beta2 Microglobulin Binds to the Tegument of Cytomegalovirus: an Immunogold Study

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Abstract
Summary Previous reports have provided evidence for the ability of human cytomegalovirus (HCMV) to bind the host protein β2 microglobulin (β2m) from body fluids or culture medium, and thus enhance infectivity of the virus, both by evasion of immune neutralization and the capacity to employ the bound β2m for attachment to the host cell. Immunocytochemical techniques and negative stain electron microscopy were used to identify the ultrastructural components of HCMV involved in its interaction with β2m. Probes comprising colloidal gold coupled to β2m were seen to bind not to the envelope as previously suspected, but to material closely surrounding the nucleocapsids. It is postulated that the tegument proteins of HCMV, via their capacity to bind β2m, play an important role in the preservation of infectivity of disrupted virions by enabling unenveloped capsids to bind to cells and gain entry by a pathway other than that normally taken by intact virions.