Quantitating therapeutically relevant T-cell responses to cancer vaccines

Successful application of active immunotherapy to the treatment of cancer w ill require stimulation of potent antigen-specific T-cell responses. It is not known how numerous or how potent these T cells must be in order to abro gate tumors, but the levels of immunity needed to control chronic viral inf ections may provide estimates for comparison. Evaluation of the efficacy of a vaccine strategy in attaining these levels of immunity will depend on th e use of assays that create a picture of T-cell number and function that co rrelates with clinical outcomes. We discuss the currently available in vivo and in vitro T-cell assays and their relevance for detecting therapeutic l evels of T-cell activity. We also propose a strategy for efficiently evalua ting the immunologic efficacy of cancer vaccines so that the most promising candidates can be brought more rapidly into definitive clinical trials.