New tools for antigen delivery to the MHC class I pathway.

At the beginning of this new millennium, pathogens and cancer remain the leading causes of death worldwide. The development of vaccines to prevent diseases for which no vaccine currently exists, such as AIDS or malaria, or to treat chronic infections or cancers, as well as the improvement of efficacy and safety of existing vaccines, remains a high priority. In most cases, the development of such vaccines requires strategies capable of stimulating CD8(+) cytotoxic T lymphocytes (CTLs) and thus, to deliver antigen to MHC class I molecules. There exists several different pathways for loading antigenic peptides onto MHC class I molecules, either based on the endogenous cytosolic MHC I pathway or on cross-presentation. The understanding of the relevance of each of these mechanisms in CTL activation will help vaccine design to progress more rationally.