Merkel cell polyomavirus T-antigen and NKG2D ligand (MCPyV T-antigen/NKG2D-L)

Merkel cell carcinoma (MCC) tumor antigens primarily consist of the Large T (LT) and Small T (sT) antigens derived from the Merkel cell polyomavirus (MCPyV), which is integrated into the genome of approximately 80% of MCC tumors. These viral oncoproteins are essential for tumor maintenance and serve as highly specific neoantigens because they are not expressed in healthy human tissue. The concept of distressed tumor cells refers to the upregulation of stress-induced ligands, such as NKG2D ligands (MICA/B and ULBPs), which occur as a result of DNA damage and oncogenic transformation within the MCC microenvironment. Targeting these antigens and stress markers allows the immune system to distinguish malignant cells from normal cells, facilitating the development of immunotherapies including checkpoint inhibitors, therapeutic vaccines, and adoptive cell transfers. Current clinical approaches focus on enhancing the visibility of these viral antigens to the host immune system or utilizing bispecific engagers that link T-cells or NK-cells to these distressed cell markers.

Other names

Merkel cell polyomavirus Large T-antigenMerkel cell polyomavirus Small T-antigenMCPyV LT/sTNKG2D ligandsMICA/BULBPDistressed tumor cell markers

Therapeutic strategies targeting this complex involve the use of immune checkpoint inhibitors to reinvigorate T-cell responses against viral antigens, or the use of investigational vaccines and TCR-T cell therapies specifically engineered to recognize MCPyV T-antigen epitopes presented on the surface of distressed tumor cells.