Expression of a factor VIII specific B-cell receptor (BCR) IgM in mouse and human B-cell lines

---

Presentation Time: 03:15 PM - 04:30 PM
Poster Board Number: B814
Abstract ID: 4503

Presenting Author:
Batsukh Dorjbal , Scientist at Uniformed Services Univ. of the Hlth. Sci., Henry M. Jackson Fndn. for the Advancement of Mil. Med.

Abstract:

Hemophilia A is a bleeding disorder in which mutations in the gene encoding factor VIII (FVIII) lead to a deficiency or absence of this essential blood coagulation protein. Treatment consists of intravenous FVIII infusions. Unfortunately, many patients develop neutralizing antibodies known as "inhibitors," making FVIII replacement therapy untenable. Attempts to tolerize patients by intensive FVIII therapy, known as immune tolerance induction (ITI), fail in approximately 30% of patients.  Current data suggest that successful ITI involves apoptosis of FVIII-specific B-memory cells, anergy of FVIII-specific T-effector cells and/or induction of regulatory T-cells (Tregs).  

Our lab has developed several novel approaches to induce tolerance to FVIII using T-cell receptor (TCR) and chimeric antigen receptor (CAR)-engineered human and mouse Tregs, and cytotoxic CD8 T cells expressing FVIII domains, to suppress or kill FVIII-specific lymphocytes. To enable mechanistic studies, we have now created B-cell lines expressing a FVIII-specific B-cell receptor (BCR) IgM that recognizes the FVIII C2 domain. Interestingly, surface expression of this BCR was greatly enhanced when it was co-expressed with CD79a (Igα) as well as exogenous light chain. Both FVIII and a recombinant FVIII-C2 domain protein bound to the engineered cells, confirming surface expression of this specific BCR. In addition to mechanistic studies, this BCR construct has provided a foundation to create BCR-transgenic mice.