This U19 TRIAD Technology Development proposal describes an innovative program aimed at developing a high-performance, pro-inflammatory and non-tolerogenic vaccine delivery system based on the dendritic cell targeting anti-DEC-205 antibody. The success of anti-DEC-205 as a stimulator of strong inflammatory immune responses depends on co-administration of non-specific dendritic cell maturation factors. In their absence, anti- DEC-205 induces antigen-specific tolerance rather than immunity. Because of the dangers associated with nonspecific activation of the immune system, we propose to develop a modified pro-inflammatory and nontolerogenic anti-DEC-205 antibody. We have discovered a set of natural regulatory T-cell epitopes derived from human immunoglobulins that induce tolerance by stimulating regulatory T cells. We have verified experimentally that these epitopes generate antigen-specific expansion of regulatory T cells and suppress inflammatory immune responses. We hypothesize that regulatory T-cell epitopes contained in anti-DEC-205 promote a tolerogenic reaction that is only overcome through co-administration of non-specific immunostimulators. We expect that modification of these epitopes will significantly diminish tolerogenicity, enabling use of anti-DEC-205 as a stand-alone, high performance antigen delivery system. We will de-tolerize anti-DEC-205 by epitope modification in a two-stage process beginning first in a (humanized) mouse model system and progressing to human blood samples. Using TRIAD Toolkit Core immuno-informatics algorithms, we will reengineer anti-DEC-205 such that key amino acids in its regulatory T-cell epitopes are replaced with those that are experimentally shown to interfere with HLA binding. We will then (1) produce a set of antibody variants recombinantly conjugated to test antigens including vaccine candidates identified in TRIAD Research Projects, (2) identify de-tolerizing mutations that do not interfere with dendritic cell targeting, and (3) evaluate variants for reduced tolerogenicity, as well as for enhanced immunogenicity for vaccine antigens.
This project will improve on a vaccine delivery vehicle targeted to cells that induce immune responses. Using computational and experimental methods, the vehicle will be optimally designed to eliminate portions that suppress immune responses. A more effective vehicle potentially will stimulate immune responses to prevent and treat disease through vaccination
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