Syngeneic reconstitution rescues mice that develop severe GVHD after allogeneic reconstitution

Abstract

Background: Our Laboratory has been investigating donor specific hematopoietic reconstitution for the purpose of tolerance induction, a therapy currently limited by GVHD. This study investigates methods by which such GVHD can be managed. Methods and Results: We have established an acute GVHD mouse model by coinjection of T-cell depleted whole bone marrow (TCD-WBM) with CD4+ and CD8+-enriched splenocytes into lethally irradiated recipients. T cell depletion (TCD) was performed by extraction of CD3+, CD4+, CD8+, and NK1.1+ cells using magnetic beads. 25 Balb/c mice were given allogeneic 5 × 106 TCD-WBM plus 8 × 104 CD44/CD8+-enriched splenocytes. 5 mice were given 5 × 106 TCD-WBM alone. At day 9, 15 mice were rescued using 2, 5 and 10 × 106 syngeneic TCD-WBM, 5 mice in each group. GVHD was monitored by observing total body weight, body habitus, coat condition, and survival. At 42 days, survival of mice given TCD-WBM alone was 100% compared to 40% for mice TCD-WBM and CD4+/CD8+ splenocytes. Survival of mice given 2, 5, and 10 × 106 TCD-WBM was 60%, 60%, and 80% respectively. Weight data correlated as well. By day 16, the group which was given TCD-WBM alone was 10% below the start up weight compared to 41% for the group given TCD-WBM/splenocytes. Autologous rescue with 2, 5, and 10 × 106 TCD-WBM resulted in weights of 28. 28, and 22% of start-up weights, respectively. Peripheral blood of mice in all experimental groups was more than 98% donor-derived at 12 weeks. The group of mice given TCD-WBM/splenocytes and rescued with 2 × 106 autologous rescue cells did not survive beyond 9 weeks, but 99% of their peripheral blood cells was donor derived at 4 weeks. Conclusion: Such data demonstrate that acute GVHD can be alleviated without reverasal of donor-derived reconstitution using syngeneic rescue. These data suggest that such a method might prove useful for treatment of GVHD in methods of tolerance induction which utilize hematpoietic reconstitution.