Re: "An ECO-Logical Way to Expand the Supply of Compatible Donor Red Blood Cells"

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.

References:

1. Linenberger M. An ECO-logical way to expand the supply of compatible donor red blood cells. The Hematologist. 2007;4:10.
   
   
2. Liu QP, Sulzenbacher G, Yuan H, et al. Bacterial glycosidases for the production of universal red blood cells. Nat Biotechnol. 2007;25:454-64.
   
   
3. Lublin DM. Universal RBCs. Transfusion. 2000;40:1285-9.
   
   
4. Garratty G. Progress in modulating the RBC membrane to produce transfusable universal/stealth donor RBCs. Transfus Med Rev. 2004;18:245-56.
   
   
5. Armstrong JK, Hempel G, Koling S, et al. Antibody against poly(ethylene glycol) adversely affects PEG-asparaginase therapy in acute lymphoblastic leukemia patients. Cancer. 2007;110:103-11.

Jonathan K. Armstrong, PhD
Assistant Professor of Research
Department of Physiology and Biophysics
Keck School of Medicine
University of Southern California

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