Mature dendritic cells pulsed with freeze-thaw cell lysates define an effective in vitro vaccine designed to elicit EBV-specific CD4(+) and CD8(+) T lymphocyte responses

Immunotherapy trials targeting the induction of tumor-reactive T-cell respo nses in cancer patients appear to hold significant promise, Because nonmuta ted lineage-specific antigens and mutated idiotypic antigens may be coexpre ssed by tumor cells, the use of autologous tumor material to promote the br oadest range of antitumor T-cell specificities has significant clinical pot ential in cancer vaccination trials. As a model for vaccination in the canc er setting, we chose to analyze the promotion of T-cell responses against E pstein-Barr virus (EBV)transformed B-lymphoblastoid cell line (B-LCL)-deriv ed antigens in vitro. A series of bulk antigenic formats (freeze-thaw lysat e, trifluoroacetic acid lysate, extracted membranes, affinity-purified MHC class I- and class Ii-presented peptides, acid-eluted peptides) prepared fr om EBV B-LCLs were tested for their ability to stimulate EBV B-LCL-reactive CD4(+) and CD8(+) T lymphocytes in vitro when pulsed onto autologous dendr itic cells (DCs). DC presentation of freeze-thaw lysate material derived fr om (either autologous or allogeneic) EBV B-LCLs with an Mr of 10 kd or larg er stimulated optimal anti-EBV B-LCL responsiveness from freshly isolated C D4(+) and CD8(+) peripheral blood T cells. These in vivo "memory" T-cell re sponses were observed only in EBV-seropositive donors. CD4(+) T-cell respon ses to lysate-pulsed DCs were Th1 type tie, strong interferon-gamma and wea k interleukin-5 responses). While CD8(+) T-cell responses were also observe d in interferon-gamma Elispot assays and in cytotoxicity assays, these resp onses were of low frequency unless the DC stimulators were induced to "matu re" after being fed with tumor lysates, Optimal-length, naturally processed , and MHC class I- or class It-presented tumor peptides were comparatively poorly immunogenic in this model system. (C) 2000 by The American Society o f Hematology.