Immune Tolerance Induction In Haemophilia Research Articles

Liver-specific Factor VIII gene therapy for immune tolerance induction in hemophilia

Liver-specific Factor VIII gene therapy for immune tolerance induction in hemophilia

Effect of B-Cell Depletion On Inhibitor Antibody Formation and Immune Tolerance Induction to Human Factor VIII in Hemophilia A Mice.

Abstract 2137Poster Board II-114B-cell depletion using anti-human CD20 monoclonal antibodies has been reported to be effective in autoimmunity and in temporarily eliminating inhibitory antibodies in hemophilia A patients. In the current study, we examined the effect of anti-murine CD20 (αCD20) depletion on the immune response to factor VIII (FVIII) and its influence on an immune tolerance induction (ITI) protocol. Previous studies have shown that IgG subclasses of anti-murine CD20 monoclonal antibody (αCD20) have differential effects on B-cell depletion in the mouse. Thus, IgG1 αCD20 selectively depletes follicular B cells, while sparing marginal zone (MZ) B cells. Combined with evidence that MZ B cells may be tolerogenic antigen-presenting cells, we tested the hypothesis that follicular B-cell depletion using αCD20 IgG1 might favor tolerance induction to human FVIII. Hemophilic (FVIII knockout) mice were primed with physiological doses of recombinant human FVIII by weekly IV injection, followed by αCD20 IgG1 or control IgG1 treatment. Ten days after the αCD20 treatment, the mice were treated with daily high dose (2μg) FVIII IV injections to model ITI in hemophilia A patients. After 4 weekly injections, 70% of the mice developed titers of anti-FVIII IgG as high as 1:12,800. Unlike whole B-cell depletion, subsequent follicular B-cell depletion did not significantly decrease the anti-FVIII IgG titer, compared with mice receiving control IgG1. Repeated high dose FVIII injections to mimic ITI significantly increased the anti-FVIII IgG titer in both groups. However, in the mice that received αCD20 IgG1 treatment, the increase of anti-FVIII IgG levels were significantly lower than that in control IgG1 treated mice. In conclusion, we found that follicular B-cell depletion by αCD20 IgG1 antibody in hemophilia A mice did not switch the immune response to tolerance, but it diminished the immunogenicity of human FVIII in vivo in hemophilic mice. (Supported by NIH R01 HL061883) Disclosures:No relevant conflicts of interest to declare.

The use of factor VIII/von Willebrand factor concentrate for immune tolerance induction in haemophilia A patients with high‐titre inhibitors: association of clinical outcome with inhibitor epitope profile

A retrospective chart review of 11 subjects with severe haemophilia A and high-titre inhibitors who received a von Willebrand factor-containing FVIII concentrate (VWF/FVIII) for immune tolerance induction (ITI) was accompanied by B cell inhibitor epitope mapping during 10/11 treatment courses. ITI was successful or partially successful in all seven subjects who received VWF/FVIII for initial ITI, and failed in all four subjects whose ITI with this product was initiated following treatment failure using recombinant factor VIII. Variables including age at inhibitor development and age at ITI initiation, interval between inhibitor detection and ITI initiation, titre at start of ITI, and peak historical titres prior to and during ITI were not statistically significant outcome predictors in this cohort. However, the B cell epitope specificity in all four successful and in one of two partially successful ITI subjects for whom information was available included the C2 and excluded the A2 domains. Conversely, FVIII B cell epitopes in one partially successful ITI and in all three failed ITI subjects for whom data were available mapped to both the C2 and the A2 domains. The FVIII B cell epitope profile was associated with ITI outcome in this VWF/FVIII-treated cohort. Its role in predicting ITI outcome and guiding choice of FVIII product for ITI requires further study.

Recent Developments in Immune Tolerance Induction in Haemophilia A

Recent Developments in Immune Tolerance Induction in Haemophilia A

Immune tolerance: critical issues of factor dose, purity and treatment complications

The current practice of immune tolerance induction (ITI) therapy has been largely influenced by the results of small institutional studies and three large registries. However, many questions remain. Successful outcome predictors for ITI in haemophilia A have been suggested by the analyses of two of these registries. Among these predictors, factor VIII (FVIII) dose/dosing regimen remains a controversial outcome parameter, demonstrating a strong direct relationship to ITI success in the international registry and a weaker inverse relationship in the North American registry. There is an international multicentre prospective randomized trial underway to further study the role of FVIII dose in successful ITI induction in a good risk haemophilia A inhibitor patient cohort. FVIII purity also remains an unproved ITI outcome predictor. Institutional experience with von-Willebrand-factor-containing products has suggested its therapeutic advantage in both inhibitor development and eradication. The International ITI Study, although not designed to answer this particular question, may be able to determine an impact on outcome depending on the final distribution of investigator choice of product among the study subjects. Much less is known about the influence of factor IX (FIX) dose and purity on ITI success in haemophilia B. Importantly, nephrotic syndrome has been a major determinant of ITI failure in FIX inhibitor patients, particularly those with the allergic phenotype. Unfortunately, large prospective randomized trials in this group will not be feasible. Rather, we will have to rely on prospectively collected registry data to build our knowledge base of inhibitors and ITI in haemophilia B.

Immune tolerance induction in hemophilia A: a review.

In this article, a comparative analysis of the data stemming from the studies conducted in the field of immune tolerance treatment (ITT) of hemophilia A was attempted. Comparisons are difficult because previous studies differ in many respects, including the dosage of factor (F) VIII, the number of FVIII administrations per day, the association with immunosuppressive drugs (prednisone, cyclophosphamide), and, most importantly, the definition of success in terms of the reacquisition of tolerance. However, a number of variables consistently influenced outcome: the inhibitor titer, either the maximum one or the one assayed before immune tolerance (IT) start and age. As to the FVIII dose, results are contrasting, even though the overall impression is that high dosages are associated with higher success rates. Treatment duration analyses appear to be fairly consistent in all the studies, with 1 year as the crucial time period useful in predicting outcome. Preliminary data suggest that concentrates containing von Willebrand factor may increase the success rate and allow patients refractory to IT procedures carried out with ultrapure or recombinant concentrates to become tolerant in the end. These data need to be formally confirmed in trials that compare the different brands. In the studies published so far, a common language and widely accepted definitions of the variables have emerged, which are important in setting up the controlled trials and improving the comparison among published data.

Immune tolerance induction in haemophilia A patients with high‐responding inhibitors to factor VIII: experience at a single institution

Inhibitor antibodies to transfused factor VIII pose significant challenges in the management of haemophilia A patients. The main concern is the inefficacy of replacement therapy in patients with high‐titre antibodies, who have a shorter life‐span and a greater morbidity compared to subjects without inhibitors. The ultimate goal in treating these patients is to eliminate the inhibitor antibody entirely, allowing the recommencement of specific replacement therapy. The results of an immune tolerance regimen based on pharmacokinetic parameters are reported here. In 12 high‐responder haemophilia A patients immune tolerance induction (ITI) was attempted with daily administration of factor VIII concentrates of very high purity, either plasma‐derived or produced by recombinant‐DNA technology. Patients were given 100 IU kg–1 day–1 until the inhibitor was shown to be absent by at least two negative assays 1 month apart, with normal recovery of infused factor VIII and normal half‐life (> 6 h), as assessed after a 3‐day washout period. After the patient was judged to be inhibitor‐free, immune tolerance treatment was continued with unmodified factor VIII doses for 2 months. Doses were thereafter gradually reduced and finally, regular prophylaxis by administration of 25 IU kg–1 three times weekly was instituted. Immune tolerance was achieved in 10 of the 12 patients (including six of seven with long‐standing inhibitors) within a median time of 8 months. Outcome of immune tolerance was not influenced by age at start of ITI nor by the interval between inhibitor development and ITI. The success rate and the inhibitor disappearance time of our immune tolerance regimen, utilizing high‐purity factor VIII, agrees with those reported by other investigators.

Immune tolerance induction in haemophilia A patients with high-responding inhibitors to factor VIII: experience at a single institution.

Inhibitor antibodies to transfused factor VIII pose significant challenges in the management of haemophilia A patients. The main concern is the inefficacy of replacement therapy in patients with high-titre antibodies, who have a shorter life-span and a greater morbidity compared to subjects without inhibitors. The ultimate goal in treating these patients is to eliminate the inhibitor antibody entirely, allowing the recommencement of specific replacement therapy. The results of an immune tolerance regimen based on pharmacokinetic parameters are reported here. In 12 high-responder haemophilia A patients immune tolerance induction (ITI) was attempted with daily administration of factor VIII concentrates of very high purity, either plasma-derived or produced by recombinant-DNA technology. Patients were given 100 IU kg(-1) day(-1) until the inhibitor was shown to be absent by at least two negative assays 1 month apart, with normal recovery of infused factor VIII and normal half-life (> 6 h), as assessed after a 3-day washout period. After the patient was judged to be inhibitor-free, immune tolerance treatment was continued with unmodified factor VIII doses for 2 months. Doses were thereafter gradually reduced and finally, regular prophylaxis by administration of 25 IU kg(-1) three times weekly was instituted. Immune tolerance was achieved in 10 of the 12 patients (including six of seven with long-standing inhibitors) within a median time of 8 months. Outcome of immune tolerance was not influenced by age at start of ITI nor by the interval between inhibitor development and ITI. The success rate and the inhibitor disappearance time of our immune tolerance regimen, utilizing high-purity factor VIII, agrees with those reported by other investigators.

Factor IX Antibody and Immune Tolerance

Prevalence of FIX inhibitor is ten times lower than factor VIII inhibitor. FIX inhibitor patients pose major challenges for treatment because of the simultaneous occurrence of severe allergy to FIX at the time of inhibitor development. Immune tolerance induction in haemophilia B inhibitor patients with allergy to FIX is complicated due to the development of nephrotic syndrome. Moreover, response to ITI usually is poor.

Low-dose immune tolerance induction in hemophilia A patients with inhibitors

In patients with hemophilia A and inhibitory alloantibodies against factor VIII, various dosage schedules are used to obtain immune tolerance. In this study, we have evaluated the results of 13 years of low-dose immune tolerance induction and factors that are predictive of a positive result. The effect of immune tolerance induction in relation to age at inhibitor development, number of exposure days, age at start of therapy, maximum inhibitor titer, factor VIII products involved, and virologic status were determined. We evaluated 24 patients with severe hemophilia A and inhibitors who were treated with regular infusions with low-dose (25 U/kg every other day) factor VIII to obtain immune tolerance. In 21 of 24 patients (87%), immune tolerance induction was successful. The response time was determined by two factors: the highest inhibitor level and the age at inhibitor development. In patients with maximum inhibitor levels of less than 40 Bethesda units (BU)/mL, immune tolerance was obtained sooner than in patients with inhibitor levels exceeding 40 BU/mL (P = .005). Patients in whom an inhibitor developed before the age of 2.5 years also tended to have a quick immune response (P = .014). Immune tolerance with low-dose factor VIII is often successful in hemophilia A patients with inhibitors. Young children and patients with maximum inhibitors of less than 40 BU/mL show a relatively rapid response.

Low-Dose Immune Tolerance Induction in Hemophilia A Patients With Inhibitors

In patients with hemophilia A and inhibitory alloantibodies against factor VIII, various dosage schedules are used to obtain immune tolerance. In this study, we have evaluated the results of 13 years of low-dose immune tolerance induction and factors that are predictive of a positive result. The effect of immune tolerance induction in relation to age at inhibitor development, number of exposure days, age at start of therapy, maximum inhibitor titer, factor VIII products involved, and virologic status were determined. We evaluated 24 patients with severe hemophilia A and inhibitors who were treated with regular infusions with low-dose (25 U/kg every other day) factor VIII to obtain immune tolerance. In 21 of 24 patients (87%), immune tolerance induction was successful. The response time was determined by two factors: the highest inhibitor level and the age at inhibitor development. In patients with maximum inhibitor levels of less than 40 Bethesda units (BU)/mL, immune tolerance was obtained sooner than in patients with inhibitor levels exceeding 40 BU/mL (P = .005). Patients in whom an inhibitor developed before the age of 2.5 years also tended to have a quick immune response (P = .014). Immune tolerance with low-dose factor VIII is often successful in hemophilia A patients with inhibitors. Young children and patients with maximum inhibitors of less than 40 BU/mL show a relatively rapid response.