Frontiers in Immunology, 10 July 2026
SUMMARY: Research published in the international journal Frontiers in Immunology (July 2026) shows that unrelated cord blood transplantation (UCBT) achieved an overall survival rate of 91.7% in pediatric patients with inborn errors of immunity and inborn errors of metabolism in Vietnam.
Background: A Lifeline for Children Lacking Matched Donors
Hematopoietic stem cell transplantation (HSCT) is a curative or disease-modifying therapy for various life-threatening genetic conditions in children, including inborn errors of immunity (IEIs) and inborn errors of metabolism (IEMs). However, finding a fully matched human leukocyte antigen (HLA) donor within the family often presents significant challenges.
In this context, unrelated umbilical cord blood transplantation (UCBT) has emerged as an optimal alternative donor source due to its immediate availability, lack of donor mobilization requirements, and tolerance for higher degrees of HLA mismatch compared to adult donor grafts.
Study Population
The clinical team at the Vietnam National Children’s Hospital, in collaboration with partner institutions, conducted a retrospective study on 12 consecutive pediatric patients who underwent single-unit UCBT between October 2020 and February 2026:
- Median age at transplantation: 19 months (range: 7–42 months).
- Time from diagnosis to transplantation: Median of 10 months. (Notably, the waiting time decreased significantly from 18–39 months prior to 2024 down to 3–6 months after 2024).
- Conditions treated:
- Wiskott-Aldrich syndrome (7 cases).
- Very early-onset inflammatory bowel disease caused by IL10R mutations (2 cases).
- Severe combined immunodeficiency – SCID (1 case).
- Major histocompatibility complex class II deficiency – MHC Class II (1 case).
- Mucopolysaccharidosis type II (1 case).
Methodology & Technical Protocols
The study implemented standardized medical protocols spanning unit selection, conditioning, and post-transplant supportive care:
- Cord Blood Unit Selection Criteria
- Cord blood units were selected using high-resolution HLA typing at the HLA-A, HLA-B, and HLA-DRB1 loci, with preference given to units matched at 5/6 or 6/6 HLA loci.
- The minimum required cell dose was a total nucleated cell (TNC) count of ≥ 4 × 10⁷/kg and a CD34⁺ cell count of ≥ 3 × 10⁵/kg recipient body weight.
- In practice, the infused cell doses substantially exceeded these minimum requirements, with a median TNC dose of 8.07 × 10⁷/kg and a median CD34⁺ cell dose of 6.92 × 10⁵/kg.
- Conditioning Regimens & GVHD Prophylaxis
- Myeloablative Conditioning (MAC): All 12 patients received myeloablative conditioning, most commonly incorporating Busulfan, Fludarabine, and Anti-thymocyte globulin (ATG).
- GVHD Prophylaxis: Combination therapy of intravenous Cyclosporin (maintaining target trough levels of 150–200 ng/mL) and Mycophenolate Mofetil (MMF) starting on day -2. MMF was discontinued after day +28, and Cyclosporin was gradually tapered from day +100 in the absence of active GVHD.
- Stem Cell Infusion Procedure
- Cryopreserved cord blood units were thawed and infused directly via central venous access over 15 to 30 minutes.
- Infection Control & Supportive Care
- Sterile Isolation: Patients were housed in single rooms with positive pressure and HEPA filtration, adhering to strict hygiene and protective gear measures.
- Prophylactic Measures:
- Antifungal prophylaxis: Intravenous Micafungin was administered during hospitalization and transitioned to oral Voriconazole before discharge.
- Antibacterial and antiviral prophylaxis: Antibacterial prophylaxis was initiated on day +3, while Acyclovir or Ganciclovir was administered to patients at risk of CMV or HSV infection.
- Pneumocystis jirovecii prophylaxis: Trimethoprim–sulfamethoxazole was given before transplantation and resumed after neutrophil engraftment.
- Immune support: Intravenous immunoglobulin (IVIG; 500 mg/kg) was administered when serum IgG concentrations fell below 500 mg/dL.
Key Clinical Outcomes
After a median follow-up of 26 months among surviving patients, the study demonstrated highly encouraging clinical outcomes:
- Overall survival (OS): 91.7% (11/12 patients).
- Neutrophil engraftment rate: 75% (9/12 patients).
- Median time to neutrophil engraftment: 15 days (range: 11–25 days).
- Median time to platelet recovery: 35 days (range: 25–57 days).
- Umbilical cord blood transplantation event-free survival (UCBT-EFS): 66.7%.
- Incidence of grade II–IV acute graft-versus-host disease (aGVHD): 41.6%, with no cases of chronic GVHD observed.
Management of Graft Failure
Two patients who experienced primary graft failure were successfully rescued with haploidentical hematopoietic stem cell transplantation from a parent using a reduced-toxicity conditioning regimen.
Immune Reconstitution
Immune recovery after transplantation followed the expected biological course:
- Natural killer (NK) cells and T lymphocytes recovered to age-adjusted reference ranges by approximately day +100 post-transplant.
- B-cell recovery occurred more gradually, with a marked acceleration between days +100 and +180.
- During follow-up, five patients successfully discontinued all immunosuppressive therapy.
Scientific Significance and Clinical Implications
This study represents the first report from Vietnam demonstrating the feasibility, safety, and effectiveness of unrelated umbilical cord blood transplantation (UCBT) for the treatment of inherited disorders and inborn errors of immunity in pediatric patients.
These findings not only offer new hope for children who lack an HLA-matched related donor but also highlight the growing expertise of Vietnamese transplant centers and the ability of their post-transplant care programs to meet international standards.
References
Cao-Viet, T., Nguyen-Ngoc-Quynh, L., Ha-Phuong, A., Dang-Thi, H., Nguyen-Thanh, B., Can-Thi-Bich, N., … & Tran-Minh, D. (2026). Unrelated cord blood transplantation for pediatric patients with inborn error of immunity and inborn error of metabolism in Vietnam: early single-center experience. Frontiers in Immunology, 17, 1871545.
Source: Frontiers in Immunology
Link: https://doi.org/10.3389/fimmu.2026.1871545
