Enhanced multiepitope-based vaccines elicit CD8+ cytotoxic T cells against both immunodominant and cryptic epitopes

A frequent issue in vaccinology is to elicit balanced T cell responses against both immunodominant and cryptic T cell epitopes. from one or several anti-ens presented at the same time to the immune system. Using HLA-A2. 1.1 restricted epitopes from the Melan A/MART-1 I or gp 100 melanoma-associated anti-ens as a model, we engineered a series of constructs in the ALVAC canary x vector system: T cell epitopes were expressed either as linear polyepitopes (with or without spacers), or as minigenes encoding a single epitope. The latter were found to allow the best processing and presentation of most T cell epitopes, following infection by ALVAC recombinants of the HLA A,A2+ bladder carcinoma cell line and stimulation of epitope-specific human TIL lines. These various constructs were also used to immunize HLA-A-2- I. I HHD transgenic mice to compare their capacity to elicit T cells responses. Polyepitopes but also minigenes encoding wild-type epilopes could not elicit in a reliable manner balanced CTL responses against all tar-get epitopes from g 100. We could rescue T cells responses against poorly immunogenic epitopes after introducing appropriate point mutations to enhance their interaction with NA, EC Class I molecules. Epitope enhancement within either polyepitope. multiepitopes (i.e. minigenes expressed under the control of separate promoters) or full length immuno-ens should be systematically considered when designing vaccines containing both cryptic and immunodominant target epitopes. (C) 2004 Elsevier Ltd. All rights reserved.