Several projects in adjuvants and vaccine delivery systems have been undertaken: The separation of several pure compounds from the commercially available Quillaja bark Saponin has been reported in the literature (QS-7, QS-17, QS-18, QS-21(a,b)). The exact structure of these powerful adjuvants is unkown. An investigation to determine the exact composition/structure of these compounds in solution has been initiated. A solution structure of these adjuvants should help elucidate the type of interactions that occur with antigens and possibly with target cells in the immune system. The constitutional structure of the two compounds that make up QS21(a,b) was detailed in a paper recently submitted for publication by a group in Biocine, but questions still remain as to their exact stereochemistry, and their structure in solution. Structural studies on the other saponins should help in understanding the interplay between adjuvanticity and toxicity observed in this class of compounds. We have successfully separated QS7, QS17, QS18, QS21 and other minor saponins from commercially available Samolaria Quillaja Saponin. We have began to study the solution structure of these molecules using NMR spectroscopy. A computatioal study of the dynamic structure of QS21 was undertaken. Langevin dynamic calculations, a single molecule in space, beginning from several different conformations, have been carried out to several nanoseconds. Inter molecular interactions have been explored by studying the Langevin dynamic trajectory of dimers. The conformational space is also being explored with Montecarlo random sampling. An investigation into the polysaccharide microspheres as a possible vaccine delivery system has been undertaken. Polysaccharides as encapsulating materials offer several advantages over the materials which are commonly used in development as vaccine carriers. First, the encapsulation is performed in the complete absence of organic solvents, avoiding the possibility of denaturing the antigens, and of retaining traces of unacceptable chemicals in the final product. Second, it is less likely that the environment inside the capsule will be unfavorable to the antigen and thus it will not destablize the antigens. Microencapsulation of BSA-TNP has been performed with dextran. Encapsulation of BSA-TNP has been carried out with dextran of different molecular weights (2 million, 72000, 40000, 93000) at different concentrations (from 40% to 25% dextran solutions). Studies of the properties of those capsules in eliciting immune responses are in process. When this is achieved their immunogenicity will be assessed. Then a study will be carried out to examine if the polysaccharide capsule itself could be an antigen for a T-dependent immune response to bacterial capsule polysaccharides when these are used to encapsulate an immunogenic protein.
