Immunogenicity of synthetic peptides corresponding to flexible and antibody-accessible segments of mouse lactate dehydrogenase (LDH)-C₄

The immunological properties of a panel of synthetic peptides that represent the most accessible and mobile segments of the lactate dehydrogenase (LDH)-C₄ molecule were characterized. Peptides corresponding to mouse LDH-C₄ amino acid sequences: 1-14b, 5-15, 49-58, 97-110, 211-220, 231-243, 274-286, 304-316, and 318-330 were synthesized and compared in terms of binding antibodies raised in rabbits against the intact protein. Six of these sequences were covalently coupled to diphtheria toxoid and used to immunize groups of rabbits. LDH-C₄-specific antibodies were detectable in immune sera by enzyme-linked immunosorbent assay, Western blotting, and immunoprecipitation assays. The immunogenicity of the mouse LDH-C₄ peptides in rabbits could be ranked in the following order: 5-15, 304-316 > 211-220, 274-286 > 49-58, 97-110. The immunological properties of these short synthetic peptides did not correlate with features of the mouse LDH-C₄ structure except that the most active sequences appeared to be those that differed from the somatic isozymes to the greatest extent. These results have direct bearing on the selection of immunogenic LDH-C₄ peptides for contraceptive vaccine studies in humans and non-human model systems.