A novel acridine flow cytometry marker to track post-transfusion amustaline/glutathione pathogen-reduced red blood cell survival in sickle cell disease patients.

Background: Measurement of transfused red blood cell (RBC) survival is relevant to the effective management of sickle cell disease (SCD). Following amustaline/glutathione pathogen-reduced (PR) RBC transfusion, small quantities of PR-RBC surface-bound acridine are detectable by flow cytometry. Concurrent biotin labeling was used to validate the acridine marker and track transfused PR-RBCs in SCD.

Methods: SCD patients (n = 6) on chronic transfusion therapy received three aliquots of different (2 μg/mL, 6 μg/mL, and 18 μg/mL) biotin-dose labeled RBCs during one transfusion episode. Aliquots were from one unit labeled before (Pre-PR) and after PR treatment (PR-RBC) and from a conventional RBC unit. The full RBC units (PR and conventional) were transfused, followed by the labeled aliquots from those units. Serial flow cytometry analyses for acridine- and biotin-labeled RBCs were performed on 10 occasions over 16 weeks. Acridine surface density was quantitated using calibrated beads.

Results: Mean acridine surface density was 5062 molecules/PR-RBC at 1-4 h post-transfusion and declined 84.5% within 7 days, remaining detectable (180 molecules/PR-RBC) at 16 weeks. The biotin-labeled PR-RBC aliquots (initial enrichment 0.6%-1.4%) demonstrated near-identical survival kinetics as the entire acridine-labeled PR-RBC units (initial enrichment 7.5%-13.7%). Pre-PR, PR, and Conventional RBCs revealed non-linear RBC survival kinetics, with similar 24-h post-transfusion recoveries (PTR24) and half-lives (T50), but PR-RBC mean predicted lifespan (mean [SD] 104.4 [4.7] days) was decreased by 9.3% (Pre-PR-RBCs 115.1 [7.2] days, p = 0.006).

Conclusions: Survival of amustaline/glutathione PR-RBCs can be tracked in vivo by flow cytometry for RBC surface acridine with similar sensitivity as biotin, without additional processing or radiolabeling.