Synthesis of Lewis Y Analogues and Their Protein Conjugates for Structure-Immunogenicity Relationship Studies of Lewis Y Antigen.

Analogues of cancer-associated Lewis Y (Ley) antigen with varying structures at the reducing end were synthesized by a highly efficient strategy involving one-pot preactivation-based iterative glycosylation to obtain the key tetra-/pentasaccharide intermediates, which was followed by stereoselective fucosylation. After global deprotection, these oligosaccharides were coupled with carrier protein keyhole limpet hemocyanin. The resultant glycan-protein conjugates were subjected to immunological studies in mice. It was disclosed that the conjugate of the pentasaccharide analogue of Lewis Y antigen was more immunogenic than that of the hexasaccharide analogue, but the antisera of both conjugates could indiscriminately recognize each carbohydrate hapten. These results suggested that the short Lewis Y analogue may be utilized to develop functional conjugate cancer vaccines. More importantly, the results also proved that the reducing-end glucose residue in the hexasaccharide analogue of Lewis Y was probably not involved in its interaction with the immune system, whose discovery can have a broad impact on the design of new cancer vaccines.