APHIA Oral Presentation Asia-Pacific Histocompatibility and Immunogenetics Association Meeting 2023

Changing laboratory requirements in the era of haploidentical transplants (96581)

Lyudmila Kostenko 1 , Cathie Hart 1 , Fiona Hudson 1 , Carmel Kanaan 1 , Theresa Cole 2 3 4 5 , Joshua Kausman 3 4 6 , Lilian Johnstone 7 8 , Samar Ojaimi 8 9 10 , Mary Diviney 1 , Andrew P Fennell 8 11 , Ari E Horton 8 11
  1. Australian Red Cross Lifeblood, West Melbourne, VIC, Australia
  2. Department of Haematology, The Royal Children's Hospital, Melbourne, VIC, Australia
  3. Department of Paediatrics, The University of Melbourne, Melbourne, VIC, Australia
  4. Murdoch Children's Research Institute, Melbourne, VIC, Australia
  5. Children's Cancer Centre, The Royal Children's Hospital, Melbourne, VIC, Australia
  6. Department of Nephrology, The Royal Children's Hospital, Melbourne, VIC, Australia
  7. Department of Nephrology, Monash Children's Centre, Monash Health, Clayton, Victoria, Australia
  8. Department of Paediatrics, Monash University, Clayton, Victoria, Australia
  9. Monash Pathology, Monash Health, Clayton, Victoria, Australia
  10. Monash Paediatric Infection and Immunity, Monash Health, Clayton, Victoria, Australia
  11. Monash Genetics, Monash Health, Melbourne, VIC, Australia, Melbourne

Traditionally, haemopoietic stem cell transplant with a fully HLA matched donor is considered the gold standard for the successful outcome of bone marrow transplantation in haemopoietic malignancies and immunodeficiencies. Increasingly, haploidentical transplantation is now considered as treatment of choice for some immunodeficiencies and has changed the requirements around laboratory testing and analytics.

A 4-year-old boy with Schimke Immuno-osseous Dysplasia, was referred to our laboratory in January 2021 for HLA typing and haploidentical stem cell transplant workup from his father. HLA typing was performed by LABType SSO and AllType Next Generation Sequencing.

B-leader matching was inferred from Exon 1 Codon -21 HLA-B sequence for the donor-recipient pair and was found to be matched (Met/Met) for the shared haplotype and mismatched (Met/Thr) for the non-shared haplotype. HLA-DPB1* mismatch between the donor and the recipient was listed as non-permissive GVH for HPC transplantation. Pre-transplant anti-HLA antibody screen was shown to be negative for HLA-Class I and borderline for Class II, with no specificity able to be determined.

Haploidentical HSCT from father took place in late 2021 and achieved 98% chimerism. Fifteen months post-HSC tx, the patient was referred to our laboratory for HLA typing and a living kidney transplant workup with the father as a potential kidney donor. The repeat HLA typing by NGS AllType demonstrated complete loss of the maternal haplotype, with the patient’s HLA being 100% identical to his father’s.

Flow crossmatch and anti-HLA ab screen prior to kidney transplant were both negative and the patient was transplanted with his father’s kidney 20 months following the HSCT.

This case demonstrates the increasing requirements around HLA testing and analytics to inform transplant centre protocols. The engrafted haploidentical stem cell transplant prior to kidney transplant from the same donor allowed for a HLA matched kidney transplant.