CD3⁺cell dose is an independent risk factor for grade II–IV aGVHD following cord blood transplantation in children with aplastic anemia

Abstract Introduction Cord blood transplantation (CBT) has been widely used in hematologic malignancies with favorable outcomes. The use of anti-thymocyte globulin (ATG) has reduced the incidence of acute graft-versus-host disease (aGVHD) but increases viral reactivation. However, clinical data on CBT for children with aplastic anemia (AA) remain limited. This study aimed to evaluate the clinical outcomes of CBT in pediatric AA, focusing on survival, GVHD, and viral complications. Methods We retrospectively analyzed clinical data of 63 pediatric patients with AA who underwent CBT at Hebei Yanda Lu Daopei Hospital and Beijing Lu Daopei Hospital between March 2013 and April 2024. Follow-up continued through August 2025. The primary endpoints included incidence of aGVHD and overall survival (OS); secondary endpoints were CMV viremia, EBV viremia, and chronic GVHD (cGVHD). Variables with univariate P<0.2 or established clinical relevance were included in multivariable Cox regression or Fine–Gray competing risk models. Results Among the 63 patients (29 males, 34 females), the median age was 5 years (range, 1–16). Most patients (98.4%) received BU/CY/FLU/ATG conditioning. Low-dose ATG (G-ATG <7.5 mg/kg or F-ATG <20 mg/kg) was administered in 28.6% of patients, while 71.4% received high-dose ATG. GVHD prophylaxis was CSA-based in 28.6% and FK506-based in 71.4%. The median infused cell doses were: MNC 0.61×10⁸/kg, CD34⁺ 0.203×10⁶/kg, CD3⁺ 0.06×10⁸/kg, CD4⁺ 0.05×10⁸/kg, CD8⁺ 0.014×10⁸/kg, and CD14⁺ 0.07×10⁸/kg. At a median follow-up of 64 months (range, 2.4–143.9), neutrophil and platelet engraftment was achieved in 95.2% and 88.9% of patients, with median times of 16 and 29 days, respectively. The cumulative incidence of grade II–IV aGVHD by day 100 was 15.9% (95% CI, 9.0–28.0), and that of moderate-to-severe cGVHD was 9.98% (95% CI, 4.67–21.34). The incidence of CMV and EBV viremia by day 100 was 69.8% (95% CI, 59.4–82.2) and 14.4% (95% CI, 7.9–26.4), respectively. The 5-year OS reached 83.6% (95% CI, 74.3–92.9). Multivariate Cox regression and Fine–Gray competing risk models included the following covariates: ATG dose (low vs. high), HLA match (≤5/10 vs. >5/10), CD34⁺ cell dose (≤0.2 vs. >0.2 ×10⁶/kg), CD3⁺ cell dose (≤0.06 vs. >0.06 ×10⁸/kg), and CD4⁺ cell dose (≤0.05 vs. >0.05 ×10⁸/kg). A lower CD3⁺ cell dose (≤0.06 ×10⁸/kg) was independently associated with a significantly reduced risk of grade II–IV aGVHD (HR = 0.25; 95% CI, 0.08–0.74; P = 0.01). A higher CD34⁺ dose (>0.2×10⁶/kg) significantly lowered the risk of CMV viremia (HR = 0.49; 95% CI, 0.26–0.89; P = 0.02). In contrast, a lower CD4⁺ dose (≤0.05×10⁸/kg) was linked to an increased risk of moderate-to-severe cGVHD (HR = 1.0 vs. 0.26–5.1; P = 0.01). No variables significantly impacted OS or EBV viremia, though lower CD34⁺ counts showed a trend toward reduced EBV risk (HR = 0.28; 95% CI, 0.07–1.05; P = 0.06). Conclusion Cord blood transplantation achieves favorable survival and engraftment in pediatric AA. CD3⁺ and CD34⁺ cell doses independently impact the risks of aGVHD and CMV viremia, highlighting their prognostic relevance.