Active Antitoxic Immunization against Ricin Using Synthetic Peptides
Final rept. 9 Mar 1987-8 Jul 1989
SRI INTERNATIONAL MENLO PARK CA
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Over the project period, 22 ricin peptides 14 from ricin A-chain and 8 from ricin B-chain sequence have been synthesized. Peptides were conjugated to BSA or KLH, and free peptides as well as conjugates were used to immunize mice. Sera were tested by ELISA for their binding to corresponding immobilized peptides, corresponding ricin subunits, and intact ricin. Five of the ricin A- chain peptides showed significant binding to anti ricin A serum. Additional peptides with overlapping sequences were synthesized and tested as above. Challenge studies were performed on peptides eliciting ricin-binding antibodies, however, none protected against ricin challenge. Longer peptides covering the loop regions, used along with T-cell epitopes, may provide protection. Keywords Antitoxins Ricin Synthetic peptides Immunization RA1.