ObjectivesThis work focuses on human cytomegalovirus (HCMV) UL73, which encodes for a putative transmembrane glycoprotein that is highly conserved among herpesviruses.Study DesignpUL73 expression was analyzed both in transiently transfected and in HCMV-infected cells using a pUL73-specific antiserum by immunoblot and immunofluorescence. Sequencing analysis from several clinical isolates and laboratory-adapted strains was also performed.ResultspUL73 expressed in transiently transfected cells consists in a polypeptide of the expected size (15–18 kd) with cytoplasmic localization. In infected cells, pUL73 is expressed with true-late kinetics and localizes both in perinuclear granular formations and on the cell surface. A broad band (39–53 kd), sensitive to O-glycosidase digestion was detected in purified virus. In addition, sequence analysis showed that the N-terminal portion of pUL73 from clinical isolates is highly polymorphic.ConclusionsUL73 encodes for a new structural glycoprotein (gpUL73) expressed on the cell surface of infected cells and highly polymorphic among clinical isolates.