Abstract Number: PB2021
Meeting: ISTH 2020 Congress
Background: Liver sinusoidal endothelial cells (LSECs) are specialized cells with unique morphology and scavenger activity related to their endocytic capacity taking part to liver tolerance. This activity relies also on the ability of stabilin-2 (Stab2), expressed on LSECs in liver, to mediate the binding of several ligands, among which are coagulation factors (e.g. vWF-FVIII complex). Since LSECs are the main source of FVIII, they could be an optimal target for gene therapy of hemophilia A, and the Stab2 promoter could be used for directing specific expression of FVIII in LSEC upon lentiviral vector (LV) delivery.
Aims: To test the hypothesis that targeting transgene expression to LSECs via Stab-2 promoter will promote robust tolerance to the transgene, thus resulting in transgene expression.
Methods: To test our hypothesis, we adoptively transferred GFP-specfic CD8+ Jedi T cells (Jedi-CD8), which are T cells that recognize the immunodominant epitope of GFP (GFP200-208), in mice previously injected with LVs carrying GFP under different promoters. Four days after Jedi-CD8 injection (14 days from LV delivery), we analyzed the expression of GFP in liver and spleen by immunofluorescence through co-staining with specific cell surface markers, while immune cell recruitment and activation was assessed by flow cytometry.
Results: The Stab2 promoter was able to restrict GFP expression mainly to LSECs in different strain of mice, where the expression was sustained for over three months. Strikingly, when we performed the adaptive transfer of Jedi-CD8, only the mice receiving LV.Stab2-GFP maintained GFP+ cells in the liver while LV.PGK-GFP injected mice showed total absence of GFP+ cells.
Conclusions: These studies demonstrate that the Stab-2 promoter mediates specific transgenes expression to LSECs. These data support the hypothesis that antigen presentation by LSECs can promote immunological tolerance to a vector-derived antigen, providing relevant new data into the biology of LSECs and a promising strategy for LSEC-directed gene therapy.
To cite this abstract in AMA style:Borroni E, Borsotti C, Bruscaggin V, Talmon M, Famà R, Brown BD, Follenzi A. Stabilin-2 Promoter Modulates Immune Response in the Liver of Lentiviral Vector Injected Mice [abstract]. Res Pract Thromb Haemost. 2020; 4 (Suppl 1). https://abstracts.isth.org/abstract/stabilin-2-promoter-modulates-immune-response-in-the-liver-of-lentiviral-vector-injected-mice/. Accessed January 21, 2022.
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