OBJECTIVETo investigate the binding mechanisms of FVIII Trp1707Ser mutation-associated inhibitor.

METHODSThe APPT, PT, TT, Fg and FVIII:C were detected to make phenotypic diagnosis of haemophilia A. Inhibitors titer were measured by Bethesda method. Long distance-PCR (LD-PCR) and sequence-specific PCR were adopted for screening the intron 22 and intron 1 inversions respectively. FVIII coding and boundary sequences were analyzed by direct DNA sequencing. Inhibitor was reacted with different segments of FVIII, including heavy chain and its components A1 and A2, light chain and its components A3, C1 and C2. Corrected test was used to measure the remaining F VIII:C (% ) by adding pooled normal plasmas. After labeling purified inhibitors with biotin, western blot was performed to further confirm the binding reactions between inhibitors and segments.

RESULTSThe haemophilia A patient had mild deficiency of FVIII:C (1.1%) and had high FVIII inhibitor titer of 18.4 BU. A mutation c.97223C>G in exon 14 of F8 gene resulted to p.Trp1707Ser was identified by DNA sequencing. Corrected test showed that the remaining F VIII:C was increased when inhibitors reacted with heavy chain and light chain, especially with heavy chain. The remaining FVIII:C was also increased in the A2 and C2 domain reactions. No significant differences were seen in the A1, A3 and C1 domain reactions. Antigen-antibody reaction bands were confirmed by western blots when degenerated B-domain deleted recombinant FVIII, A2 and C2 were used as antigens.

CONCLUSIONThe binding sites of FVIIITrp1707Ser mutation inhibitor were the A2 domain of heavy chain and C2 domain of light chain. The binding reaction with heavy chain was more intense.

Binding Sites ; genetics ; Exons ; Factor VIII ; antagonists & inhibitors ; genetics ; Hemophilia A ; genetics ; Humans ; Male ; Mutation ; Young Adult

OBJECTIVETo evaluate the clinical value of modified Bethesda assay, modified Nijmegen assay and blank assay for detection of coagulation factor VIII (FVIII) inhibitors in patients with hemophilia A and analyze the factors that affect FVIII inhibitor detection.

METHODSThe levels of FVIII inhibitors in 257 patients with hemophilia A were detected using modified Bethesda assay, modified Nijmegen assay and blank assay (in which the buffer or FVIII-deficient plasma in the control mixture was replaced by deionized water). The 3 methods were compared for positivity rates and FVIII inhibitor titers based on the positive cut-off value of FVIII inhibitors ≥0.60 BU/mL.

RESULTSThe positive rates of modified Bethesda assay, modified Nijmegen assay and blank assay were 79.38%, 85.21% and 72.37%, respectively. A strong correlation was found between the results by modified Bethesda assay and modified Nijmegen assay (r=0.996, P<0.001), and FVIII inhibitor titers (P<0.001) but not the positive rates (P=0.105) detected by the two methods differed significantly. The correlation coefficients between modified Nijmegen assay and blank assay was 0.994 (P<0.001), and a significant difference was found in FVIII inhibitor titers (P<0.001) but not the positivity rates (P=0.079) detected by the two methods. The correlation coefficient between modified Nijmegen assay and blank assay was 0.994 (r=0.994), and the two methods yielded significantly different FVIII inhibitor titers and positivity rates (P=0.001).

CONCLUSIONThe modified Bethesda assay has a lower sensitivity than modified Nijmegen assay but has a higher sensitivity than blank assay. The consistency level of coagulation factors in the reaction system and stable buffer system are important factors that affect FVIII-inhibitor detection.

Biological Assay ; Blood Coagulation Tests ; Factor VIII ; antagonists & inhibitors ; Hemophilia A ; blood ; Humans ; Plasma

In order to analyze the clinical features and laboratory findings in patients with acquired hemophilia A, one case of acquired hemophilia A was studied, the medical history, clinical features, ultrasonography and laboratory examination including activated partial thromboplastin time (APTT), prothrombin time (PT), thrombin time (TT) and FVIII:C, FIX:C, FXI:C, FXII:C ratio, as well as medical treatment were analyzed. The results showed 99.3 sec of APTT, 13 sec of PT, and 13.5 sec of TT, 2% of FVIII:C, 7% of FIX:C, 9% of FXI:C and 21% of FXII:C. The prolongation of APTT could not be completely corrected by mixing the patient plasma with an equal volume of normal fresh plasma; the APTT increased with prolongation of incubation time, when patient plasma was mixed with an equal volume of normal fresh plasma and incubated at 37 degrees C. The plasma FVIII:C, FIX:C, FXI:C and FXII:C levels in patient were 6%, 75%, 95% and 123% respectively, when patient's plasma was diluted by tenfold and mixed with an equal volume of non-diluted normal plasma. FVIII inhibitor in the patient's serum was at a level >32.0 Bethesda units/ml after acquired hemophilia was diagnosed, the patient was admitted to hospital and given orally prednisone and azathioprine therapy. One month later, clinical status of the patient were improved with 33.3 seconds of APTT, 128% of FVIII level and elimination of FVIII inhibitor. In conclusion, inquiring case history, analyzing imaging results, detecting level of APTT, performing dilution test and assaying titer of FVIII inhibitor can reduce misdiagnosis and wrong therapy for patients with acquired hemophilia A. The FVIII inhibitor can be eliminated and function of clotting can be recovered by using immunosuppressive therapy.
Factor VIII ; analysis ; antagonists & inhibitors ; Female ; Hemophilia A ; blood ; diagnosis ; Humans ; Middle Aged

Factor VIII inhibitors are produced during or after coagulation factor VIII (FVIII) therapy in hemophilia A patients. These inhibitors are usually detected by a modified Bethesda assay or an enzymelinked immunosorbent assay (ELISA). In this study, we used the Bethesda assay to determine the incidence of FVIII inhibitors in 75 fresh plasma samples obtained from 50 hemophilia A patients, and then used ELISA and the Bethesda assay to determine the titres of these inhibitors after the samples had been frozen and thawed. The samples from the screening Bethesda assay were centrifuged and stored at -70degrees C in accordance with the assay guidelines. Subsequently, these samples were thawed and analyzed using ELISA and the Bethesda assay. The incidence of inhibitors in hemophilia A patients was 20.0%. Among the 35 inhibitor-positive samples identified in the screening Bethesda assay, 16 were positive in ELISA while only 4 were positive in the repeated Bethesda assay. In this study, the ELISA technique showed a higher sensitivity than the Bethesda assay in the detection of FVIII inhibitors in samples that were subjected to freezing and thawing procedures; this was because the Bethesda assay could not identify the FVIII inhibitors that were degraded after freezing and thawing.
Blood Coagulation Factor Inhibitors/*analysis ; *Enzyme-Linked Immunosorbent Assay ; Factor VIII/*antagonists &inhibitors/metabolism ; Hemophilia A/*blood/diagnosis ; Humans ; Immunologic Tests ; Male

OBJECTIVETo study the incidence and characteristics of coagulation factor VIII (FVIII) inhibitor development in Chinese patients with hemophilia A.

METHODSA 24-month continuous follow-up was conducted among 215 Chinese patients with hemophilia A to observe the characteristics of FVIII inhibitor development and the clinical characteristics of the patients.

RESULTSThe cumulative incidence of FVIII inhibitor development in 24 months was 11.6% (25/215) in these patients. Of the 25 patients with FVIII inhibitor development, 18 (72%) had low-titer inhibitors and 7 (28%) had high-titer inhibitors. The patients developed the inhibitors after a median of 150 exposure days at a median age of 25 years (6-59 years). Fifteen patients with low-titer inhibitors (median 1.25 BU/ml) showed gradual disappearance of the inhibitors in a median of 10 months (6-15 months) without any treatment, and 5 patients with high-titer inhibitors (median 100 BU/ml) remained positive in 24 months; the other 5 FVIII inhibitor-positive cases showed no significant changes. In the 25 patients developing FVIII inhibitors, the bleeding frequency increased significantly (P=0.025), and in 18 of the patients who continued to use FVIII products, a significant increase in the dose of medication was noted (P=0.015), but the number of target joints did not increase in 24 months (P=0.329).

CONCLUSIONThe incidence and characteristics of factor VIII inhibitor development differ between Chinese patients with hemophilia A and those in developed countries.

Adolescent ; Adult ; Asian Continental Ancestry Group ; Child ; Child, Preschool ; China ; epidemiology ; Factor VIII ; antagonists & inhibitors ; Follow-Up Studies ; Hemophilia A ; epidemiology ; Humans ; Incidence ; Infant ; Male ; Middle Aged ; Young Adult

OBJECTIVETo screen for factor VIII inhibitor in patients with hemophilia A (HA) and explore the environmental risk factors for inhibitor development.

METHODSTotally 265 patients with HA were enrolled, including 107 consecutive inpatients and outpatients in Peking Union Medical College Hospital from April 2003 to April 2007 and 158 patients newly recruited from other hospitals. FVIII: C activity was measured by one-stage coagulation assay. FVIII inhibitor was determined using Bethesda method.

RESULTSIn 265 HA patients, FVIII inhibitor was detected in 22 patients (8.3%). Nine of them (86.4%) were low responders (inhibitor titers < or = 5 000 BU/L), 3 (13.6%) were high responders (the titers > 5 000 BU/L). The frequency of FVIII inhibitor was 50% in the patients aged over 50 years, which was significantly higher than those in other age groups (P = 0. 000). Among 158 newly recruited patients with full clinical data, the frequency of FVIII inhibitor was 12.8% in patients who had received infusion of FVIII products for more than 12 doses on average each year, while it was 5.8% in whom the infusion doses were less than 12 (P = 0.156). The frequency of FVIII inhibitor was 28.5% in patients with a history of continuous infusion of FVIII products whereas it was only 1.6% in patients without such history (P = 0.000). In patients who exposed to multiple-branded or single-branded FVIII products, the frequencies of FVIII inhibitor were 9.3% and 3.9%, respectively (P = 0.229).

CONCLUSIONThe development of factor VIII inhibitor in patients with hemophilia A may be related to the age and the history of continuous infusion of FVIII products.

Adolescent ; Adult ; Aged ; Child ; Child, Preschool ; Environment ; Factor VIII ; antagonists & inhibitors ; Hemophilia A ; blood ; Humans ; Infant ; Male ; Middle Aged ; Risk Factors ; Young Adult

OBJECTIVETo identify the clinical and laboratory diagnosis of a bullous pemphigoid patient with acquired hemophilia A (AH-A). To identify FVIII binding epitope and IgG subclass of the FVIII inhibitor, and explore the molecular mechanism for AH-A pathogenesis.

METHODSPlasma FVIII activity( FVIII: C) was determined by one-stage assay, the titre of FYIII inhibitor by Bethesda Unit (BU). IgG purification of patient plasma or normal pooled plasma was finished by protein A-agarose column chromatography. Activated partial thromboplastin time (APTT) was assayed for uncovering FVIII inhibitor effect on FVIII in vivo. Combined Western blot analysis by anti-IgG1, IgG2, IgG3 and IgG4 antibodies was used to determine the relative concentration of patient' s IgG subclass. IgG subclass concentrations were quantified by nephelometric method. Solid-phase binding assay of FVIII and FVIII inhibitor, combined with Western blot was used to recognize the binding epitope at which the FVIII inhibitor bound to FVIII.

RESULTS(1) Plasma APTT value of patient was prolonged evidently and could not be corrected by normal pooled plasma. Patient's FVIII: C was < 1.5%. The titre of FVIII inhibitor in patient plasma was 147.8 BU. (2) The purified patient IgG was able to inhibit FVIII: C of normal pooled plasma significantly with a dose dependent manner, and the patient plasma could prolong rabbit plasma APTT markedly with a time dependent manner. (3) The FVIII inhibitor was predominantly then of IgG4 subtype with a minority IgG1, and the concentration of IgG4 and IgG1 in the patient was higher than that in normal. The FVIII inhibitor reacted with FVIII 44 x 10(3) fragment epitope.

CONCLUSIONSThe inhibiting effect of FVIII inhibitors on FVIII: C in the bullous pemphigoid patient with AH-A is determined and the IgG subclass of the FVIII inhibitor is identified. A binding epitope for the FVIII inhibitor is a FVIII 44 x 10(3) fragment. The results provides evidence for understanding the pathogenesis of AH-A.

Animals ; Epitopes ; Factor VIII ; antagonists & inhibitors ; immunology ; Female ; Hemophilia A ; complications ; etiology ; immunology ; Humans ; Immunoglobulin G ; blood ; Middle Aged ; Pemphigoid, Bullous ; complications ; immunology ; Rabbits

Blood Coagulation Factor Inhibitors ; antagonists & inhibitors ; blood ; Factor VIII ; administration & dosage ; antagonists & inhibitors ; immunology ; Hemophilia A ; drug therapy ; genetics ; immunology ; Humans ; Immune Tolerance ; Isoantibodies ; blood ; immunology ; Recombinant Proteins ; adverse effects ; immunology ; therapeutic use ; Risk Factors ; Time Factors

In order to detect coagulation factor VIII (FVIII) inhibitor in patients with severe hemophilia A (HA) and preliminarily study the genetic mutation in patients with inhibitor positive. Totally 58 patients with HA (FVIII: C < 1%) were enrolled. FVIII: C activity was measured by one-stage coagulation assay. FVIII inhibitor was screened by using APTT method and FVIII inhibitor in screened positive patients with HA was quantitatively analyzed by using Bethesda method. Using genomic DNA as template, 12, 14, 16 exons of FVIII in screened positive patients were amplified, and the mutations of amplified products were detected by direct sequencing. The results indicated that the FVIII inhibitor could be detected in 4 patients (6.9%) from 58 HA patients, no gene mutations in 12, 14, 16 exons of FVIII were found. It is concluded that the positive rate of FVIII inhibitor in HA patients is lower than that reported in literature. The causes of inhibitor production needs to further investigate.
Adolescent ; Adult ; Blood Coagulation Factor Inhibitors ; isolation & purification ; Blood Coagulation Tests ; Child ; Child, Preschool ; Exons ; Factor VIII ; antagonists & inhibitors ; genetics ; Genetic Testing ; Hemophilia A ; diagnosis ; genetics ; Humans ; Infant ; Middle Aged ; Mutation ; Young Adult

OBJECTIVETo study the current situation of coagulation factor VIII (FVIII) inhibitor development in children with hemophilia A (HA) through a cross-sectional survey, and to explore the risk factors of inhibitor development in order to provide evidence for further prevention and management strategies.

METHODThe clinical data of outpatients with hemophilia A in Beijing Children's Hospital seen from November 2012 to May 2013 were collected, FVIII inhibitor was screened and analyzed its risk factors.

RESULTA total of 102 HA children were enrolled, 5 were mild cases, 32 were moderate, and 65 were severe cases; the median age on enrollment was 55.5 (3.0-200.0) months:19(18.6%) of patients had inhibitors and 9 (8.8%) had low-titer inhibitors, 10 (9.8%) had high-titer inhibitors. Receiving FVIII treatment for life-threatening bleeding (P = 0.03) ,OR 4.10 (95%CI:1.17-14.32) was a risk factor for inhibitor generation and patients within 20 exposure days have more chances of inhibitor development (P = 0.04) ,OR 3.32 (95%CI:1.02-10.86) . High and intense FVIII exposure within short term was the risk factor for high titer inhibitor development (P = 0.01) ,OR 5.25 (95%CI:1.45-21.92) .

CONCLUSIONIntense FVIII exposure for severe hemorrhage was the risk factor of inhibitors development especially of high titer inhibitors.

Adolescent ; Blood Coagulation Factor Inhibitors ; blood ; Child ; Child, Preschool ; Cross-Sectional Studies ; Dose-Response Relationship, Drug ; Factor VIII ; administration & dosage ; antagonists & inhibitors ; Female ; Hemophilia A ; blood ; therapy ; Humans ; Infant ; Male ; Multivariate Analysis ; Risk Factors ; Time Factors