Immune response to hemostatic proteins

Prinicipal investigator: Prof Jan Voorberg PhD

Hemophilia

Hemophilia is an X-linked bleeding disorder caused by a deficiency of factor VIII (hemophilia A) or factor IX (hemophilia B). Coagulation factor replacement therapy of hemophilia may be complicated by the formation of inhibitory or neutralizing antibodies (inhibitors). This side-effect occurs in approximately 25% of the patients with severe hemophilia A, and in about 5% of the patients with mild hemophilia A. The current focus of our studies comprises the immune recognition and processing of factor VIII by antigen-presenting cells. We have shown that factor VIII is rapidly internalized by antigen-presenting cells via an exposed loop in the C1 domain. Infusion of a monoclonal antibody directed towards the C1 domain delayed the immune response to factor VIII in a murine model for hemophilia. Together, these observations emphasize the physiological importance of C1-domain mediated endocytosis of factor VIII by antigen-presenting cells. Employing mass spectrometry we have developed a sensitive methods to probe the repertoire of peptides presented on MHC class II (van Haren et al., 2011, 2013). These studies show that a broad repertoire of FVIII peptides is presented on HLA-DR. Overall, our findings contribute to a more detailed understanding of the how the immune system deals with factor VIII.

Figure 1 Immune response 600


Figure 1: Domain structure of factor VIII. Our findings show that the C1 domain directs the uptake of factor VIII by antigen-presenting cells.  

Thrombotic thrombocytopenic purpura

Thrombotic thrombocytopenic purpura (TTP) is a micro-angiopathy that is related to an acquired or congenital deficiency of the von Willebrand Factor (VWF) cleaving protease ADAMTS13. In the absence of ADAMTS13, ultra-large VWF (UL-VWF) polymers, originating from endothelial cell specific organelles, designated Weibel-Palade bodies, accumulate in the circulation. These UL-VWF polymers mediate the formation of platelet-rich thrombi in the microcirculation that give rise to hemolytic anemia and thrombocytopenia. Several studies have shown that HLA-DRB1*11 is a risk factor for development of acquired TTP. We have pulsed dendritic cells derived of DRB1*11 positive and negative donors with purified ADAMTS13. Subsequently the HLA-DR presented peptide-repertoire was analyzed by mass spectrometry. Remarkably, a single CUB2 domain derived peptide was presented by dendritic cells from DRB1*11-positive donors pulsed with ADAMTS13. These findings raise the possibility that functional presentation of a CUB2 domain peptide on HLA-DRB1*11 contributes to the onset of acquired TTP.

Figure 2 Immune response 600

Figure 2: Left panel displays the domain structure of ADAMTS13. Dendritic cells were pulsed with different concentrations of ADAMTS13. A single CUB2 domain derived peptide is preferentially expressed by HLA-DRB11 positive dendritic cells. 

Key publications

Last edited on: 18 February 2016