Development of Carriers and Adjuvants for Use with Peptides to Induce Mucosal and Systemic Immunity against Biologic Toxins.

摘要

Novel methods were used to enhance the immunogenicity of peptides of biologic toxins in order to elicit secretory and systemic anti-toxin antibodies. Studies were focused on model peptides of two classes of toxins: (a) plant lectin toxins (Ricin), and (b) bacterial toxins (staphylococcal enterotoxin B SEB). Since Ricin toxicity was shown to be abolished by neutralizing monoclonal antibodies to either the A chain - the polypeptide chain responsible for ribosomal inhibition or the B chain containing the galactose binding site which facilitates cell entry, sets of overlapping peptides spanning regions containing putative neutralizing epitopes on the two chains were synthesized. The minimal necessary specificity for the neutralizing monoclonal antibody to the A chain was defined as the 10 amino acid sequence, NQEDAEAITH representing a small helical region projecting externally from the rim of the enzymatic cleft. Peptides were hydrophobically complexed to proteosomes through a cysteinyl-lauric acid anchor or covalently linked to KLH. Mice immunized with a conformation fixed cyclic peptide containing the neutralizing epitope on the ricin A chain were shown resistant to ricin toxicity at a limited dose range. Systemic and mucosal immunity in small animals was measured by examining the development of secretory antibodies (of all classes) in lung and gastrointestinal secretions as well as serum antibodies (especially IgA). This immunization system was used successfully for the enhancement of gastrointestinal and respiratory secretory and systemic immunity using oral and intranasal immunization protocols. The synergistic roles of associated oral adjuvants such as CTB and LPS were examined.