New graft manipulation strategies improve the outcome of mismatched stem cell transplantation in children with primary immunodeficiencies

BACKGROUND

Mismatched stem cell transplantation is associated with a high risk of graft loss, graft-versus-host disease (GvHD), and transplant-related mortality. Alternative graft manipulation strategies have been used over the last 11 years to reduce these risks.

OBJECTIVE

We investigated the outcome of using different graft manipulation strategies among children with primary immunodeficiencies.

METHODS

Between 2006 and 2017, 147 patients with primary immunodeficiencies received 155 mismatched grafts: 30 T-cell receptor (TCR) αβ/CD19-depleted grafts, 43 cord blood (CB) grafts (72% with no serotherapy), 17 CD34⁺ selection with T-cell add-back grafts, and 65 unmanipulated grafts.

RESULTS

The estimated 8-year survival of the entire cohort was 79%, transplant-related mortality was 21.7%, and the graft failure rate was 6.7%. Posttransplantation viral reactivation, grade II to IV acute graft-versus-host disease (aGvHD), and chronic graft-versus-host disease (cGvHD) complicated 49.6%, 35%, and 15% of transplantations, respectively. Use of TCRαβ/CD19 depletion was associated with a significantly lower incidence of grade II to IV aGvHD (11.5%) and cGvHD (0%), although with a greater incidence of viral reactivation (70%) in comparison with other grafts. T-cell immune reconstitution was robust among CB transplants, although with a high incidence (56.7%) of grade II to IV aGvHD. Stable full donor engraftment was significantly greater at 80% among TCRαβ⁺/CD19⁺-depleted and CB transplants versus 40% to 60% among the other groups.

CONCLUSIONS

Rapidly accessible CB and haploidentical grafts are suitable alternatives for patients with no HLA-matched donor. Cord transplantation without serotherapy and TCRαβ⁺/CD19⁺-depleted grafts produced comparable survival rates of around 80%, although with a high rate of aGvHD with the former and a high risk of viral reactivation with the latter that need to be addressed.