A quantitative cell-ELISA for alpha-galactose specific antibodies in human malaria

Naturally occurring antibodies to alpha-linked galactose (anti- gal) has been reported to be present in large quantities in normal human sera and they seem to play an important role in a variety of infectious as well as autoimmune diseases. A cell-ELISA using glutaraldehyde fixed normal rabbit erythrocytes was developed for quantification of anti-gal in human sera. This assay was compared with three other(commonly used) immunoassays viz. a) agglutination b) enhanced agglutination and c) lipid ELISA-assays for detection of anti-gal in human sera. The cell-ELISA was found to be the most sensitive assay followed by lipid-ELISA, enhanced agglutination and agglutination assay in decreasing order. Anti-gal affinity purified through a column of melibiose-agarose was tested by cell-ELISA. Monolayers of RRBC pre-treated with alpha-galactosidase was not reactive while in monolayers treated with beta-galactosidase, the anti-gal reactivity was comparable to those in untreated RRBC monolayer, thus indicating the high specificity of cell-ELISA for detection of antibodies to alpha-linked galactose.