Peptides as Vaccines

Peptide vaccines have been extensively tested both in animals and humans as minimal surrogate antigens to induce prophylactic or therapeutic T and/or B cell responses against disease. Peptides can mimic sequential B cell epitopes and sometimes even complex conformational epitopes (mimotopes), but low immunogenicity combined with high conformational diversity and the need for conjugated T helper epitopes represent major challenges for the development of vaccines based on B cell epitopes (BCE). Nevertheless experimental vaccines based on BCE that protect against viruses, bacteria, parasites, tumours, autoimmune diseases, fertility, Alzheimer’s disease and others have been developed, although none has been licensed so far. Cytotoxic T cell (CTL) epitopes of tumour-associated antigens have been used to treat cancer. Strategies based on modified peptides, cytokines and dendritic cells and others have improved peptide immunogenicity. Although clinical response rates are still relatively low, they are obtained with minimal side effects and most problems towards the development of more effective tumour vaccines are inherent to tumour immunology and not necessarily to peptide vaccines.