An Immune-Competent Murine Model to Study Elimination of AAV-Transduced Hepatocytes by Capsid-Specific CD8 + T Cells

• Published in: Molecular therapy. Methods & clinical development Vol. 5; no. C; pp. 142 - 152
• Main Authors: Palaschak, Brett, Marsic, Damien, Herzog, Roland W, Zolotukhin, Sergei, Markusic, David M
• Format: Journal Article
• Language: English
• Published: United States Elsevier Limited 16.06.2017; American Society of Gene & Cell Therapy; Elsevier
• Subjects: AAV vector; Animal models; Antigens; capsid immunity; CD8 antigen; Clinical trials; Coagulation factors; Factor IX deficiency; Gene therapy; Genomes; Hemophilia; Hepatocytes; Immunological memory; Immunology; Liver; Lymphocytes; Lymphocytes T; mouse model; Original; Peptides; Prednisolone; Proteins; Serotypes; Software; Statistical analysis; Studies; AAV vector; hemophilia; mouse model; capsid immunity
• ISSN: 2329-0501; 2329-0501
• DOI: 10.1016/j.omtm.2017.04.004

Multiple independent adeno-associated virus (AAV) gene therapy clinical trials for hemophilia B, utilizing different AAV serotypes, have reported a vector dose-dependent loss of circulating factor IX (FIX) protein associated with capsid-specific CD8 T cell (Cap-CD8) elimination of transduced hepatocytes. Hemophilia B patients who develop transient transaminitis and loss of FIX protein may be stabilized with the immune-suppressive (IS) drug prednisolone, but do not all recover lost FIX expression, whereas some patients fail to respond to IS. We developed the first animal model demonstrating Cap-CD8 infiltration and elimination of AAV-transduced hepatocytes of immune-deficient mice. Here, we extend this model to an immune-competent host where Cap-CD8 transfer to AAV2- -treated mice significantly reduced circulating and hepatocyte FIX expression. Further, we studied two high-expressing liver tropic AAV2 variants, AAV2-LiA and AAV2-LiC, obtained from a rationally designed capsid library. Unlike AAV2, Cap-CD8 did not initially reduce circulating FIX levels for either variant. However, FIX levels were significantly reduced in AAV2-LiC- -treated, but not AAV2-LiA- -treated, mice at the study endpoint. Going forward, the immune-competent model may provide an opportunity to induce immunological memory directed against a surrogate AAV capsid antigen and study recall responses following AAV gene transfer.