Modulation of antigen processing and cross presentation by endogenous and exogenous heat shock proteins for stimulation of CTL-mediated immunity.

The immune system functions to recognize and eliminate infectious agents that cause disease. Considerable success has been achieved in protecting humans and animals against infectious diseases with the use of vaccines. However, new methods of vaccination and greater understanding of ways to boost the strength of immune responses are needed to protect against new diseases and to eliminate infections that are not well seen by the immune system. New vaccine formulations and improved methods to stimulate immune responses also have the potential to protect against, and even eliminate, some cancers. Potent immunity is mediated by 'killer' T cells, which can directly destroy target cells that are infected by virus or bacteria, or that are otherwise recognized as abnormal, such as tumour cells. The components of the infectious agent or abnormal cell that are recognized by the immune system are made inside the cell, and have to be processed and displayed outside the cell to be recognized by T cells. We currently believe that immune cells called dendritic cells must also acquire the components of the infected cells, probably by 'eating' fragments of similarly infected cells, and use these foreign fragments to teach some of the T cells to become killer T cells. Some heat-induced proteins in infected cells and tumour cells, have been found to increase the stimulation of killer T cells. This research project will examine the effects of production of heat-induced proteins by target cells and dendritic cells, on inducing a strong killer T cell responses against a component of a virus which is expressed in the target cells. The target cells, or dendritic cells which have 'eaten' the target cells, will be used as a vaccine to test whether immunity against the 'infected' cells is generated. Also, the changes in the dendritic cells that induce strong killer T cell responses against the modified target cells, will be fully analysed. These experiments will reveal mechanisms that enhance immunity to intracellular components and will identify ways to improve the design of the next generation of protective vaccines.

Generation of adaptive immunity against intracellular pathogens and growing tumours requires acquisition of exogenous cell-associated antigens by professional antigen presenting cells (APCs), processing these components for loading on to MHC class I molecule, and presentation to CD8+ T cells, known as cross-priming. Pancreatic islet beta-cells containing the glycoprotein of lymphocytic choriomeningitis virus (LCMV-GP) are poor inducers of CD8+ T cell stimulation, due to inefficient cross-presentation of the immunodominant epitope peptide GP33-41. Expression of supplemental heat shock cognate protein 70 (Hsc70) in the beta-cells markedly enhances stimulation of GP33-41 specific T cells in mixed beta-cell, APCs, and T cell cultures. The research project will investigate the ability of heat shock proteins to enhance dendritic cell (DC) function and stimulate cross priming of CD8+ cytotoxic T lymphocytes (CTLs) by cellular antigen. Two mechanisms mediating enhanced T cell stimulation will be examined. First, enhanced cross presentation will be examined for requiring chaperone function of Hsc70 and the pathway of cellular LCMV-GP trafficking, processing for class I epitope loading, and surface presentation characterised. Second, the innate immune signalling function of both endogenous and exogenous Hsc70, Hsp70 and microbial Hsp71, will be investigated for stimulating cell associated antigen uptake, processing, MHC class I loading, and induction of DC co-stimulatory function for T cell activation. The enhanced T cell stimulation by HSP-associated cellular antigen loading of DCs will be tested for activation of CTL function in a mouse model of CD8 T cell mediated autoimmunity, and for the ability to mediate elimination of tumour cells expressing viral protein target epitopes. The results will identify potential improvements to adjuvant and cell based vaccine design for treatment of infectious pathogens and cancer.