Recombinant cancer vaccines based on viral vectors

Based on the observation that viral infection results in the presentation of virus-specific peptides in association with both MHC Class I and MHC Class II on the surface of infected cells, strategies have been designed to use recombinant viruses carrying tumour-associated antigen (TAA) genes as immunization vehicles to elicit tumour-specific immune responses. I report here on results from phase I clinical studies based on a canarypox viral vector system expressing TAAs of interest. Clinical studies conducted in patients with colorectal cancer to evaluate ALVAC-CEA, ALVAC-KSA, or ALVAC-p53 candidate vaccines have shown that this approach is safe and can induce tumour-specific responses. Additional clinical studies evaluating candidate vaccines against melanoma, targeting either the gp100, Mage 1 or Mage 3 molecules are in progress. On the basis of our results and in the context of parallel studies being conducted with other viral systems, the characteristics of an ideal viral vector system, as it applies to therapeutic cancer vaccination, are discussed.