The objective is to develop a glycoside adjuvant or immune agonist carrying the chemical structures needed to concurrently stimulate in a cooperative manner both innate and adaptive immunities, leading to a synergistic effect on the cellular (Th1) and humoral (Th2) immunities. It is likely that these adjuvants would also stimulate strong mucosal immunity. Studies with HIV-1 model vaccines indicate that a favorable immune protection would entail besides cytotoxic T lymphocytes (CTL), neutralizing antibodies and mucosal immunity. Yet, HIV's vast capacity to mutate may allow its escape from immune control. That HIV up regulates the CD4+ T cells'expression of the inhibitory CTLA-4 receptor, blocking the co-stimulatory ligands B7-1/B7-2 (CD80/CD86) expressed by antigen presenting cells (APCs) and required for T cell activation, means an anergic immune system that would not protect against the virus. Thus, HIV-1 vaccines would demand superior adjuvants to raise the immune response to levels not required before. The synergistic effects of the concerted stimulation of various receptors for innate and acquired immunity, deliver a much higher immune response with antigen and DNA based vaccines. The strategy to develop these adjuvants involves replacing in glycosides with aldehyde- carrying triterpenes their i) natural carbohydrate moieties with oligosaccharides that are ligands of innate immunity receptors, e.g. toll-like receptors (TLRs) and lectins, and ii) hydrophobic acyl group with new lipophilic chains, that may be design to serve as ligands for innate immunity receptors. The aldehyde group by forming imines with the amino groups of certain cell surface receptor(s) provides an alternative co-stimulatory signal needed to elicit Th1/Th2 immunity while the newly added innate immunity ligand, i.e. oligosaccharides and/or lipids, by binding to certain receptors would stimulate innate immunity. The triterpene group plays a role in the delivery of exogenous antigens directly into the cell's cytosol for processing by the endogenous pathway and CTL production, thus avoiding the need for viral vectors and production of interfering antibodies. Result of the concurrent stimulation of the receptors for both adaptive and innate immunities located on the same cell would be a synergistic effect on the immune response;i.e., the response stimulated by this immune agonist would be much higher than the aggregate of the responses elicited by the individual ligands. Phase I Specific Aims are, 1) Synthesize i) an immune agonist, having an aldehyde-carrying triterpene linked covalently to a mannan oligosaccharide and a myristoyl lipophilic chain, and ii) the controls lacking either the oligosaccharide chain or aldehyde;and 2) Study the role of this new adjuvant in i) the activation of DCs and macrophages by studying up-regulation of MHC, co-stimulatory molecules, and increased secretion of pro-inflammatory cytokines, ii) activating a protective immunity in vivo against a pathogen, by evaluating antigen specific CD4, CD8 responses, antigen specific antibodies, and protection against infection in the mouse model. The immune responses would be compared to that stimulated by well-known innate immunity ligands.
Results of this research would allow enhancing Th1and Th2 immunities with production of CTLs as well as antibodies with high avidity. As these compounds should stimulate mucosal immunity, they would provide a first line of defense against HIV-1 infection. They should also allow the improvement of vaccines'efficacy in the elderly population, which because of immune senescence, frequently shows some immune deficiencies, that interferes with the stimulation of an effective immunity. These agonists'capacity to deliver a co-stimulatory signal that is independent of the CD80/86 ligands may have applications in HIV-1 therapeutic vaccines where the CTLA-4 inhibitory receptor blocks the activity of the natural ligands leading to anergy.
