BK polyomavirus small T antigen peptide–major histocompatibility complex (BKV sT pMHC)

The BK polyomavirus small T antigen (sT) peptide–major histocompatibility complex (pMHC) is a molecular assembly consisting of a processed fragment of the BKV small T antigen bound within the groove of an MHC molecule on the surface of an infected cell. The small T antigen itself is a regulatory viral protein that plays a crucial role in viral DNA replication and cellular transformation by inhibiting protein phosphatase 2A (PP2A), thereby promoting cell cycle progression (Source: UniProt P03071; PubMed: 15650189). In the context of immunotherapy, these pMHC complexes serve as the specific targets for the host's cellular immune response, particularly CD8+ cytotoxic T cells (Source: PubMed: 25154350). Recognition of the sT pMHC by specific T-cell receptors (TCRs) is essential for the clearance of BKV infection, which otherwise causes severe complications like BK polyomavirus-associated nephropathy (BKVAN) in kidney transplant recipients (Source: PubMed: 31615971). Therapeutic interventions such as adoptive T-cell therapy (e.g., Posoleucel) and TCR-engineered T cells are designed to specifically target these complexes to restore anti-viral immunity without damaging the transplanted organ (Source: Allovir; PubMed: 35731943). Monitoring the presence of these complexes and the corresponding T-cell response is a key strategy for managing viral reactivation in immunocompromised patients.

Other names

BK virus small T antigen peptide-HLA complexBKV sT-MHC complexBKPyV small T antigen pMHCBKV sT antigen-derived peptide-MHC

T-cell receptor (TCR) binding to the pMHC complex triggers cytotoxic T-lymphocyte (CTL) activation, leading to the release of perforin and granzymes and subsequent apoptosis of the BKV-infected host cell.