Transient B cell depletion or improved transgene expression by codon optimization promote tolerance to factor VIII in gene therapy.
The major complication in the treatment of hemophilia A is the development of neutralizing antibodies (inhibitors) against factor VIII (FVIII). The current method for eradicating inhibitors, termed immune tolerance induction (ITI), is costly and protracted. Clinical protocols that prevent rather than treat inhibitors are not yet established. Liver-directed gene therapy hopes to achieve long-term correction of the disease while also inducing immune tolerance. We sought to investigate the use of adeno-associated viral (serotype 8) gene transfer to induce tolerance to human B domain deleted FVIII in hemophilia A mice. We administered an AAV8 vector with either human B domain deleted FVIII or a codon-optimized transgene, both under a liver-specific promoter to two strains of hemophilia A mice. Protein therapy or gene therapy was given either alone or in conjunction with anti-CD20 antibody-mediated B cell depletion. Gene therapy with a low-expressing vector resulted in sustained near-therapeutic expression. However, supplementary protein therapy revealed that gene transfer had sensitized mice to hFVIII in a high-responder strain but not in mice of a low-responding strain. This heightened response was ameliorated when gene therapy was delivered with anti-murine CD20 treatment. Transient B cell depletion prevented inhibitor formation in protein therapy, but failed to achieve a sustained hypo-responsiveness. Importantly, use of a codon-optimized hFVIII transgene resulted in sustained therapeutic expression and tolerance without a need for B cell depletion. Therefore, anti-CD20 may be beneficial in preventing vector-induced immune priming to FVIII, but higher levels of liver-restricted expression are preferred for tolerance.
Division of Cellular and Molecular Therapy, Department of Pediatrics, University of Florida, Gainesville, Florida, United States of America.
Brandon K
BK
Sack
Sherin
S
Merchant
David M
DM
Markusic
Amit C
AC
Nathwani
Andrew M
AM
Davidoff
Barry J
BJ
Byrne
Roland W
RW
Herzog
D000818:Animals; D000906:Antibodies / Q000276:immunology / Q000627:therapeutic use; D018951:Antigens, CD20 / Q000276:immunology*; D001402:B-Lymphocytes / Q000166:cytology / Q000276:immunology*; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology / Q000276:immunology; D003062:Codon / Q000235:genetics; D005169:Factor VIII / Q000008:administration & dosage / Q000737:chemistry / Q000235:genetics* / Q000276:immunology; D018014:Gene Transfer Techniques; D015316:Genetic Therapy / Q000379:methods*; D005822:Genetic Vectors / Q000235:genetics; D006467:Hemophilia A / Q000235:genetics* / Q000276:immunology / Q000628:therapy*; D006801:Humans; D007108:Immune Tolerance; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D017434:Protein Structure, Tertiary; D019076:Transgenes
D000906:Antibodies; D018951:Antigens, CD20; D003062:Codon; D005169:Factor VIII