Synthesis and immunochemistry of Lewis Y analogs

In the last decade, some promising results have emerged from the evaluation of synthetic, anti-cancer, carbohydrate conjugate vaccines. However, there remain large gaps in our understanding of immunology and tumor biology that hamper the rational design of vaccine candidates. In particular, the origin of antibody anti-tumor selectivity has not yet been identified, nor have the structural criteria for optimal immunogenicity in carbohydrate conjugate vaccines been delineated.; Described here is the synthesis of structurally related analogs and conjugate vaccine candidates that incorporate the tumor-associated carbohydrate antigen Lewis Y (Ley). Also reported are studies using these synthetic compounds to elucidate the relationship between the structure of the immunizing antigen, the epitope recognized by the elicited antibodies, and the selectivity shown by the elicited antibodies for tumor cells over normal cells expressing the same antigen.; Mouse monoclonal antibody B3 is notable for its selective reactivity with Ley-expressing tumor cells. Frontal affinity chromatography coupled online with mass spectrometry (FAC/MS) was employed to estimate the affinity of B3 for the synthetic Ley analogs. The results of these experiments show that B3 does bind extended structures with greater affinity than it binds the tetrasaccharide Ley determinant, thus lending credence to the previously-reported speculation that the binding specificity of anti-tumor monoclonal antibodies (e.g.B3) arises from extended epitope recognition.; The synthesis of the Ley analogs was extended to the construction of two BSA conjugate vaccine candidates. In contrast to previously-reported, synthetic Ley-based conjugate vaccines that focus either solely on the minimal carbohydrate determinant or on mimicking mucins, the vaccine candidates described here present the Ley determinant in the context of a glycosphingolipid. The aim of this study was to determine whether extending the immunizing structure to more closely mimic the natural glycolipid antigen would elicit polyclonal antibodies with better specificity for tumor cells. The results from the preliminary immunological evaluation of these glycoconjugates in BALB/c mice indicate that these compounds lack immunogenicity and thus definitive conclusions cannot be drawn about the effect of extended antigen structures on the specificity of the immune response. Further immunological evaluation may require immunization experiments in a different strain of mice.