A new method to monitor antigen-specific CD8+ T cells, avoiding additional target cells and the restriction to human leukocyte antigen haplotype.

Therapeutic vaccination of cancer patients with dendritic cells aims at inducing a strong tumor-specific T-cell response. Testing new target antigens for their immunogenicity is crucial to evaluate their suitability for this approach. Here we demonstrate a comfortable and reliable method to detect antigen-specific CD8(+) T-cell responses without the knowledge of the precise T-cell epitope and without the usage of additional target cells. We used the CD8(+) T cells themselves and electroporated them with RNA encoding the respective tumor antigen. The cells expressed, processed and presented the antigen and were capable of stimulating each other in functional readouts. For the model antigen MelanA, the number of interferon-γ-secreting cells obtained with this method highly correlated with the numbers obtained by exogenous peptide loading (R(2)=0.8). The method was also applicable for the tumor-associated antigen Wilms' tumor protein 1. This system is quick and easy to perform, independent of the donors human leukocyte antigen type and circumvents the need for additional cells as targets. It can be used in preclinical research to test new antigens for their immunogenic potential and for immunomonitoring in cancer patients.