SITC 2021: T Antigen–Specific T Cells and Checkpoint Inhibition in Merkel Cell Carcinoma
Posted: Monday, November 29, 2021
During the 2021 Society for Immunotherapy of Cancer (SITC) Annual Meeting (Abstract 299), Ulla Hansen, PhD, of the Technical University of Denmark, Kongens Lyngby, and colleagues presented their study findings regarding the correlation between broad T antigen–specific CD8-positive T cells and PD-1 inhibitor therapy in Merkel cell carcinoma. The investigators concluded that these T cells appear to be associated with a clinical benefit to checkpoint inhibitor therapy, potentially facilitating the use of this treatment on a wider scale.
Potential CD8-positive T-cell epitopes from T antigen–specific and viral capsid protein 1 were predicted for binding to 33 different human leukocyte antigen (HLA) class I types. Peripheral blood mononuclear cells were collected from 24 patients with Merkel cell polyomavirus-positive Merkel cell carcinoma before and after the initiation of anti–PD-1 therapy.
Approximately 40 T antigen–specific CD8-positive T-cell populations were observed to recognize 31 epitopes restricted to 14 different HLA class I types. Additionally, these cells were detected in responders (n = 17) during treatment, with an increased number of responses occurring after therapy was initiated. In contrast, just one T antigen–specific CD8-positive T-cell population was reported among non-responders (n = 7).
Of note, there was a reported increase in T-cell repertoire after therapy initiation among responders versus non-responders. Among these participants, the T antigen–specific T cells seemed to display an activated effector memory phenotype.
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