Deborah Brown

Neutralizing antibodies against adeno-associated virus examined prospectively in pediatric patients with hemophilia

Recombinant adeno-associated virus (rAAV) is a promising gene delivery vector and has recently been used in patients with hemophilia. One limitation of AAV application is that most humans have experienced wild-type AAV serotype 2 exposure, which frequently generates neutralizing antibodies (NAbs) that may inhibit rAAV2 vector transduction. Employing alternative serotypes of rAAV vectors may circumvent this problem. We investigated the development of NAbs in early childhood by examining sera gathered prospectively from 62 children with hemophilia A, participating in a multi-institutional hemophilia clinical trial (the Joint Outcome Study). Clinical applications in hemophilia therapy have been suggested for serotypes AAV2, AAV5 and AAV8, therefore NAbs against these serotypes were serially assayed over a median follow-up of 4 years. NAbs prevalence increased during early childhood for all serotypes. NAbs against AAV2 (43.5%) were observed more frequently and at higher titers compared with both AAV5 (25.8%) and AAV8 (22.6%). NAbs against AAV5 or AAV8 were rarely observed in the absence of co-prevalent and higher titer AAV2 NAbs, suggesting that NAbs to AAV5 and AAV8 were detected following AAV2 exposure due to partial cross-reactivity of AAV2-directed NAbs. The results may guide rational design of clinical trials using alternative AAV serotypes and suggest that younger patients who are given AAV gene therapy will benefit from the lower prevalence of NAbs.

Human immunodeficiency and hepatitis virus infections and their associated conditions and treatments among people with haemophilia.

Summary.  Treatment with contaminated plasma products before 1990 resulted in extraordinary prevalence rates of human immunodeficiency virus (HIV) and hepatitis B and C viruses (HBV, HCV). In the Second Multicentre Haemophilia Cohort Study (MHCS‐II) during 2001–03, 30% of HCV‐seropositive survivors had HIV and 4.6% were HBV carriers. Highly active antiretroviral therapy (HAART) radically altered the consequences of HIV/HCV coinfection. Whereas opportunistic infections predominated previously, current major complications are liver failure and bleeding (exacerbated by decreased clotting factor synthesis, hypersplenic thrombocytopenia, and oesophageal varices). Most HIV‐positives in MHCS‐II were HIV RNA‐negative and had > 200 CD4+ cells µL−1, but only 59% were on HAART. With HIV, especially after 41 years of age, liver disease was apparent (jaundice in 5%, ascites 7%, hepatomegaly 9%, splenomegaly 19%). HAART increases survival but may contribute to various comorbidities. Without HIV, sustained HCV clearance is obtained in > 50% with combined pegylated interferons plus ribavirin, but data in haemophilic populations, especially with HIV, are limited. In MHCS‐II, HCV RNA negativity was 41% following standard interferon plus ribavirin; among interferon‐naïve participants (implying spontaneous HCV clearance), HCV RNA negativity was 12% with and 25% without HIV. Without HIV, spontaneous HCV clearance was much more likely with early age at infection and particularly with recent birth (late 1970s or early 1980s) but not with bleeding propensity or its treatment. Most (72%) participants had received no anti‐HCV therapy. Hepatic and haematological conditions are likely to increase during the coming years unless most adult haemophiliacs are successfully treated for HIV, HCV or both.

Management of von Willebrand disease: a survey on current clinical practice from the haemophilia centres of North America.

The optimal treatment of patients with von Willebrand’s disease (vWD) remains to be defined. Moreover, it has not been firmly established which, if any, commonly measured parameters of von Willebrand factor (vWF) protein in the plasma are useful in guiding treatment. To better understand what guidelines physicians follow in the management of vWD, we surveyed 194 North American physicians who are members of the Hemophilia Research Society. Ninety‐nine per cent of responding physicians depend on factor VIII (FVIII):C, vWF:RCo activity and vWF:AG to diagnose vWD, while only 49% use the bleeding time. The minimal goals of treatment for patients undergoing major surgery/trauma or central nervous system haemorrhage were FVIII:C and vWF:RCo activity greater than 80% while levels of more than 50% for minor surgery and dental extractions were considered adequate. Treatment of vWD was based on the type of vWD with type 1 patients being treated most often with desmopressin acetate (DDAVP) alone, types 2A and 2B patients with a combination of DDAVP and a vWF‐containing FVIII product, type 3 patients with vWF‐containing concentrate. Viral infections, including human immunodeficiency virus, hepatitis A, B and C viruses, and parvovirus have been seen in vWD and the efficacy of viral attenuation processes is a major criterion for the selection of treatment by physicians. Based on this survey, prospective studies need to be designed to address the clinical efficacy, safety and predictive value of laboratory monitoring of patients with vWD.

Crucial role for the VWF A1 domain in binding to type IV collagen

Von Willebrand factor (VWF) contains binding sites for platelets and for vascular collagens to facilitate clot formation at sites of injury. Although previous work has shown that VWF can bind type IV collagen (collagen 4), little characterization of this interaction has been performed. We examined the binding of VWF to collagen 4 in vitro and extended this characterization to a murine model of defective VWF-collagen 4 interactions. The interactions of VWF and collagen 4 were further studied using plasma samples from a large study of both healthy controls and subjects with different types of von Willebrand disease (VWD). Our results show that collagen 4 appears to bind VWF exclusively via the VWF A1 domain, and that specific sequence variations identified through VWF patient samples and through site-directed mutagenesis in the VWF A1 domain can decrease or abrogate this interaction. In addition, VWF-dependent platelet binding to collagen 4 under flow conditions requires an intact VWF A1 domain. We observed that decreased binding to collagen 4 was associated with select VWF A1 domain sequence variations in type 1 and type 2M VWD. This suggests an additional mechanism through which VWF variants may alter hemostasis.

Surveillance of female patients with inherited bleeding disorders in United States Haemophilia Treatment Centres

Summary.  Inherited bleeding disorders are especially problematic for affected girls and women due to the monthly occurrence of menstrual periods and the effects on reproductive health. Although heavy menstrual bleeding (HMB) is the most common manifestation, females with inherited bleeding disorders (FBD) experience other bleeding symptoms throughout the lifespan that can lead to increased morbidity and impairment of daily activities. The purpose of this article is to describe the utility of a female‐focused surveillance effort [female Universal Data Collection (UDC) project] in the United States Haemophilia Treatment Centres (HTCs) and to describe the baseline frequency and spectrum of diagnoses and outcomes. All FBD aged 2 years and older receiving care at selected HTCs were eligible for enrolment. Demographic data, diagnoses and historical data regarding bleeding symptoms, treatments, gynaecological abnormalities and obstetrical outcomes were analysed. Analyses represent data collected from 2009 to 2010. The most frequent diagnoses were type 1 von Willebrand’s disease (VWD) (195/319; 61.1%), VWD type unknown (49/319; 15.4%) and factor VIII deficiency (40/319; 12.5%). HMB was the most common bleeding symptom (198/253; 78.3%); however, 157 (49.2%) participants reported greater than four symptoms. Oral contraceptives were used most frequently to treat HMB (90/165; 54.5%), followed by desmopressin [1‐8 deamino‐D‐arginine vasopressin (DDAVP)] (56/165; 33.9%). Various pregnancy and childbirth complications were reported, including bleeding during miscarriage (33/43; 76.7%) and postpartum haemorrhage (PPH) (41/109; 37.6%). FBD experience multiple bleeding symptoms and obstetrical‐gynaecological morbidity. The female UDC is the first prospective, longitudinal surveillance in the US focusing on FBD and has the potential to further identify complications and reduce adverse outcomes in this population.

Prevalence of conditions associated with human immunodeficiency and hepatits virus infections among persons with haemophilia, 2001-2003

Summary.  Before the mid‐1980s, haemophilia often was unknowingly treated with contaminated plasma products, resulting in high rates of human immunodeficiency virus (HIV‐1), hepatitis C virus (HCV) and hepatitis B virus (HBV) infections. To estimate the impact of these infections, a new cohort was established. All HCV‐seropositive patients, age 13–88 years, at 52 comprehensive haemophilia treatment centres were eligible. Cross‐sectional data collected during April 2001 to January 2004 (median June 2002) were analysed. Plasma HIV‐1 and HCV RNA were quantified by polymerase chain reaction. Highly active antiretroviral therapy (HAART) was defined as use of at least three recommended medications. Among 2069 participants, 620 (30%) had HIV‐1. Of 1955 with known HBV status, 814 (42%) had resolved HBV and 90 (4.6%) were HBV carriers. Although 80% of the HIV‐1‐positive participants had ≥200 CD4+ cells μL−1, only 59% were on HAART. HIV‐1 RNA was undetectable in 23% of those not taking antiretroviral medications. Most (72%) participants had received no anti‐HCV therapy. HCV RNA was detected less frequently (59%) among participants treated with standard interferon plus ribavirin (P = 0.0001) and more frequently among HIV‐1‐positive than HIV‐1‐negative participants (85% vs. 70%, P < 0.0001). HIV‐1‐positive participants were more likely to have pancytopenia and subclinical hepatic abnormalities, as well as persistent jaundice, hepatomegaly, splenomegaly and ascites. HAART recipients did not differ from HIV‐negative participants in the prevalence of ascites. The clinical abnormalities were more prevalent with older age but were not confounded by HBV status or self‐reported alcohol consumption. Eleven participants presented with or previously had hepatocellular carcinoma or non‐Hodgkin lymphoma. Although prospective analysis is needed, our data reveal the scale of hepatic and haematological disease that is likely to manifest in the adult haemophilic population during the coming years unless most of them are successfully treated for HIV‐1, HCV or both.

Experience of Advate rAHF-PFM in previously untreated patients and minimally treated patients with haemophilia A

Summary We report a prospective trial of 55 previously untreated patients (PUPs) and minimally treated patients (MTPs) with severe/moderately severe haemophilia A (baseline factor VIII [FVIII] ≤2%) treated with a single FVIII replacement product. It was the objective of this study to evaluate the immunogenicity, efficacy, and safety of rAHF-PFM (Advate ® ). Ondemand or prophylactic treatment regimens were determined at the discretion of the investigator. rAHF-PFM was also permitted for perioperative management. There were 633 bleeding episodes (BEs), including 517 treated, and 466 rated for efficacy. Haemostatic efficacy was considered excellent/good in 93% of 466 rated treatments. Of 517 treated BEs, 463/517 (90%) were managed with one (356/517 [69%]) or two infusions (107/517 [21%]). There were 27 surgeries. Intraoperative (n=22) and postoperative (n=25) haemostatic efficacies were considered excellent or good in 100% of rated surgeries. Related serious adverse events (SAEs) were inhibitor development in 16/55 (29.1%) subjects who received at least one infusion of rAHF-PFM. Nonserious, related adverse events (AEs) were few in number (14 in eight subjects). The odds ratio (OR [95% Confidence Interval, CI]) of developing inhibitors was significantly higher in subjects with a family history of inhibitor (4.95 [1.29–19.06]), non-Caucasian ethnicity (4.18, [1.18–14.82]), and intensive treatment at high dose (4.5 [1.05–19.25]) within ≤20 exposure days (EDs). In conclusion, rAHF-PFM was safe and effective for the management and perioperative coverage of PUPs/MTPs with severe/moderately severe haemophilia A. This report supports previous findings from studies in which family history of inhibitor, non-Caucasian ethnicity, and high intensity treatment were associated with high risk of inhibitor development.

No increase in bleeding identified in type 1 VWD subjects with D1472H sequence variation

The diagnosis of von Willebrand disease (VWD) is complicated by issues with current laboratory testing, particularly the ristocetin cofactor activity assay (VWF:RCo). We have recently reported a sequence variation in the von Willebrand factor (VWF) A1 domain, p.D1472H (D1472H), associated with a decrease in the VWF:RCo/VWF antigen (VWF:Ag) ratio but not associated with bleeding in healthy control subjects. This report expands the previous study to include subjects with symptoms leading to the diagnosis of type 1 VWD. Type 1 VWD subjects with D1472H had a significant decrease in the VWF:RCo/VWF:Ag ratio compared with those without D1472H, similar to the findings in the healthy control population. No increase in bleeding score was observed, however, for VWD subjects with D1472H compared with those without D1472H. These results suggest that the presence of the D1472H sequence variation is not associated with a significant increase in bleeding symptoms, even in type 1 VWD subjects.

Association of overweight and obesity with the use of self and home-based infusion therapy among haemophilic men

An elevated body mass index (BMI) may make venipuncture more difficult, potentially impacting the use of home infusion (HI) and self‐infusion (SI). We sought to determine whether above‐normal BMI is associated with decreased use of HI treatment and SI of clotting factor concentrate among haemophilic persons. We analysed data from 10 814 male patients with haemophilia A and B (45% with severe disease) aged 6–79 years enrolled in the Centers for Disease Control and Prevention Universal Data Collection surveillance project between 1998 and 2008. Associations between the use of HI and SI and BMI were evaluated using logistic regression. Fifty per cent of haemophilic men were overweight or obese, similar to rates reported among the general US population by the 2007–2008 National Health and Nutrition Examination Survey [Flegal, KM et al., JAMA 2010;303:235–241;]. Twenty per cent of children and 22% of teens were obese, as were 28% of adults [Ogden, CL et al., JAMA 2010;303:235, 242]. Overall, 70% of the study sample used HI; 44% of those who used HI also used SI. Overweight and obese men were each less likely to use HI than those of normal weight [odds ratio (OR) 0.8; 95% confidence interval (CI) 0.7–1.0 and OR 0.7; 95% CI 0.6–0.8 respectively]. Obese teens and adult men were also less likely to practice SI than teens and adults of normal weight (OR 0.8; 95% CI 0.7–0.9 for each). We conclude that overweight and obese haemophilic men are less likely to use HI and obese men are less likely to use SI than their normal‐weight counterparts.

Validation study of the composite score to identify von Willebrand disease in children

Background:The diagnosis of type 1 von Willebrand disease (VWD) presents a diagnostic challenge in children. In fact, 25% or more of children with VWD may be diagnosed only after they experience postoperative bleeding. We previously described a 4-variable composite score that has 92.5% sensitivity and 95% specificity for diagnosing VWD in children with known VWD when 2 of 4 criteria are positive: (1) Tosetto bleeding score ≥1; (2) family history of VWD; (3) personal history of iron deficiency anemia; and/or (4) positive James early bleeding score. The purpose of this study was to prospectively validate a composite score of ≥2 for identifying children with VWD. Procedure:Children without a previously diagnosed bleeding disorder presenting for hematology evaluation were enrolled. Sensitivity, specificity, positive, and negative predictive value of the composite score was determined. Results:A total of 193 subjects were enrolled from 12 participating centers were included in the analysis. Forty-seven children had type 1 VWD, including 11 with von Willebrand Ristocetin Cofactor (VWF):RCo <30 IU/dL, 14 subjects with a VWF:RCo 30 to 39 IU/dL, and 22 with a VWF:RCo 40 to 49 IU/dL. Including all 4 variables, a composite score of ≥2 had a sensitivity of 63.6% to 76.0%, specificity of 33.5% to 35.1%, negative predictive value of 76.9% to 93.8%, and positive predictive value of 5.5% to 25%. Conclusions:The negative predictive value of the composite score was robust, especially at lower VWF:RCo suggesting that VWD testing could be eliminated in nearly a third of children referred for VWD testing.