Evaluating leukemogenic transmission via blood transfusion from genetically modified leukemic mice to healthy recipients

Abstract Background: Donor-derived leukemia after stem-cell transplantation is documented, yet the risk of transmitting leukemogenic cells via routine whole-blood transfusion remains unmeasured. Aims: Assess whether whole-blood transfusion from MLL-AF9–driven leukemic mice can establish GFP⁺ chimerism and alter hematologic indices in healthy recipients. Methods: Interim cohorts: Eight mice were inoculated via tail vein injection with 1 × 10^5 GFP⁺ MLL-AF9 leukemia cells; although all developed peripheral GFP, only five yielded sufficient blood for transfer. Each of five naïve wild-type recipients then received 250 µL of donor whole blood Timing: Donor blood was collected ~6 weeks post-inoculation when peripheral GFP was detectable but mice showed no clinical signs of illness. Sampling: Two weeks after transfusion, blood was obtained by submandibular bleeds for complete blood counts and flow cytometric assessment of GFP⁺ cells, and bone marrow was harvested from the hind limbs (femur, tibia, and pelvis) for GFP flow cytometry. Endpoints: Engraftment defined as any detectable GFP⁺ cells in both bone marrow and peripheral blood. Statistics: Continuous variables (WBC, GFP %) summarized as mean ± SD and compared by Welch's t-test; engraftment incidence by Fisher's exact test. P-values are descriptive for this 6-mouse interim set; final analyses will follow full cohort completion. Interim Results (6/45 mice analyzed): Engraftment:100 % (5/5) of G3 recipients became GFP⁺ in blood and marrow versus 0/1 G4 control (P = 0.17). Chimerism level: Median marrow GFP in recipients was 52.7 % (range 24.6–97.9). Leukocytosis: Recipients' median WBC was 14.8 × 10³ µL⁻¹ (range 6.2–128) versus 7.7 × 10³ µL⁻¹ in control. Survival: No deaths occurred; bone-marrow harvest was terminal. Conclusions: These interim data indicate that transfusion of whole blood from MLL-AF9–leukemic donors reliably seeds GFP⁺ marrow clones and induces leukocytosis in healthy mice. Completion of the full 45-mouse study will establish definitive incidence, dose–response relationships, and survival outcomes—critical for evaluating transfusion-related leukemogenic risk.