A National Reference Curve for Assaying Factor VIII Inhibitors

The results of FVIII inhibitor assays obtained in different laboratories are of difficult comparison, and the dose—response curve from which the inhibitor potency is read in units appears to be one of the main variables. Differences in inhibitor kinetic behaviour make difficult to adopt as a reference the curve of a single patient. On the other hand, the use of individual curves for each patient is laborious and time consuming. We have evaluated whether the adoption of a single reference curve obtained from the mathematical elaboration of the individual experimental points of the curves of 33 inhibitors was statically acceptable and could be proposed as a national reference curve for factor VIII inhibitor assay. The experimental data have been used to make statistical series from which theoretical points were calculated by the least square method resulting in a second degree equation curve. Observed experimental values corresponded to the theoretical points of the calculated curve within a variation of ± 50%, resulting in a variation of the calculated inhibitor potency of ± 20% compared with those read on each individual inhibitor curve. A national trial to confirm the applicability of such reference curve is presently in progress.

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Human Factor VIII Inhibitor Alloantibodies with a C2 Epitope Inhibit Factor Xa-catalyzed Factor VIII Activation: A new Anti-factor VIII Inhibitory Mechanism

Thrombosis and Haemostasis ◽

10.1055/s-0037-1613026 ◽

2002 ◽

Vol 87 (03) ◽

pp. 459-465 ◽

Cited By ~ 14

Author(s):

Keiji Nogami ◽

Katsumi Nishiya ◽

Yoshihiko Sakurai ◽

Ichiro Tanaka ◽

John Giddings ◽

...

Keyword(s):

Factor Viii ◽

Factor Xa ◽

Factor Viii Inhibitor ◽

Inhibitory Mechanism ◽

Fviii Inhibitor ◽

Fviii Activity ◽

Human Factor Viii ◽

Sds Page ◽

Viii Inhibitor ◽

C1 Domains

SummaryFactor VIII (FVIII) inhibitor alloantibodies react with the A2, C2, or A3-C1 domains of FVIII and inactivate FVIII activity. We recently demonstrated that an anti-C2 monoclonal antibody with a Val2248Gly2285 epitope, inhibited factor Xa (FXa)-catalyzed FVIII activation, and that a FXa binding site for FVIII was located within residues Thr2253-Gln2270. In this study, we investigated whether anti-C2 alloantibodies inhibit FXa-catalyzed FVIII activation. Anti-C2 alloantibodies from four patients inhibited FVIII activation by FXa in onestage clotting assay. Furthermore, analysis by SDS-PAGE showed that all alloantibodies inhibited FVIII proteolytic cleavage by FXa independently of phospholipid. To confirm direct inhibition of FVIII and FXa interaction, we examined the effect of alloantibodies on FVIII binding to anhydro-FXa, a catalytically inactive FXa, in ELISA. All alloantibodies and C2-affinity purified F(ab)’2 preparations inhibited FVIII binding to anhydro-FXa dose-dependently. Our results revealed a new inhibitory mechanism of FVIII, mediated by inhibition of FXa in the presence of anti-C2 alloantibodies.

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Some factor VIII inhibitor antibodies recognize a common epitope corresponding to C2 domain amino acids 2248 through 2312, which overlap a phospholipid-binding site

Blood ◽

10.1182/blood.v86.5.1811.bloodjournal8651811 ◽

1995 ◽

Vol 86 (5) ◽

pp. 1811-1819 ◽

Cited By ~ 133

Author(s):

D Scandella ◽

GE Gilbert ◽

M Shima ◽

H Nakai ◽

C Eagleson ◽

...

Keyword(s):

Amino Acids ◽

Factor Viii ◽

Binding Site ◽

Light Chain ◽

Intrinsic Factor ◽

Factor Viii Inhibitor ◽

C2 Domain ◽

Amino Acid Residues ◽

Fviii Inhibitor ◽

Human Factor Viii

The finding that human factor VIII (fVIII) inhibitor antibodies with C2 domain epitopes interfere with the binding of fVIII to phosphatidylserine (PS) suggested that this is the mechanism by which they inactivate fVIII. We constructed a recombinant C2 domain polypeptide and demonstrated that it bound to all six human inhibitors with fVIII light chain specificity. Thus, some antibodies within the polyclonal anti-light chain population require only amino acids within C2 for binding. Recombinant C2 also partially or completely neutralized the inhibitor titer of these plasmas, demonstrating that anti-C2 antibodies inhibit fVIII activity. Immunoblotting of a series of C2 deletion polypeptides, expressed in Escherichia coli, with inhibitor plasmas showed that the epitopes for human inhibitors consist of a common core of amino acid residues 2248 through 2312 with differing extensions for individual inhibitors. The epitope of inhibitory monoclonal antibody (MoAb) ESH8 was localized to residues 2248 through 2285. Three human antibodies and anti-C2 MoAb NMC-VIII/5 bound to a synthetic peptide consisting of amino acids 2303 through 2332, a PS- binding site, but MoAb ESH8 did not. These antibodies also inhibited the binding of fVIII to synthetic phospholipid membranes of PS and phosphatidylcholine, confirming that the blocked epitopes contribute to membrane binding as well as binding to PS. In contrast, MoAb ESH8 did not inhibit binding. As the maximal function of activated fVIII in the intrinsic factor Xase complex requires its binding to a phospholipid membrane, we propose that fVIII inhibition by anti-C2 antibodies is related to the overlap of their epitopes with the PS-binding site. MoAb ESH8 did not inhibit fVIII binding to PS-containing membranes, suggesting the existence of a second mechanism of fVIII inhibition by anti-C2 antibodies.

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Marginal zone B cells are critical to factor VIII inhibitor formation in mice with hemophilia A

Blood ◽

10.1182/blood-2017-05-782912 ◽

2017 ◽

Vol 130 (23) ◽

pp. 2559-2568 ◽

Cited By ~ 14

Author(s):

Patricia E. Zerra ◽

Courtney Cox ◽

W. Hunter Baldwin ◽

Seema R. Patel ◽

Connie M. Arthur ◽

...

Keyword(s):

B Cells ◽

Factor Viii ◽

Marginal Zone ◽

Hemophilia A ◽

Factor Viii Inhibitor ◽

Marginal Zone B Cells ◽

Inhibitor Development ◽

Fviii Inhibitor ◽

Key Points ◽

Viii Inhibitor

Key Points FVIII colocalizes with MZ B cells following infusion into hemophilia A mice. Depletion of MZ B cells prevents FVIII inhibitor development in hemophilia A mice.

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A Mathematical Model for Predicting the Winnowing Efficiency of Bambara Groundnut Sheller

European Journal of Engineering Research and Science ◽

10.24018/ejers.2020.5.2.1683 ◽

2020 ◽

Vol 5 (2) ◽

pp. 225-228

Author(s):

Inimfon Samuel Ossom ◽

Akindele Folarin Alonge ◽

Kingsley Charles Umani ◽

Edidiong J. Bassey

Keyword(s):

Experimental Data ◽

Mathematical Model ◽

Moisture Content ◽

Model Equation ◽

Model Simulation ◽

Least Square Method ◽

Bambara Groundnut ◽

Least Square ◽

Predicted Model ◽

Experimental Values

A mathematical model for predicting the winnowing efficiency of bambara groundnut sheller was developed. The regression equation for model simulation was developed using Least Square Method. The model was verified and validated by fitting it into established experimental data from winnowing efficiency of already existed Bambara groundnut sheller. The result revealed that the fitted model correlated well with the experimental data with R-square value of 0.99. The winnowing efficiency obtained from the predicted model was approximately the same values with the experimental values. Therefore, the model equation was considered to be reasonably good for predicting the winnowing efficiency of bambara groundnut sheller for known values of moisture content and blower speed.

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Spontaneous disappearance of high titre factor VIII inhibitor 15 years after unsuccessful ITI

Hämostaseologie ◽

10.1055/s-0037-1617023 ◽

2009 ◽

Vol 29 (02) ◽

pp. 149-150

Author(s):

K. Thom ◽

J. Falger ◽

I. Pabinger ◽

C. Male

Keyword(s):

Factor Viii ◽

Tolerance Induction ◽

High Titre ◽

Bleeding Complications ◽

Factor Viii Inhibitor ◽

Fviii Inhibitor ◽

Spontaneous Disappearance ◽

Viii Inhibitor ◽

Bypassing Agents ◽

High Doses

SummaryThe most serious complication of haemophilia A is development of a high-titre factor VIII (FVIII) inhibitor which renders the patient unresponsive to FVIII replacement. Bleeding complications can only be controlled using FVIII-inhibitor bypassing agents but their effect is less certain. The ultimate goal is to eliminate the inhibitor by immune tolerance induction therapy (ITI) using daily high doses of FVIII. The success rate of ITI using various protocols is between 56 and 79% (1, 2). If ITI is unsuccessful, the inhibitor usually persists throughout life.We report on a patient with a high titre FVIII inhibitor that persisted after ITI but spontaneously disappeared 15 years later.

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Non-Classical Anti-Factor VIII C2 Domain Inhibitors Are Present in the Plasmas of Most Factor VIII Inhibitor Patients.

Blood ◽

10.1182/blood.v110.11.786.786 ◽

2007 ◽

Vol 110 (11) ◽

pp. 786-786

Author(s):

Shannon L. Meeks ◽

John F. Healey ◽

Rachel T. Barrow ◽

Ernest T. Parker ◽

Pete Lollar

Keyword(s):

Factor Viii ◽

Hemophilia A ◽

Factor Viii Inhibitor ◽

C2 Domain ◽

Proteolytic Activation ◽

Autoimmune Antibodies ◽

Fviii Inhibitor ◽

Fviii Activity ◽

Viii Inhibitor ◽

Murine Mabs

Abstract Approximately 30% of patients with severe hemophilia A will develop inhibitory antibodies to factor VIII (fVIII inhibitors). The immune response to fVIII currently is the most significant complication in the management of patients with hemophilia A. In addition, autoimmune antibodies to fVIII can develop in non-hemophiliacs, producing acquired hemophilia A, which frequently produces life- or limb-threatening bleeding. These inhibitors primarily are directed against the A2 or C2 domains of fVIII. The human response to the C2 domain of fVIII classically has been thought to inhibit fVIII activity by blocking its binding to phospholipid. We recently characterized the antibody response to the C2 domain of human fVIII in a murine hemophilia model and described 5 structural groups of antibodies. Groups A, AB, and B are classical anti-C2 antibodies. Groups BC and C consist of non-classical anti-C2 antibodies that inhibit the proteolytic activation of fVIII but do not block the binding of fVIII to phospholipid. Most non-classical antibodies have inhibitor titers greater than 10,000 Bethesda units/mg IgG. To determine if non-classical antibodies are present in fVIII inhibitor patients, patient plasmas were tested in an ELISA for their ability to block the binding of representative antibodies from the different anti-human fVIII C2 antibody groups. Classical and non-classical monoclonal antibodies (MAbs) were biotinylated and serially diluted into either fVIII deficient plasma or patient inhibitor plasma and then added to microtiter wells coated with fVIII. The ability of patient plasma to block the binding of the murine MAbs to fVIII was determined. A total of 16 patient plasmas were assessed: 4 from patients with a C2 predominant response, 2 with a non-C2 predominant response, and 10 with unknown specificities. Three of the 4 patients with C2 predominant responses had non-classical anti-C2 antibodies, while the 2 with non-C2 predominant responses did not. In the unknown plasmas, 6 of 10 had evidence of non-classical antibodies. Figure 1 shows representative results of the effect of 3 patient plasmas on the binding of a biotinylated non-classical MAb to fVIII. Patient plasmas 1 and 2 blocked MAb binding while patient plasma 3 did not. This study indicates that the majority of patients with fVIII inhibitors have non-classical anti-C2 antibodies in their response to fVIII. Figure Figure

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Anti-CD3 prevents factor VIII inhibitor development in hemophilia A mice by a regulatory CD4+CD25+-dependent mechanism and by shifting cytokine production to favor a Th1 response

Blood ◽

10.1182/blood-2008-04-151597 ◽

2009 ◽

Vol 113 (1) ◽

pp. 193-203 ◽

Cited By ~ 59

Author(s):

Braden Waters ◽

Mohammad Qadura ◽

Erin Burnett ◽

Rouzbeh Chegeni ◽

Andrea Labelle ◽

...

Keyword(s):

Factor Viii ◽

Cytokine Production ◽

Hemophilia A ◽

Phenotypic Characterization ◽

Factor Viii Inhibitor ◽

Related Complication ◽

Fviii Inhibitor ◽

Short Course ◽

Viii Inhibitor

Abstract Non–Fc-receptor binding anti-CD3 Ab therapy, in the setting of several different autoimmune disorders, can induce antigen-specific and long-lasting immunologic tolerance. Because factor VIII (FVIII) inhibitor formation is the most serious treatment-related complication for hemophilia A patients, we tested the efficacy of anti-CD3 to prevent FVIII inhibitor formation in hemophilia A BALB/c and C57BL/6 mice. A short course of low-dose anti-CD3 significantly increased expression of CD25 and the proportion of CD4+CD25+ regulatory T cells in the spleen and potently prevented the production of inhibitory and non-neutralizing anti-FVIII antibodies in both strains of mouse. Depleting the CD4+CD25+ cells during anti-CD3 therapy completely ablated tolerance to FVIII. Further phenotypic characterization of regulatory cells in tolerant mice showed a consistently higher number of CD4+GITR+ and CD4+FoxP3+ cells in both strains of mice. In addition, in tolerant C57BL/6 mice we observed an increase in CD4+CD25+CTLA-4+ and CD4+CD25+mTGF-β1+ cells. Finally, in vitro cytokine profiling demonstrated that splenocytes from tolerant BALB/c and C57BL/6 were polarized toward a Th1-immune response. Taken together, these findings indicate that anti-CD3 induces tolerance to FVIII and that the mechanism(s) regulating this response almost certainly occurs through the generation of several distinct regulatory T-cell lineages and by influencing cytokine production and profile.

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A Comparison of the Accuracy of Semi-empirical PM3, PDDG and PM6 methods in Predicting Heats of Formation for Organic Compounds

Journal of the Mexican Chemical Society ◽

10.29356/jmcs.v58i2.182 ◽

2017 ◽

Vol 58 (2) ◽

Cited By ~ 2

Author(s):

Yang-Yang Wu ◽

Feng-Qi Zhao ◽

Xue-Hai Ju

Keyword(s):

Organic Compounds ◽

Least Square Method ◽

Least Square ◽

Heats Of Formation ◽

Regression Equations ◽

Chemical Calculation ◽

Average Deviation ◽

Experimental Values ◽

Isomerization Energy ◽

Semi Empirical

<p>Gas phase heats of formation (HOF) of 18 kinds of 390 organic compounds were calculated by quantum chemical calculation using semi-empirical PM3, PDDG and PM6 methods. The calculated HOFs were compared with the experimental data to illustrate the accuracy for different kinds of organics. Furthermore, the calculated values were linearly fitted with experimental values using the least square method, and were afterward substituted into the fitted regression equations to obtain the calibrated ones. The results show that, for 10 kinds of the selected organics, PM6 is more accurate, and PDDG is more accurate for 7 kinds of organics, while PM3 is only good for amino acid. As a whole, PM6 predicts the HOFs more accurately, with its weighted total mean average deviation (WTMAD) being 0.4 kJ/mol and 2.4 kJ/mol smaller than those of PM3 and PDDG, respectively. On the other hand, our results show that PDDG is the best to differentiate the isomers, with its mean average deviation (MAD) for isomerization energy being 7.8 kJ/mol and 11.0 kJ/mol smaller than PM6 and PM3, respectively. After the calibration, the values of MADs from the PM3, PDDG and PM6 results for most organics are reduced by 0.1 to 18.2 kJ/mol, with exceptions of the PM3 for amines, PDDG for carboxylic acids, and PM6 for ethers.</p>

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Immunoblot analysis shows changes in factor VIII inhibitor chain specificity in factor VIII inhibitor patients over time

Blood ◽

10.1182/blood.v72.4.1348.1348 ◽

1988 ◽

Vol 72 (4) ◽

pp. 1348-1356 ◽

Cited By ~ 39

Author(s):

CA Fulcher ◽

K Lechner ◽

S de Graaf Mahoney

Keyword(s):

Factor Viii ◽

Heavy Chain ◽

Immunoblot Analysis ◽

Factor Viii Inhibitor ◽

Plasma Samples ◽

Anamnestic Response ◽

Fviii Inhibitor ◽

Viii Inhibitor ◽

Inhibitor Patient ◽

Over Time

Abstract We have used immunoblotting of purified factor VIII (FVIII) to determine whether or not changes in FVIII chain specificity occur during the course of an inhibitor. Serial plasma samples from 15 inhibitor patients (13 hemophilic and two spontaneous) were analyzed. Nine of the 15 antibodies, all with epitopes on the 44-kilodalton (Kd) thrombin fragment of the 92-Kd FVIII heavy chain and/or the 72-Kd thrombin fragment of the 80-Kd FVIII light chain, showed no change in FVIII chain specificity. However, six of the inhibitors analyzed showed changes in FVIII fragment specificity. Four inhibitors (three hemophilic and one spontaneous) reactive with 72-Kd thrombin fragment also became reactive with the 44-Kd thrombin fragment after an anamnestic response to FVIII infusion. Another inhibitor with epitopes on both the 54-Kd and 44-Kd thrombin fragments lost most of its reactivity with the 44-Kd fragment but retained its reactivity with the 54-Kd fragment following a FVIII infusion. The inhibitor later regained its 44-Kd-fragment reactivity but lost its 54-Kd-fragment reactivity following treatment with FEIBA, FVIII inhibitor bypassing activity. The last inhibitor studied had an antibody to either the 44-Kd fragment or to both the 44-Kd and 72-Kd fragments during anamnestic responses to FVIII. These data indicate that a FVIII inhibitor patient can potentially produce antibody to multiple areas on the FVIII molecule and that this must be taken into account in the design of specific therapeutic products.

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Computer Mathematical Modeling Based on the Improved Genetic Algorithm and Mobile Computing

Wireless Communications and Mobile Computing ◽

10.1155/2021/1584435 ◽

2021 ◽

Vol 2021 ◽

pp. 1-7

Author(s):

Huixian Wei ◽

Jia Liu

Keyword(s):

Genetic Algorithm ◽

Mathematical Model ◽

Mobile Computing ◽

Optimal Solution ◽

Least Square Method ◽

Search Space ◽

Least Square ◽

Improved Genetic Algorithm ◽

Operation Rate ◽

The Individual

In order to change the problem of data redundancy in a genetic algorithm, this paper proposes a computer mathematical model based on the combination of an improved genetic algorithm and mobile computing. Combined with the least square method, MATLAB software is used to solve the equations, determine the range of parameters, and solve the estimation parameter range and identification problems. The improved genetic algorithm combined with mobile computing and least square method to establish a mathematical model greatly increased the individual search space and increased the operation rate of 90% compared to the basic genetic algorithm or mobile computing. The results show that the improved genetic algorithm and mobile computing have a certain ability to identify the optimal solution and greatly improve the work efficiency.

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