Modulation of HLA expression in human cytomegalovirus immune evasion

Human cytomegalovirus (hCMV) has evolved multiple mechanisms to escape the host immune recognition and innate or adaptive immune responses. Among them, hCMV has developed strategies to modulate the expression and/or function of human leukocyte antigens (HLAs), including by encoding series of infection stage-dependent hCMV proteins to detain and destroy the expression of HLA molecules on the surface of infected cells. This disturbs the antigen presentation and processing, by encoding MHC class I homologues or selective up-regulation of particular HLA class I molecules binding to NK cell inhibitory receptors, and by encoding specific ligand antagonists to interfere with NK cell activating receptors. Here we discussed the molecular mechanisms utilized by the hCMV to alter the formation, transportation and expression of HLA antigens on the infected cell surface. The knowledge about hCMV modulating HLA expression could benefit us to further understand the pathogenesis of viral diseases and may eventually develop novel effective immunotherapies to counteract viral infections and viral associated diseases.