Merkel cell polyomavirus Large T antigen (MCPyV LT)

The Merkel cell polyomavirus Large T antigen (MCPyV LT) is a multifunctional viral oncoprotein that plays a central role in the pathogenesis of approximately 80% of Merkel cell carcinoma (MCC) cases [1, 2, 3]. In its full-length form, LT is essential for viral DNA replication, utilizing its origin-binding and helicase domains to initiate the viral life cycle [2, 5, 10]. However, in MCC, the LT gene is characteristically integrated into the host genome and undergoes truncating mutations that eliminate the helicase domain while preserving the N-terminal LXCXE motif [6, 7, 12]. This truncated LT (truncLT) binds to and inactivates the retinoblastoma (Rb) tumor suppressor protein, thereby promoting uncontrolled cell cycle progression and malignant transformation [7, 12, 13]. Because truncLT is constitutively expressed in virus-positive MCC cells and is absent in healthy human tissues, it serves as a highly specific and promising therapeutic target [3, 7, 27]. Current clinical development efforts focus on immunotherapy, including therapeutic DNA vaccines such as ITI-3000 and adoptive T-cell therapies (e.g., TCR-MCC1) designed to elicit or enhance immune responses against LT-derived epitopes presented on the surface of tumor cells [15, 16, 27]. These strategies aim to overcome the immune evasion mechanisms often employed by MCC, such as the downregulation of HLA class I molecules [3, 7].

Other names

MCV LTLarge tumor antigentruncated Large T antigentruncLTtLT

Therapeutic vaccination to induce antigen-specific CD4+ and CD8+ T-cell responses; Adoptive transfer of T-cell receptor (TCR) engineered T cells to recognize and lyse cells presenting LT-derived epitopes.