Immunoelectron microscopy analysis of HCMV gpUL73 (gN) localization.

Human Cytomegalovirus (HCMV) UL73 encodes for a polymorphic structural glycoprotein, gpUL73(gN), conserved among herpesviruses. This study analyzed the intracellular and intraviral localization of gpUL73 by immunoelectron-microscopy comparing the reactivity of two different antibodies. We found that gN is an envelope component of the mature viral particle with at least a portion exposed at the virus surface and another at the internal side of the envelope. Furthermore, gpUL73 is also present in the matrix of dense bodies and "black holes". These results, as well as immunoblotting analysis, suggest that the two antibodies recognize different forms, fully processed or unprocessed, of gpUL73-gN.