The egress of alphaherpesviruses from the cell

Excerpt

A commonly accepted concept in herpesvirology holds that herpesvirions are formed by budding of nucleocapsids at the inner nuclear membrane and the enveloped virions are released into the perinuclear space (see Chapter 13). This is a closed compartment that virions need to exit, in order to reach the extracellular space and start a new infection cycle. How alphaherpesviruses accomplish this goal is a controversial issue. Of the two pathways of virus exit proposed, the single envelopment and the double envelopment, also referred to as de-envelopment–re-envelopment, each has evidence and supporters in the literature (the topic has been covered in excellent reviews and papers (Enquist et al., ; Skepper et al., ; Johnson and Huber, ; Mettenleiter, 2002). Part of the uncertainties that still dominate this topic comes from the difficulties in interpreting static electron microscopy images. Thus cytoplasmic virions juxtaposed to curved vesicles were interpreted in some studies as budding virions, i.e., as evidence for secondary envelopment and for the deenvelopment-reenvelopment pathway. In other studies they were interpreted as virions undergoing fusion with encasing vesicles, i.e., as evidence of de-envelopment (Campadelli-Fiume et al, : Roizman and Knipe, 2001). To solve these ambiguities, several approaches have been undertaken in recent years, including the generation of genetically modified mutants and cytochemistry.