This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. 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. a vaccine (RiVaxtm) has been developed 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. 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 nonhuman primates and humans that can passively confer protection to nonhuman primates 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 project represents a critical step in the further development of Rivax towards additional clinical trials and ultimately registration. 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. Ongoing research at the TNPRC includes evaluation of the ricin vaccine candidate in nonhuman primates. We are presently engaged in a nonhuman primate study (n=18) to determine immunogenicity and efficacy against aerosol ricin challenge. To date, the first phase of this study is underway;animals have been immunized with the vaccine candidate and await aerosol challenge.
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