To the Editor:
I read with interest the article by Dr. Michael Linenberger1 for the enzymatic conversion of red blood cell (RBC) antigens A, B, and AB to group O (ECO)2 . However, the covalent attachment of poly(ethylene glycol) to RBCs (PEG-RBCs) to mask minor blood group antigens was presented as a competing technology that has not progressed due to technical limitations.
A very nice review was presented by Lublin in 2000 where he envisioned the blood bank factory of the future in which ECO was complemented by PEG-coating and also encompassed white blood cell reduction and pathogen inactivation to create a truly "universal" and safe blood supply3 .
Unfortunately, the potential advantages of PEG-RBCs were negated after the discovery of a 25 percent occurrence of antibodies specific to PEG (anti-PEG) in healthy blood donors and also the rapid clearance of PEG-RBCs observed in rabbits with anti-PEG4 .
Although disappointing for the future widespread use of PEG-RBCs, we have recently shown a close association between anti-PEG and rapid clearance of PEG-asparaginase in pediatric patients treated for acute lymphoblastic leukemia5 . If confirmed in a prospective clinical trial, our findings may be of value in improving the outcome of patients for whom a PEG-conjugated therapy is a consideration.
-Jonathan K. Armstrong, PhD, Assistant Professor of Research, Department of Physiology and Biophysics, Keck School of Medicine, University of Southern California
