Pre-existing anti-factor VIII immunity alters therapeutic platelet-targeted factor VIII engraftment following busulfan conditioning through cytotoxic CD8 T cells. J Thromb Haemost 2023 Mar;21(3):488-498
Date
01/26/2023Pubmed ID
36696197Pubmed Central ID
PMC11249136DOI
10.1016/j.jtha.2022.10.006Scopus ID
2-s2.0-85149175901 (requires institutional sign-in at Scopus site) 2 CitationsAbstract
BACKGROUND: We previously demonstrated that busulfan preconditioning enabled sustained therapeutic platelet-derived factor VIII (FVIII) expression in naïve FVIIInull mice transplanted with 2bF8-transduced Sca-1+ cells. However, in mice with pre-existing inhibitors, platelet-FVIII expression was lost.
OBJECTIVE: In this study, we aimed to describe the mechanism of this platelet-FVIII loss.
METHODS: We monitored platelet-FVIII expression in FVIIInull mice that were immunized with rhFVIII to induce inhibitors and subsequently conditioned with busulfan before whole bone marrow transplantation or Sca-1+ hematopoietic stem cell transplantation (HSCT) from 2bF8 transgenic (2bF8Tg) mice. Busulfan with or without antithymocyte globulin or anti-CD8 antibody was employed before 2bF8Tg HSCT. Interferon gamma-ELISpot assay was used to assess which subset of cells was the target in platelet-FVIII loss. B-cell-deficient homozygous mutant mice were used to determine whether platelet-FVIII loss in FVIII-primed mice was mediated by antibody-dependent cellular cytotoxicity.
RESULTS: Platelet-FVIII expression was sustained in 2bF8Tg bone marrow transplantation but not in 2bF8Tg HSCT recipients. CD8 T-cell depletion in addition to busulfan preconditioning restored platelet-FVIII expression in 2bF8Tg-HSCT recipients. ELISpot analyses showed that FVIII-primed CD8 T cells were efficiently restimulated by 2bF8Tg-Sca-1+ cells and secreted interferon gamma, but were not stimulated by 2bF8Tg platelets/megakaryocytes, suggesting that 2bF8Tg-Sca-1+ cells are targets for FVIII-primed CD8 T cells. When 2bF8Tg-Sca-1+ cells were transplanted into FVIII-primed homozygous mutant mice preconditioned with busulfan, no FVIII expression was detected, suggesting that antibody-dependent cellular cytotoxicity was not the mechanism of platelet-FVIII loss in FVIII-primed mice.
CONCLUSION: Pre-existng immunity can alter the engraftment of 2bF8Tg-Sca-1+ cells through the cytotoxic CD8 T-cell-mediated pathway. Sufficient eradication of FVIII-primed CD8 T cells is critical for the success of platelet gene therapy in hemophilia A with inhibitors.
Author List
Jing W, Baumgartner CK, Xue F, Schroeder JA, Shi QAuthor
Qizhen Shi MD, PhD Professor in the Pediatrics department at Medical College of WisconsinMESH terms used to index this publication - Major topics in bold
AnimalsBlood Platelets
Busulfan
CD8-Positive T-Lymphocytes
Hemophilia A
Hemostatics
Interferon-gamma
Mice
Mice, Knockout
