Prevalence of natural and acquired antibodies to amustaline/glutathione pathogen reduced red blood cells

Abstract

Background: The INTERCEPT™ Blood System for Red Blood Cells (RBCs) utilizes amustaline (S-303) and glutathione (GSH) to inactivate pathogens and leukocytes in transfused RBCs. Treatment-emergent low titer non-hemolytic antibodies to amustaline/GSH RBC were detected in clinical trials using a prior version of the process. The amustaline/GSH process was re-formulated to decrease S-303 RBC adduct formation. Study Design and Methods: A standard three-cell antibody screening panel was modified to include reagent red cells (RRC) with high (S-303H) or low (S-303L) S-303 adduct density as assessed by flow cytometry, representative of the original and current amustaline/GSH treatment processes, respectively. General hospital and RBC transfusion-dependent patients never exposed, and clinical trial subjects exposed to amustaline/GSH RBC were screened for antibodies to amustaline/GSH RBC using a standardized agglutination assay. Results: Twelve (0.1%) of 10,721 general hospital and 5 (0.5%) of 998 repeatedly-transfused patients not previously exposed to amustaline/GSH RBCs expressed natural, low titer (2-32) IgM and/or IgG (non-IgG 1 or IgG 3 isotype) antibodies with acridine (a structural element of amustaline) (n = 14) or nonacridine (n = 3) specificity. 11 of 17 sera reacted with S-303L panel RRCs. In clinical studies 81 thalassemia and 25 cardiac surgery patients were transfused with a total of 1085 amustaline/GSH RBCs and no natural or treatmentemergent S-303 antibodies were detected. Conclusion: Standardized RRC screening panels are sensitive for the detection of natural and acquired S-303-specific antibodies. Natural low titer antibodies to amustaline/GSH RBC are present in 0.15% of naïve patients. The clinical relevance of these antibodies appears minimal but is under further investigation.

New ultraviolet C light‐based method for pathogen inactivation of red blood cell units

“…Neoantigens produced from UVC‐induced modifications of macromolecules on the surface of RBC could potentially be identified as foreign by the RBC recipient's immune system, resulting in the formation of antibodies that can bind to the altered RBCs and clear them from the circulation. Clinical studies of pathogen‐reduced RBCs, have shown that acquired or natural antibodies to chemical‐dependent neoantigens such as S‐303 occur 21,22 . Our serologic tests did not detect any alterations of blood group antigens, non‐specific IgG binding on UVC‐treated RBCs or preformed antibodies reactive with UVC‐treated RBCs.…”

“…Clinical studies of pathogen-reduced RBCs, have shown that acquired or natural antibodies to chemical-dependent neoantigens such as S-303 occur. 21,22 Our serologic tests did not detect any alterations of blood group antigens, non-specific IgG binding on UVC-treated RBCs or preformed antibodies reactive with UVC-treated RBCs. Nevertheless, the potential immunogenicity of UVC-treated RBCs remains an important issue to be evaluated in future clinical studies.…”

Evaluation of the Efficacy & Safety of Amustaline/Glutathione Pathogen Reduced RBCs in Complex Cardiac Surgery: the Red Cell Pathogen Inactivation (ReCePI) Study - Protocol for a Phase 3, Randomized, Controlled Trial

“…None were found to be IgG1 or IgG3 subclass, the antibody subclasses most associated with physiologic hemolytic activity. The majority demonstrated specificity for acridine (19). The ReCePI study is designed to exclude subjects with natural antibodies to amustaline/GSH RBCs at baseline and to detect and thoroughly investigate the clinical significance of treatment emergent antibodies.…”

Commentary on the 1985 transfusion paper by Horowitz, Wiebe, Lippin, and Stryker

“…In a phase 3 clinical trial, the potential for immune responses to neoantigens was detected among recipients of amustaline‐HCl‐treated red cells, 30 leading to modification of the process with apparent reduced potential for immune responses to neoantigens 31 . The experience with the first‐generation amustaline process stimulated research into native immune responses to pathogen‐reduced red cells and the development of enhanced techniques to identify cross‐reactive antibodies in donors naïve to red cell components treated with pathogen inactivation/reduction methods 32 . More work will be required to definitively characterize the clinical relevance of these antibodies.…”

“…31 The experience with the first-generation amustaline process stimulated research into native immune responses to pathogen-reduced red cells and the development of enhanced techniques to identify cross-reactive antibodies in donors naïve to red cell components treated with pathogen inactivation/reduction methods. 32 More work will be required to definitively characterize the clinical relevance of these antibodies. Again, the stimulus for these investigations has its roots in the earlier work of Horowitz, emphasizing the importance of assessing the potential for neoantigen formation with the solvent/detergent treatment.…”