New tools, new approaches and new ideas for vaccine development 'A number of recent papers point a clear path from the genome to the immunome, bringing us closer to understanding just what information about a pathogen is required for effective host immune defense.'

Vaccine developers would do well to pay moreattention to the explosion of informationregarding T-cell epitopes and T-cell responsesthat is emerging from the nexus of bio-informatics, immunology and autoimmunity.Invasive pathogens may express thousands ofproteins containing potentially millions ofT-cell epitopes, yet a much smaller set ofsequences plucked from this protein haystackinterfaces with the cellular network that sets inmotion events leading to immunity. The set ofpathogen epitopes that interface with the hostimmune system is nowknown as the ‘immunome’. Anumber of recent paperspoint a clear path from thegenome to the immunome,bringing us closer to under-standing just what informa-tion about a pathogen isrequired for effective host immune defense.Indeed, we now have several approximations ofhow many epitopes are required to protectagainst infection. Similarly, the heterogeneity ofhost immune responses to T-cell epitopesresponsible for producing immunity andself-tolerance is beginning to be better defined. Exposure to foreign antigens induces theadaptive immune system to eliminate infectionand develop protective im munity. Central to thiseffort are T lymphocytes, which operate asactivators of B-lymphocyte growth and differen-tiation and as effector cells of cell-mediatedimmunity. T cells carry out these roles inresponse to peptide fragments of pathogen (orself) proteins that are displayed to them bymajor histocompatibility complex (MHC) pro-teins at the surface of antigen-presenting cells.One of the critical determinants of immuno-genicity is the strength of peptide binding toMHC molecules