Human cytomegalovirus Immediate-Early 1 protein-derived peptide–HLA class I complex (CMV IE1–HLA-I complex)

Human cytomegalovirus (HCMV) Immediate-Early 1 (IE1) protein-derived peptide–HLA class I complexes are cell-surface molecular assemblies consisting of an 8-10 amino acid peptide from the IE1 protein (UL123) bound to a Human Leukocyte Antigen (HLA) class I molecule. IE1 is a critical 72-kDa regulatory protein expressed at the earliest stages of the viral lytic cycle, making it a primary target for immune surveillance. These complexes are recognized by CD8+ cytotoxic T lymphocytes (CTLs), which trigger an immune response characterized by the release of perforin, granzymes, and interferon-gamma to eliminate infected cells. In clinical practice, these complexes serve as targets for adoptive T-cell therapies and vaccines designed to prevent or treat CMV reactivation in immunocompromised patients, such as those undergoing hematopoietic stem cell or solid organ transplantation. Furthermore, novel therapeutic strategies like ReTARG fusion proteins and TCR-like antibodies utilize these complexes to redirect potent, inflationary CMV-specific T cells against tumor cells. A significant therapeutic challenge involves the potential for cross-reactivity between CMV-derived peptides and human self-peptides, which may contribute to the development of graft-versus-host disease (GVHD). Additionally, CMV has evolved mechanisms to downregulate HLA class I expression, potentially allowing infected cells to evade detection by the immune system.

Other names

HCMV IE1 peptide-MHC complexIE1-pMHCCMV IE1-HLA complexUL123 peptide-HLA complexCMV IE1-derived peptide–HLA class I complexes

Recognition by CD8+ T cells via the T-cell receptor (TCR), leading to targeted cell lysis and cytokine production; redirection of CMV-specific T cells to non-viral targets (e.g., cancer cells) using bispecific or fusion proteins; and stimulation of antigen-specific T-cell expansion for adoptive transfer or vaccination.