Robust Immune Reconstitution in Fanconi Anemia Mice Post in Utero Hematopoietic Stem Cell Transplantation

• Published in: Blood 2024-11, Vol.144 (Supplement 1), p.4095-4095
• Main Authors: Swartzrock, Leah, Pan, Wenjing, Krampf, Mark R., Hoang, Hana, Denis, Morgane, Cool, Taylor, Ho, Katie, Steele, Miranda, Brown, Brittany, Han, Jian, MacKenzie, Tippi C., Czechowicz, Agnieszka D.
• Format: Article
• Language: English
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood-2024-206296

Background: Fanconi anemia (FA) is the most common inherited DNA-repair disorder and leads to bone marrow failure, immune defects and systemic malignancies in almost all patients. In utero hematopoietic stem cell transplantation (IUHSCT) presents a promising prenatal treatment for FA that avoids the toxicities associated with current postnatal therapies by leveraging fetal immune tolerance and the competitive advantage of normal HSCs over failing FA HSCs. While our prior work has demonstrated multi-lineage donor engraftment post-IUHSCT, detailed characterization of immune reconstitution has been limited. Assessing the postnatal immune repertoire (IR) as well as macrophage composition is crucial for evaluating IUHSCT safety and efficacy in ensuring a robust and functional immune recovery. Methods: IUHSCT was performed in FA mice (Fancd2-/- or Fanca-/-, CD45.2) by breeding parental FA carriers and at E13.5-14.5 all fetuses received 1x106 CD117+ enriched HSCs from bone marrow of wildtype mice (WT, CD45.1) via intrahepatic injection. At 36-weeks post-IUHSCT peripheral blood was obtained and high-throughput sequencing of the CDR3 in both the T-cell receptor (TCR) and B-cell receptor (BCR) was performed in collaboration with iRepertoire, Inc. The repertoires of FA and WT IUHSCT treated mice were compared to untreated age and sex-matched FA and WT mice (n=4 total). The sequencing and subsequent analysis utilized the iRWeb data analysis suite. To assess the diversity and clonality of T- and B-cell populations, Diversity50 (D50) scores were calculated within the TCR and BCR IR across mice providing a quantitative measure where scores closer to 50 indicate higher diversity. Donor tissue-resident macrophages were also assessed at 48-weeks post IUHSCT in skin, liver, spleen, lung, and brain by analysis of %45.1 (n=3 FA mice). Results: IUHSCT resulted in only 1-3% donor HSC chimerism in WT and FA carrier littermates, with 18-87% donor HSC chimerism in FA mice at 48-weeks. Notable differences in IR diversity were observed between groups. Strikingly, in the non-transplanted FA setting, lower TCR diversity with D50 scores for TCRα/β/γ/δ of 20.5/36.2/41.7/13.3, respectively, and BCR heavy, kappa, and light of 2.5/1/0.9, respectively, was observed. In the FA post-IUHSCT setting, D50 scores for TCRα/β/γ/δ of 26.9/42.3/37.4/17.9, and for BCR heavy, kappa, and light chains of 2.8/1.1/0.7, was observed underscoring the selective impact on T-cell diversity enhancement. Important