No abstract

The goal of tumor immunotherapy is to elicit immune responses against autologous tumors. It would be highly desirable that such responses include multiple T cell clones against multiple tumor antigens. This could be obtained using the antigen presenting capacity of dendritic cells (DCs) and cross-priming. That is, one could load the DC with tumor lines of any human histocompatibility leukocyte antigen (HLA) type to elicit T cell responses against the autologous tumor. In this study, we show that human DCs derived from monocytes and loaded with killed melanoma cells prime naive CD45RA+CD27+CD8+ T cells against the four shared melanoma antigens: MAGE-3, gp100, tyrosinase, and MART-1. HLA-A201+ naive T cells primed by DCs loaded with HLA-A201− melanoma cells are able to kill several HLA-A201+ melanoma targets. Cytotoxic T lymphocyte priming towards melanoma antigens is also obtained with cells from metastatic melanoma patients. This demonstration of cross-priming against shared tumor antigens builds the basis for using allogeneic tumor cell lines to deliver tumor antigens to DCs for vaccination protocols.

No abstract

The specificity of recognition of pMHC complexes by T lymphocytes is determined by the V regions of the TCR α- and β-chains. Recent experimental evidence has suggested that Ag-specific TCR repertoires may exhibit a more Vα- than Vβ-restricted usage. Whether Vα usage is narrowed during immune responses to Ag or if, on the contrary, restricted Vα usage is already defined at the early stages of TCR repertoire selection, however, has remained unexplored. Here, we analyzed V and CDR3 TCR regions of single circulating naive T cells specifically detected ex vivo and isolated with HLA-A2/melan-A peptide multimers. Similarly to what was previously observed for melan-A-specific Ag-experienced T cells, we found a relatively wide Vβ usage, but a preferential Vα 2.1 usage. Restricted Vα 2.1 usage was also found among single CD8+ A2/melan-A multimer+ thymocytes, indicating that Vα-restricted selection takes place in the thymus. Vα 2.1 usage, however, was independent from functional avidity of Ag recognition. Thus, interaction of the pMHC complex with selected Vα-chains contributes to set the broad Ag specificity, as underlined by preferential binding of A2/melan-A multimers to Vα 2.1-bearing TCRs, whereas functional outcomes result from the sum of these with other interactions between pMHC complex and TCR.