The use of intravenous immunoglobulin in immune tolerance induction in inherited haemophilia A: a single-centre experience and a review of literature

Co-administration of FVIII with IVIG reduces immune response to FVIII in hemophilia A mice

Hemophilia A is an X-linked recessive congenital bleeding disorder. Exogenous infusion of FVIII is the treatment of choice, and the development of immunoglobulins against FVIII (inhibitors) remains the major challenge in clinical management of the disease. Here, we investigated the effect of co-administration of FVIII with intravenous immunoglobulin (IVIG) on the development of inhibitors in previously untreated hemophilia A mice. A group of hemophilia A mice (C57BL/6^FVIII-/-) received weekly injections of recombinant human FVIII (rFVIII) for twelve consecutive weeks while a second group received co-injections of rFVIII + IVIG. An in-house enzyme-linked immunosorbent assay (ELISA) was designed to detect antibodies to rFVIII. Every mouse in the first group developed antibodies to rFVIII. In contrast, mice treated with rFVIII + IVIG showed significantly lower antibody titers. Interestingly, when co-administration of IVIG was discontinued after 12 weeks in some mice (rFVIII continued), these mice experienced an increase in antibody titer. In contrast, mice that continued to receive rFVIII + IVIG retained significantly lower titers. In conclusion, prophylactic rFVIII co-administration with IVIG modulated the immune response to FVIII and resulted in decreased anti-FVIII antibody titer. These findings suggest that co-injection therapy with IVIG could potentially be effective in the management of hemophilia A patients at risk of inhibitor development.

Hemophilia A with inhibitor: Immune tolerance induction (ITI) in the mirror of time

Inhibitor (neutralizing antibodies) development remains the most significant complication in patients with severe congenital hemophilia A receiving exogenous factor VIII (FVIII). Although our understanding of the pathophysiology of inhibitor development has advanced, the knowledge gained has not yet translated into a robust decline in incidence, with the overall risk remaining at ∼30%. Immune Tolerance Induction (ITI) is the only current method to successfully eradicate an inhibitor and achieve long-term tolerance. Although current practice utilizes a wide variety of ITI regimens, identification of an optimal regimen has not emerged. Over the last decade, the number of replacement products available in hemophilia has greatly expanded. The cumulative evidence with each product for use in ITI is often lacking. Most recently emicizumab, a humanized monoclonal bi-specific antibody that substitutes for the scaffolding effect of FVIIIa was approved; this agent prevents bleeding in both inhibitor and non-inhibitor patients. The use of emicizumab will bring about a new era in care that will require clinicians to challenge current practice paradigms including use and administration of ITI. This review will summarize the main clinical ITI data and practices for patients with severe congenital hemophilia A with inhibitors (CHAwI) over the last four decades and will highlight current studies in the field, with attention to open questions.

Massive immune response against IVIg interferes with response against other antigens in mice: A new mode of action?

Administration of high dose intravenous immunoglobulin (IVIg) is widely used in the clinic to treat autoimmune and severe inflammatory diseases. However, its mechanisms of action remain poorly understood. We assessed the impact of IVIg on immune cell populations using an in vivo ovalbumin (Ova)-immunization mouse model. High dose IVIg significantly reduced the Ova-specific antibody response. Intriguingly, the results obtained indicate an immediate and massive immune reaction against IVIg, as shown by the activation and expansion of B cells and CD4+ T cells in the spleen and draining lymph nodes and the production of IVIg-specific antibodies. We propose that IVIg competes at the T-cell level with the response against Ova to explain the immunomodulatory properties of IVIg. Two monoclonal antibodies did not succeeded in reproducing the effects of IVIg. This suggests that in addition to the mouse response against human constant domains, the enormous sequence diversity of IVIg may significantly contribute to this massive immune response against IVIg. While correlation of these findings to IVIg-treated patients remains to be explored, our data demonstrate for the first time that IVIg re-directs the immune response towards IVIg and away from a specific antigen response.