Inhibitory antibodies to factor VIII (fVIII) develop in approximately 30% of patients with severe hemophilia A in response to infusions of fVIII. Inhibitor development is associated with a lower quality of life and an increased economic burden and is currently is considered the most significant complication of the management of hemophilia A. Additionally, factor VIII inhibitors can occur in nonhemophiliacs, i.e. acquired hemophilia A, in which there can be life and limb- threatening complications. Patients with severe hemophilia A have no circulating fVIII protein and thus normal recognition of fVIII as """"""""self"""""""" does not develop. Accordingly, the therapeutic replacement fVIII protein is seen as """"""""foreign"""""""" by the immune system. Given that fVIII is an immunologically foreign protein, it may not seem surprising that an antibody response to fVIII would occur. However, in both rodents and humans, intravenous injection of soluble proteins usually fails to induce immunity and often induces a tolerogenic state. For this reason, the substantial immunogenicity of fVIII is unexpected. The central question of this grant is why, and by what mechanism, does fVIII induce an immune response. There are 3 Specific Aims in this proposal.
In Aim 1, the role of the physiological site of fVIII presentation to the immune system, i.e. a site of inflammation where a clot is forming and where fVIII is released from its large carrier protein von Willebrand factor, will be characterized by comparing the immunogenicity of fVIII with an inactive form of fVIII in a murine hemophilia A immunogenicity model.
In Aim 2, a novel fVIII molecule (HOVA) will be constructed that has a well characterized T cell epitope of ovalbumin inserted into the B domain. A wide array of immunologic reagents specific for this T cell epitope, including tetramer reagents and TCR transgenic mice, are available to investigate the mechanism of CD4+ T cell response to intravenous infusion of HOVA. There is evidence that early exposure to fVIII at the time of a """"""""danger signal"""""""" such as surgery or a major bleed increases the risk of antibody development.
In Aim 3 the role of toll like receptor activation on fVIII immunity will be addressed by comparing the CD4+ T cell response to intravenous infusion of HOVA as well as the ultimate antibody production in the presence and absence of toll like receptor agonists. The results of these experiments will allow for a deeper understanding of the substantial immunogenicity of fVIII and might provide insights for future design of novel fVIII molecules with decreased immunogenicity. This research plan along with the formal coursework and structured mentorship laid out in this proposal should provide the candidate with the training necessary to establish her as an independent investigator.

Public Health Relevance

Patients with hemophilia A have a deficiency in the blood coagulation protein factor VIII. Some patients with hemophilia A develop antibodies to factor VIII that worsens their bleeding problems and makes therapy difficult and expensive. In this project, we will develop a better understanding of the immune response to the factor VIII protein, which may lead to better treatment alternatives.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Clinical Investigator Award (CIA) (K08)
Project #
5K08HL102262-05
Application #
8626435
Study Section
Special Emphasis Panel (ZHL1-CSR-U (F1))
Program Officer
Sarkar, Rita
Project Start
2010-04-15
Project End
2015-02-28
Budget Start
2014-03-01
Budget End
2015-02-28
Support Year
5
Fiscal Year
2014
Total Cost
$128,250
Indirect Cost
$9,500
Name
Emory University
Department
Pediatrics
Type
Schools of Medicine
DUNS #
066469933
City
Atlanta
State
GA
Country
United States
Zip Code
30322
Chao, B N; Baldwin, W H; Healey, J F et al. (2016) Characterization of a genetically engineered mouse model of hemophilia A with complete deletion of the F8 gene. J Thromb Haemost 14:346-55
Batsuli, Glaivy; Deng, Wei; Healey, John F et al. (2016) High-affinity, noninhibitory pathogenic C1 domain antibodies are present in patients with hemophilia A and inhibitors. Blood 128:2055-2067
Eubanks, Joshua; Baldwin, W Hunter; Markovitz, Rebecca et al. (2016) A subset of high-titer anti-factor VIII A2 domain antibodies is responsive to treatment with factor VIII. Blood 127:2028-34
Nguyen, Phuong-Cac T; Lewis, Kenneth B; Ettinger, Ruth A et al. (2014) High-resolution mapping of epitopes on the C2 domain of factor VIII by analysis of point mutants using surface plasmon resonance. Blood 123:2732-9
Markovitz, Rebecca C; Healey, John F; Parker, Ernest T et al. (2013) The diversity of the immune response to the A2 domain of human factor VIII. Blood 121:2785-95
Walter, Justin D; Werther, Rachel A; Brison, Caileen M et al. (2013) Structure of the factor VIII C2 domain in a ternary complex with 2 inhibitor antibodies reveals classical and nonclassical epitopes. Blood 122:4270-8
Walter, Justin D; Werther, Rachel A; Polozova, Maria S et al. (2013) Characterization and solution structure of the factor VIII C2 domain in a ternary complex with classical and non-classical inhibitor antibodies. J Biol Chem 288:9905-14
Meeks, Shannon L; Cox, Courtney L; Healey, John F et al. (2012) A major determinant of the immunogenicity of factor VIII in a murine model is independent of its procoagulant function. Blood 120:2512-20
Doshi, Bhavya S; Gangadharan, Bagirath; Doering, Christopher B et al. (2012) Potentiation of thrombin generation in hemophilia A plasma by coagulation factor VIII and characterization of antibody-specific inhibition. PLoS One 7:e48172
Summers, Ryan J; Meeks, Shannon L; Healey, John F et al. (2011) Factor VIII A3 domain substitution N1922S results in hemophilia A due to domain-specific misfolding and hyposecretion of functional protein. Blood 117:3190-8