Abstract Merkel Cell Carcinoma (MCC) is an aggressive skin tumor caused by Merkel Cell Polyomavirus (MCV) in ~80% of cases that responds poorly to standard chemotherapies. Virus positive tumors have a low mutational burden, and are driven by alternatively spliced T-antigens (TAG), small T (sT) and truncated large T antigen (LTT). These intracellular proteins are constitutively expressed in MCC tumors and are required for tumor survival. We hypothesized that MCV TAG can be targeted by cytotoxic T lymphocytes for potential use as an adoptive T cell immunotherapy to treat MCC. Peripheral blood T cells were stimulated with autologous dendritic cells pulsed with overlapping peptide libraries derived from MCV sT and LTT in the presence of a pro-inflammatory cytokine cocktail (IL-1β, IL-6, IL-7, IL-15, IL-21, IL-23, and TGFβ). This culturing method increases yields by 6 fold of antigen-specific T cells that produce TNFα and IFNγ, from both MCC subjects and healthy donors. These expanded TAG-specific cells are predominately CD4+ cells of a memory phenotype that expresses low levels of PD-1, but no expression of IL-17A. Growing evidence suggests that CD4+ Th1 and Th17 cells can have potent anti-tumor activities, especially against MHC class II positive tumors. Three virus-positive and two virus-negative MCC cell lines were tested for HLA-DR expression by flow cytometry. We found that MCC cell lines, both virus positive and virus negative, can be induced to express HLA-DR in a dose-dependent fashion in response to IFNγ in vitro. These results suggest that MCC virus positive tumors can likely be directly recognized and destroyed by adoptively transferred Th1 or Th17 CD4+ T cells and offers a promising avenue for adoptive T cell immunotherapy as a MCC treatment.