes and 221+/-28 minutes, respectively (p<0.05). Single subcutaneous administration of rNAP5 sustained the coronary artery blood flow after reperfusion, such that at the end of protocol the flow was 47% of the preocclusion value as compared to the vehicle group in which the flow was 11% (p<0.05). Cyclic flow reductions were most prominent during rt-PA-induced reperfusion and were similar in both groups. The results indicate that a single subcutaneous administration of rNAP5 provides a sustained antithrombotic effect in maintaining the coronary artery patency during rt-PA-induced thrombolysis.

Vaccination against Schistosoma mansoni infection using 74 kDa Schistosoma protein antigen

An IgG2a anti-Schistosoma mansoni mouse monoclonal antibody was shown to passively protect Swiss mice. The 74 kDa target antigen was isolated from antigenic extracts of S. mansoni adult worms. Swiss and C57 BL/6J mice were immunized with 30, 50, 100 and 200 microg antigen/mouse doses with and without Freund's adjuvant. Sera of immunized mice showed high reactivity against 74 kDa antigen. The highest protection level (76.6% in Swiss mice and 50.1% in C57 BL/6J mice) was obtained using the 50 microg antigen dose with and without Freund's adjuvant. A marked reduction in granuloma number and intensity of collagen and reticular granuloma fibers was observed. The 74 kDa antigen has the ability to protect mice of different strains and to modulate the host immune system.

Immunization with an affinity purified protein extract from the adult parasite protects lambs against infection with Haemonchus contortus

Young lambs were immunized with membrane protein extracts from adult Haemonchus contortus which had been enriched for cysteine protease activity using Thiol-Sepharose chromatography. The resulting extract comprised several peptides including cysteine as well as serine and metallo-protease activities although the former predominated. A limited number of the peptide components were glycosylated. Following a single challenge infection with the same parasite, vaccinated lambs had substantially reduced faecal egg outputs and final worm burdens (overall means of 77% and 47%, respectively, from three trials) compared with challenge controls. Antibody in sera from vaccinated lambs was almost exclusively bound to the surface of the parasite gut indicating that protection may be mediated by the inhibition of parasite digestion.

Ancylostoma caninum anticoagulant peptide blocks metastasis in vivo and inhibits factor Xa binding to melanoma cells in vitro

We evaluated the in vivo anti-metastatic activity of recombinant Ancylostoma caninum Anticoagulant Peptide (rAcAP), a potent (Ki = 265 pM) and specific active site inhibitor of human coagulation factor Xa originally isolated from bloodfeeding hookworms. Subcutaneous injection of SCID mice with rAcAP (0.01-0.2 mg/mouse) prior to tail vein injection of LOX human melanoma cells resulted in a dose dependent reduction in pulmonary metastases. In order to elucidate potential mechanisms of rAcAP's anti-metastatic activity, experiments were carried out to identify specific interactions between factor Xa and LOX. Binding of biotinylated factor Xa to LOX monolayers was both specific and saturable (Kd = 15 nM). Competition experiments using antibodies to previously identified factor Xa binding proteins, including factor V/Va, effector cell protease receptor-1, and tissue factor pathway inhibitor failed to implicate any of these molecules as significant binding sites for Factor Xa. Functional prothrombinase activity was also supported by LOX, with a half maximal rate of thrombin generation detected at a factor Xa concentration of 2.4 nM. Additional competition experiments using an excess of either rAcAP or active site blocked factor Xa (EGR-Xa) revealed that most of the total factor Xa binding to LOX is mediated via interaction with the enzyme's active site, predicting that the vast majority of cell-associated factor Xa does not participate directly in thrombin generation. In addition to establishing two distinct mechanisms of factor Xa binding to melanoma, these data raise the possibility that rAcAP's antimetastatic effect in vivo might involve novel non-coagulant pathways, perhaps via inhibition of active-site mediated interactions between factor Xa and tumor cells.

Neutrophil inhibitory factor treatment of focal cerebral ischemia in the rat

The present study was designed to determine whether a hookworm-derived recombinant neutrophil inhibitory factor (rNIF) is neuroprotective when administered after initiation of focal cerebral ischemia in the rat. We measured the rNIF dose-response on cerebral infarct volume, the therapeutic time window, the therapeutic response to permanent ischemia, and whether rNIF treatment delays the maturation of the ischemic lesion (2 days), or reduces cerebral infarct volume at 7 days after middle cerebral artery occlusion (MCAO). MCAO was induced by an insertion of intraluminal 4-0 monofilament nylon suture into internal carotid artery (n=195). We demonstrate a significant neuroprotective effect of rNIF administration 48 h after MCAO in a dose-dependent fashion when treatment was initiated upon reperfusion after 2 h MCAO and maintained until 48 h after MCAO. The beneficial effect was lost under conditions of permanent MCAO. The therapeutic time window is 4 h after MCAO. Brief treatment (6 h) is not sufficient to provide protection for the final ischemic damage. Continuous treatment with a high dose of rNIF for a long duration (7 days) is necessary to achieve maximum neuroprotection.

Antithrombotic efficacy of a recombinant nematode anticoagulant peptide (rNAP5) in canine models of thrombosis after single subcutaneous administration

We describe the antithrombotic effects of recombinant nematode anticoagulant peptide (rNAP5), a selective and direct factor Xa inhibitor, after a single s.c. administration in canine models of arterial and venous thrombosis. The systemic anticoagulant effects of rNAP5 were evaluated initially in conscious dogs after s.c. dosing (0.03, 0.1 and 0.3 mg/kg) that resulted in a dose-dependent increase in the activated clotting time and the activated partial thromboplastin time. The antithrombotic effects of rNAP5 were evaluated in anesthetized dogs where saline or rNAP5 (0.03, 0.1 and 0.3 mg/kg s.c.) was administered 1 hr before the left circumflex coronary artery was subjected to electrolytic injury. In the saline group (n = 10), the left circumflex artery occluded in 79 +/- 9 min, and 5 of 10 animals progressed to sudden death due to ventricular fibrillation. rNAP5 significantly prolonged the time to occlusion in the 0.03 mg/kg (163 +/- 62 min) and 0.1 mg/kg (327 +/- 62) treatment groups (n = 6). In the 0.3 mg/kg group (n = 5), all of the injured vessels remained patent for 8 hr. There was a dose-dependent reduction in the thrombus mass in the rNAP5-treated animals as compared with controls, as well as a lower mortality rate. rNAP5, in the doses of 0.03 and 0.1 mg/kg, did not alter the bleeding time, whereas 0.3 mg/kg produced a 5-fold increase. In a separate study, we evaluated the efficacy of rNAP5 (0.1 mg/kg) in the prevention of carotid artery and jugular vein thrombosis. In response to endothelial injury, the carotid artery and jugular vein in the saline group (n = 6) occluded in 142 +/- 16 and 100 +/- 11 min, respectively, compared with rNAP5, which maintained vessel patency in the carotid artery (6/6) and jugular vein (5/6) and significantly decreased the thrombus weights. The results demonstrate that rNAP5 has antithrombotic efficacy in canine models of arterial and venous thrombosis after a single s.c. administration.

A natural glycoprotein inhibitor (NIF) of CD11b/CD18 reduces leukocyte adhesion in the liver after hemorrhagic shock

This study was designed to assess the effect of neutrophil inhibitory factor (NIF), a novel specific inhibitor of CD11b/CD18 on hepatic leukocyte trafficking by intravital microscopy 5 h after hemorrhagic shock. Anesthetized rats were instrumented for invasive hemodynamical monitoring. Hemorrhagic shock was induced for 60 min by withdrawal of arterial blood (mean arterial blood pressure = 40 mmHg). Rats were adequately resuscitated for 5 h to achieve a mean arterial blood pressure > 100 mmHg and were randomly assigned to blinded treatment with NIF or placebo control protein administered as a single intravenous bolus (10 mg/kg) at the time of resuscitation. Intrahepatic leukocyte adhesion was evaluated by in vivo fluorescence microscopy. There were no significant differences observed in hemodynamic parameters between the shock groups throughout the study, however, NIF significantly reduced firm leukocyte adhesion in liver sinusoids. The results suggest that NIF may be beneficial in the attenuation of the pathological shock-induced leukocyte adhesion.