Blood cells having modified antigenicity

Abstract

This invention relates to enzymatic removal of type A and B antigens from blood group A, B, and AB reactive cells in blood products, and thereby converting these to non-A and non-B reactive cells. The invention further relates to using unique alpha N-acetylgalactosaminidases and alpha-galactosidases with superior kinetic properties for removing the immunodominant monosaccharides of the blood group A and B antigens and improved performance in enzymatic conversion of red blood cells. The preferred unique alpha-N-acetylgalactosaminidases and alpha-galactosidases exhibit the following characteristics: (i) exclusive, preferred or no less than 10% substrate specificity for the type A and B branched polysaccharide structures relative to measurable activity with simple mono- and disaccharide structures and aglycon derivatives hereof; (ii) optimal performance at neutral pH with blood group oligosaccharides and in enzymatic conversion of cells; and (iii) a favorable kinetic constant Km with mono- and oligosaccharide substrates. The conversion methods of the invention use significantly lower amounts of recombinant glycosidase enzymes than previous and result in complete sero-conversion of all blood group A and B red cells.

Description

RELATED APPLICATIONS [0001] This application is a continuation of and claims priority to U.S. Ser. No. 10 / 251,271 filed Sep. 20, 2002, which in turn claims priority to U.S. Provisional Application No. 60 / 324,970, filed on Sep. 25, 2001, and No. 60 / 361,769, filed on Mar. 5, 2002; the entire contents of each application is hereby incorporated herein by reference.FIELD OF THE INVENTION [0002] This invention relates to enzymatic removal of type A and B antigens from blood group A, B, and AB reactive cells in blood products, and thereby converting these to non-A and non-B reactive cells. Specifically this invention relates to enzymatic removal of the immunodominant monosaccharides specifying the blood group A and B antigens, namely alpha 1,3-D-galactose and alpha 1,3-D-N-acetylgalactosamine, respectively. More particularly, this invention relates to the use of unique alpha-N-acetylgalactosaminidases and alpha-galactosidases with superior kinetic properties for removal of the immunodomina...

AI Technical Summary

Benefits of technology

"The present invention provides methods and compositions for enzymatically removing type A and B antigens from blood group A, B, and AB cells. This is achieved by using specific glycosidase enzymes that have been selected for their ability to remove the immunodominant monosaccharides that make up the antigens. The enzymes have been found to be effective in removing all detectable A antigens from group A and B cells, as well as B antigens from group B cells. The methods involve contacting the blood product with the enzyme for a period of time sufficient to remove the antigens, and then removing the enzyme from the blood product. The invention also provides sero-converted red cells that have been converted from a type A or type AB erythrocyte to a non-A erythrocyte."

Problems solved by technology

However, there is a paucity of blood type O donors.

However, conversion of the more abundant A cells has only been achieved with the less abundant weak A subgroup cells.

The major obstacle for development and utilization of enzyme converted universal O cells has, in the past, been the failure to enzymatically convert the strong A1 cells.

This obstacle has remained.

As will be explained below in detail the enzymes and methods used in the prior art are inefficient, impractical, and / or too costly to be used in a commercial process to supply universal type O cells.

Nevertheless, the quantities of enzymes used in these studies, even with present days most effective recombinant expression technology, renders ECO cells impractical mainly for economical reasons.

However, the kinetic properties and fine substrate specificities of glycosidase enzymes may not necessarily be reflected in assays with such simple structures.

It is also possible that novel enzymes with high degree of specificity and / or selective efficiency for complex oligosaccharide and unique glycoconjugate structures exists, but that these may have been overlooked and remain unrecognized due to methods of analysis.

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