HLA-DP4 expression and immunity to NY-ESO-1: correlation and characterization of cytotoxic CD4+ CD25- CD8- T cell clones.

NY-ESO-1 is one of the most immunogenic cancer antigens known to date, eliciting spontaneous immune responses in approximately 50% of patients with NY-ESO-1+ cancers. Spontaneous CD4+ and CD8+ T cell responses were found in patients with detectable NY-ESO-1 serum antibody, indicating an integrated type of immune response induced by NY-ESO-1+ malignancies. A close association between spontaneous NY-ESO-1 immunity and the HLA-DP4 allele was suggested in a recent study. To address these results, we assessed the NY-ESO-1 antibody and HLA-DP4 status of 102 patients with NY-ESO-1+ malignancies. However, no correlation between HLA-DP4 and NY-ESO-1 immunity was found. To explore the role of HLA-DP4-restricted CD4+ T cells in cancer immunity, we established HLA-DP4- restricted NY-ESO-1-specific CD4+ T cell clones by limiting dilution and repeated stimulation with NY-ESO-1 peptide p157-170 from NY-ESO-1 seropositive patients. A subset of CD4+ T cell clones was reactive with naturally processed NY-ESO-1 presented by autologous DCs that were pulsed with recombinant NY-ESO-1 protein, lysates of NY-ESO-1-expressing tumor cell lines, or transduced with recombinant NY-ESO-1 viral constructs in ELISPOT assays. Three different CD4+ T cell clones were used to mediate the specific lysis of allogeneic HLA-DP4+ Epstein-Barr virus-transformed B cells (EBV-B) pulsed with NY-ESO-1 p157-170. The Th1 phenotype and effector functions of the CD4+ T cell clones described here provide an important rationale for the activation of antigen-specific CD4+ T cells along with CD8+ T cells in cancer vaccination strategies.