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The core fusion machinery of all herpesviruses consists of glycoproteins gH, gL and gB. However, additional glycoproteins are often required for infection of different cell types. Human cytomegalovirus (HCMV) infects a variety of human cells, and the switch of cell tropism is believed to be controlled by the additional glycoproteins that can be incorporated into the gHgL complex. Expression of glycoprotein gO, which makes a trimeric complex of gH/gL/gO, is required for fibroblast infection. Expression of UL128, UL130 and UL131, comprising the pentameric complex of gH/gL/UL131-128, is essential for monocyte, epithelial and endothelial cell tropism. Thus different HCMV strains demonstrate different cell tropism, and dissecting the initial steps of their attachment to cells is key for our understanding of the consequent events that lead to productive cell infection, persistence, and viral-mediated disease.
Supported by a grant from the National Institute of General Medical Sciences (P30-GM110703).