Afshin Ameri

Endogenous factor VIII synthesis from the intron 22-inverted F8 locus may modulate the immunogenicity of replacement therapy for hemophilia A

Neutralizing antibodies (inhibitors) to replacement Factor-VIII impair the effective management of hemophilia-A1. Individuals with hemophilia-A due to major F8 gene disruptions lack antigenically cross-reactive material in their plasma (CRM-negative) and prevalence of inhibitors is >60%. Conversely, subjects with missense mutations are CRM-positive and the prevalence of inhibitors is <10%2. Individuals with the intron-22-inversion (~50% of individuals with severe hemophilia-A) should be in the former group based on the genetic defect. Although these individuals are CRM-negative, only 20% of them develop inhibitors3. Here we demonstrate the presence of comparable levels of F8 mRNA and intracellular Factor-VIII protein in B-lymphoblastoid cells and liver biopsies from healthy controls and subjects with the intron-22-inversion. These results support the hypothesis that most individuals with the intron-22-inversion are tolerized to Factor-VIII and thus do not develop inhibitors. Furthermore we developed a pharmacogenetic algorithm that permits the stratification of inhibitor risk for sub-populations by predicting immunogenicity using, as input, the number of putative T-cell epitopes in the infused FVIII and the competence of MHC-Class-II molecules to present such epitopes. The algorithm exhibited significant accuracy in predicting inhibitors in 25 unrelated individuals with the intron-22-inversion (AUC = 0.890; P = 0.001).Neutralizing antibodies (inhibitors) to replacement factor VIII (FVIII, either plasma derived or recombinant) impair the effective management of hemophilia A. Individuals with hemophilia A due to major deletions of the FVIII gene (F8) lack antigenically cross-reactive material in their plasma (“CRM-negative”), and the prevalence of inhibitors in these individuals may be as high as 90%. Conversely, individuals with hemophilia A caused by F8 missense mutations are CRM-positive, and their overall prevalence of inhibitors is <10% (ref. 2). Individuals with the F8 intron 22 inversion (found in ∼50% of individuals with severe hemophilia A) have been grouped with the former on the basis of their genetic defect and CRM-negative status. However, only ∼20% of these individuals develop inhibitors. Here we demonstrate that the levels of F8 mRNA and intracellular FVIII protein in B lymphoblastoid cells and liver biopsies from individuals with the intron 22 inversion are comparable to those in healthy controls. These results support the hypothesis that most individuals with the intron 22 inversion are tolerized to FVIII and thus do not develop inhibitors. Furthermore, we developed a new pharmacogenetic algorithm that permits the stratification of inhibitor risk for individuals and subpopulations by predicting the immunogenicity of replacement FVIII using, as input, the number of putative T cell epitopes in the infused protein and the competence of major histocompatibility complex class II molecules to present such epitopes. This algorithm showed statistically significant accuracy in predicting the presence of inhibitors in 25 unrelated individuals with the intron 22 inversion.

Recombinant factor VIIa analog in the management of hemophilia with inhibitors: results from a multicenter, randomized, controlled trial of vatreptacog alfa

Vatreptacog alfa, a recombinant factor VIIa (rFVIIa) analog with three amino acid substitutions and 99% identity to native FVIIa, was developed to improve the treatment of hemophilic patients with inhibitors.

Genetic determinants of normal variation in coagulation factor (F) IX levels: Genome-wide scan and examination of the FIX structural gene

Summary.  Background: High‐normal and elevated plasma FIX activity (FIX:C) levels are associated with increased risk for venous‐ and possibly arterial‐thrombosis. Objective: Because the broad normal range for FIX:C involves a substantial unknown genetic component, we sought to identify quantitative‐trait loci (QTLs) for this medically important hemostasis trait. Methods: We performed a genome‐wide screen and a resequencing‐based variation scan of the known functional regions of every distinct FIX gene (F9) in the genetic analysis of idiopathic thrombophilia project (GAIT), a collection of 398 Spanish‐Caucasians from 21 pedigrees. Results: We found no evidence for linkage (LOD scores <1.5) despite genotyping more than 540 uniformly‐spaced microsatellites. We identified 27 candidate F9 polymorphisms, including three in cis‐elements responsible for the increase in FIX:C that occurs with aging, but found no significant genotype‐specific differences in mean FIX:C levels (P‐values ≥ 0.11) despite evaluating every polymorphism in GAIT by marginal multicovariate measured‐genotype association analysis. Conclusions: The heritable component of interindividual FIX:C variability likely involves a collection of QTLs with modest effects that may reside in genes other than F9. Nevertheless, because the alleles of these 27 polymorphisms exhibited a low overall degree of linkage disequilibrium, we are currently defining their haplotypes to interrogate several highly‐conserved non‐exonic sequences and other F9 segments not examined here.

Changes in the amino acid sequence of the recombinant human factor VIIa analog, vatreptacog alfa, are associated with clinical immunogenicity.

Vatreptacog alfa, a recombinant human factor VIIa (rFVIIa) analog developed to improve the treatment of bleeds in hemophilia patients with inhibitors, differs from native FVIIa by three amino acid substitutions. In a randomized, double‐blind, crossover, confirmatory phase III trial (adept™2), 8/72 (11%) hemophilia A or B patients with inhibitors treated for acute bleeds developed anti‐drug antibodies (ADAs) to vatreptacog alfa.

An age-related homeostasis mechanism is essential for spontaneous amelioration of hemophilia B Leyden

Regulation of age-related changes in gene expression underlies many diseases. We previously discovered the first puberty-onset gene switch, the age-related stability element (ASE)/age-related increase element (AIE)-mediated genetic mechanism for age-related gene regulation. Here, we report that this mechanism underlies the mysterious puberty-onset amelioration of abnormal bleeding seen in hemophilia B Leyden. Transgenic mice robustly mimicking the Leyden phenotype were constructed. Analysis of these animals indicated that ASE plays a central role in the puberty-onset amelioration of the disease. Human factor IX expression in these animals was reproducibly nullified by hypophysectomy, but nearly fully restored by administration of growth hormone, being consistent with the observed sex-independent recovery of factor IX expression. Ets1 was identified as the specific liver nuclear protein binding only to the functional ASE, G/CAGGAAG, and not to other Ets consensus elements. This study demonstrates the clinical relevance of the first discovered puberty-onset gene switch, the ASE/AIE-mediated regulatory mechanism.

Observations regarding the immunogenicity of BDD-rFVIII derived from a mechanistic personalized medicine perspective

Author(s): Sauna, ZE; Ameri, A; Kim, B; Yanover, C; Viel, KR; Rajalingam, R; Cole, SA; Howard, TE

Genetic and molecular mechanisms of age regulation (homeostasis) of blood coagulation.

Blood coagulation plays a critical role not only in hemostasis but also in many physiological and pathological conditions. Epidemiological studies have shown that blood coagulation capacity in humans increases with age. Towards understanding the underlying mechanisms, the age regulation of factor IX, a key blood coagulation factor, was extensively studied. A series of human factor IX minigenes, consisting of various components of the human factor IX gene, were constructed and subjected to systematic analyses with HepG2 cells in culture and over the entire life span of transgenic mice. These studies identified critical gene structures that are essential for the unique age‐dependent expression patterns of the human factor IX gene?one acting by stabilizing gene transcription and another increasing the amount of mRNA present, presumably by augmenting mRNA stability. These studies have set the stage for analyzing the overall age‐based regulatory mechanisms of blood coagulation.

Successful management of intramural ureteral hemorrhage in a patient with factor VIII deficiency and high‐titer inhibitor

Meyer D, Fressinaud E, Mazurier C and the INSERM Network on molecular abnormalities in von Willebrand disease. Two novel mutations, Q1053H and C1060R, located in the D3 domain of von Willebrand factor, are responsible for decreased FVIII-binding capacity. Br J Haematol 2003; 120: 627–32. 3 Allen S, Abuzenadah AM, Blagg JL, Hinks J, Nesbitt IM, Goodeve AC, Gursel T, Ingerslev J, Peake IR, Daly ME. Two novel type 2N von Willebrand disease-causingmutations that result in defective factor VIII binding, multimerization, and secretion of vonWillebrand factor. Blood 2000; 95: 2000–7. 4 Jorieux S, Fressinaud E, Goudemand J, Gaucher C, Meyer D, Mazurier C and the INSERM Network on Molecular Abnormalities in von Willebrand disease. Conformational changes in the D’ domain of von Willebrand factor induced by Cys 25 and Cys 95 mutations lead to factor VIII binding defect and multimeric impairment. Blood 2000; 95: 3139–45. 5 Hilbert L, Gaucher C, Mazurier C. Identification of two mutations (Arg611Cys and Arg611His) in the A1 loop of von Willebrand factor (vWF) responsible for type 2 von Willebrand disease with decreased platelet-dependent function of vWF. Blood 1995; 86: 1010–8.

Two new γ chain variants: Hb F-Augusta GA [Gγ59(E3)Lys→Arg; HBG2: C.179A>G] and Hb F-Port Royal-II [Aγ125(H3)Glu→Ala; HBG1: C.377A>C]

Abstract The total number of hemoglobin (Hb) variants so far reported to the HbVar database is 1598 (April 9 2014) and 130 of them are fetal Hb variants. Fetal Hb are categorized as two different subunits, Gγ- and Aγ-globin chains, and γ chain variants can be observed in both subunits. There are 72 Gγ- and 58 Aγ-globin chain variants. Most of them are clinically silent and detected during newborn screening programs in the USA and outside the USA. In this report, we discuss the molecular characteristics and diagnostic difficulties of two new γ-globin chain variants found in an African American baby with no clinical symptoms. One is a new Gγ-globin chain variant, Hb F-Augusta GA [Gγ59(E3)Lys → Arg; HBG2: c.179A > G] and the other one is Hb F-Port Royal-II [Aγ125(H3)Glu → Ala; HBG1: c.377A > C].

Age-related regulation of genes: slow homeostatic changes and age-dimension technology

Through systematic studies of pro- and anti-blood coagulation factors, we have determined molecular mechanisms involving two genetic elements, age-related stability element (ASE), GAGGAAG and age-related increase element (AIE), a unique stretch of dinucleotide repeats (AIE). ASE and AIE are essential for age-related patterns of stable and increased gene expression patterns, respectively. Such age-related gene regulatory mechanisms are also critical for explaining homeostasis in various physiological reactions as well as slow homeostatic changes in them. The age-related increase expression of the human factor IX (hFIX) gene requires the presence of both ASE and AIE, which apparently function additively. The anti-coagulant factor protein C (hPC) gene uses an ASE (CAGGAG) to produce age-related stable expression. Both ASE sequences (G/CAGAAG) share consensus sequence of the transcriptional factor PEA-3 element. No other similar sequences, including another PEA-3 consensus sequence, GAGGATG, function in conferring age-related gene regulation. The age-regulatory mechanisms involving ASE and AIE apparently function universally with different genes and across different animal species. These findings have led us to develop a new field of research and applications, which we named “age-dimension technology (ADT)”. ADT has exciting potential for modifying age-related expression of genes as well as associated physiological processes, and developing novel, more effective prophylaxis or treatments for age-related diseases.