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D Lillicrap

Publications and source records attributed to D Lillicrap.

At least 19 recordsLinked to original sources
PubMed2006

Update on the pathophysiology and classification of von Willebrand disease: a report of the Subcommittee on von Willebrand Factor.

von Willebrand disease (VWD) is a bleeding disorder caused by inherited defects in the concentration, structure, or function of von Willebrand factor (VWF). VWD is classified into three primary categories. Type 1 includes partial quantitative deficiency, type 2 includes qualitative defects, and type 3 includes virtually complete deficiency of VWF. VWD type 2 is divided into four secondary categories. Type 2A includes variants with decreased platelet adhesion caused by selective deficiency of high-molecular-weight VWF multimers. Type 2B includes variants with increased affinity for platelet glycoprotein Ib. Type 2M includes variants with markedly defective platelet adhesion despite a relatively normal size distribution of VWF multimers. Type 2N includes variants with markedly decreased affinity for factor VIII. These six categories of VWD correlate with important clinical features and therapeutic requirements. Some VWF gene mutations, alone or in combination, have complex effects and give rise to mixed VWD phenotypes. Certain VWD types, especially type 1 and type 2A, encompass several pathophysiologic mechanisms that sometimes can be distinguished by appropriate laboratory studies. The clinical significance of this heterogeneity is under investigation, which may support further subdivision of VWD type 1 or type 2A in the future.

ADAM Proteins↗
PubMed2006

Induction of partial immune tolerance to factor VIII through prior mucosal exposure to the factor VIII C2 domain.

BACKGROUND: The development of anti-factor VIII (FVIII) neutralizing antibodies (inhibitors) is a significant obstacle to FVIII replacement therapy. OBJECTIVE: As mucosal administration of an antigen may induce immune tolerance we have evaluated the efficacy of mucosal antigen exposure to achieve tolerance to FVIII. METHODS: We investigated the effects of oral and nasal administration of the purified FVIII C2 domain (FVIII-C2) to FVIII-deficient BALB/c mice prior to FVIII protein challenge. Mice received oral or nasal doses of FVIII-C2, followed by a subcutaneous challenge of either FVIII-C2 or FVIII. The development of anti-FVIII inhibitors, cytokine production by splenocytes in vitro, and adoptive transfer assays were analyzed. RESULTS AND CONCLUSIONS: Mucosal administration of FVIII-C2 decreases the titer of anti-FVIII-C2 inhibitors after FVIII-C2 challenge, and decreases the percentage of FVIII-C2 specific antibodies after challenge with full-length FVIII. Tolerance induction to FVIII-C2 is associated with increased IL-10 production by splenocytes in vitro, and can be adoptively transferred to naïve mice. This study is the first to demonstrate that tolerance to the FVIII-C2 domain can be induced via the mucosal route. Based on these results, the potential use of FVIII-specific mucosal tolerance induction as an immunotherapy treatment for anti-FVIII inhibitor development warrants further investigation.

Administration, Intranasal↗
PubMed2006

The value of genetic testing for type 2B Von Willebrand disease.

Von Willebrand disease (VWD) is an inherited bleeding disorder that may be associated with significant morbidity, but is often a diagnostic challenge. While an appropriate clinical bleeding history suggests the condition, current laboratory screening investigations lack the sensitivity and specificity to confirm the diagnosis in many cases. Recently, much work has gone into characterizing the genetic mutations associated with the various subtypes of VWD. We report a case in which the diagnosis of VWD type 2B was made via genetic testing, illustrating its value as a useful diagnostic tool.

DNA Mutational Analysis↗
PubMed2006

Ethical issues in haemophilia.

Ethical issues surrounding both the lack of global access to care as well as the implementation of advancing technologies, continue to challenge the international haemophilia community. Haemophilia is not given the priority it deserves in most developing countries. Given the heavy burdens of sickness and disease and severe resource constraints, it may not be possible to provide effective treatment to all who suffer from the various 'orphan' diseases. Nevertheless, through joint efforts, some package of effective interventions can be deployed for a significant number of those who are afflicted with 'orphan' diseases. With cost-effective utilization of limited resources, a national standard of care is possible and affordable. Gene-based diagnosis carries attendant ethical concerns whether for clinical testing or for research purposes, even as the list of its potential benefits to the haemophilia community grows rapidly. As large-scale genetic sequencing becomes quicker and cheaper, moving from the research to the clinic, we will face decisions about the implementation of prenatal, neonatal and other screening programs. Such debates will require input from not just the health care professionals but from all stakeholders in the haemophilia community. Finally, long-term therapeutic success gene transfer in small and large animal models raises the question of when and in which patient population the novel therapeutic approach should first be studied in humans with haemophilia. Although gene therapy represents a worthy goal, the central question for the haemophilia community should be whether it wishes to volunteer itself as a model for a much broader set of innovations.

Adult↗
PubMed2006

Cellular and genetic therapies for haemophilia.

Haemophilia continues to be a prime target for a variety of gene and cell-based therapies. Pre-clinical successes in both mouse and dog models of the disease have been documented with a variety of approaches over the past decade, and there have now been six small clinical trials of gene transfer in haemophilia. To date, the only significant adverse events documented in these trials have been related to host immune responses, indicating that immunologic barriers continue to represent the major obstacle to achieving success of gene transfer in humans. Despite these challenges, new strategies are being explored with novel serotypes of viral vectors and with the use of transient periods of immunosuppression to attenuate the immune response to the vector and transgene product following gene delivery. Two new clinical trials, both using AAV vectors, will likely start within the next year, and additional large animal pre-clinical studies using other viral vector-mediated approaches for gene transfer are expected in the near future.

Animals↗
PubMed2006

Laboratory issues in bleeding disorders.

The clinical history of the patient and of his/her relatives is the most important tool for making correct diagnosis of inherited or acquired bleeding disorders. Several attempts have been made by clinicians to evaluate the sensitivity and specificity of bleeding symptoms. Specific and detailed questionnaires have been designed to quantify the bleeding tendency of patients with von Willebrand's disease (VWD) and a bleeding score has been calculated. VWD is considered the most frequent inherited bleeding disorder according to population studies: however, due to the complexity of its diagnosis, the number of patients with correct diagnosis of VWD in many developing countries is relatively low and most cases remain still under- or misdiagnosed. Once bleeding history is carefully evaluated by means of a bleeding score, the laboratory workout should be organized to find out the specific defect of haemostasis responsible for bleeding. Since factors involved in haemostasis are many, the correct approach must include first level screening tests with the aim to identify the abnormal phase of haemostasis involved: then, second level tests should be focused on the specific factors within the abnormal step of haemostasis. Among many other acquired bleeding disorders related to clinical conditions or to the use of drugs, the acquired inhibitors of haemostasis are rare but should be immediately characterized by appropriate laboratory tests because they can be often life-threatening for the patients.

Blood Coagulation Disorders↗
PubMed2006

Genetic linkage and association analysis in type 1 von Willebrand disease: results from the Canadian type 1 VWD study.

BACKGROUND: von Willebrand disease (VWD) is the most common bleeding disorder known in humans, with type 1 VWD representing the majority of cases. Unlike the other variant forms of VWD, type 1 disease represents a complex genetic trait, influenced by both genetic and environmental factors. AIM: To evaluate the contribution of the von Willebrand factor (VWF) and ABO blood group loci to the type 1 VWD phenotype, and to assess the potential for locus heterogeneity in this condition, we have performed genetic linkage and association studies on a large, unselected type 1 VWD population. METHOD: We initially collected samples from 194 Canadian type 1 VWD families for analysis. After the exclusion of families found to have either type 2 or type 3 VWD, and pedigrees with samples from single generations, linkage and association analysis was performed on 155 type 1 VWD families. RESULTS AND CONCLUSION: The linkage study has shown a low heterogeneity LOD score of 2.13 with the proportion of families linked to the VWF gene estimated to be 0.41. Linkage was not detected to the ABO locus in this type 1 VWD population. In the family-based association test, significant association was found between the type 1 VWD phenotype, the quantitative traits, VWF:Ag, VWF:RCo, and FVIII:C and the ABO 'O' and 'A' alleles and the VWF codon 1584 variant. There was also weak association with the -1185 promoter polymorphism and VWF:Ag, VWF:RCo, and FVIII:C plasma levels. These studies provide further evidence to support the role for genetic loci other than VWF and ABO in the pathogenesis of type 1 VWD.

ABO Blood-Group System↗
PubMed2006

Tailored prophylaxis in severe hemophilia A: interim results from the first 5 years of the Canadian Hemophilia Primary Prophylaxis Study.

BACKGROUND: Prophylactic treatment for severe hemophilia A is likely to be more effective than treatment when bleeding occurs, however, prophylaxis is costly. We studied an inception cohort of 25 boys using a tailored prophylaxis approach to see if clotting factor use could be reduced with acceptable outcomes. METHODS: Ten Canadian centers enrolled subjects in this 5-year study. Children were followed every 3 months at a comprehensive care hemophilia clinic. They were initially treated with once-weekly clotting factor; the frequency was escalated in a stepwise fashion if unacceptable bleeding occurred. Bleeding frequency, target joint development, physiotherapy and radiographic outcomes, as well as resource utilization, were determined prospectively. RESULTS: The median follow-up time was 4.1 years (total 96.9 person-years). The median time to escalate to twice-weekly therapy was 3.42 years (lower 95% confidence limit 2.05 years). Nine subjects developed target joints at a rate of 0.09 per person-year. There was an average of 1.2 joint bleeds per person-year. The cohort consumed on average 3656 IU kg(-1)year(-1) of factor (F) VIII. Ten subjects required central venous catheters (three while on study); no complications of these devices were seen. One subject developed a transient FVIII inhibitor. End-of-study joint examination scores--both clinically and radiographically--were normal or near-normal. CONCLUSIONS: Most boys with severe hemophilia A will probably have little bleeding and good joint function with tailored prophylaxis, while infusing less FVIII than usually required for traditional prophylaxis.

Canada↗
PubMed2006

DNA microarray analysis for the detection of mutations in hemophilia A.

BACKGROUND: Congenital deficiency of factor (F) VIII results in the inherited X-linked bleeding disorder hemophilia A. More than 900 different mutations are reported in the hemophilia A mutation database with the largest number of mutations being single nucleotide substitutions distributed throughout the gene. Complicating the molecular characterization of this disease is the complexity of the F8 gene, the mutational heterogeneity, and technical limitations of the current mutation detection techniques. OBJECTIVE: Development of a DNA oligonucleotide microarray-based technique for F8 gene analysis to detect hemophilia A mutations. METHODS: To construct the oligonucleotide DNA microarray system: a total of 720, one base pair overlapping, 25-mer perfect match probes were designed from six exons of the F8 gene. Twenty-two different F8 gene mutations previously identified by CSGE and DNA sequence analysis were tested by using a loss-of-signal analysis approach. Differentially labeled wild type and hemophilic samples were co-hybridized to the array. Sequence alterations were detected by quantifying relative losses of test sample hybridization signals to the perfectly matched probes. RESULTS: A total of 22 different F8 mutations were tested. To test the sensitivity of the system, a blinded study was performed on 16 of the samples. F8 gene mutations can be detected with 96% efficiency with this microarray system. CONCLUSION: This proof-of-principle study has demonstrated that a F8 DNA microarray platform is an alternative gene mutation analysis approach that has a high sensitivity, and reproducibility. The methodology is, however, expensive and time consuming, and with the reduction in sequencing costs, direct sequencing is now the most cost and time efficient strategy for hemophilia A mutation analysis.

DNA Mutational Analysis↗
PubMed2005

Can activated recombinant factor VII be used to postpone the exposure of infants to factor VIII until after 2 years of age?

Two retrospective studies have suggested that exposure to factor VIII (FVIII) in early infancy is associated with an increased risk of FVIII inhibitor development. We prospectively studied 11 infants who needed replacement therapy for bleeding episodes before the age of 2 years. They received activated recombinant factor VII (rFVIIa) concentrate on demand, with the intention of postponing their first exposure to FVIII after 2 years of age. Thirty-three bleeding episodes were treated with 154 doses of rFVIIa with no evidence of adverse effect. Bleeding was controlled in 27 of 33 episodes. Mouth bleeds were most difficult to treat. The use of rFVIIa allowed postponement of the use of FVIII for a mean of 5.5 months (median 4, range 0-12) but in only three of 11 children could be the first exposure to factor postponed after the age of 2 years. With this modest effect of rFVIIa in postponing the first exposure to FVIII, more convincing evidence for the benefit of such a postponement will have to be demonstrated before rFVIIa could be recommended for this indication.

Age Factors↗
PubMed2004

Home management of haemophilia.

The demonstrated benefits of home care for haemophilia include improved quality of life, less pain and disability, fewer hospitalizations, and less time lost from work or school. Although reduced mortality has not been demonstrated, the substantial increase in longevity since the early 1980s correlates with the introduction of home treatment and prophylaxis programmes. These programmes must be designed and monitored by haemophilia treatment centres (HTC), which are staffed with professionals with broad and complementary expertise in the disease and its complications. In return, patients and their families must be willing to accept the reciprocal responsibilities that come from administering blood products or their recombinant equivalents at home. Patients with inhibitors to factors VIII or IX pose special challenges, but these complications do not obviate participation in home care programmes. Home care was an essential prerequisite to the introduction of effective prophylactic factor replacement therapy. Prophylaxis offers significant improvements in quality of life, but requires a substantial commitment. The use of implantable venous access devices can eliminate some of the difficulty and discomfort of peripheral venous access in small children, but brings additional risks. The future holds the promise of factor concentrates for home use that have longer half-lives, or can be administered by alternate routes. Knowledge of patient genotypes may allow treatments tailored to avoid complications such as inhibitor development. Gene therapy trials, which are currently ongoing, will ultimately lead to gene-based treatments as a complement to traditional protein-based therapy.

Blood Coagulation Factors↗
PubMed2004

von Willebrand disease: laboratory aspects of diagnosis and treatment.

von Willebrand disease is the most common inherited bleeding disorder in humans. VWD can be classified into three major types, designated Types 1, 2 and 3; Type 2 can be further separated into subtypes 2A, 2B, 2M and 2N. The diagnosis of VWD requires a personal and family history of bleeding and confirmation by laboratory analysis. Although Types 2 and 3 are relatively straightforward to diagnose, there may be a risk of overdiagnosis of Type 1 because of an overlap within the normal range. We also report on the clinical profile and diagnosis of VWD in a South American cohort of patients and on the in vitro characteristics of some factor concentrates available for treatment of VWD.

Adolescent↗
PubMed2004

Factors influencing therapeutic efficacy and the host immune response to helper-dependent adenoviral gene therapy in hemophilia A mice.

BACKGROUND: Adenoviral-based methods of gene therapy have been ineffective at providing sustained factor (F)VIII expression in outbred populations of large animal hemophilic models primarily due to the immunogenicity of these vectors. Improvements have been made in vector design leading to the development of the helper-dependent adenoviral (HD) system. Unfortunately, it remains unclear whether these modifications are sufficient to circumvent the induction of inhibitor formation associated with adenoviral gene transfer. OBJECTIVE: To develop an HD vector capable of mediating sustained FVIII expression and to determine the variables that influence inhibitor development. METHODS: HD vectors were constructed encoding the canine FVIII B-domain deleted transgene under the control of either the cytomegalovirus (CMV) promoter or a tissue-restricted hybrid element consisting of five HNF-1 binding sites, located upstream of the human FVIII proximal promoter. Inbred and outbred populations of hemophilic mice were treated, and monitored for vector-induced toxicity, therapeutic efficacy, and inhibitor formation. RESULTS: When HD vectors utilizing the CMV promoter were administered, all hemophilic mice developed high levels of FVIII inhibitors. In contrast, vectors under the control of the HNF/FVIII element were capable of achieving sustained elevations of FVIII for over 6 months. Strain-specific differences were also observed, with outbred animals showing a greater propensity towards inhibitor development in response to treatment. CONCLUSIONS: HD vectors can be used to provide long-term FVIII expression in hemophilic animals, but treatment outcome and the induction of inhibitors is dependent on a number of variables including the transgene promoter, the vector dose, and the genetic background of the host.

Adenoviridae↗
PubMed2004

A novel type 2A (Group II) von Willebrand disease mutation (L1503Q) associated with loss of the highest molecular weight von Willebrand factor multimers.

Type 2A von Willebrand disease (VWD) is characterized by decreased platelet-dependent function of von Willebrand factor (VWF) associated with an absence of high-molecular-weight multimers. In this study, sequence analysis of the VWF gene from a Type 2A VWD patient showed a novel, heterozygous T-->A transversion at nucleotide 4510, resulting in the non-conservative substitution of L1503Q in the mature VWF subunit. This substitution, which was not found in 55 unrelated normal individuals, was reproduced by in vitro site directed mutagenesis of a full-length VWF cDNA and was subsequently expressed in COS-7 cells. The corresponding recombinant mutant VWF protein was partially retained in COS-7 cells yet the full spectrum of multimers was observed, suggesting that the absence of the highest molecular weight multimers results from increased proteolysis. The recombinant mutant VWF protein was digested with the ADAMTS13 protease from VWF-depleted plasma and the aberrant VWF multimer pattern was observed. These results suggest that the L1503Q substitution induces a conformational change in the VWF protein, which increases the protein's susceptibility to proteolysis. A three-dimensional model of the A2 domain demonstrates that the L1503Q mutation and the physiological proteolytic cleavage site for ADAMTS13 (Y(1605)-M(1606)) are localized close together in two adjacent parallel beta-sheets. The mutation L1503Q does not significantly disrupt the conformation of the protein; thus the subtle loss of multimers in this patient may be due to altered interactions with the ADAMTS13 protease.

ADAM Proteins↗
PubMed2003

Intensive exposure to factor VIII is a risk factor for inhibitor development in mild hemophilia A.

BACKGROUND: Inhibitors are rare in boys with mild hemophilia A (MHA; factor (F)VIII:C > 5%) but may arise following intense FVIII exposure, e.g. continuous infusion (CI). OBJECTIVES: To determine the impact of intense FVIII exposure in inhibitor formation in MHA at our institution and to compare this with previous reports. PATIENTS AND METHODS: We reviewed FVIII exposure and inhibitor development in boys (ages 0-18 years) with MHA followed at our institution from 1996 to 2001 and conducted a Medline search (1966-2002) on the experience of inhibitor development following intensive/CI exposure to FVIII. RESULTS: We identified 54 boys with MHA. Twenty-nine (54%) had been exposed to FVIII. Seven had received FVIII by CI. Four developed inhibitors; three high titer (at ages 10 years, 16 years and 17 years) and one low titer (at 1 month old). All four had received a CI of recombinant (r) FVIII of at least 6 days within 6 weeks of developing inhibitors. Baseline FVIII levels fell to < 1% in all cases and the three with high-titer inhibitors developed severe bleeding. Immune tolerance therapy (ITT) was attempted in two boys and was successful in one. Our literature search identified 35 cases (only four children) with MHA developing inhibitors following intense FVIII exposure often in the context of surgery. CONCLUSIONS: The incidence of inhibitors in our MHA population was 7.4%. If expressed according to exposure the incidence was significantly higher: 14% (4/29) for any exposure to FVIII and 57% (4/7) for exposure by CI. A prospective study to address whether CI is associated with an increased incidence of inhibitor development in MHA is warranted.

Adolescent↗