PROTEASE-ACTIVATED RECEPTOR 2 (PAR-2) A NOVEL TARGET TO PREVENT FIX INHIBITOR FORMATION

Abstract number: P-W-222

Baila¹ S., Furlan Freguia² C., Favaro² P., Schuettrumpf² J., Mingozzi² F., Andrade-Gordon³ P., Arruda² V.

¹¹Pediatric, Children Hospital of Philadelphia ²²Pediatric, Children'sHospital of Philadelphia, Philadelphia ³³R&D, Johnson and Johnson Pharmaceutical, Spring House, United States

How-to-cite Baila S, Furlan Freguia C, Favaro P, Schuettrumpf J, Mingozzi F, Andrade-Gordon P, Arruda V. PROTEASE-ACTIVATED RECEPTOR 2 (PAR-2) A NOVEL TARGET TO PREVENT FIX INHIBITOR FORMATION. J Thromb Haemost 2007; 5 Supplement 2: P-W-222

Abstract

Introduction: Intramuscular injection (IM) of adeno-associated viral (AAV) is a promising therapeutic strategy for the treatment of hemophilia B. AAV serotype 1 (AAV-1) resulted in high level of transgene expression but the immune response to the transgene is a major complication. We sought to determine whether inhibition of PARs, which modulate inflammatory and immune responses, could prevent immune responses to the FIX following IM injection of AAV1-FIX.

Methods: We used three animal models. PAR-1 and PAR-2 knockout (-/-) mice were generated on C57Bl/6 background. In addition, hemophilia B mice were also crossed to PAR-2 (-/-) mice. Experiments were carried out by comparing littermate mice. AAV-1 vector encoding human FIX under the control of a CMV promoter were delivered at 2 IM sites. We monitored circulating FIX antigen and formation of antibody to the transgene by both an specific-ELISA IgG and neutralizing assay (Bethesda assay).

Results: PAR-1 and PAR-2 (-/-) mice received IM injections of AAV1-hFIX at doses range from 5×10¹¹ to 1×10¹²vg/kg and inhibitor were monitored by Bethesda assay (BU) and ELISA (IgG-FIX). PAR-2 (-/-) mice did not develop inhibitory antibodies (0/12), whereas, 70% (10-14) of the PAR-2 (+/+)/(+/-) mice developed FIX inhibitor (BU up to 3.6) In contrast, at similar vector doses, the absence of PAR-1 did not prevent antibodies formation. PAR-2 (-/-) developed tolerance to FIX and no inhibitor to the protein was detected upon repetitive exposure to FIX-CFA and no INF-gamma was secreted from splenocytes harvest from these animals. In addition, hemophilia B mice crossed with PAR-2 (-/-) challenged with FIX protein presented a delay in the formation of antibody compared to littermates controls.

Conclusions: The data suggest a role of PARs in the immune response to FIX. Inhibition of PAR-2 (but not PAR-1) could be a novel target in preventing inhibitor formation in hemophilia gene therapy.

To cite this abstract use the following format:

Journal of Thrombosis and Haemostasis 2007; Volume 5, Supplement 2: abstract number

Session Details

Date:	01/08/2007
Time:	00:00-00:00
Session name:	XXIst ISTH Congress
Subject:
Location:	Oxford, UK
Presentation type:
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