(221) Cold Case Files: A curious anti-HLA sensitization event

Body: A 52-year-old Hispanic male, ABO A+, with type 1 diabetes and end-stage renal disease secondary to diabetic nephropathy, presented for kidney transplant evaluation in September 2023 after 2 years of dialysis. Initial anti-HLA antibody testing (HLAab) revealed few weak specificities, and a calculated panel reactive antibody (cPRA) of 0%. With no living donors, he was listed active status 1 on the deceased donor waitlist and monitored quarterly for HLAab changes. Over 9 months and 3 samples, his HLAab remained negligible. In September 2024, his HLAab resulted as 100% cPRA with broad Class I and II HLAab. This was confirmed with native antigen screening and testing of a requested fresh sample. No sensitizing events were reported to the HLA lab or clinical team. Patient interview and a thorough review of the medical record (EMR) between the last 0% cPRA sample (6/6/2024) and 100% cPRA sample (9/17/2024) revealed no transfusions, infections, vaccines, device implants, or transplants. An obscure external facility EMR note was located, documenting a fistula repair on 6/14/2024 secondary to dialysis AV fistula steal syndrome. The repair used “CryoVein,” a cryopreserved deceased donor saphenous vein graft (CDDSV). Unlike more common autologous vein harvest or synthetic grafts, CryoVein is allogeneic tissue distributed only with ABO typing, but no HLA typing. Due to extensive vascular disease, autologous vein harvest wasn’t feasible for our patient, and synthetic grafts posed infection risks. Sample of our patient’s CryoVein graft wasn’t available, but our laboratory was able to successfully isolate DNA from and HLA type a different CryoVein source. Literature supports CDDSV immunogenicity, and immunogenicity studies of the sample in our lab are ongoing. This is the only identified sensitization source in our patient. Transplant nursing has now added CDDSV and implant-related education and screening questions to patient materials and donor offer discussions.

Conclusion: Allogeneic CDDSV grafts are not uncommonly applied in bypass and fistula revision procedures. These graft products can be immunogenic, as they are only assessed for ABO type, but not HLA type or patient HLA compatibility. This poses a sensitization risk to transplant patients. Every effort should be made to avoid use of allogeneic CDDSV grafts in transplant patients and to communicate the risks of these products to patients and primary care providers.