Separation of Broad Spectrum Anti-LPS IgA From Human Milk Using LPS Chitosan Affinity Chromatography

Abstract

An affinity chromatography technique was developed for separation of broad spectrum antilipopolysaccharide (LPS) IgA antibodies from human milk. The affinity column was prepared by immobilizing LPS from Escherichia coli O111:B4 on to porous chitosan beads using glutaraldehyde activation. IgA separated from human milk using a Jacalin column was cycled through the LPS-chitosan column at a slow rate. Bound IgA was eluted with glycineHCl, pH 2.6, and presence of IgA in the eluate was confirmed by radial immunodiffusion (RID) and by visualization on sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). Column binding capacity was 0.22 mg of LPS-specific IgA ml−1. The stability of immobilized LPS was confirmed upon repeated uses of the column with negligible leaching of the ligand. The affinity purified anti-LPS IgA accounted for 12.3% of Jacalin purified IgA and was found to cross-react highly with E. coli O128:B12, and Klebsiella pneumoniae using LPS-ELISA, demonstrating the use of this technique for purification of broad spectrum, cross reactive immunoglobulins. There is a great potential for application of this technique in preparation of antibodies for prevention of enteric gram-negative infections in high risk individuals. The low cost column material used (chitosan beads) makes large scale utilization of this technique more practical.