Finding a New Vaccine in the Ricin Protein Fold
Abstract
Previous attempts to produce a vaccine for ricin toxin have been hampered by safety concerns arising from residual toxicity, and the undesirable aggregation or precipitation caused by exposure of hydrophobic surfaces on the ricin A-chain (RTA) in the absence of its natural B-chain partner. We undertook a structure-based solution to this problem by reversing evolutionary selection on the "ribosome inactivating protein" fold of RTA to arrive at a non-functional, compacted single-domain scaffold (sequence RTA1-198) for presentation of a specific protective epitope (RTA loop 95-110). An optimized protein based upon our modeling design (RTA1-33/44-198) showed greater resistance to thermal denaturation, less precipitation under physiological conditions, and a reduction in toxic activity of at least three orders of magnitude compared with RTA. Most importantly, RTA1-198 or RTA1-33/44-198 protected 100% of vaccinated animals against supra-lethal challenge with aerosolized ricin. We conclude that comparative protein analysis and engineering yielded a superior vaccine by exploiting a component of the toxin that is inherently more stable than is the parent RTA molecule.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 08, 2004
- Accession Number
- ADA428611
Entities
People
- John H. Carra
- Leonard A. Smith
- Mark A Olson
- Robert W. Wannemacher
- Virginia Roxas-duncan
Organizations
- United States Army Medical Research Institute of Infectious Diseases