SEQUENTIAL ORDER OF T-CELL AND B-CELL EPITOPES AFFECTS IMMUNOGENICITYBUT NOT ANTIBODY RECOGNITION OF THE B-CELL EPITOPE

Synthetic peptide constructs, co-linearly linking a MUC1 mucin B cell epitope peptide to a known murine T cell epitope, both in T-B and B-T orientations, show that induction of high murine anti-MUC1 antibody ti ters is dependent on the presence and orientation of the T cell determ inant. However the sequential order of the epi topes does not affect b inding of anti-B cell epitope antibodies to the constructs. Haplotype mismatching lends to a significant lowering of the anti-MUC1 antibody responses, implicating a central role for the T cell epitope in elicit ing anti-B cell epitope responses. Secondary structure analysis by cir cular dichroism spectroscopy reveals the T-B construct to be partially ordered, while the B-T peptide adopts a highly ordered conformation i n trifluoroethanol. These studies suggest that the sequential order of epitopes may significantly alter the immunogenicity of the peptide bu t may not necessarily affect its antigenicity. Immunogenicity of the p eptide constructs may be governed by subtle differences in secondary s tructure, leading to variation in the way peptides are pre sented or p rocessed within cells governing immune responses. These findings have relevance for the construction of peptides to be utilized as potential synthetic vaccines; and for the design of peptide immunogens.