Figure 1.

Entry and uncoating of HSV-1. Ultrathin Epon sections of Vero cells infected with HSV-1 at an MOI of 500 in the presence of cycloheximide (CH). After 2 h of virus binding at 4°C, the cells were either fixed immediately (a and b), or warmed up for 30 (c–f) or 60 min (g and h). (a and b) Binding. The main morphological features of the intact virus bound to the plasma membrane (PM) are the viral envelope (b, arrowhead) with the viral spikes (a, arrowhead), the viral capsid (arrow), and the electron-dense viral DNA genome within the capsid. (c and d) Fusion. Upon warming up, the viral envelope fuses with the plasma membrane, and the capsid (arrow) and the tegument proteins are released into the cytosol. (e and f) Release of the capsid. Preparations, which display a prominent contrast of the tegument, show that the tegument (arrowheads) stays behind at the PM. (g and h) Binding to the nuclear pore. At later time points, the capsids (arrows) have arrived at the nuclear envelope (NE), where they are exclusively located in close apposition to the nuclear pore complexes. Occasionally, fibers emanating from the pores (arrowheads) are visible, to which the capsids seem to bind. Almost all of the capsids at the nuclear pores appear empty and have lost the electron-dense DNA core. Bar, 100 nm.