Objective: In vitro endothelialization has significantly improved the overall outcome of artificial prostheses in cardiovascular bypass surgery. A drawback of this tissue-engineering method remains the limited availability of suitable autologous endothelial cells (EC), especially in aged patients. Allogeneic EC with high proliferative capacity represent a potentially valuable alternative to a patient-specific vascular transplant. However, such cells carry the risk of being rejected due to Major Histocompatibility Complex (MHC) mismatches.
Methods: We investigated the effects of a very potent, intracellularly expressed antibody directed against MHC class I molecules, referred to as alpha-rat MHC I single chain variable fragment (sFv) intrabody. The intrabody was stably expressed in rat aortic EC (RAEC) following lentiviral vector-mediated gene transfer. The functional consequence of the MHC I down-regulation was tested in an allogeneic setting in two different in vitro assays.
Results: Stable expression of the alpha-rat MHC I sFv intrabody resulted in a highly efficient depletion of surface MHC I. Thereby those RAEC which displayed low MHC I levels over extended periods of time were protected against killing by allo-specific, cytotoxic T cells (CTL) and by allo-antibody/complement-mediated lysis.
Conclusions: These results demonstrate that intrabody-mediated down-regulation of MHC I reduces the immunogenicity of RAEC which may provide a suitable alternative supply for the lining of vascular prostheses.