Several advances in basic immunology over the last few years have forced a re-evaluation of cancer vaccine development. The most important finding has been that human tumors are immunogenic. The HER2/neu oncogenic protein is a tumor antigen. Existent antibody, helper T-cell, and cytotoxic T-cell immunity to HER2/neu have been detected in patients with cancer. The HER2/neu protein is an excellent therapeutic target for the immune system. Passive immunotherapy strategies, such as the infusion of monoclonal antibodies specific for HER2/neu, have been shown to be of clinical benefit in patients with HER2/neu-overexpressing malignancies. Inducing an active immune response by generating endogenous HER2/neu-specific antibodies and T cells may result in long-lived immunity and, hopefully, therapeutic benefit. In the majority of patients with pre-existent HER2/neu immunity, the antigen-specific antibodies and T cells detected are of low magnitude. Therefore, vaccine strategies aimed at boosting immunity already present may be effective in generating significant levels of HER2/neu-specific antibodies and T cells.
