Auto- and alloantibodies against factor XIII: laboratory diagnosis and clinical consequences

Cloning of human anti-factor XIII monoclonal antibody dissects mechanisms of polyclonal antibodies in a single patient

BACKGROUND

Coagulation factor XIII (FXIII) consists of 2 A (FXIII-A) and 2 B (FXIII-B) subunits that cross-link and strengthen the hemostatic fibrin thrombus; thus, abnormal bleeding occurs when FXIII is significantly reduced. Autoimmune-acquired FXIII deficiency (AiF13D) is characterized by lethal bleeding secondary to the development of autoantibodies against FXIII. However, since anti-FXIII autoantibodies are polyclonal, the mechanism underlying FXIII dysfunction is unclear.

OBJECTIVES

The objective of this study was to dissect the inhibitory mechanisms of polyclonal anti-FXIII autoantibodies.

METHODS

In this study, we prepared the human monoclonal antibodies (hmAbs) from the peripheral blood of an 86-year-old man with AiF13D by using a new complementary DNA cloning method and analyzed the properties of each autoantibody.

RESULTS

Seventeen clones obtained from hmAbs were divided into the following 3 groups: dissociation inhibitors of FXIII-A₂B₂ (6 clones), assembly inhibitors of FXIII-A₂B₂ (3 clones), and nonneutralizing/inhibitory hmAbs (8 clones). Dissociation inhibitors strongly inhibited fibrin cross-linking and amine incorporation. Assembly inhibitors extracted FXIII-A from FXIII-A₂B₂, strongly inhibited binding of FXIII-A to FXIII-B, and activation peptide cleavage. However, the patient's plasma presented a strong inhibition of A₂B₂ heterodimer assembly but only a slight inhibition of thrombin-Ca²⁺-dependent dissociation, suggesting that the assembly inhibitors concealed the effect of dissociation inhibitors in plasma. By contrast, nonneutralizing antibodies had little effect on the function of FXIII, suggesting that nonneutralizing hmAbs (and/or dissociation inhibitors and/or assembly inhibitors) promoted the clearance of FXIII-A from the blood.

CONCLUSION

Cloning of anti-FXIII autoantibodies enabled us to not only elucidate the mechanism and pathophysiology of AiF13D but also develop a completely new type of anticoagulant.

Genetic landscape in coagulation factor XIII associated defects – Advances in coagulation and beyond

Coagulation factor XIII (FXIII) acts as a fine fulcrum in blood plasma that maintains the balance between bleeding and thrombosis by covalently crosslinking the pre-formed fibrin clot into an insoluble one that is resistant to premature fibrinolysis. In plasma, FXIII circulates as a pro-transglutaminase complex composed of the dimeric catalytic FXIII-A encoded by the F13A1 gene and dimeric carrier/regulatory FXIII-B subunits encoded by the F13B gene. Growing evidence accumulated over decades of exhaustive research shows that not only does FXIII play major roles in both pathological extremes of hemostasis i.e. bleeding and thrombosis, but that it is, in fact, a pleiotropic protein with physiological roles beyond coagulation. However, the current FXIII genetic-epidemiological literature is overwhelmingly derived from the bleeding pathology associated with its deficiency. In this article we review the current clinical, functional, and molecular understanding of this fascinating multifaceted protein, especially putting into the same perspective its genetic landscape.

Hyperfibrinolysis secondary to acquired factor XIII deficiency A case report

INTRODUCTION

Hyperfibrinolysis induced by factor XIII deficiency (FXIIID) is extremely rare, and patients with no manifestations of active bleeding can easily and frequently be neglected in clinical practice, leading to a missed diagnosis. Herein, we report a rare case of idiopathic FXIIID with secondary hyperfibrinolysis.

PATIENT CONCERNS

A 69-year-old man presented with ecchymosis of the right arm and chest wall.

DIAGNOSIS

Considering the clinical picture, coagulation function test results, and FXIII activity, the patient was finally diagnosed with hyperfibrinolysis secondary to acquired factor XIII deficiency.

INTERVENTIONS

The patient was treated with fresh frozen plasma, aminomethylbenzoic acid, a prothrombin complex, etamsylate, dexamethasone, and cryoprecipitate.

OUTCOMES

The patient improved and was discharged after factor replacement therapy, and no further bleeding was reported 1 month after discharge.

CONCLUSION

This case report illustrates that the complications of Factor XIII deficiency may include hyperfibrinolysis. Since timely diagnosis of FXIIID is challenging, detailed coagulation factor examinations are needed for definitive diagnosis. It has been suggested that gene testing and antibody testing can help in diagnosis. If ideal treatment is not available, alternative treatment should be provided to reduce bleeding.

Hemostasis components in cerebral amyloid angiopathy and Alzheimer's disease

Increased cerebrovascular amyloid-β (Aβ) deposition represents the main pathogenic mechanisms characterizing Alzheimer's disease (AD) and cerebral amyloid angiopathy (CAA). Whereas an increasing number of studies define the contribution of fibrin(ogen) to neurodegeneration, how other hemostasis factors might be pleiotropically involved in the AD and CAA remains overlooked. Although traditionally regarded as pertaining to hemostasis, these proteins are also modulators of inflammation and angiogenesis, and exert cytoprotective functions. This review discusses the contribution of hemostasis components to Aβ cerebrovascular deposition, which settle the way to endothelial and blood-brain barrier dysfunction, vessel fragility, cerebral bleeding, and the associated cognitive changes. From the primary hemostasis, the process that refers to platelet aggregation, we discuss evidence regarding the von Willebrand factor (vWF) and its regulator ADAMTS13. Then, from the secondary hemostasis, we focus on tissue factor, which triggers the extrinsic coagulation cascade, and on the main inhibitors of coagulation, i.e., tissue factor pathway inhibitor (TFPI), and the components of protein C pathway. Last, from the tertiary hemostasis, we discuss evidence on FXIII, involved in fibrin cross-linking, and on components of fibrinolysis, including tissue-type plasminogen activator (tPA), urokinase-type plasminogen activator (uPA) and its receptor uPA(R), and plasminogen activator inhibitor-1 (PAI-1). Increased knowledge on contributors of Aβ-related disease progression may favor new therapeutic approaches for early modifiable risk factors.

Autoimmune Acquired Factor XIII Deficiency: A Case Report

Autoimmune acquired factor XIII (FXIII) deficiency is a rare disorder characterized by severe spontaneous hematomas and autoantibodies against FXIII. High mortality rates have been reported (18% within a year of diagnosis). We present a 70-year-old patient with recurrent muscular hematomas. The basic hemostasis study and the coagulation factors were within normal ranges. The aggregation platelet study was also normal and von Willebrand disease was excluded. Bearing in mind the recurrent bleeding history and the described laboratory results, we considered a FXIII deficiency, that was confirmed (FXIII<10%). In addition, we suspected an acquired FXIII deficiency since the patient did not report a personal or family history of bleeding and FXIII gene sequencing study was normal. Non-immune causes were ruled out, and plasma autoantibodies against FXIII were detected. Immunosuppression was rapidly initiated to eradicate inhibitor as was hemostatic treatment to obtain bleeding control. Currently, the patient is asymptomatic, but a low level of FXIII inhibitor remains.

Congenital Factor XIII Deficiency With the Presence of Inhibitor: A Case Study

Coagulation factor XIII (FXIII) is a fibrin-stabilizing factor with additional roles in wound healing and interactions between the decidua and fetus. Congenital FXIII deficiency is rare bleeding disorder. Inhibitor development against FXIII in inherited FXIII deficency is also uncommon, but may cause severe, life-threatening bleeding. FXIII is the last step in the coagulation cascade with normal coagulation paramaters (PT, aPTT), the detection of inhibitor to FXIII is quite difficult. The treatment of inhibitor-positive congenital FXIII deficiency is challenging due to the lack of a role of by-pass agents such as FVII. The best known ways of treatment in these cases are the use of high-dose FXIII concentrates and immunosuppression. Herein, we report the management of postoperative bleeding diathesis in a patient with FXIII deficiency who developed inhibitors, and to follow the clinical course of the disease with FXIII concentrate and immunosuppression.

Sustained depletion of FXIII-A by inducing acquired FXIII-B deficiency

The activated form of coagulation factor XIII (FXIII-A2B2), FXIII-A*, is a hemostatic enzyme essential for inhibiting fibrinolysis by irreversibly crosslinking fibrin and antifibrinolytic proteins. Despite its importance, there are no modulatory therapeutics. Guided by the observation that humans deficient in FXIII-B have reduced FXIII-A without severe bleeding, we hypothesized that a suitable small interfering RNA (siRNA) targeting hepatic FXIII-B could safely decrease FXIII-A. Here we show that knockdown of FXIII-B with siRNA in mice and rabbits using lipid nanoparticles resulted in a sustained and controlled decrease in FXIII-A. The concentration of FXIII-A in plasma was reduced by 90% for weeks after a single injection and for more than 5 months with repeated injections, whereas the concentration of FXIII-A in platelets was unchanged. Ex vivo, crosslinking of α2-antiplasmin and fibrin was impaired and fibrinolysis was enhanced. In vivo, reperfusion of carotid artery thrombotic occlusion was also enhanced. Re-bleeding events were increased after challenge, but blood loss was not significantly increased. This approach, which mimics congenital FXIII-B deficiency, provides a potential pharmacologic and experimental tool to modulate FXIII-A2B2 activity.

Laboratory Assessment of Coagulation Factor XIII

Laboratory diagnosis of congenital and acquired deficiencies of coagulation factor XIII (FXIII) can be challenging. Determination of FXIII function requires specific and sensitive assays which are not always available. This brief review article summarizes currently used FXIII assay methods, their principles and difficulties, and discusses the recommended diagnostic workup in case of a suspected FXIII deficiency. The article also briefly touches on experimental methods used in FXIII research.

Autoimmune factor XIII deficiency with unusual laboratory and clinical phenotype

Hemorrhagic diathesis due to anti-factor XIII (FXIII) autoantibody is a rare but severe disorder. Challenges of the diagnosis and treatment is demonstrated by the case of a 67-year-old female without previous bleeding history, who suffered a huge muscular hematoma. Without blank subtraction 18% plasma FXIII activity was measured; however, after correction for blank the activity was below the limit of detection and the lack of fibrin cross-linking in the patient's plasma confirmed the latter result. FXIII-A2 antigen was not detectable by enzyme-linked immunosorbent assay (ELISA); however, it was well detected by western blotting. The autoantibody showed high affinity toward FXIII-A2 . Its considerable inhibitory activity was demonstrated by high titer in Bethesda units and the low immunoglobulin G concentration required for inhibition. The main biochemical effect was the inhibition of Ca2+ -induced activation. Eradication therapy was only partially successful. Four months after the last hemorrhagic event the patient suffered deep vein thrombosis complicated by pulmonary embolism.

Management of rare coagulation disorders in 2018

Rare bleeding disorders (RBDs) comprise inherited deficiencies of factors I (fibrinogen), II (prothrombin), V, VII, X, XI, and XIII as well as combined factor V + VIII and vitamin K-dependent factors. They represent 3-5% of all congenital bleeding disorders and are usually transmitted as autosomal recessive traits. These disorders often manifest during childhood and have varied clinical presentations from mucocutaneous bleeding to life-threatening symptoms such as central nervous system and gastrointestinal bleeding. Bleeding manifestations generally vary within the same RBD and may also vary from 1 RBD to the other. Laboratory diagnosis is based on coagulation screening tests and specific factor assays, with molecular techniques providing diagnostic accuracy and enabling prenatal counseling. The approach to treatment of bleeding episodes and invasive procedures needs to be individualized and depends on the severity, frequency and procedure-related risk of bleeding. The first line of treatment of RBDs is replacement of the deficient factor, using specific plasma-derived or recombinant products and using fresh frozen plasma or cryoprecipitate when specific products are not available or in resource-limited countries. Prophylaxis may be considered in individuals with recurrent serious bleeding and especially after life-threatening bleeding episodes. Novel no-replacement strategies promoting hemostasis by through different mechanisms need to be studied in RBDs as alternative therapeutic options.