The eradication of global pathogens responsible for endemic and pandemic diseases hinges upon the development of effective vaccines. This is certainly the case for malaria. However, our inability to elicit ?strong and long-lasting? protective T cell responses, particularly CD8+ T cell responses, has been a major obstacle to successful vaccine development. Accordingly, adjuvant technologies will likely be critical not only to overcome pre-existing immunity to viral vaccine vectors but also to further enhance vaccine immunogenicity. Our previous studies have demonstrated that a CD1d molecule-binding, natural killer T (NKT) cell ligand, a-galactosylceramide (a-GalCer), can enhance protective CD8+ T cell responses elicited by murine malaria vaccines, including a recombinant adenovirus expressing a malarial antigen. In collaboration with two eminent chemistry groups directed by Dr. Chi-Huey Wong and Dr. Richard Franck, we have successfully identified several a- GalCer analogs that act as NKT cell ligands. In this proposal, we aim to first screen a focused library of one hundred a-GalCer analogs that we have recently generated, and then select a smaller panel of candidate glycolipids based on the in vitro cytokine production profiles they elicit upon cultivation with murine or human NKT cells. We will also determine the in vivo cytokine production profiles elicited by the selected glycolipids upon administration to mice. These in vitro and in vivo screening processes will lead us to choose a dozen of promising candidate glycolipids that display strong Th1-biased, Th2-biased, or bipolar activities.
Our second aim will be to determine the magnitude of adjuvant effect that each of these newly identified glycolipids contributes to the immunogenicity of a malaria vaccine. We will subsequently characterize the anti-malarial CD8+ T cell responses augmented by the glycolipids in a mouse model. Our third and final aim will be to determine the organs and cell types that present the malarial antigen to CD8+ T cells, and subsequently to uncover the mechanisms underlying the adjuvant effects of a-GalCer and its analogs. This work will involve the utilization of a recombinant adenovirus, co-expressing a malarial antigen and green fluorescent protein (GFP). Project Narrative Malaria continues to pose a grave threat to the global community and in particular to adults and children traveling to or living in tropical and subtropical regions of the world. The purpose of this proposal is to develop a novel strategy to enhance the efficacy of malaria vaccines by employing glycolipids as immuno-enhancing compounds or ?adjuvants.? The development of a suitable malaria vaccine/glycolipid adjuvant combination would have the potential to decrease the incidence of malaria and diminish the morbidity and mortality attributable to this pathogen.
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