Miguel Candela

Analysis of factor VIII gene intron 1 inversion in Argentinian families with severe haemophilia A and a review of the literature.

Besides intron 22 factor VIII gene inversion (Inv22), intron 1 inversion (Inv1) has recently been reported as a further recurrent mutation that causes approximately 5% of severe haemophilia A (HA) cases. We analysed the presence of the Inv1 in a group of 64 severe HA-affected families from Argentina, and found only one positive case. This Inv1 patient has not developed a factor VIII inhibitor, and the screening for small mutations in the coding sequences of the factor VIII gene did not detect any additional defect in this case. The Inv1 genotyping was further applied to analyse the haemophilia carrier status of the probands sister. In addition, we studied the accuracy of the current polymerase chain reaction-based method to investigate the Inv1, and confirmed the absence of amplimer length polymorphisms associated to the Inv1-specific polymerase chain reaction amplifications in 101 X-chromosome haplotypes from unrelated Argentinian healthy males. In order to discuss Inv1 mutation frequency in severe HA and the risk of inhibitor formation, a review of the literature was included. Our data highlight the importance of analysis of the Inv1 in Inv22-negative severe HA cases. This will benefit both genetic counselling and the study of the relationship between genotype and inhibitor development.

Assessment of the F9 genotype-specific FIX inhibitor risks and characterisation of 10 novel severe F9 defects in the first molecular series of Argentinian patients with haemophilia B

In haemophilia B (HB) (factor IX [FIX] deficiency), F9 genotype largely determines clinical phenotype. Aimed to characterise Argentinian families with HB, this study presents F9 genotype frequencies and their specific FIX inhibitor risk and 10 novel F9 mutations. Ninety-one DNA samples from HB patients and relatives were subjected to a new scheme: a primary screen for large deletions, a secondary screen for point mutations using conformation sensitive gel electrophoresis, DNA-sequencing and bioinformatic analysis. Our unbiased HB population (N=52) (77% with severe, 11.5% moderate and 11.5% mild HB) showed 32 missense (61.5%), including three novel mutations predicting specific structural/functional defects in silico , seven nonsense (13.5%) (one novel), five large deletions, four splice including three novel mutations affecting predicted splicing scores, three indels (two novel) and one Leiden mutation. Our comprehensive HB population included five patients with long-lasting FIX inhibitors: three nonsense (p.E35* (novel), p.R75*, p.W240*) and two entire- F9 deletions. Another patient with an indel (p.A26Rfs*14) developed transient inhibitors. A case-control analysis, based on our global prevalence of 3.05% for developing inhibitors in HB revealed that missense mutations were associated with a low risk odds ratio (OR) of 0.05 and a prevalence of 0.39%, whereas nonsense and entire- F9 deletions had significantly higher risks (OR 11.0 and 32.7) and prevalence (14.3% and 44.5%, respectively). Our cost-effective practical approach enabled identification of the causative mutation in all 55 Argentine families with HB, analysis of the molecular pathology of novel F9 defects and determination of mutation-associated FIX inhibitor risks.

A flow cytometry evaluation of anti-FVIII antibodies: correlation with ELISA and Bethesda assay

Summary.  In this study, we describe a flow cytometry (FC) system for detecting antibodies to factor VIII (FVIII) and compare its results with those of enzyme‐linked immunosorbent assay (ELISA) that detects both inhibitory (I‐Ab) and non‐inhibitory (NI‐Ab) antibodies and the Nijmegen modification of the Bethesda method, detecting I‐Ab. FC was set up in our laboratory. Recombinant FVIII (rFVIII) was coupled to microspheres (FVIII‐m) and reacted with different plasma dilutions. Microspheres without rFVIII were used as control (control‐m). Captured anti‐FVIII antibodies were detected using anti‐human IgG. Plasma samples from the following patients with severe haemophilia A (SHA) patients were evaluated: 17 P (patients without I‐Ab, <0.5 BU mL−1); 13 PI (patients with I‐Ab, 1.1–8200 BU mL−1). Of these 13, two PI were referred during immune tolerance induction (ITI), and plasmas from 12 healthy donors (HD) were evaluated. Semiquantitative results were given as an index (the highest mean fluorescence intensity ratio between FVIII‐m and control‐m multiplied by the inverse of the corresponding plasma dilution). Both plasma and serum were suitable for the test. FC agreed with the Bethesda method (r = 0.8; P = 0.0001). FC and ELISA had 80% of coincidence. Four of 17 patients (23.5%) had NI‐Ab by FC, and two of them developed high levels of I‐Ab later on. This test provides a useful alternative for measuring FVIII antibodies supplementing Bethesda assay. FC is fast and easy to perform. No more than 200 μL of plasma or serum is required especially making it useful for paediatric patients.

Phenotype-genotype correlations in hemophilia A carriers are consistent with the binary role of the phase between F8 and X-chromosome inactivation.

The recessive X‐linked disorder hemophilia A (HA) is rarely expressed in female carriers, most of whom express about half of normal factor VIII activity (FVIII:C).

Are int22h-mediated deletions a common cause of hemophilia?

Dear Editor, Hemophilia A (HA) (OMIM 306700) is an X-linked inherited bleeding disorder caused by deleterious mutations in the coagulation factor VIII gene (F8). Even though there is a broad diversity of HA-causative mutations, an uncommon type of rearrangement—a large DNA inversion involving F8 intron 22 (Inv22)—accounts for approximately one half of severely affected patients. Inv22 was formerly described by Lakich et al. [1] and Naylor et al. [2]. A collaborative international effort estimated that Inv22 is the cause of 43% (35%, 7%, and 1% for Inv22 type I, type II, and rare types, respectively) of severe HA cases worldwide with minor geographical or ethnical differences [3], in close agreement with our corresponding Argentinean series (42% of Inv22, and 34% and 7% for type I and type II, respectively) [4]. Naylor et al. [5] indicated that Inv22 originates by homologous recombination between well-defined duplicons (int22h) of 9.5 kb located one copy within F8 intron 22 (int22h-1, h1) and the other, inversely oriented, from a group of two extragenic copies (int22h-3, h3 for Inv22 type I and int22h-2, h2 for type II). It was formerly believed that h2 and h3 were equally oriented (i.e., head to tail). However, Ross et al. [6] determined that h2 and h3 are inversely oriented (i.e., head to head), both embedded in the arms of a large imperfect palindrome (Fig. 1). This finding prompted Bagnall et al. [7] to hypothesize recombination between these arms interchanging the location of the extragenic int22h copies and generating a non-deleterious inversion polymorphism in Xq28, i.e., h123 and h132. In this scenario, Inv22 type I may be generated from intrachromosomal recombination between h1 and h3 on the most frequent variant h123 whereas Inv22 type II may be generated between h1 and h2 on the least frequent h132 (Fig. 1). Moreover, on each of these normal structural variants of the X chromosome, recombination between h1 with either equally oriented copies (h2 or h3) may generate deletions (Del22) or duplications (Dup22) but not inversions [7]. More precisely, Del22 type I would be generated by recombination between h1 and h3 on variant h132 whereas Del22 type II by recombination between h1 and h2 on variant h123 [8] (Fig. 1). Notwithstanding these theoretical speculations, until recently, no such Del22 mutation has been unequivocally reported in the literature, and Del22 has been suspected to be extremely deleterious, even to compromise the viability of hemizygous males [8]. Unexpectedly, a recent paper by Abou-Elew et al. [9] detected three cases of Del22 (two Del22 type II and one type I) by the use of inverse-shifting PCR (IS-PCR) [10] in a group of 13 Egyptian patients with severe HA. In this scenario and previous beliefs on the phenotype of int22h-mediated deletions (Del22), the aims of this scientific letter are, first, to report the lack of Del22 in a series of int22h-mediated rearrangements from Argentina and, second, to provide a simple practical approach to Electronic supplementary material The online version of this article (doi:10.1007/s00277-011-1295-z) contains supplementary material, which is available to authorized users. M. M. Abelleyro : L. C. Rossetti : C. P. Radic : I. B. Larripa : C. D. De Brasi (*) Departamento de Genetica, Instituto de Investigaciones Hematologicas, Academia Nacional de Medicina de Buenos Aires, Pacheco de Melo 3081, Buenos Aires 1425, Argentina e-mail: cdebrasi@hematologia.anm.edu.ar

Musculoskeletal evaluation in severe haemophilia A patients from Latin America

There is a paucity of literature on haemophilia treatment in Latin American countries, a region characterized by rapidly improving systems of care, but with substantial disparities in treatment between countries. The aim of this study was to evaluate the musculoskeletal status of haemophilia patients from Latin America and to examine the relationship between musculoskeletal status and treatment practices across countries. The Committee of Latin America on the Therapeutics of Inhibitor Groups conducted a survey of its member country representatives on key aspects of haemophilia treatment in 10 countries. Musculoskeletal status of patients was obtained during routine comprehensive evaluations between March 2009 and March 2011. Eligible patients had severe haemophilia A (factor VIII <1%) without inhibitors (<0.6 BU mL−1) and were ≥5 years of age. Musculoskeletal status was compared between three groups of countries, based primarily on differences in the availability of long‐term prophylaxis. Overall, 143 patients (5–66 years of age) were enrolled from nine countries. In countries where long‐term prophylaxis had been available for at least 10 years (Group A), patients aged 5–10 years had significantly better mean World Federation of Hemophilia clinical scores, fewer target joints and fewer affected joints than patients from countries where long‐term prophylaxis has been available for about 5 years (Group B) or was not available (Group C). In Latin America, the musculoskeletal status of patients with severe haemophilia without inhibitors has improved significantly in association with the provision of long‐term prophylaxis. As more countries in Latin America institute this practice, further improvements are anticipated.

A prevalent CTLA4 missense variant significantly associates with inhibitor development in Argentine patients with severe haemophilia A.

Fil: Marchione, Vanina Daniela. Consejo Nacional de Investigaciones Cientificas y Tecnicas; Argentina. Fundacion de la Hemofilia Alfredo Pavlovsky; Argentina. Academia Nacional de Medicina de Buenos Aires. Instituto de Investigaciones Hematologicas ; Argentina

Severe haemophilia A patients have reduced numbers of peripheral memory B cells.

Summary.  The development of inhibitors is a complication of replacement treatment in Haemophilia. Loss of factor VIII‐specific memory B cells in the spleen is associated with down regulation of antibodies in mice treated with high doses of FVIII, but changes in B cell memory have not been described in haemophilic patients. The aim of this study was to evaluate the phenotype of circulating lymphocytes in severe haemophilia A. Twenty patients with inhibitors (PI), 22 without inhibitors (P), nine patients during immune tolerance induction (ITI) treatment and 20 healthy donors (HD) were included. Peripheral blood lymphocytes were examined using flow cytometry. Anti‐FVIII antibodies were measured using Bethesda and flow cytometry. Percentages of T subsets and B lymphocytes were similar in all groups. In contrast, memory B cells (CD27+) were decreased in PI and P compared with HD, but the level of significance was higher in PI (P = 0.001) than P (P = 0.01). PI with high level of anti‐FVIII antibodies presented the lowest B memory values. CD70 expression was also lowest in PI. Non‐switched CD27+ subpopulation (IgD+) was prevalent in PI, but did not show statistical significance. When ITI failed, the percentages of CD27+ B cells after 12 months of ITI were lowest. In a longitudinal study performed in four patients, an increased percentage of CD27+ and CD70+ B cells during ITI was found. This work suggests that different peripheral lymphocyte markers, such as CD27 and CD70 on B cells, may be helpful to evaluate anti‐FVIII response and to monitor the success of ITI.

Intrafamilial transmission of hepatitis C virus in patients with severe haemophilia A

Summary.  The history behind the production of clotting factor concentrates produced differences in the prevalence of Hepatitis C Virus (HCV) and other blood‐borne infections in haemophilic patients. Prevalence rates of HCV infection up to 100% were reported in patients treated with concentrates before 1985. Conversely, nowadays, viral inactivation and recombinant technologies have effectively prevented transfusion‐transmitted viral pathogens. Recently, new HCV infections in three young brothers were observed. In the absence of any other risk of transmission, their HIV/HCV coinfected uncle, who was living in the same house, was subject to study. Plasma samples of the four relatives were investigated in order to test whether the infections have a common source. A phylogenetic approach using the most variable (E2) viral sequences was carried out using samples from the four family members. The HCV sequences from the study resulted highly related, being those obtained from the uncle the most ancestral ones. Because of the chronological order in which the infections occurred and the relatedness of the sequences, an infection from the uncle to his nephews is the most likely explanation. Special cares must be applied in the case of household contact among members of a family with inherited bleeding disorders.

IgG subclasses of FVIII inhibitors in an argentine cohort of severe hemophilia A patients: Analysis by flow cytometry

FVIII inhibitors consist of a polyclonal population of antibodies. Previous studies have demonstrated different distribution of IgG subclasses. IgG4 was associated to high level of FVIII inhibitors and failure of immune tolerance induction (ITI) treatment. This study monitored the relative distribution of IgG subclasses of anti‐FVIII in patients with severe hemophilia A (SHA).