Regulation of C1 inhibitor synthesis

Circulating levels of endogenous complement inhibitors correlate inversely with complement consumption in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is marked by excessive complement activation, contributing to tissue damage. Complement activation can be detected in many organs including the skin, kidney, and brain. The involvement of the central nervous system is particularly relevant to understanding neuropsychiatric SLE (NPSLE), one of the poorest understood manifestations of SLE for which no biomarkers are available. We studied the levels of complement inhibitors in SLE in relation to disease activity and as possible biomarkers to identify NPSLE. Serum levels of complement inhibitors C1-inhibitor (C1-INH), C4b-binding protein (C4BP), Factor I, and Factor H were measured in 345 SLE patients (including 102 with NPSLE) and 108 healthy controls. Compared with controls, SLE patients had higher C1-INH and C4BP but lower Factor I and H levels. All inhibitors positively correlated with total C3 and C4 levels. While correlating with the SLE Disease Activity Index (SLEDAI), no distinction in inhibitor levels was found between SLE and NPSLE patients. Over time, C1-INH and Factor H levels normalized, but no significant changes were observed for C4BP and Factor I. In SLE the levels of circulating complement inhibitors are inversely correlated to complement consumption but do not serve as biomarkers for NPSLE.

In-silico docking platform with serine protease inhibitor (SERPIN) structures identifies host cysteine protease targets with significance for SARS-CoV-2

Serine Protease Inhibitors (SERPINs) regulate protease activity in various physiological processes such as inflammation, cancer metastasis, angiogenesis, and neurodegenerative diseases. However, their potential in combating viral infections, where proteases are also crucial, remains underexplored. This is due to our limited understanding of SERPIN expression during viral-induced inflammation and of the SERPINs' full spectrum of target proteases. Here, we demonstrate widespread expression of human SERPINs in response to respiratory virus infections, both in vitro and in vivo , alongside classical antiviral effectors. Through comprehensive in-silico docking with full-length SERPIN and protease 3D structures, we confirm known inhibitors of specific proteases; more importantly, the results predict novel SERPIN-protease interactions. Experimentally, we validate the direct inhibition of key proteases essential for viral life cycles, including the SERPIN PAI-1's capability to inhibit select cysteine proteases such as cathepsin L, and the serine protease TMPRSS2. Consequently, PAI-1 suppresses spike maturation and multi-cycle SARS-CoV-2 replication. Our findings challenge conventional notions of SERPIN selectivity, underscore the power of in-silico docking for SERPIN target discovery, and offer potential therapeutic interventions targeting host proteolytic pathways to combat viruses with urgent unmet therapeutic needs.

SIGNIFICANCE

Serine protease inhibitors (SERPINs) play crucial roles in various physiological processes, including viral infections. However, our comprehension of the full array of proteases targeted by the SERPIN family has traditionally been limited, hindering a comprehensive understanding of their regulatory potential. We developed an in-silico docking platform to identify new SERPIN target proteases expressed in the respiratory tract, a critical viral entry portal. The platform confirmed known and predicted new targets for every SERPIN examined, shedding light on previously unrecognized patterns in SERPIN selectivity. Notably, both key proteases for SARS-CoV-2 maturation were among the newly predicted targets, which we validated experimentally. This underscores the platform's potential in uncovering targets with significance in viral infections, paving the way to define the full potential of the SERPIN family in infectious disease and beyond.

Screening for type II hereditary angioedema-the "poor man's c1-inhibitor function"

Background

Hereditary angioedema (HAE) is a rare genetic disease. Patients with type II HAE have normal or elevated C1-inhibitor (C1-INH) levels but C1-INH protein is dysfunctional. C1-INH function requires careful sample handling and technical expertise and may account for the lack of diagnosed patients with type II HAE in resource-limited countries.

Objective

We sought to assess the diagnostic performance of elevated C1-INH levels in diagnosing type II HAE.

Methods

All patients with confirmed type II HAE in Hong Kong and India were analyzed. Diagnosis was confirmed by persistent low C1-INH function and/or pathogenic SERPING1 gene mutations. Their C1-INH levels were compared with those of matched controls.

Results

A total of 31 (14 Chinese, 17 Indian) patients with type II HAE and 31 matched controls were analyzed. Overall, 77.4% (24/31) of patients with type II HAE had elevated C1-INH levels compared with 38.7% (12 of 31) of controls (odds ratio, 2.00; 95% CI, 1.34-2.98; P = .017). C1-INH levels in patients with type II HAE were significantly higher than in controls (52.2 ± 20.0 mg/dL vs 29.1 ±3.6 mg/dL; P < .001). Findings were consistent when C1-INH values in the Chinese and Indian subgroups were analyzed separately. Receiver-operating characteristic curve demonstrated excellent performance for elevated C1-INH levels to diagnose patients with type II HAE with an area under the curve of 0.953 (95% CI, 0.941-0.992; P < .001). Positive and negative predictive values of both a low C4 and an elevated C1-INH level for patients with type II HAE were 100% and 82.9%, respectively.

Conclusions

Low C4 and elevated C1-INH levels may be considered as a screening tool for type II HAE, especially in countries where C1-INH function testing is not readily available.

Citrullination of C1-inhibitor as a mechanism of impaired complement regulation in rheumatoid arthritis

Background

Dysregulated complement activation, increased protein citrullination, and production of autoantibodies against citrullinated proteins are hallmarks of rheumatoid arthritis (RA). Citrullination is induced by immune cell-derived peptidyl-Arg deiminases (PADs), which are overactivated in the inflamed synovium. We characterized the effect of PAD2- and PAD4-induced citrullination on the ability of the plasma-derived serpin C1-inhibitor (C1-INH) to inhibit complement and contact system activation.

Methods

Citrullination of the C1-INH was confirmed by ELISA and Western blotting using a biotinylated phenylglyoxal probe. C1-INH-mediated inhibition of complement activation was analyzed by C1-esterase activity assay. Downstream inhibition of complement was studied by C4b deposition on heat-aggregated IgGs by ELISA, using pooled normal human serum as a complement source. Inhibition of the contact system was investigated by chromogenic activity assays for factor XIIa, plasma kallikrein, and factor XIa. In addition, autoantibody reactivity to native and citrullinated C1-INH was measured by ELISA in 101 RA patient samples.

Results

C1-INH was efficiently citrullinated by PAD2 and PAD4. Citrullinated C1-INH was not able to bind the serine protease C1s and inhibit its activity. Citrullination of the C1-INH abrogated its ability to dissociate the C1-complex and thus inhibit complement activation. Consequently, citrullinated C1-INH had a decreased capacity to inhibit C4b deposition via the classical and lectin pathways. The inhibitory effect of C1-INH on the contact system components factor XIIa, plasma kallikrein, and factor XIa was also strongly reduced by citrullination. In RA patient samples, autoantibody binding to PAD2- and PAD4-citrullinated C1-INH was detected. Significantly more binding was observed in anti-citrullinated protein antibody (ACPA)-positive than in ACPA-negative samples.

Conclusion

Citrullination of the C1-INH by recombinant human PAD2 and PAD4 enzymes impaired its ability to inhibit the complement and contact systems in vitro. Citrullination seems to render C1-INH more immunogenic, and citrullinated C1-INH might thus be an additional target of the autoantibody response observed in RA patients.

Targeting thromboinflammation in COVID-19 - A narrative review of the potential of C1 inhibitor to prevent disease progression

Coronavirus disease 2019 (COVID-19) caused by SARS-CoV-2 is associated with a clinical spectrum ranging from asymptomatic carriers to critically ill patients with complications including thromboembolic events, myocardial injury, multisystemic inflammatory syndromes and death. Since the beginning of the pandemic several therapeutic options emerged, with a multitude of randomized trials, changing the medical landscape of COVID-19. The effect of various monoclonal antibodies, antiviral, anti-inflammatory and anticoagulation drugs have been studied, and to some extent, implemented into clinical practice. In addition, a multitude of trials improved the understanding of the disease and emerging evidence points towards a significant role of the complement system, kallikrein-kinin, and contact activation system as drivers of disease in severe COVID-19. Despite their involvement in COVID-19, treatments targeting these plasmatic cascades have neither been systematically studied nor introduced into clinical practice, and randomized studies with regards to these treatments are scarce. Given the multiple-action, multiple-target nature of C1 inhibitor (C1-INH), the natural inhibitor of these cascades, this drug may be an interesting candidate to prevent disease progression and combat thromboinflammation in COVID-19. This narrative review will discuss the current evidence with regards to the involvement of these plasmatic cascades as well as endothelial cells in COVID-19. Furthermore, we summarize the evidence of C1-INH in COVID-19 and potential benefits and pitfalls of C1-INH treatment in COVID-19.

Physicochemical and Biological Characterization of rhC1INH Expressed in CHO Cells

The disfunction or deficiency of the C1 esterase inhibitor (C1INH) is associated with hereditary or acquired angioedema (HAE/AAE), a rare life-threatening condition characterized by swelling in the skin, respiratory and gastrointestinal tracts. The current treatment options may carry the risks of either viral infection (plasma-derived Berinert^®) or immune reaction (human recombinant C1INH from rabbit milk, Ruconest^®). This study describes the physicochemical and biological characterization of a novel recombinant human C1 esterase inhibitor (rhC1INH) from Chinese hamster ovary (CHO) cells for the treatment of hereditary angioedema compared to the marketed products Berinert^® and Ruconest^®. The mass spectrometry results of total deglycosylated rhC1INH revealed a protein with a molecular mass of 52,846 Da. Almost full sequence coverage (98.6%) by nanoLC-MS/MS peptide mapping was achieved. The purity and C1s inhibitory activity of rhC1INH from CHO cells are comparable with Ruconest^®, although we found differences in charge isoforms distribution, intact mass values, and N-glycans profile. Comparison of the specific activity (IC₅₀ value) of the rhC1INH with human C1 esterase inhibitor from blood serum showed similar inhibitory properties. These data allow us to conclude that the novel rhC1INH molecule could become a potential therapeutic option for patients with HAE/AAE.

The role of C1 inhibitor and complement as acute phase reactants: are we missing the diagnosis of hereditary angioedema?

Background

C1 inhibitor (C1-INH) and complement 4 (C4) have historically been referred to as positive acute phase reactants, however this has never been evaluated in hereditary angioedema (HAE) patients. Low function of C1-INH and low levels of C4 are important in the diagnosis of HAE type 1 and 2. If C1-INH and/or C4 are significant acute phase reactants, their levels may be falsely “normal” in patients with HAE when measured during times of infection or inflammation resulting in missed or delayed diagnosis.

Case presentation

We present a case series of four HAE patients who had C4, C1-INH, c-reactive protein (CRP) and ferritin measured at baseline and again during a self-reported upper respiratory tract infection (URTI) or flu-like illness. We did not identify any HAE patients who had a significant change in their C1-INH functional level in the context of a mild infection. However, the C4 level did increase into the normal range on three occasions (2 patients, with 1 patient having elevation during two separate illnesses).

Conclusions

C1 inhibitor may not be a clinically significant acute phase protein and appears to still be a reliable diagnostic marker of hereditary angioedema, even in times of modest acute inflammation, unlike complement C4 which can be elevated in this setting.

C1-Inhibitor: Structure, Functional Diversity and Therapeutic Development

Human C1-Inhibitor (C1INH), also known as C1-esterase inhibitor, is an important multifunctional plasma glycoprotein that is uniquely involved in a regulatory network of complement, contact, coagulation, and fibrinolytic systems. C1INH belongs to a superfamily of serine proteinase inhibitor (serpins) and exhibits its inhibitory activities towards several target proteases of plasmatic cascades, operating as a major anti-inflammatory protein in the circulation. In addition to its inhibitory activities, C1INH is also involved in non-inhibitory interactions with some endogenous proteins, polyanions, cells and infectious agents. While C1INH is essential for multiple physiological processes, it is better known for its deficiency with regards to Hereditary Angioedema (HAE), a rare autosomal dominant disease clinically manifested by recurrent acute attacks of increased vascular permeability and edema. Since the link was first established between functional C1INH deficiency in plasma and HAE in the 1960s, tremendous progress has been made in the biochemical characterization of C1INH and its therapeutic development for replacement therapies in patients with C1INH-dependent HAE. Various C1INH biological activities, recent advances in the HAE-targeted therapies, and availability of C1INH commercial products have prompted intensive investigation of the C1INH potential for treatment of clinical conditions other than HAE. This article provides an updated overview of the structure and biological activities of C1INH, its role in HAE pathogenesis, and recent advances in the research and therapeutic development of C1INH; it also considers some trends for using C1INH therapeutic preparations for applications other than angioedema, from sepsis and endotoxin shock to severe thrombotic complications in COVID-19 patients.

Hormonal Effects on Urticaria and Angioedema Conditions

Women appear to be more frequently affected with urticaria and angioedema. Sex hormones are believed to have an important mechanistic role in regulating pathways involved in these conditions. This effect is likely nonspecific for chronic spontaneous urticaria (CSU) or many forms of angioedema (AE), because many other chronic diseases such as asthma are also affected by sex hormones. The role of sex hormones has been better elucidated for hereditary AE, because they have been shown to have multiple effects including upregulation of FXII, an important activator of the kallikrein pathway. However, their role in the underlying pathogenesis for CSU is less clear. Autoimmunity is clearly linked to CSU, which is more common in women. This suggests that sex hormones could act as adjuvants in activating or upregulating autoimmune pathways. The purpose of this review is to discuss in detail the role of sex hormones in CSU and AE and how a better understanding of the impact hormones has on these conditions might lead to new treatment advancements with better clinical outcomes.

SARS-CoV-2 suppresses anticoagulant and fibrinolytic gene expression in the lung

Extensive fibrin deposition in the lungs and altered levels of circulating blood coagulation proteins in COVID-19 patients imply local derangement of pathways that limit fibrin formation and/or promote its clearance. We examined transcriptional profiles of bronchoalveolar lavage fluid (BALF) samples to identify molecular mechanisms underlying these coagulopathies. mRNA levels for regulators of the kallikrein-kinin (C1-inhibitor), coagulation (thrombomodulin, endothelial protein C receptor), and fibrinolytic (urokinase and urokinase receptor) pathways were significantly reduced in COVID-19 patients. While transcripts for several coagulation proteins were increased, those encoding tissue factor, the protein that initiates coagulation and whose expression is frequently increased in inflammatory disorders, were not increased in BALF from COVID-19 patients. Our analysis implicates enhanced propagation of coagulation and decreased fibrinolysis as drivers of the coagulopathy in the lungs of COVID-19 patients.

Recurrent angioedema in childhood: hereditary angioedema or histaminergic angioedema?

BACKGROUND

Recurrent angioedema is a rare entity during childhood. This study aimed to clarify differences between hereditary angioedema (HAE) and histaminergic angioedema (HA) in children.

METHODS

Fifty-seven children with HAE (male 36.8%, 8.9 years [5.4-12.5]) and 42 children with recurrent HA (male 42.9%, 11.5 years [8.1-16.8]) were analyzed.

RESULTS

The median age at symptom onset (6 [3-10]; 7.8 [4.5-13] years), frequency of angioedema episodes within last year (3 [2-5]; 5 [2-10]), and duration of symptoms (48 [24-48]; 24 [12-48] hours) were similar in the HAE and HA group, respectively. Recurrent urticaria was observed in 7.3% (n = 3) of patients in the HAE group and in 45.2% (n = 19) of the HA group (P < .001). While angioedema episodes involving the lips (n = 30; 71.4%; P = .035) and eyelids (n = 28; 66.7%; P = .012) were observed more frequently in the HA group, gastrointestinal involvement/abdominal pain (n = 15; 36.6%) was more common in HAE (P < .001). Itching as a prodromal symptom was detected in 47.6% (n = 20) of HA patients versus 14.6% (n = 6) of those with HAE (P = .002). In the logistic regression analysis for the diagnosis of HAE, a family history of angioedema (OR = 58.289 [95% CI 10.656-318.853], P < 001) and trauma (OR = 35.208 [95% CI [4.368-283.794]], P = .001) as a triggering factor were determined to be independent variables.

CONCLUSION

A family history of angioedema, trauma as a triggering factor, and abdominal pain should suggest the diagnosis of HAE and the need for further investigation.

Hereditary Angioedema Attack in Utero and Treatment of the Mother and Fetus

Hereditary angioedema (HAE), an inherited deficiency of functional C1 esterase inhibitor (C1-INH), is characterized by unpredictable recurrent episodes of painful and often disabling swelling in subcutaneous and/or submucosal tissues. We report the case of a 23-year-old woman with type I HAE who had abdominal, facial, and peripheral attacks throughout her first pregnancy. A facial HAE attack occurred at week 38 of her pregnancy, and symptoms improved after self-administration of 50 U/kg of recombinant human C1-INH (total dose, 3500 U), but soon after she had an unusual abdominal sensation. Ultrasonography detected fetal lower lip swelling (∼3 times the normal size) and limb swelling. Physical examination of the mother found cervical dilatation, indicating the final stages of labor. Two hours after treatment of her HAE attack, she spontaneously delivered a healthy male infant. Photographs taken within 2 minutes of delivery revealed resolution of the infant’s facial edema, and the limb edema was resolved within 30 minutes. By 10 minutes postdelivery, the mother’s facial attack had almost completely resolved. Ten months after birth, genetic analysis confirmed that the infant had type I HAE. This is the first documented case of an HAE attack in utero. Treatment of the mother with recombinant human C1-INH was effective for the maternal and fetal attacks, with resolution within approximately 2 to 2.5 hours for both patients.

Endothelial PAI-1 (Plasminogen Activator Inhibitor-1) Blocks the Intrinsic Pathway of Coagulation, Inducing the Clearance and Degradation of FXIa (Activated Factor XI)

Objective- Activation of coagulation FXI (factor XI) by FXIIa (activated factor XII) is a prothrombotic process. The endothelium is known to play an antithrombotic role by limiting thrombin generation and platelet activation. It is unknown whether the antithrombotic role of the endothelium includes sequestration of FXIa (activated factor XI) activity. This study aims to determine the role of endothelial cells (ECs) in the regulation of the intrinsic pathway of coagulation. Approach and Results- Using a chromogenic assay, we observed that human umbilical veins ECs selectively blocked FXIa yet supported kallikrein and FXIIa activity. Western blotting and mass spectrometry analyses revealed that FXIa formed a complex with endothelial PAI-1 (plasminogen activator inhibitor-1). Blocking endothelial PAI-1 increased the cleavage of a chromogenic substrate by FXIa and the capacity of FXIa to promote fibrin formation in plasma. Western blot and immunofluorescence analyses showed that FXIa-PAI-1 complexes were either released into the media or trafficked to the early and late endosomes and lysosomes of ECs. When baboons were challenged with Staphylococcus aureus to induce a prothrombotic phenotype, an increase in circulating FXIa-PAI-1 complex levels was detected by ELISA within 2 to 8 hours postchallenge. Conclusions- PAI-1 forms a complex with FXIa on ECs, blocking its activity and inducing the clearance and degradation of FXIa. Circulating FXIa-PAI-1 complexes were detected in a baboon model of S. aureus sepsis. Although ECs support kallikrein and FXIIa activity, inhibition of FXIa by ECs may promote the clearance of intravascular FXIa. Visual Overview- An online visual overview is available for this article.

Circulating microparticle proteins obtained in the late first trimester predict spontaneous preterm birth at less than 35 weeks' gestation: a panel validation with specific characterization by parity

BACKGROUND

We have previously shown that protein biomarkers associated with circulating microparticles proteins (CMPs) obtained at the end of the first trimester may detect physiologic changes in maternal-fetal interaction such that the risk of spontaneous preterm delivery ≤35 weeks can be stratified.

OBJECTIVES

We present here a study extension and validation of the CMP protein multiplex concept using a larger sample set from a multicenter population that allows for model derivation in a training set and characterization in a separate testing set.

MATERIALS AND METHODS

Ethylenediaminetetraacetic acid (EDTA) plasma was obtained from 3 established biobanks (Seattle, Boston, and Pittsburgh). Samples were from patients at a median of 10-12 weeks' gestation, and the CMPs were isolated via size-exclusion chromatography followed by protein identification via targeted protein analysis using liquid chromatography-multiple reaction monitoring-mass (LC-MRM) spectrometry. A total of 87 women delivered at ≤35 weeks, and 174 women who delivered at term were matched by maternal age (±2 years) and gestational age at sample draw (±2 weeks). From our prior work, the CMP protein multiplex comprising F13A, FBLN1, IC1, ITIH2, and LCAT was selected for validation.

RESULTS

For delivery at ≤35 weeks, the receiver operating characteristic (ROC) curve for a panel of CMP proteins (F13A, FBLN1, IC1, ITIH2, and LCAT) revealed an associated area under the ROC curve (AUC) of 0.74 (95% CI, 0.63-0.81). A separate panel of markers (IC1, LCAT, TRFE, and ITIH4), which stratified risk among mothers with a parity of 0, showed an AUC of 0.77 (95% CI, 0.61-0.90).

CONCLUSION

We have identified a set of CMP proteins that provide, at 10-12 weeks gestation, a clinically useful AUC in an independent test population. Furthermore, we determined that parity is pertinent to the diagnostic testing performance of the biomarkers for risk stratification.

Dominant-negative SERPING1 variants cause intracellular retention of C1 inhibitor in hereditary angioedema

Hereditary angioedema (HAE) is an autosomal dominant disease characterized by recurrent edema attacks associated with morbidity and mortality. HAE results from variations in the SERPING1 gene that encodes the C1 inhibitor (C1INH), a serine protease inhibitor (serpin). Reduced plasma levels of C1INH lead to enhanced activation of the contact system, triggering high levels of bradykinin and increased vascular permeability, but the cellular mechanisms leading to low C1INH levels (20%-30% of normal) in heterozygous HAE type I patients remain obscure. Here, we showed that C1INH encoded by a subset of HAE-causing SERPING1 alleles affected secretion of normal C1INH protein in a dominant-negative fashion by triggering formation of protein-protein interactions between normal and mutant C1INH, leading to the creation of larger intracellular C1INH aggregates that were trapped in the endoplasmic reticulum (ER). Notably, intracellular aggregation of C1INH and ER abnormality were observed in fibroblasts from a heterozygous carrier of a dominant-negative SERPING1 gene variant, but the condition was ameliorated by viral delivery of the SERPING1 gene. Collectively, our data link abnormal accumulation of serpins, a hallmark of serpinopathies, with dominant-negative disease mechanisms affecting C1INH plasma levels in HAE type I patients, and may pave the way for new treatments of HAE.

The complex alteration in the network of IL-17-type cytokines in patients with hereditary angioedema

Hereditary angioedema (HAE) is a rare autosomic-dominant disorder characterized by a deficiency of C1 esterase inhibitor which causes episodic swellings of subcutaneous tissues, bowel walls and upper airways that are disabling and potentially life-threatening. We evaluated n = 17 patients with confirmed HAE diagnosis during attack and remission state and n = 19 healthy subjects. The samples were tested for a panel of IL (Interleukin)-17-type cytokines (IL-1β, IL-6, IL-10, granulocyte-macrophage colony stimulating factor (GM-CSF), IL-17, IL-21, IL-22, IL-23) and transforming growth factor-beta (TGF-β) subtypes. Data indicate that there are variations of cytokine levels in HAE subjects comparing the condition during the crisis respect to the value in the remission phase, in particular type 17 signature cytokines are increased, whereas IL-23 is unmodified and TGF-β3 is significantly reduced. When comparing healthy and HAE subjects in the remission state, we found a significant difference for IL-17, GM-CSF, IL-21, TGF-β1 and TGF-β2 cytokines. These results confirm and extend our previous findings indicating that in HAE there is operating an inflammatory activation process, which involves also T helper 17 (Th17) cytokines and TGF-β isoforms, associated with localized angioedema attacks and characterized by elevated bradykinin levels.

Transcriptional profiling, molecular cloning, and functional analysis of C1 inhibitor, the main regulator of the complement system in black rockfish, Sebastes schlegelii

C1-inhibitor (C1inh) plays a crucial role in assuring homeostasis and is the central regulator of the complement activation involved in immunity and inflammation. A C1-inhibitor gene from Sebastes schlegelii was identified and designated as SsC1inh. The identified genomic DNA and cDNA sequences were 6837 bp and 2161 bp, respectively. The genomic DNA possessed 11 exons, interrupted by 10 introns. The amino acid sequence possessed two immunoglobulin-like domains and a serpin domain. Multiple sequence alignment revealed that the serpin domain of SsC1inh was highly conserved among analyzed species where the two immunoglobulin-like domains showed divergence. The distinctiveness of teleost C1inh from other homologs was indicated by the phylogenetic analysis, genomic DNA organization, and their extended N-terminal amino acid sequences. Under normal physiological conditions, SsC1inh mRNA was most expressed in the liver, followed by the gills. The involvement of SsC1inh in homeostasis was demonstrated by modulated transcription profiles in the liver and spleen upon pathogenic stress by different immune stimulants. The protease inhibitory potential of recombinant SsC1inh (rSsC1inh) and the potentiation effect of heparin on rSsC1inh was demonstrated against C1esterase and thrombin. For the first time, the anti-protease activity of the teleost C1inh against its natural substrates C1r and C1s was proved in this study. The protease assay conducted with recombinant black rockfish C1r and C1s proteins in the presence or absence of rSsC1inh showed that the activities of both proteases were significantly diminished by rSsC1inh. Taken together, results from the present study indicate that SsC1inh actively plays a significant role in maintaining homeostasis in the immune system of black rock fish.

Hereditary angioedema (HAE): a cause for recurrent abdominal pain

A 44-year-old Hispanic woman presented to the emergency room with a 2-day history of sudden onset of severe cramping left lower quadrant abdominal pain associated with ∼20 episodes diarrhoea. Abdominal CT scan exhibited bowel wall oedema and acute extensive colitis. On the basis of the preliminary diagnosis of acute abdomen, the patient was admitted under the surgical team and treated for acute colitis. Since her family history was significant for hereditary angioedema (HAE), complement studies were performed which revealed low complement C4 levels and abnormally low values of C1q esterase inhibitor. Thus, the diagnosis of HAE type I was established. This case report summarises that the symptoms of HAE are often non-specific, hence making the underlying cause difficult to diagnose.

Endogenous C1-inhibitor production and expression in the heart after acute myocardial infarction

BACKGROUND

Complement activation contributes significantly to inflammation-related damage in the heart after acute myocardial infarction. Knowledge on factors that regulate postinfraction complement activation is incomplete however. In this study, we investigated whether endogenous C1-inhibitor, a well-known inhibitor of complement activation, is expressed in the heart after acute myocardial infarction.

MATERIALS AND METHODS

C1-inhibitor and complement activation products C3d and C4d were analyzed immunohistochemically in the hearts of patients who died at different time intervals after acute myocardial infarction (n=28) and of control patients (n=8). To determine putative local C1-inhibitor production, cardiac transcript levels of the C1-inhibitor-encoding gene serping1 were determined in rats after induction of acute myocardial infarction (microarray). Additionally, C1-inhibitor expression was analyzed (fluorescence microscopy) in human endothelial cells and rat cardiomyoblasts in vitro.

RESULTS

C1-inhibitor was found predominantly in and on jeopardized cardiomyocytes in necrotic infarct cores between 12h and 5days old. C1-inhibitor protein expression coincided in time and colocalized with C3d and C4d. In the rat heart, serping1 transcript levels were increased from 2h up until 7days after acute myocardial infarction. Both endothelial cells and cardiomyoblasts showed increased intracellular expression of C1-inhibitor in response to ischemia in vitro (n=4).

CONCLUSIONS

These observations suggest that endogenous C1-inhibitor is likely involved in the regulation of complement activity in the myocardium following acute myocardial infarction. Observations in rat and in vitro suggest that C1-inhibitor is produced locally in the heart after acute myocardial infarction.

Paediatric hereditary angioedema: a survey of UK service provision and patient experience

Hereditary angioedema (HAE) is a rare disease characterized by episodes of potentially life-threatening angioedema. For affected children in the United Kingdom, there are relatively few data regarding disease prevalence, service organization and the humanistic burden of the disease. To improve knowledge in these areas, we surveyed major providers of care for children with HAE. A questionnaire was sent to major paediatric centres to determine patient numbers, symptoms, diagnostic difficulties, management and available services. In addition, all patients at a single centre were given a questionnaire to determine the experiences of children and their families. Sixteen of 28 centres responded, caring for a total of 111 UK children. Seven children had experienced life-threatening crises. One-third of patients were on long-term prophylactic medication, including C1 inhibitor prophylaxis in four children. Eight centres reported patients who were initially misdiagnosed. Broad differences in management were noted, particularly regarding indications for long-term prophylaxis and treatment monitoring. We also noted substantial variation in the organization of services between centres, including the number of consultants contributing to patient care, the availability of specialist nurses, the availability of home therapy training and the provision of patient information. Ten of 12 patient/carer questionnaires were returned, identifying three common themes: the need to access specialist knowledge, the importance of home therapy and concerns around the direct effect of angioedema on their life. To our knowledge, this study represents the first dedicated survey of paediatric HAE services in the United Kingdom and provides useful information to inform the optimization of services.

Meta-analysis of the association between CR1 polymorphisms and risk of late-onset Alzheimer's disease

CR1 polymorphisms have been reported to be associated with late-onset Alzheimer's disease (LOAD) susceptibility. The findings of these studies, however, have been inconsistent. Therefore, we performed a meta-analysis to assess the association between CR1 variants and LOAD susceptibility. We retrieved all relevant studies of the associations between CR1 polymorphisms and the susceptibility to LOAD for the period up to March 30, 2014. The strength of the association between CR1 polymorphisms and LOAD risk was estimated by odds ratios (ORs) and their 95% confidence intervals (CIs). A total of 6 articles were eventually identified with 2752 LOAD cases and 2313 controls for the rs6656401 polymorphism, and 4 studies containing 2547 LOAD cases and 2338 controls were included for the rs3818361 polymorphism. Overall, the pooled data showed that the CR1 rs6656401 polymorphism was significantly associated with LOAD risk in the overall population (A vs. G: OR=1.32, 95%CI=1.17-1.50, P=0.000; AG+AA vs. GG: OR=1.39, 95%CI=1.20-1.61, P=0.000). With respect to the CR1 rs3818361 polymorphism, a statistically significant increased LOAD risk was observed in the overall population (T vs. C: OR=1.24, 95% CI=1.13-1.37, P=0.000; TT+TC vs. CC: OR=1.30, 95% CI=1.15-1.46, P=0.000; TT vs. TC+CC: OR=1.35, 95% CI=1.06-1.71, P=0.014). This meta-analysis demonstrated significant associations of both the CR1 rs6656401 and CR1 rs3818361 polymorphisms with LOAD susceptibility.

A C1 inhibitor ortholog from rock bream (Oplegnathus fasciatus): molecular perspectives of a central regulator in terms of its genomic arrangement, transcriptional profiles and anti-protease activities of recombinant peptide

C1 inhibitor (C1Inh), a member of serpin superfamily, is a crucial regulator of the activation of various plasmatic cascades associated with immunity and inflammation. This study describes the identification and characterization of a C1Inh gene from rock bream Oplegnathus fasciatus (OfC1Inh) at structural, expressional and functional levels. The cDNA-(2245bp) and corresponding gDNA-sequences (5.2kbp) of OfC1Inh were isolated from rock bream transcriptome- and BAC-libraries, respectively. Predicted amino acid sequence of OfC1Inh revealed a two-domain architecture composed of an N-terminal region with two Ig-like domains and a C-terminal region with a serpin domain. Tertiary model of OfC1Inh disclosed its active site topology. In the multi-exonic genomic arrangement of OfC1Inh, it consisted of eleven exons disjoined by ten introns as observed in few other fish homologs. Our comparative analysis indicated that the teleostean C1Inhs were distinct from their non-teleostean vertebrate counterparts in terms of their (1) extended N-terminal domains, (2) evolutionary divergence and (3) exon-intron distribution. The OfC1Inh had a TATA-deficient promoter with a putative initiator element, and two tandemly arranged downstream promoter elements. Several components associated with the immune and inflammatory transcriptional activation were also predicted to exist in 5' flanking region of OfC1Inh. The exclusive mRNA levels in liver and moderate levels in extra-hepatic tissues intimated the diversified importance of OfC1Inh in rock bream physiology. We also provide an evidence for the involvement of OfC1Inh in immune balance, based on its modulated transcription upon different PAMP (lipopolysaccharide and poly I:C)- or pathogen (Streptococcus iniae and rock bream irido virus)-challenges. A recombinantly expressed fusion protein [(r)OfC1Inh] was employed in demonstrating the anti-protease function of OfC1Inh. The (r)OfC1Inh exhibited detectable inhibitory activity against C1 esterase and thrombin, where the anti-C1 esterase role was shown to be potentiated by heparin. Taken together, the results of this study provide the first line of evidence for the possible involvement of a teleostean C1Inh in fish immunity, based on its expressional response(s) and inhibitory properties against two enzymes involved in biological cascades.

Acquired form of angioedema of the head and neck related to a deficiency in c1-inhibitor: a case report with a review of the literature

Angioedema related to a deficiency in the C1-inhibitor protein is characterized by its lack of response to therapies including antihistamine, steroids, and epinephrine. In the case of laryngeal edema, mortality rate is approximately 30 percent. The first case of the acquired form of angioedema related to a deficiency in C1-inhibitor was published in 1972. In our paper, we present a case of an acquired form of angioedema of the oropharyngeal region secondary to the simultaneous occurrence of two causative factors: neutralization of C1-inhibitor by an autoantibody and the use of an angiotensin convertin enzyme inhibitor.

Long-term prophylaxis in hereditary angio-oedema: a systematic review

OBJECTIVE

To systematically review the evidence regarding long-term prophylaxis in the prevention or reduction of attacks in hereditary angio-oedema (HAE).

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

Electronic databases were searched up to April 2011. Two reviewers selected the studies and extracted the study data, patient characteristics and outcomes of interest.

ELIGIBILITY CRITERIA FOR SELECTED STUDIES

Controlled trials for HAE prophylaxis.

RESULTS

7 studies were included, for a total of 73 patients and 587 HAE attacks. Due to the paucity of studies, a meta-analysis was not possible. Since two studies did not report the number of HAE attacks, five studies (52 patients) were finally included in the summary analysis. Four classes of drugs with at least one controlled trial have been proposed for HAE prophylaxis. All those drugs, except heparin, were found to be more effective than placebo. In the absence of direct comparisons, the relative efficacies of these drugs were determined by calculating a RR of attacks (drug vs placebo). The results were as follows: danazol (RR=0.023, 95% CI 0.003 to 0.162), methyltestosterone (RR=0.054, 95% CI 0.013 to 0.163), ε-aminocaproic acid (RR=0.095, 95% CI 0.025 to 0.356), tranexamic acid (RR=0.308, 95% CI 0.195 to 0.479) and C1-INH 0.491 (95% CI 0.395 to 0.607).

CONCLUSIONS

Few trials have evaluated the benefits of HAE prophylaxis, and all drugs but heparin seem to be effective in this setting. Since there are no direct comparisons of HAE drugs, it was not possible to draw definitive conclusions on the most effective one. Thus, to accumulate evidence for HAE prophylaxis, further studies are needed that consider the dose-efficacy relationship and include a head-to-head comparison between drugs, with the active group, rather than placebo, as the control.

Cinryze (C1-inhibitor) for the treatment of hereditary angioedema

Cinryze is a pasteurized, nanofiltered plasma derived concentrate of C1-inhibitor (pdC1-INH) licensed for the prophylactic treatment of hereditary angioedema. In a double-blind placebo-controlled crossover trial to evaluate Cinryze as prophylaxis, the frequency of attacks was halved (6.26 per 12 weeks on Cinryze versus 12.73 per 12 weeks on placebo). Furthermore, attacks were generally milder and of shorter duration. For treatment of acute attacks in patients receiving Cinryze, 1000 units, within 4 h of the start of an attack, the estimated time to the onset of unequivocal relief was reduced to 2 h, compared with more than 4 h in those treated with placebo. Cinryze and other similar products are going to change the future management of hereditary angioedema and have potential in other areas of medicine.

New therapeutics in C1INH deficiency: a review of recent studies and advances

Hereditary angioedema (HAE) is a genetic condition causing a significant burden of illness for affected individuals. Episodes of angioedema involving the skin, gastrointestinal tract, as well as the larynx and oropharynx are often unpredictable and cause significant morbidity and mortality. Isolation of the underlying protein deficiency, specifically the serine protease C1 inhibitor, and further description of its role in multiple physiologic cascades has led to the development of several specific therapies for HAE. This report provides a brief overview of HAE but focuses primarily on reviewing recently published clinical studies of therapeutics developed for medical management of the condition.

Long-term efficacy of danazol treatment in hereditary angioedema

BACKGROUND

No systematic study has been published yet on the long-term efficacy of attenuated androgens in hereditary angioedema (HAE). Our aim was to conduct a follow-up study in two (German and Hungarian) cohorts of HAE patients (45 and 39 patients, respectively) undergoing uninterrupted treatment for 6 years with similar (starting dose 128 ± 78 mg per day and 136 ± 70 mg per day, respectively) and constant doses of danazol.

DESIGN

The frequencies of subcutaneous, abdominal and laryngeal attacks were recorded each year.

RESULTS

The annual frequency of all the three types of attacks was significantly lower during the first year of danazol treatment, compared to the last year before baseline. During subsequent years in Hungarian patients, the frequency of both subcutaneous and abdominal attacks - but not that of laryngeal attacks - increased significantly. In the case of abdominal attacks, a significant increase in the attack frequency was observed only in female patients. In the German cohort, by contrast, no change in the frequency of either type of attack was found during the 6-year study period.

CONCLUSIONS

The differences observed between these cohorts cannot be related to drug dose, the age or gender distribution of subjects or the age at the onset of symptoms or the length of diagnostic delay in the patients. There were, however, marked differences in the baseline pattern of attacks: significantly - 3 times - more abdominal attacks were recorded in German patients. Further studies are necessary to clarify the mechanism of these findings.

Transcriptional control of genes for soluble complement cascade regulatory proteins

The complement cascade of the immune system is an important mediator of the inflammatory response to infection; however it is crucial that this pathway is tightly regulated to prevent uncontrolled activation, which can lead to damage to host tissues. The complement system has many regulators that control activation; both membrane-bound and soluble factors. This review will focus on what is currently known about the transcriptional regulation of the soluble complement regulatory genes C1-inhibitor, complement factor I, complement factor H and C4-binding protein. The absence or mutation of these regulators is all associated with specific disease, and yet their contribution to disease is often poorly understood. It is through full understanding of these genes that we can comprehend the diseases with which they are implicated, and thus prove why knowledge of the transcriptional regulation of these genes is valuable.

HAE therapies: past present and future

Advances in understanding the pathophysiology and mechanism of swelling in hereditary angioedema (HAE) has resulted in the development of multiple new drugs for the acute and prophylactic treatment of patients with HAE. This review will recap the past treatment options, review the new current treatment options, and discuss potential future treatment options for patients with HAE.

EDEMA4: a phase 3, double-blind study of subcutaneous ecallantide treatment for acute attacks of hereditary angioedema

BACKGROUND

Hereditary angioedema (HAE) is a genetic disorder resulting from low levels of C1-inhibitor activity that manifests as acute attacks of variable and sometimes life-threatening edema. Ecallantide is a novel potent inhibitor of human plasma kallikrein, a key mediator of the excessive formation of bradykinin associated with the signs and symptoms of an HAE attack.

OBJECTIVE

To evaluate the efficacy and safety of ecallantide in the treatment of acute HAE attacks.

METHODS

In this double-blind, placebo-controlled study, patients with a moderate to severe HAE attack were randomized 1:1 to receive 30 mg of subcutaneous ecallantide or placebo. The primary efficacy end point was change from baseline in mean symptom complex severity score 4 hours after dosing. Additional end points included treatment outcome score 4 hours after dosing and maintenance of significant overall improvement through 24 hours.

RESULTS

Ninety-six patients were enrolled. Mean (SD) change from baseline in mean symptom complex severity score 4 hours after dosing was significantly greater with ecallantide use (-0.8 [0.6]) compared with placebo use (-0.4 [0.8]) (P = .01 comparing distributions). Ecallantide therapy was also associated with a significantly larger mean (SD) treatment outcome score 4 hours after dosing vs placebo use (ecallantide: 53.4 [49.7]; placebo: 8.1 [63.2]; P = .003 comparing distributions). The benefit of ecallantide was apparent within 2 hours after dosing and was maintained through 24 hours after dosing. The safety profile was similar between the treatment groups.

CONCLUSION

Ecallantide appears to be an effective and safe treatment for acute attacks of HAE.

Hereditary angioedema: current and emerging treatment options

Angioedema can result from allergic, hereditary, and acquired conditions. Hereditary angioedema (HAE) attacks are disabling at the time of occurrence and can be life threatening; they often result in hospitalization and intensive care unit admission. Although there are several variants of HAE, they share a final common pathway: unopposed activation of multiple kinins and mediators including kallikrein and bradykinin. This leads to increased vascular permeability, which in turn produces the edema after which the condition is named. Older treatment options licensed in the United States, anabolic steroids and antifibrinolytics, have troublesome side effect profiles and may not reverse a severe acute attack. In Europe, C1 esterase inhibitor (C1-INH) concentrates have been used since 1974 for both preventing and terminating attacks. Two of these have now been licensed in the United States for use in HAE patients, one for prophylaxis and the other for treating acute abdominal and facial HAE attacks. The first kinin pathway modulator, ecallantide, has also been licensed recently in the United States for treating HAE attacks. The objective of this article is to describe HAE and review the available options for managing patients, as well as different drugs currently under investigation. Specific attention is given to the perioperative management of patients with HAE.

The relationship between brachial ankle pulse wave velocity and complement 1 inhibitor

Complement 1 (C1) inhibitor is an acute phase protein with anti-inflammatory properties. The aim of the present study was to elucidate the relationship between brachial ankle pulse wave velocity (baPWV), the parameter of arterial stiffness, and C1 inhibitor. One hundred subjects were randomly enrolled in this study. Data about baPWV, age, gender, hypertension, smoking, and body mass index (BMI) were measured. Blood tests for total cholesterol, low density lipoprotein, high density lipoprotein, triglycerides, hemoglobin A1c, erythrocyte sedimentation rate, C-reactive protein, complement 3, and C1 inhibitor were performed. Based on the Pearson correlation, the C1 inhibitor showed a positive relation to the baPWV (P<0.001). Multiple regression analysis revealed the significant predictors of baPWV were not only the conventional risk factors of arteriosclerosis and/or atherosclerosis, such as age (P<0.001), gender (P<0.001), hypertension (P<0.001), and BMI (P=0.006), but also the acute phase protein, C1 inhibitor (P=0.025). In conclusion, C1 inhibitor is associated with arterial stiffness through its association with increased inflammation.

Hereditary angioedema and pregnancy: successful management of recurrent and frequent attacks of angioedema with C1-inhibitor concentrate, danazol and tranexamic acid - a case report

Hereditary angioedema (HAE) is a rare but potentially life-threatening condition caused by deficiency of C1 esterase inhibitor. It is characterized by subcutaneous swelling in any part of the skin, gastrointestinal and respiratory tracts. We present the case of a pregnant woman with known HAE that deteriorated during pregnancy with frequent attacks that were managed successfully with danazol, tranexamic acid and regular intravenous administration of C1 esterase inhibitor.

Hereditary angioedema: a current state-of-the-art review, V: attenuated androgens for the treatment of hereditary angioedema

OBJECTIVE

To provide a summary of the literature regarding the use of attenuated androgens during the past 40 to 50 years for the treatment of hereditary angioedema (HAE).

DATA SOURCES

MEDLINE and PubMed were searched to identify studies involving the treatment of HAE with androgens.

STUDY SELECTION

Studies were selected based on their relevance to the use of androgens for the treatment of HAE.

RESULTS

Attenuated androgens have proven successful for the short- and long-term treatment of HAE. Adverse effects are still concerning, and their use in children and pregnant women must be undertaken with great caution. Scheduled monitoring of liver function tests and lipid profiles in patients treated with these medications is critical.

CONCLUSIONS

Attenuated androgens have been successful in the short- and long-term treatment of HAE, and they are still the most frequently used medications in the United States for the treatment of this disease. There is a lack of readily available options for the treatment of acute HAE attacks apart from the administration of fresh frozen plasma or safe prophylactic therapies; however, several appropriate agents currently in clinical trials in the United States appear promising.

Lack of dehydroepiandrosterone in type I and II hereditary angioedema and role of danazol in steroid hormone conversion

BACKGROUND

Hereditary angioedema (HAE) is successfully treated with danazol, a therapeutic steroid compound. To investigate hormones of the hypothalamic-pituitary-adrenal (HPA) and hypothalamic-pituitary-gonadal (HPG) axis in patients with HAE with and without danazol.

METHODS

We included 16 patients with type I HAE, nine patients with type II HAE, and 16 healthy subjects. Serum levels of adrenocorticotropic hormone (ACTH), cortisol, androstenedione, dehydroepiandrosterone (DHEA), free testosterone, and 17beta-oestradiol were measured.

RESULTS

Serum levels of ACTH were markedly decreased in patients with type II HAE compared to the other groups (P < 0.001). Serum cortisol was similar between groups but danazol treatment decreased cortisol levels, particularly in women (P = 0.019). Serum levels of DHEA were significantly decreased in all patients with type I and II HAE compared to controls (P < 0.05), which was only partly dependent on prior danazol therapy as patients without danazol had also decreased serum levels of DHEA (P < 0.05). Furthermore, free testosterone serum levels were markedly increased in patients under danazol (P < 0.005) and the ratio of 17beta-oestradiol/free testosterone was significantly decreased in these patients (P < 0.005).

CONCLUSIONS

This study demonstrated decreased DHEA in patients with type I and II HAE independent of danazol therapy, which was particularly evident in women. It also demonstrates that danazol induced a marked up-regulation of free testosterone in relation to precursors and downstream 17beta-oestradiol. In HAE, there seems to be a primary lack of the adrenal androgen DHEA.

The initiating proteases of the complement system: controlling the cleavage

The complement system is a vital component of the host immune system, but when dysregulated, can also cause disease. The system is activated by three pathways: classical, lectin and alternative. The initiating proteases of the classical and lectin pathways have similar domain structure and employ similar mechanisms of activation. The C1r, C1s and MASP-2 proteases have the most defined roles in the activation of the system. This review focuses on the mechanisms whereby their interaction with substrates and inhibitors is regulated.

C1-inhibitor deficiencies (hereditary angioedema): where are we with therapies?

Hereditary angioedema, an autosomal dominant disorder, presents clinically as recurrent episodes of swelling. It results from either deficient production or function of C1 inhibitor. Acquired angioedema is associated with lymphoproliferative or autoimmune disease. Conventionally attenuated androgens and antifibrinolytics have been used for prophylaxis, both for the long term and presurgically. Fresh frozen plasma and plasma-derived C1 inhibitor concentrate have been used primarily for treatment of acute attacks. All have drawbacks in side effects or potential for infection transmission. New treatments (recombinant C1 inhibitor, icatibant, DX-88, and for acquired angioedema, rituximab) so far show good safety profiles. Early data suggest these may be effective treatment alternatives. The efficacy of current treatment and the potential held by newer agents that target specific elements in complement or kinin pathways are examined. Some agents are likely to have a wider role in treatment of other, more common, forms of angioedema.

C1 inhibitor deficiency: diagnosis

This is the first of two articles on C1 inhibitor deficiency based on a recent UK consensus document covering diagnosis and management of the disorder in both adults and children. This paper focuses on diagnosis of this disorder.

C1 inhibitor deficiency: consensus document

We present a consensus document on the diagnosis and management of C1 inhibitor deficiency, a syndrome characterized clinically by recurrent episodes of angio-oedema. In hereditary angio-oedema, a rare autosomal dominant condition, C1 inhibitor function is reduced due to impaired transcription or production of non-functional protein. The diagnosis is confirmed by the presence of a low serum C4 and absent or greatly reduced C1 inhibitor level or function. The condition can cause fatal laryngeal oedema and features indistinguishable from gastrointestinal tract obstruction. Attacks can be precipitated by trauma, infection and other stimulants. Treatment is graded according to response and the clinical site of swelling. Acute treatment for severe attack is by infusion of C1 inhibitor concentrate and for minor attack attenuated androgens and/or tranexamic acid. Prophylactic treatment is by attenuated androgens and/or tranexamic acid. There are a number of new products in trial, including genetically engineered C1 esterase inhibitor, kallikrein inhibitor and bradykinin B2 receptor antagonist. Individual sections provide special advice with respect to diagnosis, management (prophylaxis and emergency care), special situations (childhood, pregnancy, contraception, travel and dental care) and service specification.

Current and future therapy for hereditary angioedema

Hereditary angioedema (HAE) is an autosomal dominant disease characterized by recurrent episodes of potentially life-threatening angioedema. Attacks of angioedema in HAE patients typically last 3 or more days, begin during childhood, and continue to occur throughout life. Tragically, patients with HAE continue to die as a direct consequence of the disease. Minimizing the morbidity and mortality associated with HAE requires both effective treatment of acute attacks as well as strategies to prevent HAE attacks. While there is currently no effective therapy available in the United States for the treatment of acute attacks of HAE, several molecules have demonstrated impressive efficacy in this setting, and it is likely that one or more of these new drugs will become available in the United States soon. This article will review both the current and the future therapeutic options for the treatment of HAE.