Uveal melanoma cell-based vaccines express MHC II molecules that traffic via the endocytic and secretory pathways and activate CD8+ cytotoxic, tumor-specific T cells

Abstract

We are exploring cell-based vaccines as a treatment for the 50% of patients with large primary uveal melanomas who develop lethal metastatic disease. MHC II uveal melanoma vaccines are MHC class I+ uveal melanoma cells transduced with CD80 genes and MHC II genes syngeneic to the recipient. Previous studies demonstrated that the vaccines activate tumor-specific CD4+ T cells from patients with metastatic uveal melanoma. We have hypothesized that vaccine potency is due to the absence of the MHC II-associated invariant chain (Ii). In the absence of Ii, newly synthesized MHC II molecules traffic intracellularly via a non-traditional pathway where they encounter and bind novel tumor peptides. Using confocal microscopy, we now confirm this hypothesis and demonstrate that MHC II molecules are present in both the endosomal and secretory pathways in vaccine cells. We also demonstrate that uveal melanoma MHC II vaccines activate uveal melanoma-specific, cytolytic CD8+ T cells that do not lyse normal fibroblasts or other tumor cells. Surprisingly, the CD8+ T cells are cytolytic for HLA-A syngeneic and MHC I-mismatched uveal melanomas. Collectively, these studies demonstrate that MHC II uveal melanoma vaccines are potent activators of tumor-specific CD4+ and CD8+ T cells and suggest that the non-conventional intracellular trafficking pattern of MHC II may contribute to their enhanced immunogenicity. Since MHC I compatibility is unnecessary for the activation of cytolytic CD8+ T cells, the vaccines could be used in uveal melanoma patients without regard to MHC I genotype.

Tumor Cell Programmed Death Ligand 1-Mediated T Cell Suppression Is Overcome by Coexpression of CD80

“…To determine if costimulation is optional in the boosting phase of CD4 + T cells when tumor cells are the APCs, we used uveal melanoma (MEL202) and lung adenocarcinoma (H358) tumor cells transfected with genes encoding HLADR and the costimulatory molecule CD80 (B7.1; MEL202/DR1/CD80 and H358/DR7/CD80, respectively). Because of their ability to activate tumor-reactive CD4 + T cells that do not react with nonmalignant tissue, we have called these genetically modified tumor cells “MHC II vaccines” (22, 25, 41). Priming and boosting HLA-DR7 + or HLA-DR1 + PBMCs with HLA-DR syngeneic MHC II lung adenocarcinoma (Fig.…”

Immunotherapy of Uveal Melanoma

“…For uveal melanoma, these vaccines are called MHC II uveal melanoma vaccines (Oculovax™) and were specifically designed to activate uveal melanoma-specific, HLA-DR-restricted CD4+ T cells and thereby generate protective antitumor immunity and immune memory in uveal melanoma patients who are at high risk of developing metastatic disease [46]. Our studies demonstrated that MHC II uveal melanoma vaccines efficiently activate tumor-reactive, IFN-γ-secreting, HLA-DR-restricted CD4+ T cells as well as tumorspecific, cytotoxic CD8+ T cells from healthy donors and uveal melanoma patients [46,47]. Vaccines prepared from individual patients' primary uveal melanoma cells activated CD4+ and CD8+ T cells that cross-reacted with aggressive primary and metastatic tumor cells derived from other uveal melanoma patients.…”

“…However, HLA class I matching will be feasible, since the HLA-A2 allele is expressed by approximately 50% of uveal melanoma patients [49]. Interestingly, CD8+ T cells activated by the vaccines are cytolytic for HLA class I mismatched, as well as syngeneic, uveal melanoma targets [47]. Kan-Mitchell and colleagues [20,42] also found that CD8+ T cells from patients with uveal melanoma recognized targets independent of HLA class I genotype.…”

Major Histocompatibility Complex Class II+ Invariant Chain Negative Breast Cancer Cells Present Unique Peptides that Activate Tumor-specific T Cells from Breast Cancer Patients

“…The absence of Ii and its intrinsic endosomal trafficking sequence (36) may or may not affect MHC II trafficking because the MHC II ␤ chain also contains an endosomal trafficking signal (37). Our previous antigen presentation studies using endosomal and proteosomal inhibitors support peptide loading in the endosomal route (38,39); however, confocal microscopy studies indicate that vaccine cell MHC II molecules also traffic via the secretory pathway (40).…”