Details

Autor(en) / Beteiligte

• SU, RUI-JUN
• EPP, ANGELA
• WU, XIAOPING
• JOSEPHSON, NEIL C.
• PIPE, STEVEN W.

Titel

Reduction of inhibitor titres by infusion of FVIII gene transduced tolerogenic dendritic cells in haemophilic mice

Ist Teil von

• Haemophilia : the official journal of the World Federation of Hemophilia, 2009-03, Vol.15 (2), p.634-634

Ort / Verlag

Oxford, UK: Blackwell Publishing Ltd

Erscheinungsjahr

2009

Quelle

Wiley Blackwell Single Titles

Beschreibungen/Notizen

• Background:  The development of anti‐factor VIII (FVIII) inhibitory antibodies is a major complication of FVIII replacement therapy in the management of patients with haemophilia A. Evidence is accumulating that tolerogenic dendritic cells (tDCs) generated in vitro can induce regulatory T cells and promote durable antigen‐specific tolerance in vivo. Objective:  In this study we used human FVIII transgene expressing tDCs to reduce inhibitor formation in haemophilic mice. Methods and results:  The tDCs were generated by cell sorting the CD11clowCD45RBhigh population of cells resulting from culture of lineage negative bone marrow cells in media supplemented with IL‐10 and the neural peptides VIP and PACAP38. Expression of co‐stimulatory molecules CD40, CD80 and CD86 and MHC Class II was negative or low on these cells and they remain unactivated even after stimulation with lipopolysaccharide (LPS) or transduction by foamy virus (FV) vectors. Following transduction by a FV vector expressing a B domain deleted human FVIII transgene, 3–5 × 105 tDCs were infused by tail vein injection into Bal/c haemophilic mice (tDC‐F8) weekly for two doses. Real‐time PCR showed that the transduction efficiency of our FV vector in this population of tDCs was approximately 70%. Subsequently, mice were challenged with four weekly intravenous doses of 0.2 μg rhFVIII. Mice that received no cells (Neg‐Ctrl) and mice that received an equivalent number of non‐transduced tDCs (tDC‐Ctrl) were used as controls. After immunization with rhFVIII, the spleen size, weight and total cell numbers in tDC‐F8 mice were consistently lower than in Neg‐Ctrl and tDC‐Ctrl mice by approximately 50%. Flow cytometry assessment of CD4+ splenocytes showed there were an increased number of cells expressing the regulatory T‐cell markers FOXP3, CD25, CD103, CTLA4 and GITR in tDC‐F8 treated mice. We observed a 60% and 61% reduction in the level of inhibitor titres from tDC‐F8 mice compared with Neg‐Ctrl and tDC‐Ctrl mice. Splenic CD4+ T cell proliferation in response to FVIII stimulation in cells from tDC‐F8 mice was suppressed by approximately 90% compared with proliferation of cells from Neg‐Ctrl and tDC‐Ctrl mice. We also showed that pre‐immunized mice treated with four infusions of hFVIII FV vector transduced tDCs had a reduction in their inhibitor titres by 54% (P < 0.05). No significant change in inhibitor titres were seen in untreated controls or mice given four doses of untransduced tDCs. Summary:  These data indicate that hFVIII gene transduced tolerogenic DCs are useful in decreasing inhibitory antibodies in haemophilic mice. More in vivo studies are in progress to confirm the antigen‐specificity and durability of these effects. Our future studies will focus on isolating and characterizing the regulatory T cell populations induced by in vivo administration of transgene modified tDCs.