Impact of the Underlying Mutation and the Route of Vector Administration on Immune Responses to Factor IX in Gene Therapy for Hemophilia B

• Published in: Molecular therapy 2009-10, Vol.17 (10), p.1733-1742
• Main Authors: Cao, Ou, Hoffman, Brad E, Moghimi, Babak, Nayak, Sushrusha, Cooper, Mario, Zhou, Shangzhen, Ertl, Hildegund CJ, High, Katherine A, Herzog, Roland W
• Format: Article
• Language: English
• Subjects: Adenoviridae - genetics; Amino acids; Animals; Antibodies; Antigens; CD8-Positive T-Lymphocytes - immunology; Clinical trials; Dogs; Enzyme-Linked Immunosorbent Assay; Factor IX - genetics; Factor IX - immunology; Gene therapy; Genetic Therapy - adverse effects; Genetic Therapy - methods; Genetic Vectors - administration & dosage; Genetic Vectors - genetics; Hemophilia; Hemophilia B - therapy; Humans; Immunity, Humoral - genetics; Immunity, Humoral - immunology; Immunohistochemistry; Liver; Lymphocytes; Mice; Microscopy, Fluorescence; Musculoskeletal system; Mutation; Mutation, Missense; Original; Pediatrics; Proteins; Vectors (Biology)
• ISSN: 1525-0016; 1525-0024
• DOI: 10.1038/mt.2009.159

Immune responses to factor IX (F.IX), a major concern in gene therapy for hemophilia, were analyzed for adeno-associated viral (AAV-2) gene transfer to skeletal muscle and liver as a function of the F9 underlying mutation. Vectors identical to those recently used in clinical trials were administered to four lines of hemophilia B mice on a defined genetic background [C3H/HeJ with deletion of endogenous F9 and transgenic for a range of nonfunctional human F.IX (hF.IX) variants]. The strength of the immune response to AAV-encoded F.IX inversely correlated with the degree of conservation of endogenous coding information and levels of endogenous antigen. Null mutation animals developed T- and B-cell responses in both protocols. However, inhibitor titers were considerably higher upon muscle gene transfer (or protein therapy). Transduced muscles of Null mice had strong infiltrates with CD8+ cells, which were much more limited in the liver and not seen for the other mutations. Sustained expression was achieved with liver transduction in mice with crm− nonsense and missense mutations, although they still formed antibodies upon muscle gene transfer. Therefore, endogenous expression prevented T-cell responses more effectively than antibody formation, and immune responses varied substantially depending on the protocol and the underlying mutation.