Overexpression of factor VIII after AAV delivery is transiently associated with cellular stress in hemophilia A mice

• Published in: Molecular therapy. Methods & clinical development Vol. 3; no. C; p. 16064
• Main Authors: Lange, Amy M, Altynova, Ekaterina S, Nguyen, Giang N, Sabatino, Denise E
• Format: Journal Article
• Language: English
• Published: United States Elsevier Limited 01.01.2016; Nature Publishing Group; Elsevier
• Subjects: Antigens; Apoptosis; CCAAT/enhancer-binding protein; Cell activation; Cellular stress response; Children & youth; Coagulation factors; Dogs; Enzymes; Factor VIII deficiency; Gene transfer; Hemophilia; Immune response; Immunoglobulins; Laboratories; Liver; Pathology; Polypeptides; Protein folding; Proteins; Toxicity
• ISSN: 2329-0501; 2329-0501
• DOI: 10.1038/mtm.2016.64

Factor VIII (FVIII) is a large glycoprotein that is challenging to express both and . Several studies suggest that high levels of FVIII expression can lead to cellular stress. After gene transfer, transgene expression is restricted to a subset of cells and the increased FVIII load per cell may impact activation of the unfolded protein response. We sought to determine whether increased FVIII expression in mice after adeno-associated viral liver gene transfer would affect the unfolded protein response and/or immune response to the transgene. The FVIII gene was delivered as B-domain deleted single chain or two chain (light and heavy chains) at a range of doses in hemophilia A mice. A correlation between FVIII expression and anti-FVIII antibody titers was observed. Analysis of key components of the unfolded protein response, binding immunoglobulin protein (BiP), and C/EBP homologous protein (CHOP), showed transient unfolded protein response activation in the single chain treated group expressing >200% of FVIII but not after two chain delivery. These studies suggest that supraphysiological single chain FVIII expression may increase the likelihood of a cellular stress response but does not alter liver function. These data are in agreement with the observed long-term expression of FVIII at therapeutic levels after adeno-associated viral delivery in hemophilia A dogs without evidence of cellular toxicity.