Analysis of cytokine genes polymorphism as markers for inhibitor development in haemophilia A

Immune gene polymorphisms associated with poor response to platelet transfusion and recombinant factor VII administration in Glanzmann thrombasthenia

INTRODUCTION

Poor response to platelet and recombinant factor VII administration is a major problem in patients with Glanzmann Thrombasthenia (GT). The risk factors associated with poor response to treatment in these patients are unknown. Some genetic variations of cytokines may contribute to therapy resistance.

AIMS

We evaluated, for the first time, whether genetic polymorphisms on cytokine genes are related to poor treatment response in GT patients.

METHODS

We enrolled 30 patients with GT (15 resistant and 15 non-resistant) and 100 healthy controls. Gene polymorphisms of IL-10 and TNF-α were analysed using TaqMan Realtime PCR, and IL-1, IL-1R1 and IL-1RN were investigated with the RFLP method. In-silico analyses were performed to predict the potential impact of these polymorphisms.

RESULTS

In the resistant group, all patients had a variant of the IL-10 gene at the -1082 position (rs1800896), with a GG genotype that was significantly more frequent than the non-resistant group. Analysis between healthy controls and GT patients revealed a probable correlation between rs3783550, rs3783553, rs3917356 and rs2234463 and GT. The In-silico study indicated that TNF-α rs1800629 and IL-10 rs1800896 polymorphisms result in different allelic expressions which may contribute to poor response to therapy.

CONCLUSIONS

These findings suggest that polymorphisms in the IL-10 and IL-1 receptor antagonist genes may play a role in poor therapy response in GT patients. In addition, some polymorphisms in IL-1α, IL1-β, IL-1R1 and IL-R antagonists might be involved in the GT progression.

Immunogenicity of Therapeutic Biological Modalities - Lessons from Hemophilia A Therapies

The introduction and development of biologics such as therapeutic proteins, gene-, and cell-based therapy have revolutionized the scope of treatment for many diseases. However, a significant portion of the patients develop unwanted immune reactions against these novel biological modalities, referred to as immunogenicity, and no longer benefit from the treatments. In the current review, using Hemophilia A (HA) therapy as an example, we will discuss the immunogenicity issue of multiple biological modalities. Currently, the number of therapeutic modalities that are approved or recently explored to treat HA, a hereditary bleeding disorder, is increasing rapidly. These include, but are not limited to, recombinant factor VIII proteins, PEGylated FVIII, FVIII Fc fusion protein, bispecific monoclonal antibodies, gene replacement therapy, gene editing therapy, and cell-based therapy. They offer the patients a broader range of more advanced and effective treatment options, yet immunogenicity remains the most critical complication in the management of this disorder. Recent advances in strategies to manage and mitigate immunogenicity will also be reviewed.

Can T-cell and B-cell excision circles predict development of inhibitors in pediatric hemophilia A?

BACKGROUND

Hemophilia A (HA) therapy requires intravenous replacement infusions of factor (F) VIII concentrate. Inhibitors are high-affinity immunoglobulin G that are directed against FVIII and thereby render replacement therapy ineffective. This complication has significant prognostic implications. We aimed to examine the immune system involvement in inhibitor formation specifically T-cell excision circles (TRECs) and B-cell excision circles (KRECs), markers of new T and B cells, respectively, and examine them as surrogate markers for inhibitor formation.

METHODS

Blood samples were collected from 35 children with severe HA. Children were divided into two groups: with FVIII inhibitors and without FVIII inhibitors. TRECs and KRECs were measured in peripheral blood.

RESULTS

A total of 11 patients with inhibitors and 24 without were evaluated. Children with inhibitors had higher levels of TRECs however not statistically significant (p = 0.085). CjKREC levels were higher in the inhibitor patients (p = 0.003). Moreover, the sj/cjKREC ratio was lower in the inhibitor patients (p = 0.015).

CONCLUSIONS

Our findings may add to the notion that inhibitor formation is attributed to humoral immunity due to peripheral B-cell expansion and loss of peripheral tolerance. Improved knowledge regarding the involvement of the immune system in the formation of FVIII inhibitors will enable better therapy tailoring in the era of non-replacement therapies.

IMPACT

The etiology of FVIII inhibitor formation is multifactorial, in which the immune system plays a pivotal role. Our findings may add to the notion that inhibitor formation is attributed to humoral immunity due to peripheral B-cell expansion and production of antibodies against FVIII. Improved knowledge regarding the involvement of the immune system in the development of FVIII inhibitors will enable the identification of patients prone to inhibitor development and better therapy tailoring in the new era of non-replacement therapies.

Genome-Wide Association Study and Gene-Based Analysis of Participants With Hemophilia A and Inhibitors in the My Life, Our Future Research Repository

Introduction

Up to 30% of individuals with hemophilia A develop inhibitors to replacement factor VIII (FVIII), rendering the treatment ineffective. The underlying mechanism of inhibitor development remains poorly understood. The My Life, Our Future Research Repository (MLOF RR) has gathered F8 and F9 mutational information, phenotypic data, and biological material from over 11,000 participants with hemophilia A (HA) and B as well as carriers enrolled across US hemophilia treatment centers, including over 5,000 whole-genome sequences. Identifying genes associated with inhibitors may contribute to our understanding of why certain patients develop those neutralizing antibodies.

Aim and Methods

Here, we performed a genome-wide association study and gene-based analyses to identify genes associated with inhibitors in participants with HA from the MLOF RR.

Results

We identify a genome-wide significant association within the human leukocyte antigen (HLA) locus in participants with HA with F8 intronic inversions. HLA typing revealed independent associations with the HLA alleles major histocompatibility complex, class II, DR beta 1 (HLA DRB1*15:01) and major histocompatibility complex, class II, DQ beta 1 (DQB1*03:03). Variant aggregation tests further identified low-frequency variants within GRID2IP (glutamate receptor, ionotropic, delta 2 [GRID2] interacting protein 1) significantly associated with inhibitors.

Conclusion

Overall, our study confirms the association of DRB1*15:01 with FVIII inhibitors and identifies a novel association of DQB1*03:03 in individuals with HA carrying intronic inversions of F8. In addition, our results implicate GRID2IP, encoding GRID2-interacting protein, with the development of inhibitors, and suggest an unrecognized role of this gene in autoimmunity.

Relationship Between Single-Nucleotide Polymorphisms of Tumor Necrosis Factor Alpha, Interleukin-10, Factor II and Factor V with Risk of Inhibitor Development in Patients with Severe Hemophilia A

BACKGROUND

About one-fourth of patients with hemophilia A (HA) develop alloantibodies against factor (F) VIII, as the main treatment challenge. Here, we assessed the relationship between interleukin-10 (IL-10), tumor necrosis factor alpha (TNF-α), FII and FV polymorphisms and risk of inhibitor formation in patients with severe HA.

METHODS

We divided 39 patients with severe HA in two groups of case (n: 19) and control (n: 20). Genotyping was performed by multiplex amplification tetra arms refractory mutation systempolymerase chain reaction (ARMS-PCR) and PCR-restriction fragment-length polymorphism (PCR-RFLP).

RESULTS

TNFα rs1800629 G>A polymorphism decreased the risk of inhibitor development in codominant and dominant inheritance pattern. Moreover, TNFα rs1800629 A allele, decrease the risk of inhibitor formation, while IL10 rs1800896 A>G, FV rs6025 G>A, and FII rs1799963 G>A polymorphisms were not associated with risk of inhibitor development.

CONCLUSION

It seems that TNFα rs1800629 G>A polymorphism decreased the risk of inhibitor formation in Iranian patients with HA.

Anti-Drug Antibodies: Emerging Approaches to Predict, Reduce or Reverse Biotherapeutic Immunogenicity

The development of anti-drug antibodies (ADAs) following administration of biotherapeutics to patients is a vexing problem that is attracting increasing attention from pharmaceutical and biotechnology companies. This serious clinical problem is also spawning creative research into novel approaches to predict, avoid, and in some cases even reverse such deleterious immune responses. CD4⁺ T cells are essential players in the development of most ADAs, while memory B-cell and long-lived plasma cells amplify and maintain these responses. This review summarizes methods to predict and experimentally identify T-cell and B-cell epitopes in therapeutic proteins, with a particular focus on blood coagulation factor VIII (FVIII), whose immunogenicity is clinically significant and is the subject of intensive current research. Methods to phenotype ADA responses in humans are described, including T-cell stimulation assays, and both established and novel approaches to determine the titers, epitopes and isotypes of the ADAs themselves. Although rational protein engineering can reduce the immunogenicity of many biotherapeutics, complementary, novel approaches to induce specific tolerance, especially during initial exposures, are expected to play significant roles in future efforts to reduce or reverse these unwanted immune responses.

A Retrospective Study of the Cytokine Profile Changes in Mice with FVIII Inhibitor Development After Adeno-Associated Virus-Mediated Gene Therapy in a Hemophilia A Mouse Model

The development of inhibitory autoantibodies to the infused clotting factor VIII (FVIII) is a major complication for severe hemophilia A management. Novel therapy options for hemophilia have significantly progressed in the last decade, and a gene therapy cure for hemophilia is becoming a reality. However, mechanistic studies of FVIII autoantibodies (FVIII inhibitors) have lagged behind and remain a challenge for both protein replacement and gene therapy. FVIII inhibitor formation is assumed to be a classical T cell-dependent immune response in which cytokines/chemokines play an important role. The study of cytokine profile changes during FVIII inhibitor development may be helpful to understand the mechanism of inhibitor development and to explore potential novel approaches that will minimize the risk. After FVIII^-/- mice were treated with intravenous administration of an adeno-associated virus 8 vector encoding human FVIII, FVIII expression peaked at week 2 (W2), and FVIII inhibitor was thoroughly developed at week 8 (W8). W8 plasma that showed positive FVIII inhibitor, and W2 samples with negative FVIII inhibitor (anti-FVIII[+]), were subjected to multiplex cytokines measurement. W8 and W2 samples were both negative for FVIII inhibitor (anti-FVIII[-]) as the control. In comparison to mice in the anti-FVIII(-) group, mice in the anti-FVIII(+) group exhibited significantly elevated pro-inflammatory cytokines of interleukin (IL)-1, IL-6, IL-12p40, monocyte chemoattractant protein-1, macrophage inflammatory protein (MIP)-1, MIP-2, and tumor necrosis factor alpha (TNF-α), especially at higher titers. The anti-inflammatory cytokine of transforming growth factor beta (TGF-β) was decreased at W2 in both groups. Multivariate analysis of the risk factors for FVIII inhibitor development showed peak FVIII activity at W2. IL-6 and TNF-α at W8 were positively correlated with inhibitor formation, and negatively correlated with the age starting gene therapy. Collectively, the elevated monocyte derived pro-inflammatory cytokines/chemokines, together with the decreased anti-inflammatory cytokine of TGF-β at an early time point, may contribute to the persistent inflammatory environment in favor of an immune response toward FVIII inhibitor development.

Interleukin-10 haplotypes are not associated with acute cerebral ischemia or high-risk transcranial Doppler in a newborn cohort of 395 children with sickle cell anemia

Background

The etiology of stroke, a severe complication of sickle cell anemia, involves inflammatory processes. However, the pathogenetic mechanisms are unknown. The aim of this study was to evaluate the influence of interleukin-10 polymorphisms and haplotypes on the risk of acute cerebral ischemia and high-risk transcranial Doppler in 395 children with sickle cell anemia from the state of Minas Gerais, Brazil.

Methods

Interleukin-10 haplotypes were determined by polymerase chain reaction-restriction fragment length polymorphism and sequencing. The outcomes studied were acute cerebral ischemia and high-risk transcranial Doppler. Clinical data were retrieved from the children's records.

Results

There was no statistically significant difference in the frequencies of polymorphisms and haplotypes between children with and without acute cerebral ischemia or children with or without high-risk transcranial Doppler. These data are consistent with a previous report that showed an absence of association between interleukin-10 plasma levels and high-risk transcranial Doppler velocity in children with sickle cell anemia.

Conclusion

Interleukin-10 haplotypes were not associated with the risk of acute cerebral ischemia or high-risk transcranial Doppler velocity in children with sickle cell anemia from the state of Minas Gerais, Brazil.

Genetic risk factors for inhibitors in haemophilia A

The current most serious side effect of haemophilia treatment is inhibitor development. Significant progress has been made over the last decades to understand why this complication occurs in some patients and it seems clear that both genetic and non-genetic factors are involved. Several issues however remain to be settled. A review was undertaken to summarise some key findings regarding the current view and available data on genetic markers of potential importance within this area. The causative F8 mutation, together with the HLA class II alleles, plays a pivotal pathophysiological role in inhibitor development. The types of mutation most frequently associated with inhibitors are large deletions, nonsense mutations, inversions, small deletions/insertions without A-runs, splice-site mutations at conserved nucleotides and certain missense mutations. Regarding HLA class II allele, it has been hard to consistently identify risk alleles. Ethnicity has consistently been associated with inhibitor risk, but the causality of this has so far not been resolved. Among immune regulatory molecules, several polymorphic molecules have been suggested to be of importance. Most of these need additional studies and immune system challenges have to be fully evaluated. Inhibitor risk should be further defined, as patients in the future may be offered non-immunogenic treatments.

Violating the theory of single gene-single disorder: inhibitor development in hemophilia

Hemophilia is clinically and genetically heterogeneous blood disorder with several known gene defects accounting for the diversity of disease phenotype and inhibitor production. Although increasing number of causative mutations have been reported, not much is known regarding the root cause of inhibitor development against infused blood clotting factors, which represents a major challenge in the treatment of disease. The variations in the severity and frequency of bleeding in hemophiliacs with same molecular defect, indicates the role of modifier genes in the pathogenesis of disease. Herein, we aim to review and summarise the literature over the past decade, to gain insight into what is critical for the development of inhibitors in hemophilia. Aside from potential mutations in factor VIII and IX, polymorphisms in various genes such as human leukocyte antigen-I (HLA-I), HLA-II, tumor necrosis factor-alpha, interleukin-10 and cytotoxic T-lymphocyte associated antigen-4, also tends to contribute to the development of inhibitors. Violating the theory of single gene-single disorder, new research indicates that inhibitor arise from a complex interplay of multiple genetic, immunological and environmental factors. With the revolutionary advances in whole genome sequencing, we propose a detailed genome wide study to identify the spectrum of genetic markers involved in the development of inhibitors for better diagnostics and therapeutics.

FVIII inhibitors: pathogenesis and avoidance

The pathogenesis of inhibitory antibodies has been the focus of major scientific interest over the last decades, and several studies on underlying immune mechanisms and risk factors for formation of these antibodies have been performed with the aim of improving the ability to both predict and prevent their appearance. It seems clear that the decisive factors for the immune response to the deficient factor are multiple and involve components of both a constitutional and therapy-related nature. A scientific concern and obstacle for research in the area of hemophilia is the relatively small cohorts available for studies and the resulting risk of confounded and biased results. Careful interpretation of data is recommended to avoid treatment decisions based on a weak scientific platform. This review will summarize current concepts of the underlying immunological mechanisms and risk factors for development of inhibitory antibodies in patients with hemophilia A and discuss how these findings may be interpreted and influence our clinical management of patients.

Managing haemophilia for life: 4th Haemophilia Global Summit

The 4th Haemophilia Global Summit was held in Potsdam, Germany, in September 2013 and brought together an international faculty of haemophilia experts and delegates from multidisciplinary backgrounds. The programme was designed by an independent Scientific Steering Committee of haemophilia experts and explored global perspectives in haemophilia care, discussing practical approaches to the optimal management of haemophilia now and in the future. The topics outlined in this supplement were selected by the Scientific Steering Committee for their relevance and potential to influence haemophilia care globally. In this supplement from the meeting, Jan Astermark reviews current understanding of risk factors for the development of inhibitory antibodies and discusses whether this risk can be modulated and minimized. Factors key to the improvement of joint health in people with haemophilia are explored, with Carlo Martinoli and Víctor Jiménez-Yuste discussing the utility of ultrasound for the early detection of haemophilic arthropathy. Other aspects of care necessary for the prevention and management of joint disease in people with haemophilia are outlined by Thomas Hilberg and Sébastian Lobet, who highlight the therapeutic benefits of physiotherapy and sports therapy. Riitta Lassila and Carlo-Federico Perno describe current knowledge surrounding the risk of transmission of infectious agents via clotting factor concentrates. Finally, different types of extended half-life technology are evaluated by Mike Laffan, with a focus on the practicalities and challenges associated with these products.

The IL-10 polarized cytokine pattern in innate and adaptive immunity cells contribute to the development of FVIII inhibitors

BACKGROUND

Hemophilia A (HA) is an X-linked inherited bleeding disorder, resulting from a qualitative or quantitative deficiency of clotting factor VIII (FVIII). Antibodies against FVIII, also called inhibitors, block the procoagulant activity of FVIII; thus, impairing hemostatic activity in patients with HA. The exact mechanism underlying the immunological events behind the development of inhibitors remains unknown. This study aimed to understand immune response to FVIII in patients with HA who were either positive [HAα-FVIII(+)] or negative [HAα-FVIII(-)] for inhibitors.

METHODS

Cytokine profiles [interferon-γ (IFN - γ), tumor necrosis factor-α (TNF-α), interleukin-4 (IL-4), IL-5, and IL-10] of innate and adaptive immune cells present in the peripheral blood of participants were characterized.

RESULTS

Presence of inhibitors was significantly associated with decreased frequencies of TNF-α-positive monocytes and neutrophils, IL-5-positive monocytes, IL-4-positive neutrophils, and increased frequencies of IL-10-positive neutrophils and T cells. T cells from HAα-FVIII(-) patients expressed increased levels of almost all cytokines. In contrast, HAα-FVIII(+) patients showed lower levels of all cytokines in CD4(+) and CD8(+) T cells, except IL-10. B cells from HAα-FVIII(-) patients expressed increased levels of IL-4 while those from HAα-FVIII(+) patients expressed increased levels of IL-10.

CONCLUSIONS

The global cytokine profiles of innate and adaptive immune cells showed an anti-inflammatory/regulatory pattern in HAα-FVIII(+) patients and a mixed pattern, with a bias toward inflammatory cytokine profile, in HAα-FVIII(-) patients. The occurrence of these profiles seems to be associated with presence FVIII inhibitors.

Impact of HLA alleles and cytokine polymorphisms on inhibitors development in children with severe haemophilia A

Human Leucocyte Antigen (HLA) alleles, cytokine polymorphisms and the type of factor VIII (FVIII) gene mutation are among predisposing factors for inhibitors (inh) development in children with severe haemophilia A (HA). The aim was to investigate the correlations among (i) FVIII gene intron-22 inversion, (ii) HLA alleles and haplotypes and (iii) certain cytokine polymorphisms, with the risk for FVIII inhibitors development in 52 Greek severe HA children, exclusively treated with recombinant concentrates. We performed Long-Range PCR for detection of intron-22 inversion and PCR-SSP, PCR-SSO for genotyping of HLA-A, B, C, DRB1, DQB1 alleles and also for cytokine polymorphisms of TNF-α, TGF-β1, IL-10, IL-6 and IFN-γ. Chi-squared test and Fischer's exact test were used for statistical analysis. A total of 28 children had developed inhibitors (Group I), 71.4% high responding, while 24 had not (Group II). No statistically increased intron-22 inversion prevalence was found in Group I compared with Group II (P = 0.5). Comparison of HLA allele frequencies between the two groups showed statistically significant differences in the following genotypes (i) promoting inhibitors development: DRB1*01(P = 0.014), DRB1*01:01(P = 0.011) and DQB1*05:01 (P = 0.005) and (ii) possibly protecting from inhibitors development: DRB1*11 (P = 0.011), DRB1*11:01 (P = 0.031), DQB1*03 (P = 0.004) and DQB1*03:01 (P = 0.014). Analysis of cytokines revealed a higher incidence of inhibitor detection only in homozygotes of the haplotypes ACC and ATA for IL-10 polymorphisms (P = 0.05). There is evidence that HLA alleles and cytokine polymorphisms play an important role in FVIII inh development. On the contrary, no statistically significant results were obtained for intron-22 inversion and its impact on FVIII inhibitors formation.

The polygenic nature of inhibitors in hemophilia A: results from the Hemophilia Inhibitor Genetics Study (HIGS) Combined Cohort

Studies of determinants of development of inhibitory Abs to factor VIII in people with hemophilia A indicate a complex process involving multiple factors. The Hemophilia Inhibitor Genetics Study (HIGS) Combined Cohort was formed to extend our understanding of the genetic background of risk. The study group contains 833 subjects from 3 independent cohorts: brother pairs and singletons with and without a history of inhibitors, as well as 104 brother pairs discordant for inhibitor status. Using an Illumina iSelect platform, 13 331 single-nucleotide polymorphisms from 1081 genes, primarily immune response and immune modifier genes, were typed. Each cohort was analyzed separately with results combined using a meta-analytic technique. After adjustment for potential confounders, 53 single-nucleotide polymorphisms were found to be significant predictors of inhibitor status using the criteria of odds ratios in the same direction in all cohorts or allowing for a 20% interval around an odds ratio = 1 in 1 of the 3 and significant in at least 2. Of the 53 markers, 13 had meta P < .001. Eight of the 53 were significant predictors among the discordant pairs. Results support the complexity of the immune response and encourage further research with the goal of understanding the pathways involved.

Immune regulatory gene polymorphisms as predisposing risk factors for the development of factor VIII inhibitors in Indian severe haemophilia A patients

Development of inhibitors to factor VIII, a serious complication of replacement therapy in haemophilia A patients, leads to increased bleeding, morbidity and mortality. There is no data on the risk factors for inhibitor development in Indian patients with severe haemophilia A. Our aim was to study the role of immune regulatory gene polymorphisms in the development of inhibitors. Fourteen immune regulatory gene polymorphisms (IL1β, IL4, IL10, TNFA and CTLA4) were analysed in 120 patients with severe haemophilia A, i.e. 50 inhibitor positive patients, and 70 inhibitor negative control patients, by PCR-RFLP, DNA sequencing and allele-specific PCRs. The IL10 promoter 'GCC' haplotypes overall (P: 0.002, OR: 3.452, 95% CI: 1.607-7.416), and 'GCC/ATA' (P: 0.011, OR: 3.492, 95% CI: 1.402-8.696) haplotype, associated with high and intermediate IL10 production, respectively, were significantly higher in inhibitor positive patients, whereas the 'non-GCC' haplotypes overall (P: 0.002,OR: 0.290, 95% CI 0.135-0.622) and 'ATA/ATA' haplotype (P: 0.025, OR: 0.278, 95% CI: 0.096-0.802), associated with low IL10 synthesis, were significantly higher among inhibitor negative patients. The TNFA rs1799724 C/T heterozygote prevalence was significantly higher in the inhibitor positive group (P: 0.021, OR: 3.190, 95% CI: 1.273-7.990), whereas the other polymorphisms showed no statistically significant association with the presence of inhibitors. Different immune regulatory gene polymorphisms play a significant role as possible risk factors for the development of inhibitors in severe haemophilia A patients.

A shift towards a T cell cytokine deficiency along with an anti-inflammatory/regulatory microenvironment may enable the synthesis of anti-FVIII inhibitors in haemophilia A patients

Despite the clinical relevance of anti-factor VIII (FVIII) antibodies (anti-FVIII inhibitors) impairing haemostatic activity of haemophilia A (HA) patients, the immunological mechanisms underlying their production are unknown. Aiming to understand more clearly the immune response in patients with [HAα-FVIII(+)] and without [HAα-FVIII(-)] anti-FVIII inhibitors, we have characterized the cytokine pattern of peripheral blood leucocytes, using an in vitro stimulation of whole blood samples with plasma-derived (pFVIII) or recombinant FVIII (rFVIII). The results highlighted decreased levels of tumour necrosis factor (TNF)-α(+) neutrophils with higher interleukin (IL)-5/TNF-α ratio in HAα-FVIII(+). All HA samples displayed decreased levels of IL-10(+) monocytes when compared to the blood donor (BD) samples. HAα-FVIII(+) showed lower levels of TNF-α(+) monocytes and increased IL-10/TNF-α ratio. Analysis of adaptive immunity revealed increased levels of interferon (IFN)-γ(+) , TNF-α(+) and IL-4(+) T-cells, from both CD4(+) and CD8(+) T cells, in HAα-FVIII(-) when compared to BD. Moreover, increased frequency of IL-10(+) B cells and higher levels of α-FVIII IgG1 were observed in HAα-FVIII(-). Basal levels of cytokine(+) B-cells, similar to BD, and higher levels of α-FVIII IgG4 are major features in HAα-FVIII(+). The global cytokine profile demonstrated a major anti-inflammatory/regulatory pattern in HAα-FVIII(+), confirmed by the in vitro stimuli with pFVIII or rFVIII. The polarized anti-inflammatory/regulatory immune response in HAα-FVIII(+) and the mixed pattern with a bias towards an inflammatory cytokine profile, modulated by IL-4 in HAα-FVIII(-), may be the key element to drive the development of distinct subclasses of anti-FVIII antibodies. These finding have implications for the design of safe and effective therapeutic protocols to control inhibitors synthesis in HA patients.