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

Linenberger M.
An ECO-logical way to expand the supply of compatible donor red blood cells.
The Hematologist.
Liu QP, Sulzenbacher G, Yuan H, et al.
Bacterial glycosidases for the production of universal red blood cells.
Nat Biotechnol.
Garratty G.
Progress in modulating the RBC membrane to produce transfusable universal/stealth donor RBCs.
Transfus Med Rev.
Armstrong JK, Hempel G, Koling S, et al.
Antibodyagainst poly(ethylene glycol) adversely affects PEG-asparaginase therapy in acute lymphoblastic leukemia patients.