Ricin is one of the most potent biological toxins known, and is classified by the CDC as a category B biothreat. Much attention has been recently focused on the potential threat of actual ricin use. Since post exposure treatment is ineffective unless administered within a narrow window of time, vaccination may be the only ways to prevent lethality and damage to tissue caused by ricin. We have developed a safe and effective vaccine (RiVax(tm)) based on a recombinant mutant that eliminates the toxicities of the A chain. A robust, high yield and scalable process for manufacturing the vaccine has been achieved. Based on preclinical safety and efficacy data, a small Phase I trial was initiated to test the tolerability and immunogenicity of the vaccine in human volunteers. We have characterized adjuvant formulations of the vaccine which will be tested next in volunteers. The vaccine has passed the initial development hurdles. The purpose of this project is to continue development of this established candidate. Specifically, we will conduct long term stability studies of the protein in solution and adsorbed to aluminum salts adjuvant. We will assess the conformational aspects of the protein and relate them to potency. Secondly, we aim to demonstrate that the vaccine will generate antibodies in rabbits and humans that can passively confer protection to rabbits after aerosol or oral ricin exposure. The use of an additional animal species other than mice will lay the groundwork for pivotal animal efficacy trials which must be conducted in place of human trials (under the FDA animal rule). Thirdly, we will conduct GLP preclinical toxicology and efficacy trials in mice and rabbits to support the clinical evaluation an adjuvanted vaccine. Our goal is to obtain several thousand doses of released vaccine that has been evaluated for stability. And finally, we intend to perform the regulatory work necessary for IND submission. This proposal represents a critical step in the further development of Rivax towards additional clinical trials and ultimately registration and marketing. There is a very real worldwide threat for the use of ricin in bioterrorism. A safe and effective FDA-approved vaccine is urgently needed for military personnel and, in the event of a domestic attack, for first responders and perhaps for the general public. ? ? ?
| Vance, David J; Mantis, Nicholas J (2012) Resolution of two overlapping neutralizing B cell epitopes within a solvent exposed, immunodominant ?-helix in ricin toxin's enzymatic subunit. Toxicon 60:874-7 |
| Mantis, N J; Morici, L A; Roy, C J (2012) Mucosal vaccines for biodefense. Curr Top Microbiol Immunol 354:181-95 |
| Neal, Lori M; O'Hara, Joanne; Brey 3rd, Robert N et al. (2010) A monoclonal immunoglobulin G antibody directed against an immunodominant linear epitope on the ricin A chain confers systemic and mucosal immunity to ricin. Infect Immun 78:552-61 |
