Human cytomegalovirus encodes a glycoprotein homologous to MHC class-I antigens

Primary infection with human cytomegalovirus (HCMV) is persistent and widespread, with symptoms that are mostly subclinical but can cause serious illness or death, particularly in immunosuppressed patients. Recently, proteins from HCMV were shown to bind beta 2-microglobulin (beta 2-m) a protein that is normally found associated with the class-I major histocompatibility complex (MHC) antigens, which are essential for self-non-self recognition in the immune response. These findings led to the proposal that the virus may use beta 2-m binding as an infection mechanism. Here we present evidence from DNA sequence analysis that HCMV encodes a molecule similar to the MHC class-I antigens of higher eucaryotes, and propose that this protein is responsible for the observed beta 2-m binding. The deduced amino-acid sequence of the HCMV class-I-like protein reveals conservation of typical features of class-I structure, but we predict that the gene is not spliced, in contrast to the cellular genes.