Role of the vector genome and underlying factor IX mutation in immune responses to AAV gene therapy for hemophilia B.
BACKGROUND
Self-complementary adeno-associated virus (scAAV) vectors have become a desirable vector for therapeutic gene transfer due to their ability to produce greater levels of transgene than single-stranded AAV (ssAAV). However, recent reports have suggested that scAAV vectors are more immunogenic than ssAAV. In this study, we investigated the effects of a self-complementary genome during gene therapy with a therapeutic protein, human factor IX (hF.IX).


METHODS
Hemophilia B mice were injected intramuscularly with ss or scAAV1 vectors expressing hF.IX. The outcome of gene transfer was assessed, including transgene expression as well as antibody and CD8⁺ T cell responses to hF.IX.


RESULTS
Self-complementary AAV1 vectors induced similar antibody responses (which eliminated systemic hF.IX expression) but stronger CD8⁺ T cell responses to hF.IX relative to ssAAV1 in mice with F9 gene deletion. As a result, hF.IX-expressing muscle fibers were effectively eliminated in scAAV-treated mice. In contrast, mice with F9 nonsense mutation (late stop codon) lacked antibody or T cell responses, thus showing long-term expression regardless of the vector genome.


CONCLUSIONS
The nature of the AAV genome can impact the CD8⁺ T cell response to the therapeutic transgene product. In mice with endogenous hF.IX expression, however, this enhanced immunogenicity did not break tolerance to hF.IX, suggesting that the underlying mutation is a more important risk factor for transgene-specific immunity than the molecular form of the AAV genome.
Geoffrey L
GL
Rogers
Ashley T
AT
Martino
Irene
I
Zolotukhin
Hildegund C J
HC
Ertl
Department of Pediatrics, Division of Cellular and Molecular Therapy, University of Florida, Gainesville, Florida, USA. rherzog@ufl.edu.
Roland W
RW
Herzog
D000818:Animals; D000914:Antibodies, Viral / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D002213:Capsid / Q000276:immunology; D018389:Codon, Nonsense / Q000235:genetics; D000229:Dependovirus / Q000235:genetics*; D005164:Factor IX / Q000235:genetics* / Q000627:therapeutic use*; D018014:Gene Transfer Techniques; D015316:Genetic Therapy; D005822:Genetic Vectors / Q000235:genetics*; D016678:Genome / Q000235:genetics; D002836:Hemophilia B / Q000235:genetics / Q000276:immunology / Q000628:therapy*; D006801:Humans; D007109:Immunity / Q000235:genetics*; D051379:Mice
D000914:Antibodies, Viral; D018389:Codon, Nonsense; D005164:Factor IX