Cancer vaccines

The observation that tumors can regress spontaneously or concurrently with an unrelated infection dates back to antiquity. Hippocrates was thought to have noticed the effect of erysipelas infection on concurrent malignant disease,(65) although it was not until the end of the nineteenth century that the beginnings of modem immunologic concepts paved the way for attempts at eradicating tumors, in particular through induction of skin infections.(25, 39) Conversely, immunodeficiency states may increase the risks of tumor development. An understanding of immunologic mechanisms that underlies these effects is more recent and has benefited from advances in molecular and cellular biology. Identification of tumor-associated and tumor-specific antigens (Table 1) and a better understanding of the mechanisms involved in antigen presentation, lymphocyte activation, and tumor escape from immune surveillance have given investigators tools to manipulate the immune system to induce an efficient immune response in the tumor-bearing host. Manipulating the immune system has taken two forms (Table 2). Passive immunotherapy consists of the adoptive transfer of specific antitumor immune effectors generated ex vivo or of specific antibodies to the tumor cells. Active immunotherapy using cancer vaccines aims at inducing an efficient and long-lasting immune response by stimulating the tumor-bearing host. Active immunotherapy and cancer vaccines are described in this article.