Engraftment kinetics after transplantation of double unit cord blood grafts combined with haplo-identical CD34+ cells without antithymocyte globulin.

Double unit cord blood (dCB) transplantation (dCBT) is associated with high engraftment rates but delayed myeloid recovery. We investigated adding haplo-identical CD34+ cells to dCB grafts to facilitate early haplo-identical donor-derived neutrophil recovery (optimal bridging) prior to CB engraftment. Seventy-eight adults underwent myeloablation with cyclosporine-A/mycophenolate mofetil immunoprophylaxis (no antithymocyte globulin, ATG). CB units (median CD34+ dose 1.1 × 105/kg/unit) had a median 5/8 unit-recipient human leukocyte antigen (HLA)-match. Haplo-identical grafts had a median CD34+ dose of 5.2 × 106/kg. Of 77 evaluable patients, 75 had sustained CB engraftment that was mediated by a dominant unit and heralded by dominant unit-derived T cells. Optimal haplo-identical donor-derived myeloid bridging was observed in 34/77 (44%) patients (median recovery 12 days). Other engrafting patients had transient bridging with second nadir preceding CB engraftment (20/77 (26%), median first recovery 12 and second 26.5 days) or no bridge (21/77 (27%), median recovery 25 days). The 2 (3%) remaining patients had graft failure. Higher haplo-CD34+ dose and better dominant unit-haplo-CD34+ HLA-match significantly improved the likelihood of optimal bridging. Optimally bridged patients were discharged earlier (median 28 versus 36 days). ATG-free haplo-dCBT can speed neutrophil recovery but successful bridging is not guaranteed due to rapid haplo-identical graft rejection.

HLA-genotyping of clinical specimens using Ion Torrent-based NGS.

We have evaluated and validated the NXType™ workflow (One Lambda, Inc.) and the accompanying TypeStream™ software on the Ion Torrent Next Generation Sequencing (NGS) platform using a comprehensive testing panel. The panel consisted of 285 genomic DNA (gDNA) samples derived from four major ethnic populations and contained 59 PT samples and 226 clinical specimens. The total number of alleles from the six loci interrogated by NGS was 3420. This validation panel provided a wide range of HLA sequence variations including many rare alleles, new variants and homozygous alleles. The NXType™ system (reagents and software) was able to correctly genotype the vast majority of these specimens. The concordance rate between SBT-derived genotypes and those generated by TypeStream™ auto-analysis ranged from 99.5% to 99.8% for the HLA-A, B, C, DRB1 and DQB1 loci, and was 98.9% for HLA-DPB1. A strategy for data review was developed that would allow correction of most of the few remaining typing errors. The entire NGS workflow from gDNA amplification to genotype assignment could be completed within 3 working days. Through this validation study, the limitations and shortcomings of the platform, specific assay system, and software algorithm were also revealed for further evaluation and improvement.