Factor VIII brand and the incidence of factor VIII inhibitors in previously untreated UK children with severe hemophilia A, 2000-2011.

The effect of recombinant factor VIII (rFVIII) brand on inhibitor development was investigated in all 407 severe hemophilia A previously untreated patients born in the United Kingdom (UK) between 1 January 2000 and 31 December 2011. Eighty-eight (22%) had been in the RODIN study. Information was extracted from the National Haemophilia Database. Because exposure days (EDs) were not known for some patients, time from first treatment was used as a surrogate for rFVIII exposure. An inhibitor developed in 118 (29%) patients, 60 high and 58 low titer, after a median (interquartile range) of 7.8 (3.3-13.5) months from first exposure and 16 (9-30) EDs. Of 128 patients treated with Kogenate Bayer/Helixate NexGen, 45 (35.2%, 95% confidence interval [CI] 27.4-43.8) developed an inhibitor compared with 42/172 (24.4%, 95% CI 18.6% to 31.4%) with Advate (P = .04). The adjusted hazard ratio (HR) (95% CI) for Kogenate Bayer/Helixate NexGen compared with Advate was 2.14 (1.12-4.10) (P = .02) for high titer and 1.75 (1.11-2.76) (P = .02) for all inhibitors. When excluding UK-RODIN patients, the adjusted HR (95% CI) for high-titer inhibitors was 2.00 (0.93-4.34) (P = .08). ReFacto AF was associated with a higher incidence of all, but not high-titer, inhibitors than Advate. These results will help inform debate around the relative immunogenicity and use of rFVIII brands.

Whole exome sequencing identifies genetic variants in inherited thrombocytopenia with secondary qualitative function defects.

Inherited thrombocytopenias are a heterogeneous group of disorders characterized by abnormally low platelet counts which can be associated with abnormal bleeding. Next-generation sequencing has previously been employed in these disorders for the confirmation of suspected genetic abnormalities, and more recently in the discovery of novel disease-causing genes. However its full potential has not yet been exploited. Over the past 6 years we have sequenced the exomes from 55 patients, including 37 index cases and 18 additional family members, all of whom were recruited to the UK Genotyping and Phenotyping of Platelets study. All patients had inherited or sustained thrombocytopenia of unknown etiology with platelet counts varying from 11×109/L to 186×109/L. Of the 51 patients phenotypically tested, 37 (73%), had an additional secondary qualitative platelet defect. Using whole exome sequencing analysis we have identified "pathogenic" or "likely pathogenic" variants in 46% (17/37) of our index patients with thrombocytopenia. In addition, we report variants of uncertain significance in 12 index cases, including novel candidate genetic variants in previously unreported genes in four index cases. These results demonstrate that whole exome sequencing is an efficient method for elucidating potential pathogenic genetic variants in inherited thrombocytopenia. Whole exome sequencing also has the added benefit of discovering potentially pathogenic genetic variants for further study in novel genes not previously implicated in inherited thrombocytopenia.

A genome-wide association study of resistance to HIV infection in highly exposed uninfected individuals with hemophilia A.

Human genetic variation contributes to differences in susceptibility to HIV-1 infection. To search for novel host resistance factors, we performed a genome-wide association study (GWAS) in hemophilia patients highly exposed to potentially contaminated factor VIII infusions. Individuals with hemophilia A and a documented history of factor VIII infusions before the introduction of viral inactivation procedures (1979-1984) were recruited from 36 hemophilia treatment centers (HTCs), and their genome-wide genetic variants were compared with those from matched HIV-infected individuals. Homozygous carriers of known CCR5 resistance mutations were excluded. Single nucleotide polymorphisms (SNPs) and inferred copy number variants (CNVs) were tested using logistic regression. In addition, we performed a pathway enrichment analysis, a heritability analysis, and a search for epistatic interactions with CCR5 Δ32 heterozygosity. A total of 560 HIV-uninfected cases were recruited: 36 (6.4%) were homozygous for CCR5 Δ32 or m303. After quality control and SNP imputation, we tested 1 081 435 SNPs and 3686 CNVs for association with HIV-1 serostatus in 431 cases and 765 HIV-infected controls. No SNP or CNV reached genome-wide significance. The additional analyses did not reveal any strong genetic effect. Highly exposed, yet uninfected hemophiliacs form an ideal study group to investigate host resistance factors. Using a genome-wide approach, we did not detect any significant associations between SNPs and HIV-1 susceptibility, indicating that common genetic variants of major effect are unlikely to explain the observed resistance phenotype in this population.

Enrichment of FLI1 and RUNX1 mutations in families with excessive bleeding and platelet dense granule secretion defects.

We analyzed candidate platelet function disorder genes in 13 index cases with a history of excessive bleeding in association with a significant reduction in dense granule secretion and impaired aggregation to a panel of platelet agonists. Five of the index cases also had mild thrombocytopenia. Heterozygous alterations in FLI1 and RUNX1, encoding Friend leukemia integration 1 and RUNT-related transcription factor 1, respectively, which have a fundamental role in megakaryocytopoeisis, were identified in 6 patients, 4 of whom had mild thrombocytopenia. Two FLI1 alterations predicting p.Arg337Trp and p.Tyr343Cys substitutions in the FLI1 DNA-binding domain abolished transcriptional activity of FLI1. A 4-bp deletion in FLI1, and 2 splicing alterations and a nonsense variation in RUNX1, which were predicted to cause haploinsufficiency of either FLI1 or RUNX1, were also identified. Our findings suggest that alterations in FLI1 and RUNX1 may be common in patients with platelet dense granule secretion defects and mild thrombocytopenia.