Immune evasion by human cytomegalovirus: lessons in immunology and cell biology

The human cytomegalovirus (HCMV) has dedicated a significant part of its genome to genes encoding molecules that modulate the host immune response. Many of these genes have homologues in the host genome. Others, however, are unique in the sense that no obvious primary sequence identity is found in the available databases. The HCMV gene products interfere with the activation of MHC class I and class II restricted T cells and NK cells, modify the function of cytokines and their receptors, interact with complement factors and modulate signal transduction and transcription factor activity, in addition to interference with many other cellular functions. Investigation of these evasion strategies has not only improved our understanding of HCMV pathogenesis, but has also provided unexpected, novel insights into basic cell biological and immunological processes.